最近在做一个小的应用，里面有处理从sdcard 中取得图片的的操作，但是发现会oom（out of memory ）异常。于是google 看到了一篇帖子引用过来做个备份以后也有一个好的经验和总结
package cn.gridview;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.Display;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
public class GridviewTestActivity extends Activity implements OnItemClickListener {
/**
* Grid view holding the images.
*/
private GridView sdcardImages;
/**
* Image adapter for the grid view.
*/
private ImageAdapter imageAdapter;
/**
* Display used for getting the width of the screen.
*/
private Display display;
/**
* Creates the content view, sets up the grid, the adapter, and the click listener.
*
* @see android.app.Activity#onCreate(android.os.Bundle)
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Request progress bar
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.main);
display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
setupViews();
setProgressBarIndeterminateVisibility(true);
loadImages();
}
/**
* Free up bitmap related resources.
*/
protected void onDestroy() {
super.onDestroy();
final GridView grid = sdcardImages;
final int count = grid.getChildCount();
ImageView v = null;
for (int i = 0; i < count; i++) {
v = (ImageView) grid.getChildAt(i);
((BitmapDrawable) v.getDrawable()).setCallback(null);
}
}
/**
* Setup the grid view.
*/
private void setupViews() {
sdcardImages = (GridView) findViewById(R.id.sdcard);
sdcardImages.setNumColumns(display.getWidth()/95);
sdcardImages.setClipToPadding(false);
sdcardImages.setOnItemClickListener(GridviewTestActivity.this);
imageAdapter = new ImageAdapter(getApplicationContext());
sdcardImages.setAdapter(imageAdapter);
}
/**
* Load images.
*/
private void loadImages() {
final Object data = getLastNonConfigurationInstance();
if (data == null) {
new LoadImagesFromSDCard().execute();
} else {
final LoadedImage[] photos = (LoadedImage[]) data;
if (photos.length == 0) {
new LoadImagesFromSDCard().execute();
}
for (LoadedImage photo : photos) {
addImage(photo);
}
}
}
/**
* Add image(s) to the grid view adapter.
*
* @param value Array of LoadedImages references
*/
private void addImage(LoadedImage... value) {
for (LoadedImage image : value) {
imageAdapter.addPhoto(image);
imageAdapter.notifyDataSetChanged();
}
}
/**
* Save bitmap images into a list and return that list.
*
* @see android.app.Activity#onRetainNonConfigurationInstance()
*/
@Override
public Object onRetainNonConfigurationInstance() {
final GridView grid = sdcardImages;
final int count = grid.getChildCount();
final LoadedImage[] list = new LoadedImage[count];
for (int i = 0; i < count; i++) {
final ImageView v = (ImageView) grid.getChildAt(i);
list[i] = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap());
}
return list;
}
/**
* Async task for loading the images from the SD card.
*
* @author Mihai Fonoage
*
*/
class LoadImagesFromSDCard extends AsyncTask<Object, LoadedImage, Object> {
/**
* Load images from SD Card in the background, and display each image on the screen.
*
* @see android.os.AsyncTask#doInBackground(Params[])
*/
@Override
protected Object doInBackground(Object... params) {
//setProgressBarIndeterminateVisibility(true);
Bitmap bitmap = null;
Bitmap newBitmap = null;
Uri uri = null;
// Set up an array of the Thumbnail Image ID column we want
String[] projection = {MediaStore.Images.Thumbnails._ID};
// Create the cursor pointing to the SDCard
Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null, // Return all rows
null,
null);
int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);
int size = cursor.getCount();
// If size is 0, there are no images on the SD Card.
if (size == 0) {
//No Images available, post some message to the user
}
int imageID = 0;
for (int i = 0; i < size; i++) {
cursor.moveToPosition(i);
imageID = cursor.getInt(columnIndex);
uri = Uri.withAppendedPath(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID);
try {
bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
if (bitmap != null) {
newBitmap = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
bitmap.recycle();
if (newBitmap != null) {
publishProgress(new LoadedImage(newBitmap));
}
}
} catch (IOException e) {
//Error fetching image, try to recover
}
}
cursor.close();
return null;
}
/**
* Add a new LoadedImage in the images grid.
*
* @param value The image.
*/
@Override
public void onProgressUpdate(LoadedImage... value) {
addImage(value);
}
/**
* Set the visibility of the progress bar to false.
*
* @see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
@Override
protected void onPostExecute(Object result) {
setProgressBarIndeterminateVisibility(false);
}
}
/**
* Adapter for our image files.
*
* @author Mihai Fonoage
*
*/
class ImageAdapter extends BaseAdapter {
private Context mContext;
private ArrayList<LoadedImage> photos = new ArrayList<LoadedImage>();
public ImageAdapter(Context context) {
mContext = context;
}
public void addPhoto(LoadedImage photo) {
photos.add(photo);
}
public int getCount() {
return photos.size();
}
public Object getItem(int position) {
return photos.get(position);
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
final ImageView imageView;
if (convertView == null) {
imageView = new ImageView(mContext);
} else {
imageView = (ImageView) convertView;
}
imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
imageView.setPadding(8, 8, 8, 8);
imageView.setImageBitmap(photos.get(position).getBitmap());
return imageView;
}
}
/**
* A LoadedImage contains the Bitmap loaded for the image.
*/
private static class LoadedImage {
Bitmap mBitmap;
LoadedImage(Bitmap bitmap) {
mBitmap = bitmap;
}
public Bitmap getBitmap() {
return mBitmap;
}
}
/**
* When an image is clicked, load that image as a puzzle.
*/
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
int columnIndex = 0;
String[] projection = {MediaStore.Images.Media.DATA};
Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection,
null,
null,
null);
if (cursor != null) {
columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToPosition(position);
String imagePath = cursor.getString(columnIndex);
FileInputStream is = null;
BufferedInputStream bis = null;
try {
is = new FileInputStream(new File(imagePath));
bis = new BufferedInputStream(is);
Bitmap bitmap = BitmapFactory.decodeStream(bis);
Bitmap useThisBitmap = Bitmap.createScaledBitmap(bitmap, parent.getWidth(), parent.getHeight(), true);
bitmap.recycle();
//Display bitmap (useThisBitmap)
}
catch (Exception e) {
//Try to recover
}
finally {
try {
if (bis != null) {
bis.close();
}
if (is != null) {
is.close();
}
cursor.close();
projection = null;
} catch (Exception e) {
}
}
}
}
} main.xml的写法<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<GridView
android:id="@+id/sdcard"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:columnWidth="90dp"
android:numColumns="auto_fit"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp"
android:stretchMode="columnWidth"
android:gravity="center"
/>
</LinearLayout> 
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
