三级缓存加载图片-优快云博客

本文链接：https://blog.youkuaiyun.com/Guiyide/article/details/78590752
package com.lbs.sanjierji;

import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

import com.lbs.sanjierji.Utils.ImagesUtils;

public class MainActivity extends AppCompatActivity {
    private GridView gv;
    ImagesUtils imagUtils;
    String[] imageUrls = new String[] {
            "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",
    };


    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);


            if (msg.what == 0) {
                Bitmap bitmap = (Bitmap) msg.obj;
                // 设置给imageView
                String tag = msg.getData().getString("tag");
                // 根据标记取出imageView
                ImageView imageView = (ImageView) gv.findViewWithTag(tag);
                if (imageView != null && bitmap != null) {
                    // 从网络获取图片
                    imageView.setImageBitmap(bitmap);
                    Log.i("tag", "从网络中获取图片");
                }
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imagUtils = new ImagesUtils(this,handler);
        gv = (GridView) findViewById(R.id.gv);
        gv.setAdapter(new MyAdapter());
    }
    class MyAdapter extends BaseAdapter {
        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return imageUrls.length;
        }
        @Override
        public Object getItem(int position) {
            return null;
        }
        @Override
        public long getItemId(int position) {
            return position;
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView iv = new ImageView(MainActivity.this);
            iv.setTag(imageUrls[position]);
            //去图片;
            Bitmap bitmap = imagUtils.getBitMap(imageUrls[position]);
            // 从内存中或者缓存中
            if (bitmap != null) {
                iv.setImageBitmap(bitmap);
            }
            // 获取图片
            return iv;
        }
    }
}












package com.lbs.sanjierji.Utils;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.util.LruCache;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
 * author:Created by WangZhiQiang on 2017-09-04.
 * 处理三级缓存
 * 内存缓存(LruCache-->最近最少使用算法,当缓存慢的时候,自动把最近使用最少的删除,腾出来的空间添加新的缓存内容)
 * sd卡缓存
 * 网络
 */
public class ImagesUtils {
    Handler handler;
    private File cacheDir;
    private ExecutorService newFixedThreadPool;
    private LruCache<String, Bitmap> lruCache;
    /**
     * @param context
     * @param handler
     */
    public ImagesUtils(Context context, Handler handler) {
        //获得你手机上的最大内存
        long maxMemory = Runtime.getRuntime().maxMemory();
        int maxSize = (int) (maxMemory / 8);
        this.handler = handler;
        //得到本app在sd上的缓存文件夹
        cacheDir = context.getCacheDir();
        // 初始化线程池;初始化5个现成,供程序使用
        newFixedThreadPool = Executors.newFixedThreadPool(5);
        lruCache = new LruCache<String, Bitmap>(maxSize) {
            //每次缓存图片都要调用这个方法;
            @Override
            protected int sizeOf(String key, Bitmap value) {
                return value.getRowBytes() * value.getHeight();
            }
        };
    }
    /**
     * 取图片,
     *
     * @param path
     * @return
     */
    public Bitmap getBitMap(String path) {
        Bitmap bitmap = lruCache.get(path);
        if (bitmap != null) {
            System.out.println("我走了内存");
            return bitmap;
        }
        //从本直去取，sd卡去取bitmap
        bitmap = getBitMapFromLocal(path);
        if (bitmap != null) {
            System.out.println("我走了本地缓存");
            return bitmap;
        }
        // 从网络去取
        getBitmapFromNet(path);
        return null;
    }
    /**
     * 从sd卡获取图片
     *
     * @param path
     * @return
     */
    private Bitmap getBitMapFromLocal(String path) {
        try {
            String encode = EncoderUtils.encode(path);
            FileInputStream fileInputStream = new FileInputStream(cacheDir
                    + "/" + encode);
            Bitmap bitmap = BitmapFactory.decodeStream(fileInputStream);
            //存到内存
            lruCache.put(path, bitmap);
            return bitmap;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
    /**
     * 从网络
     *
     * @param path
     */
    private void getBitmapFromNet(final String path) {
        //用线程池里的线程执行请求网络操作;
        newFixedThreadPool.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    URL url = new URL(path);
                    HttpURLConnection connection = (HttpURLConnection) url
                            .openConnection();
                    connection.setConnectTimeout(5000);
                    connection.setReadTimeout(5000);
                    int responseCode = connection.getResponseCode();
                    if (responseCode == 200) {
                        InputStream inputStream = connection.getInputStream();
                        Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                        Message msg = new Message();
                        msg.what = 111;
                        msg.obj = bitmap;
                        Bundle data = new Bundle();
                        data.putString("tag", path);
                        msg.setData(data);
                        handler.sendMessage(msg);
                        //缓存到本地
                        saveBitmapToLocal(bitmap, path);
                        //缓存到内存
                        lruCache.put(path, bitmap);
                    }
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
    }
    protected void saveBitmapToLocal(Bitmap bitmap, String path) {
        try {
            String encode = EncoderUtils.encode(path);
            FileOutputStream fileOutputStream = new FileOutputStream(cacheDir + "/" + encode);
            //图片二次裁剪
            bitmap.compress(Bitmap.CompressFormat.JPEG, 80, fileOutputStream);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}










package com.lbs.sanjierji.Utils;

import java.security.MessageDigest;

/**
 * author:Created by WangZhiQiang on 2017/11/21.
 */

public class EncoderUtils {
    /**
     * Md5Encoder
     *
     * @param string
     * @return
     * @throws Exception
     */
    public static String encode(String string) throws Exception {
        byte[] hash = MessageDigest.getInstance("MD5").digest(
                string.getBytes("UTF-8"));
        StringBuilder hex = new StringBuilder(hash.length * 2);
        for (byte b : hash) {
            if ((b & 0xFF) < 0x10) {
                hex.append("0");
            }
            hex.append(Integer.toHexString(b & 0xFF));
        }
        return hex.toString();
    }
}











<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.lbs.sanjierji.MainActivity">

    <GridView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/gv"
        android:numColumns="2"></GridView>

</android.support.constraint.ConstraintLayout>



<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>