即使在项目不会使用自定义的方法来记载图片（往往使用第三方类库），但是探究图片加载的过程，对程序员能力的提升还是很有意义的。
参考了Android官方学习文档
展示一下效果图
大体描述一下图片加载的流程
1.在内存中查找，如果命中则显示。否则，进行下一步；
2.在SD卡上查找，如果命中则显示。否则，进行下一步；
3.发送网络请求，将下载图片，保存到内存、SD卡，显示图片。
参照代码进行解释说明
- 1.首先实例化用于图片缓存的内存和sd卡（这里使用了DiskLruCache）
public void init(Context applicationContext) {
this.mAppContext = applicationContext;
if (instance == null) {
final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
final int cacheSize = maxMemory / 8;
//使用安卓系统分配给APP 1/8的内存作为图片缓存的空间
mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {
@Override
protected int sizeOf(String key, Bitmap bitmap) {
return bitmap.getRowBytes() * bitmap.getHeight()/1024+1;
}
};
//实例化SD卡缓存空间
File cacheDir = getDiskCacheDir(mAppContext, DISK_CACHE_SUBDIR);
new InitDiskCacheTask().execute(cacheDir);
}
instance = this;
}
class InitDiskCacheTask extends AsyncTask<File, Void, Void> {
@Override
protected Void doInBackground(File... params) {
synchronized (mDiskCacheLock) {
File cacheDir = params[0];
try {
//下面是DiskLruCache的逻辑。mDiskCacheLock：这是一个SD缓存的锁，保证仅仅只有一个线程在操作SD卡。
//当实例化SD缓存后，调用notifyAll，唤醒其他因为等待mDiskCacheLock而阻塞的线程
mDiskLruCache = DiskLruCache.open(cacheDir,
getAppVersion(mAppContext), 1, DISK_CACHE_SIZE);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mDiskCacheStarting = false; // Finished initialization
mDiskCacheLock.notifyAll(); // Wake any waiting threads
}
return null;
}
}
- 2.加载图片
private void loadBitmap(ImageView imageView, String imageUrl, Bitmap placeHolder) {
//1.判断图片的内存缓存中是否存在，如果存在直接加载
final Bitmap bitmap = getBitmapFromMemCache(imageUrl);
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
//2.判断该图片是否downloading，如果是，取消后续操作。你可能会问，不是还没有判断sd卡吗？由于将sd卡上的图片解码到内存是比较“麻烦的”，将它放到工作线程里面了。
if (cancelPotentialWork(imageUrl, imageView)) {
//这是一个“循环三角”，任何一个都有路径找到其他两个
//BitmapWorkerTask->ImageView
final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
//AsyncDrawable->BitmapWorkerTask
final AsyncDrawable asyncDrawable = new AsyncDrawable(
mAppContext.getResources(), placeHolder, task);
//ImageView->AsyncDrawable
imageView.setImageDrawable(asyncDrawable);
//如果安卓系统在3.0以上，允许task并执行，并发数为5；否则只能顺序执行
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
imageUrl);
} else {
task.execute(imageUrl);
}
}
}
}
- 3.下面看一下工作线程BitmapWorkerTask
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
private WeakReference<ImageView> imageViewReference;
private String imageUrl;
public BitmapWorkerTask(ImageView imageView) {
//这里使用了弱引用，当组件不存在了（eg.页面已经销毁了），不会导致内存泄露
imageViewReference = new WeakReference<ImageView>(imageView);
}
@Override
protected Bitmap doInBackground(String... params) {
imageUrl = params[0];
//这里就是解码sd卡上的图片了
Bitmap bitmap = getBitmapFromDiskCache(imageUrl, ,
);
if (bitmap == null) {
bitmap = downloadBitmap(imageUrl);
}
// 将图片保存到内存缓存和sd卡上
if (bitmap != null) {
addBitmapToCache(imageUrl, bitmap);
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
//防止图片下载失败，导致APP崩溃
if (bitmap != null && imageViewReference != null) {
ImageView imageView = imageViewReference.get();
//防止该页面已经关闭
if (imageView != null) {
imageView.setImageBitmap(bitmap);
}
}
}附上完整版代码用于参考
- 由于图片原始路径中可能包含特殊字符不能用于标志文件名，用下面的工具类，对文件路径进行一下hash运行
package libcore.io;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5Utils {
public static String hashKeyForDisk(String key) {
String cacheKey;
try {
final MessageDigest mDigest = MessageDigest.getInstance("MD5");
mDigest.update(key.getBytes());
cacheKey = bytesToHexString(mDigest.digest());
} catch (NoSuchAlgorithmException e) {
cacheKey = String.valueOf(key.hashCode());
}
return cacheKey;
}
private static String bytesToHexString(byte[] bytes) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < bytes.length; i++) {
String hex = Integer.toHexString(0xFF & bytes[i]);
if (hex.length() == 1) {
sb.append('0');
}
sb.append(hex);
}
return sb.toString();
}
} - 这就是大名鼎鼎的DiskLruCache
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package libcore.io;
import java.io.BufferedInputStream;
import java.io.BufferedWriter;
import java.io.Closeable;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.reflect.Array;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
/**
******************************************************************************
* Taken from the JB source code, can be found in:
* libcore/luni/src/main/java/libcore/io/DiskLruCache.java
* or direct link:
* https://android.googlesource.com/platform/libcore/+/android-4.1.1_r1/luni/src/main/java/libcore/io/DiskLruCache.java
******************************************************************************
*
* A cache that uses a bounded amount of space on a filesystem. Each cache
* entry has a string key and a fixed number of values. Values are byte
* sequences, accessible as streams or files. Each value must be between {@code
* 0} and {@code Integer.MAX_VALUE} bytes in length.
*
* <p>The cache stores its data in a directory on the filesystem. This
* directory must be exclusive to the cache; the cache may delete or overwrite
* files from its directory. It is an error for multiple processes to use the
* same cache directory at the same time.
*
* <p>This cache limits the number of bytes that it will store on the
* filesystem. When the number of stored bytes exceeds the limit, the cache will
* remove entries in the background until the limit is satisfied. The limit is
* not strict: the cache may temporarily exceed it while waiting for files to be
* deleted. The limit does not include filesystem overhead or the cache
* journal so space-sensitive applications should set a conservative limit.
*
* <p>Clients call {@link #edit} to create or update the values of an entry. An
* entry may have only one editor at one time; if a value is not available to be
* edited then {@link #edit} will return null.
* <ul>
* <li>When an entry is being <strong>created</strong> it is necessary to
* supply a full set of values; the empty value should be used as a
* placeholder if necessary.
* <li>When an entry is being <strong>edited</strong>, it is not necessary
* to supply data for every value; values default to their previous
* value.
* </ul>
* Every {@link #edit} call must be matched by a call to {@link Editor#commit}
* or {@link Editor#abort}. Committing is atomic: a read observes the full set
* of values as they were before or after the commit, but never a mix of values.
*
* <p>Clients call {@link #get} to read a snapshot of an entry. The read will
* observe the value at the time that {@link #get} was called. Updates and
* removals after the call do not impact ongoing reads.
*
* <p>This class is tolerant of some I/O errors. If files are missing from the
* filesystem, the corresponding entries will be dropped from the cache. If
* an error occurs while writing a cache value, the edit will fail silently.
* Callers should handle other problems by catching {@code IOException} and
* responding appropriately.
*/
public final class DiskLruCache implements Closeable {
static final String JOURNAL_FILE = "journal";
static final String JOURNAL_FILE_TMP = "journal.tmp";
static final String MAGIC = "libcore.io.DiskLruCache";
static final String VERSION_1 = "1";
static final long ANY_SEQUENCE_NUMBER = -1;
private static final String CLEAN = "CLEAN";
private static final String DIRTY = "DIRTY";
private static final String REMOVE = "REMOVE";
private static final String READ = "READ";
private static final Charset UTF_8 = Charset.forName("UTF-8");
private static final int IO_BUFFER_SIZE = 8 * 1024;
/*
* This cache uses a journal file named "journal". A typical journal file
* looks like this:
* libcore.io.DiskLruCache
* 1
* 100
* 2
*
* CLEAN 3400330d1dfc7f3f7f4b8d4d803dfcf6 832 21054
* DIRTY 335c4c6028171cfddfbaae1a9c313c52
* CLEAN 335c4c6028171cfddfbaae1a9c313c52 3934 2342
* REMOVE 335c4c6028171cfddfbaae1a9c313c52
* DIRTY 1ab96a171faeeee38496d8b330771a7a
* CLEAN 1ab96a171faeeee38496d8b330771a7a 1600 234
* READ 335c4c6028171cfddfbaae1a9c313c52
* READ 3400330d1dfc7f3f7f4b8d4d803dfcf6
*
* The first five lines of the journal form its header. They are the
* constant string "libcore.io.DiskLruCache", the disk cache's version,
* the application's version, the value count, and a blank line.
*
* Each of the subsequent lines in the file is a record of the state of a
* cache entry. Each line contains space-separated values: a state, a key,
* and optional state-specific values.
* o DIRTY lines track that an entry is actively being created or updated.
* Every successful DIRTY action should be followed by a CLEAN or REMOVE
* action. DIRTY lines without a matching CLEAN or REMOVE indicate that
* temporary files may need to be deleted.
* o CLEAN lines track a cache entry that has been successfully published
* and may be read. A publish line is followed by the lengths of each of
* its values.
* o READ lines track accesses for LRU.
* o REMOVE lines track entries that have been deleted.
*
* The journal file is appended to as cache operations occur. The journal may
* occasionally be compacted by dropping redundant lines. A temporary file named
* "journal.tmp" will be used during compaction; that file should be deleted if
* it exists when the cache is opened.
*/
private final File directory;
private final File journalFile;
private final File journalFileTmp;
private final int appVersion;
private final long maxSize;
private final int valueCount;
private long size = 0;
private Writer journalWriter;
private final LinkedHashMap<String, Entry> lruEntries
= new LinkedHashMap<String, Entry>(0, 0.75f, true);
private int redundantOpCount;
/**
* To differentiate between old and current snapshots, each entry is given
* a sequence number each time an edit is committed. A snapshot is stale if
* its sequence number is not equal to its entry's sequence number.
*/
private long nextSequenceNumber = 0;
/* From java.util.Arrays */
@SuppressWarnings("unchecked")
private static <T> T[] copyOfRange(T[] original, int start, int end) {
final int originalLength = original.length; // For exception priority compatibility.
if (start > end) {
throw new IllegalArgumentException();
}
if (start < 0 || start > originalLength) {
throw new ArrayIndexOutOfBoundsException();
}
final int resultLength = end - start;
final int copyLength = Math.min(resultLength, originalLength - start);
final T[] result = (T[]) Array
.newInstance(original.getClass().getComponentType(), resultLength);
System.arraycopy(original, start, result, 0, copyLength);
return result;
}
/**
* Returns the remainder of 'reader' as a string, closing it when done.
*/
public static String readFully(Reader reader) throws IOException {
try {
StringWriter writer = new StringWriter();
char[] buffer = new char[1024];
int count;
while ((count = reader.read(buffer)) != -1) {
writer.write(buffer, 0, count);
}
return writer.toString();
} finally {
reader.close();
}
}
/**
* Returns the ASCII characters up to but not including the next "\r\n", or
* "\n".
*
* @throws java.io.EOFException if the stream is exhausted before the next newline
* character.
*/
public static String readAsciiLine(InputStream in) throws IOException {
// TODO: support UTF-8 here instead
StringBuilder result = new StringBuilder(80);
while (true) {
int c = in.read();
if (c == -1) {
throw new EOFException();
} else if (c == '\n') {
break;
}
result.append((char) c);
}
int length = result.length();
if (length > 0 && result.charAt(length - 1) == '\r') {
result.setLength(length - 1);
}
return result.toString();
}
/**
* Closes 'closeable', ignoring any checked exceptions. Does nothing if 'closeable' is null.
*/
public static void closeQuietly(Closeable closeable) {
if (closeable != null) {
try {
closeable.close();
} catch (RuntimeException rethrown) {
throw rethrown;
} catch (Exception ignored) {
}
}
}
/**
* Recursively delete everything in {@code dir}.
*/
// TODO: this should specify paths as Strings rather than as Files
public static void deleteContents(File dir) throws IOException {
File[] files = dir.listFiles();
if (files == null) {
throw new IllegalArgumentException("not a directory: " + dir);
}
for (File file : files) {
if (file.isDirectory()) {
deleteContents(file);
}
if (!file.delete()) {
throw new IOException("failed to delete file: " + file);
}
}
}
/** This cache uses a single background thread to evict entries. */
private final ExecutorService executorService = new ThreadPoolExecutor(0, 1,
60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
private final Callable<Void> cleanupCallable = new Callable<Void>() {
@Override public Void call() throws Exception {
synchronized (DiskLruCache.this) {
if (journalWriter == null) {
return null; // closed
}
trimToSize();
if (journalRebuildRequired()) {
rebuildJournal();
redundantOpCount = 0;
}
}
return null;
}
};
private DiskLruCache(File directory, int appVersion, int valueCount, long maxSize) {
this.directory = directory;
this.appVersion = appVersion;
this.journalFile = new File(directory, JOURNAL_FILE);
this.journalFileTmp = new File(directory, JOURNAL_FILE_TMP);
this.valueCount = valueCount;
this.maxSize = maxSize;
}
/**
* Opens the cache in {@code directory}, creating a cache if none exists
* there.
*
* @param directory a writable directory
* @param appVersion
* @param valueCount the number of values per cache entry. Must be positive.
* @param maxSize the maximum number of bytes this cache should use to store
* @throws java.io.IOException if reading or writing the cache directory fails
*/
public static DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize)
throws IOException {
if (maxSize <= 0) {
throw new IllegalArgumentException("maxSize <= 0");
}
if (valueCount <= 0) {
throw new IllegalArgumentException("valueCount <= 0");
}
// prefer to pick up where we left off
DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
if (cache.journalFile.exists()) {
try {
cache.readJournal();
cache.processJournal();
cache.journalWriter = new BufferedWriter(new FileWriter(cache.journalFile, true),
IO_BUFFER_SIZE);
return cache;
} catch (IOException journalIsCorrupt) {
// System.logW("DiskLruCache " + directory + " is corrupt: "
// + journalIsCorrupt.getMessage() + ", removing");
cache.delete();
}
}
// create a new empty cache
directory.mkdirs();
cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
cache.rebuildJournal();
return cache;
}
private void readJournal() throws IOException {
InputStream in = new BufferedInputStream(new FileInputStream(journalFile), IO_BUFFER_SIZE);
try {
String magic = readAsciiLine(in);
String version = readAsciiLine(in);
String appVersionString = readAsciiLine(in);
String valueCountString = readAsciiLine(in);
String blank = readAsciiLine(in);
if (!MAGIC.equals(magic)
|| !VERSION_1.equals(version)
|| !Integer.toString(appVersion).equals(appVersionString)
|| !Integer.toString(valueCount).equals(valueCountString)
|| !"".equals(blank)) {
throw new IOException("unexpected journal header: ["
+ magic + ", " + version + ", " + valueCountString + ", " + blank + "]");
}
while (true) {
try {
readJournalLine(readAsciiLine(in));
} catch (EOFException endOfJournal) {
break;
}
}
} finally {
closeQuietly(in);
}
}
private void readJournalLine(String line) throws IOException {
String[] parts = line.split(" ");
if (parts.length < 2) {
throw new IOException("unexpected journal line: " + line);
}
String key = parts[1];
if (parts[0].equals(REMOVE) && parts.length == 2) {
lruEntries.remove(key);
return;
}
Entry entry = lruEntries.get(key);
if (entry == null) {
entry = new Entry(key);
lruEntries.put(key, entry);
}
if (parts[0].equals(CLEAN) && parts.length == 2 + valueCount) {
entry.readable = true;
entry.currentEditor = null;
entry.setLengths(copyOfRange(parts, 2, parts.length));
} else if (parts[0].equals(DIRTY) && parts.length == 2) {
entry.currentEditor = new Editor(entry);
} else if (parts[0].equals(READ) && parts.length == 2) {
// this work was already done by calling lruEntries.get()
} else {
throw new IOException("unexpected journal line: " + line);
}
}
/**
* Computes the initial size and collects garbage as a part of opening the
* cache. Dirty entries are assumed to be inconsistent and will be deleted.
*/
private void processJournal() throws IOException {
deleteIfExists(journalFileTmp);
for (Iterator<Entry> i = lruEntries.values().iterator(); i.hasNext(); ) {
Entry entry = i.next();
if (entry.currentEditor == null) {
for (int t = 0; t < valueCount; t++) {
size += entry.lengths[t];
}
} else {
entry.currentEditor = null;
for (int t = 0; t < valueCount; t++) {
deleteIfExists(entry.getCleanFile(t));
deleteIfExists(entry.getDirtyFile(t));
}
i.remove();
}
}
}
/**
* Creates a new journal that omits redundant information. This replaces the
* current journal if it exists.
*/
private synchronized void rebuildJournal() throws IOException {
if (journalWriter != null) {
journalWriter.close();
}
Writer writer = new BufferedWriter(new FileWriter(journalFileTmp), IO_BUFFER_SIZE);
writer.write(MAGIC);
writer.write("\n");
writer.write(VERSION_1);
writer.write("\n");
writer.write(Integer.toString(appVersion));
writer.write("\n");
writer.write(Integer.toString(valueCount));
writer.write("\n");
writer.write("\n");
for (Entry entry : lruEntries.values()) {
if (entry.currentEditor != null) {
writer.write(DIRTY + ' ' + entry.key + '\n');
} else {
writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
}
}
writer.close();
journalFileTmp.renameTo(journalFile);
journalWriter = new BufferedWriter(new FileWriter(journalFile, true), IO_BUFFER_SIZE);
}
private static void deleteIfExists(File file) throws IOException {
// try {
// Libcore.os.remove(file.getPath());
// } catch (ErrnoException errnoException) {
// if (errnoException.errno != OsConstants.ENOENT) {
// throw errnoException.rethrowAsIOException();
// }
// }
if (file.exists() && !file.delete()) {
throw new IOException();
}
}
/**
* Returns a snapshot of the entry named {@code key}, or null if it doesn't
* exist is not currently readable. If a value is returned, it is moved to
* the head of the LRU queue.
*/
public synchronized Snapshot get(String key) throws IOException {
checkNotClosed();
validateKey(key);
Entry entry = lruEntries.get(key);
if (entry == null) {
return null;
}
if (!entry.readable) {
return null;
}
/*
* Open all streams eagerly to guarantee that we see a single published
* snapshot. If we opened streams lazily then the streams could come
* from different edits.
*/
InputStream[] ins = new InputStream[valueCount];
try {
for (int i = 0; i < valueCount; i++) {
ins[i] = new FileInputStream(entry.getCleanFile(i));
}
} catch (FileNotFoundException e) {
// a file must have been deleted manually!
return null;
}
redundantOpCount++;
journalWriter.append(READ + ' ' + key + '\n');
if (journalRebuildRequired()) {
executorService.submit(cleanupCallable);
}
return new Snapshot(key, entry.sequenceNumber, ins);
}
/**
* Returns an editor for the entry named {@code key}, or null if another
* edit is in progress.
*/
public Editor edit(String key) throws IOException {
return edit(key, ANY_SEQUENCE_NUMBER);
}
private synchronized Editor edit(String key, long expectedSequenceNumber) throws IOException {
checkNotClosed();
validateKey(key);
Entry entry = lruEntries.get(key);
if (expectedSequenceNumber != ANY_SEQUENCE_NUMBER
&& (entry == null || entry.sequenceNumber != expectedSequenceNumber)) {
return null; // snapshot is stale
}
if (entry == null) {
entry = new Entry(key);
lruEntries.put(key, entry);
} else if (entry.currentEditor != null) {
return null; // another edit is in progress
}
Editor editor = new Editor(entry);
entry.currentEditor = editor;
// flush the journal before creating files to prevent file leaks
journalWriter.write(DIRTY + ' ' + key + '\n');
journalWriter.flush();
return editor;
}
/**
* Returns the directory where this cache stores its data.
*/
public File getDirectory() {
return directory;
}
/**
* Returns the maximum number of bytes that this cache should use to store
* its data.
*/
public long maxSize() {
return maxSize;
}
/**
* Returns the number of bytes currently being used to store the values in
* this cache. This may be greater than the max size if a background
* deletion is pending.
*/
public synchronized long size() {
return size;
}
private synchronized void completeEdit(Editor editor, boolean success) throws IOException {
Entry entry = editor.entry;
if (entry.currentEditor != editor) {
throw new IllegalStateException();
}
// if this edit is creating the entry for the first time, every index must have a value
if (success && !entry.readable) {
for (int i = 0; i < valueCount; i++) {
if (!entry.getDirtyFile(i).exists()) {
editor.abort();
throw new IllegalStateException("edit didn't create file " + i);
}
}
}
for (int i = 0; i < valueCount; i++) {
File dirty = entry.getDirtyFile(i);
if (success) {
if (dirty.exists()) {
File clean = entry.getCleanFile(i);
dirty.renameTo(clean);
long oldLength = entry.lengths[i];
long newLength = clean.length();
entry.lengths[i] = newLength;
size = size - oldLength + newLength;
}
} else {
deleteIfExists(dirty);
}
}
redundantOpCount++;
entry.currentEditor = null;
if (entry.readable | success) {
entry.readable = true;
journalWriter.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');
if (success) {
entry.sequenceNumber = nextSequenceNumber++;
}
} else {
lruEntries.remove(entry.key);
journalWriter.write(REMOVE + ' ' + entry.key + '\n');
}
if (size > maxSize || journalRebuildRequired()) {
executorService.submit(cleanupCallable);
}
}
/**
* We only rebuild the journal when it will halve the size of the journal
* and eliminate at least 2000 ops.
*/
private boolean journalRebuildRequired() {
final int REDUNDANT_OP_COMPACT_THRESHOLD = 2000;
return redundantOpCount >= REDUNDANT_OP_COMPACT_THRESHOLD
&& redundantOpCount >= lruEntries.size();
}
/**
* Drops the entry for {@code key} if it exists and can be removed. Entries
* actively being edited cannot be removed.
*
* @return true if an entry was removed.
*/
public synchronized boolean remove(String key) throws IOException {
checkNotClosed();
validateKey(key);
Entry entry = lruEntries.get(key);
if (entry == null || entry.currentEditor != null) {
return false;
}
for (int i = 0; i < valueCount; i++) {
File file = entry.getCleanFile(i);
if (!file.delete()) {
throw new IOException("failed to delete " + file);
}
size -= entry.lengths[i];
entry.lengths[i] = 0;
}
redundantOpCount++;
journalWriter.append(REMOVE + ' ' + key + '\n');
lruEntries.remove(key);
if (journalRebuildRequired()) {
executorService.submit(cleanupCallable);
}
return true;
}
/**
* Returns true if this cache has been closed.
*/
public boolean isClosed() {
return journalWriter == null;
}
private void checkNotClosed() {
if (journalWriter == null) {
throw new IllegalStateException("cache is closed");
}
}
/**
* Force buffered operations to the filesystem.
*/
public synchronized void flush() throws IOException {
checkNotClosed();
trimToSize();
journalWriter.flush();
}
/**
* Closes this cache. Stored values will remain on the filesystem.
*/
public synchronized void close() throws IOException {
if (journalWriter == null) {
return; // already closed
}
for (Entry entry : new ArrayList<Entry>(lruEntries.values())) {
if (entry.currentEditor != null) {
entry.currentEditor.abort();
}
}
trimToSize();
journalWriter.close();
journalWriter = null;
}
private void trimToSize() throws IOException {
while (size > maxSize) {
// Map.Entry<String, Entry> toEvict = lruEntries.eldest();
final Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next();
remove(toEvict.getKey());
}
}
/**
* Closes the cache and deletes all of its stored values. This will delete
* all files in the cache directory including files that weren't created by
* the cache.
*/
public void delete() throws IOException {
close();
deleteContents(directory);
}
private void validateKey(String key) {
if (key.contains(" ") || key.contains("\n") || key.contains("\r")) {
throw new IllegalArgumentException(
"keys must not contain spaces or newlines: \"" + key + "\"");
}
}
private static String inputStreamToString(InputStream in) throws IOException {
return readFully(new InputStreamReader(in, UTF_8));
}
/**
* A snapshot of the values for an entry.
*/
public final class Snapshot implements Closeable {
private final String key;
private final long sequenceNumber;
private final InputStream[] ins;
private Snapshot(String key, long sequenceNumber, InputStream[] ins) {
this.key = key;
this.sequenceNumber = sequenceNumber;
this.ins = ins;
}
/**
* Returns an editor for this snapshot's entry, or null if either the
* entry has changed since this snapshot was created or if another edit
* is in progress.
*/
public Editor edit() throws IOException {
return DiskLruCache.this.edit(key, sequenceNumber);
}
/**
* Returns the unbuffered stream with the value for {@code index}.
*/
public InputStream getInputStream(int index) {
return ins[index];
}
/**
* Returns the string value for {@code index}.
*/
public String getString(int index) throws IOException {
return inputStreamToString(getInputStream(index));
}
@Override public void close() {
for (InputStream in : ins) {
closeQuietly(in);
}
}
}
/**
* Edits the values for an entry.
*/
public final class Editor {
private final Entry entry;
private boolean hasErrors;
private Editor(Entry entry) {
this.entry = entry;
}
/**
* Returns an unbuffered input stream to read the last committed value,
* or null if no value has been committed.
*/
public InputStream newInputStream(int index) throws IOException {
synchronized (DiskLruCache.this) {
if (entry.currentEditor != this) {
throw new IllegalStateException();
}
if (!entry.readable) {
return null;
}
return new FileInputStream(entry.getCleanFile(index));
}
}
/**
* Returns the last committed value as a string, or null if no value
* has been committed.
*/
public String getString(int index) throws IOException {
InputStream in = newInputStream(index);
return in != null ? inputStreamToString(in) : null;
}
/**
* Returns a new unbuffered output stream to write the value at
* {@code index}. If the underlying output stream encounters errors
* when writing to the filesystem, this edit will be aborted when
* {@link #commit} is called. The returned output stream does not throw
* IOExceptions.
*/
public OutputStream newOutputStream(int index) throws IOException {
synchronized (DiskLruCache.this) {
if (entry.currentEditor != this) {
throw new IllegalStateException();
}
return new FaultHidingOutputStream(new FileOutputStream(entry.getDirtyFile(index)));
}
}
/**
* Sets the value at {@code index} to {@code value}.
*/
public void set(int index, String value) throws IOException {
Writer writer = null;
try {
writer = new OutputStreamWriter(newOutputStream(index), UTF_8);
writer.write(value);
} finally {
closeQuietly(writer);
}
}
/**
* Commits this edit so it is visible to readers. This releases the
* edit lock so another edit may be started on the same key.
*/
public void commit() throws IOException {
if (hasErrors) {
completeEdit(this, false);
remove(entry.key); // the previous entry is stale
} else {
completeEdit(this, true);
}
}
/**
* Aborts this edit. This releases the edit lock so another edit may be
* started on the same key.
*/
public void abort() throws IOException {
completeEdit(this, false);
}
private class FaultHidingOutputStream extends FilterOutputStream {
private FaultHidingOutputStream(OutputStream out) {
super(out);
}
@Override public void write(int oneByte) {
try {
out.write(oneByte);
} catch (IOException e) {
hasErrors = true;
}
}
@Override public void write(byte[] buffer, int offset, int length) {
try {
out.write(buffer, offset, length);
} catch (IOException e) {
hasErrors = true;
}
}
@Override public void close() {
try {
out.close();
} catch (IOException e) {
hasErrors = true;
}
}
@Override public void flush() {
try {
out.flush();
} catch (IOException e) {
hasErrors = true;
}
}
}
}
private final class Entry {
private final String key;
/** Lengths of this entry's files. */
private final long[] lengths;
/** True if this entry has ever been published */
private boolean readable;
/** The ongoing edit or null if this entry is not being edited. */
private Editor currentEditor;
/** The sequence number of the most recently committed edit to this entry. */
private long sequenceNumber;
private Entry(String key) {
this.key = key;
this.lengths = new long[valueCount];
}
public String getLengths() throws IOException {
StringBuilder result = new StringBuilder();
for (long size : lengths) {
result.append(' ').append(size);
}
return result.toString();
}
/**
* Set lengths using decimal numbers like "10123".
*/
private void setLengths(String[] strings) throws IOException {
if (strings.length != valueCount) {
throw invalidLengths(strings);
}
try {
for (int i = 0; i < strings.length; i++) {
lengths[i] = Long.parseLong(strings[i]);
}
} catch (NumberFormatException e) {
throw invalidLengths(strings);
}
}
private IOException invalidLengths(String[] strings) throws IOException {
throw new IOException("unexpected journal line: " + Arrays.toString(strings));
}
public File getCleanFile(int i) {
return new File(directory, key + "." + i);
}
public File getDirtyFile(int i) {
return new File(directory, key + "." + i + ".tmp");
}
}
}
这个是我的主要拙作
package libcore.io;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ref.WeakReference;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.atomic.AtomicInteger;
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Environment;
import android.support.v4.util.LruCache;
import android.text.TextUtils;
import android.util.Log;
import android.widget.ImageView;
/**
* @author Chuanhang.Gu
*
*/
public class ImageLoadGCH {
// TODO 用户测试并发数
private AtomicInteger currencyNum = new AtomicInteger();
private static ImageLoadGCH instance;
private static LruCache<String, Bitmap> mMemoryCache;
private static DiskLruCache mDiskLruCache = null;
private final Object mDiskCacheLock = new Object();
private boolean mDiskCacheStarting = true;
private Context mAppContext;
private static final int DISK_CACHE_SIZE = 1024 * 1024 * 40;
private static final String DISK_CACHE_SUBDIR = "thumbnails_gch";
private void init(Context applicationContext) {
this.mAppContext = applicationContext;
final int maxMemory = (int) (Runtime.getRuntime().maxMemory());
final int cacheSize = maxMemory / 8;
mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {
@Override
protected int sizeOf(String key, Bitmap bitmap) {
return bitmap.getRowBytes() * bitmap.getHeight();
}
};
File cacheDir = getDiskCacheDir(mAppContext, DISK_CACHE_SUBDIR);
new InitDiskCacheTask().execute(cacheDir);
}
private ImageLoadGCH(Context appContext) {
init(appContext);
}
public static synchronized ImageLoadGCH getInstance(Context appContext) {
if (instance == null) {
instance = new ImageLoadGCH(appContext);
}
return instance;
}
/**
* 在onPause中调用，将保存到sd卡上的记录，同步到journal 文件上
*/
public void flushSDJournal() {
try {
if (mDiskLruCache != null) {
mDiskLruCache.flush();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void loadImage(ImageView imageView, String imageUrl, int defaultResId) {
Bitmap defaultBitmap = BitmapFactory.decodeResource(
mAppContext.getResources(), defaultResId);
loadBitmap(imageView, imageUrl, defaultBitmap);
}
@SuppressLint("NewApi")
private File getDiskCacheDir(Context context, String uniqueName) {
String cachePath = null;
if (Environment.MEDIA_MOUNTED.equals(Environment
.getExternalStorageState())) {
cachePath = context.getExternalCacheDir().getPath();
} else {
if (Build.VERSION.SDK_INT >= 9) {
if (!Environment.isExternalStorageRemovable()) {
cachePath = context.getExternalCacheDir().getPath();
} else {
cachePath = context.getCacheDir().getPath();
}
}
}
return new File(cachePath + File.separator + uniqueName);
}
class InitDiskCacheTask extends AsyncTask<File, Void, Void> {
@Override
protected Void doInBackground(File... params) {
synchronized (mDiskCacheLock) {
File cacheDir = params[0];
try {
mDiskLruCache = DiskLruCache.open(cacheDir,
getAppVersion(mAppContext), 1, DISK_CACHE_SIZE);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mDiskCacheStarting = false; // Finished initialization
mDiskCacheLock.notifyAll(); // Wake any waiting threads
}
return null;
}
}
private int getAppVersion(Context context) {
try {
PackageInfo info = context.getPackageManager().getPackageInfo(
context.getPackageName(), 0);
return info.versionCode;
} catch (NameNotFoundException e) {
e.printStackTrace();
}
return 1;
}
public Bitmap getBitmapFromMemCache(String imageUrl) {
return mMemoryCache.get(imageUrl);
}
static class AsyncDrawable extends BitmapDrawable {
private final WeakReference<BitmapWorkerTask> bitmapWorkerTaskReference;
public AsyncDrawable(Resources res, Bitmap bitmap,
BitmapWorkerTask bitmapWorkerTask) {
super(res, bitmap);
bitmapWorkerTaskReference = new WeakReference<BitmapWorkerTask>(
bitmapWorkerTask);
}
public BitmapWorkerTask getBitmapWorkerTask() {
return bitmapWorkerTaskReference.get();
}
}
public Bitmap getBitmapFromMem(String url) {
return mMemoryCache.get(url);
}
public void putBitmapToMem(String url, Bitmap bitmap) {
mMemoryCache.put(url, bitmap);
}
@SuppressLint("NewApi")
private void loadBitmap(ImageView imageView, String imageUrl,
Bitmap placeHolder) {
final Bitmap bitmap = getBitmapFromMemCache(imageUrl);
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
if (cancelPotentialWork(imageUrl, imageView)) {
final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
final AsyncDrawable asyncDrawable = new AsyncDrawable(
mAppContext.getResources(), placeHolder, task);
imageView.setImageDrawable(asyncDrawable);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
imageUrl);
} else {
task.execute(imageUrl);
}
}
}
}
public boolean cancelPotentialWork(String imageUrl, ImageView imageView) {
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (bitmapWorkerTask != null) {
final String lastRequestUrl = bitmapWorkerTask.imageUrl;
if (TextUtils.isEmpty(lastRequestUrl)
|| !lastRequestUrl.equals(imageUrl)) {
bitmapWorkerTask.cancel(true);
} else {
// The same work is already in progress
return false;
}
}
// No task associated with the ImageView, or an existing task was
// cancelled
return true;
}
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
private WeakReference<ImageView> imageViewReference;
private String imageUrl;
public BitmapWorkerTask(ImageView imageView) {
imageViewReference = new WeakReference<ImageView>(imageView);
}
@Override
protected Bitmap doInBackground(String... params) {
currencyNum.getAndIncrement();
System.err.println("xxxxxx" + currencyNum.get());
imageUrl = params[0];
Bitmap bitmap = getBitmapFromDiskCache(imageUrl);
if (bitmap == null) {
bitmap = downloadBitmap(imageUrl);
}
// Add final bitmap to caches
if (bitmap != null) {
addBitmapToCache(imageUrl, bitmap);
}
currencyNum.decrementAndGet();
return bitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
if (bitmap != null && imageViewReference != null) {
ImageView imageView = imageViewReference.get();
if (imageView != null) {
imageView.setImageBitmap(bitmap);
}
}
}
// TODO improve
Bitmap downloadBitmap(String urlInString) {
try {
URL url = new URL(urlInString);
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
urlConnection.connect();
final int statusCode = urlConnection.getResponseCode();
if (statusCode != 200) {
Log.w("ImageDownloader", "Error " + statusCode
+ " while retrieving bitmap from " + url);
return null;
}
Bitmap bitmap = null;
InputStream inputStream = null;
try {
inputStream = urlConnection.getInputStream();
bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
} finally {
if (inputStream != null) {
inputStream.close();
}
}
} catch (Exception e) {
// Could provide a more explicit error message for IOException
// or
// IllegalStateException
Log.w("ImageDownloader", "Error while retrieving bitmap from "
+ urlInString + " " + e.toString());
} finally {
}
return null;
}
public void addBitmapToCache(String imageUrl, Bitmap bitmap) {
// Add to memory cache as before
if (getBitmapFromMemCache(imageUrl) == null) {
mMemoryCache.put(imageUrl, bitmap);
}
// Also add to disk cache
synchronized (mDiskCacheLock) {
try {
if (mDiskLruCache != null
&& mDiskLruCache.get(MD5Utils
.hashKeyForDisk(imageUrl)) == null) {
DiskLruCache.Editor editor = mDiskLruCache
.edit(MD5Utils.hashKeyForDisk(imageUrl));
if (editor != null) {
OutputStream outputStream = editor
.newOutputStream(0);
if (bitmap.compress(CompressFormat.PNG, 100,
outputStream)) {
editor.commit();
} else {
editor.abort();
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
public Bitmap getBitmapFromDiskCache(String imageUrl) {
synchronized (mDiskCacheLock) {
// Wait while disk cache is started from background thread
while (mDiskCacheStarting) {
try {
mDiskCacheLock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if (mDiskLruCache != null) {
DiskLruCache.Snapshot snapShot = null;
try {
snapShot = mDiskLruCache.get(MD5Utils
.hashKeyForDisk(imageUrl));
} catch (IOException e) {
e.printStackTrace();
}
if (snapShot != null) {
InputStream is = snapShot.getInputStream(0);
Bitmap bitmap = BitmapFactory.decodeStream(is);
return bitmap;
}
}
}
return null;
}
}
private BitmapWorkerTask getBitmapWorkerTask(ImageView imageView) {
if (imageView != null) {
final Drawable drawable = imageView.getDrawable();
if (drawable != null && drawable instanceof AsyncDrawable) {
final AsyncDrawable asyncDrawable = (AsyncDrawable) drawable;
return asyncDrawable.getBitmapWorkerTask();
}
}
return null;
}
}- 测试的图片内容类（这是某个csdn大牛的贡献，找不到名字了，在此谢过了）
package libcore.io;
public class Images {
public final static String[] imageThumbUrls = new String[] {
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383299_1976.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383291_6518.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383291_8239.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383290_9329.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383290_1042.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383275_3977.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383265_8550.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383264_3954.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383264_4787.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383264_8243.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383248_3693.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383243_5120.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383242_3127.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383242_9576.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383242_1721.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383219_5806.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383214_7794.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383213_4418.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383213_3557.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383210_8779.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383172_4577.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383166_3407.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383166_2224.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383166_7301.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383165_7197.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383150_8410.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383131_3736.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383130_5094.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383130_7393.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383129_8813.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383100_3554.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383093_7894.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383092_2432.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383092_3071.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383091_3119.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383059_6589.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383059_8814.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383059_2237.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383058_4330.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406383038_3602.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382942_3079.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382942_8125.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382942_4881.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382941_4559.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382941_3845.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382924_8955.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382923_2141.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382923_8437.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382922_6166.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382922_4843.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382905_5804.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382904_3362.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382904_2312.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382904_4960.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382900_2418.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382881_4490.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382881_5935.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382880_3865.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382880_4662.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382879_2553.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382862_5375.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382862_1748.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382861_7618.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382861_8606.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382861_8949.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382841_9821.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382840_6603.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382840_2405.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382840_6354.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382839_5779.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382810_7578.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382810_2436.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382809_3883.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382809_6269.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382808_4179.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382790_8326.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382789_7174.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382789_5170.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382789_4118.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382788_9532.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382767_3184.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382767_4772.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382766_4924.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382766_5762.jpg",
"https://img-my.youkuaiyun.com/uploads/201407/26/1406382765_7341.jpg" };
}- 图片展示的adapter
package com.gch.loadimage;
import libcore.io.ImageLoadGCH;
import libcore.io.Images;
import android.app.Activity;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
public class ImageAdapter extends BaseAdapter {
Context mContext;
int mScreenWidth = 0;
public ImageAdapter(Context context) {
mContext = context;
mScreenWidth = FileUtil.getScreenWidth((Activity) context);
}
@Override
public int getCount() {
return Images.imageThumbUrls.length;
}
@Override
public Object getItem(int position) {
return Images.imageThumbUrls[position];
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder = null;
if (convertView == null) {
viewHolder = new ViewHolder();
LinearLayout outerLayout = new LinearLayout(mContext);
ImageView imageView = new ImageView(mContext);
outerLayout.addView(imageView);
AbsListView.LayoutParams outerParams = new AbsListView.LayoutParams(
new LayoutParams(mScreenWidth / 3, mScreenWidth / 3));
outerLayout.setLayoutParams(outerParams);
convertView = outerLayout;
viewHolder.iconView = imageView;
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
ImageLoadGCH.getInstance(mContext.getApplicationContext()).loadImage(
viewHolder.iconView, Images.imageThumbUrls[position],
R.drawable.ic_launcher);
viewHolder.iconView.setEnabled(false);
return convertView;
}
class ViewHolder {
ImageView iconView;
}
}
- 这是测试的MainActivity
package com.gch.loadimage;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.GridView;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.activity_main);
GridView gridView = new GridView(this);
setContentView(gridView);
gridView.setNumColumns(3);
gridView.setAdapter(new ImageAdapter(this));
}
}
不要忘记添加权限哦
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
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