图片三级缓存

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;

public class MainActivity extends AppCompatActivity {
    private GridView gv;
    ImagesUtils imagUtils;
    String[] imageUrls = new String[] {
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uplds/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383299_1976.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383291_6518.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383291_8239.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383290_9329.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383290_1042.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383275_3977.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383265_8550.jpg",
            "http://img.my.csdn.net/uploads/201407/26/1406383264_3954.jpg",
            "http://img.my.csdn.net/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;
        }


    }

}

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.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();
        }

    }


}

import java.security.MessageDigest;

/**
 * author:Created by WangZhiQiang on 2017-09-04.
 * 工具类,把对url进行md5加密,加密后以字符串的形式返回;
 * 缓存的时候用key(url加密后的字符串)对应value(bitmap)
 */

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();
    }


}