网络获取图片的优化

public class EncoderUtils {
    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();
    }

}

//第二个类

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;

/**
 * Created by Administrator on 2017/11/6.
 */

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 {
            //自己定义的加密工具类
            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();
        }

    }

}

//Activity的代码

//全部全局

ImagesUtils imagUtils;
String urlBitmap = "https://img-my.youkuaiyun.com/uploads/201407/26/1406383264_4787.jpg";

private ImageView iv;
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     iv为你要赋值的控件
            ImageView imageView = (ImageView) iv.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");
            }
        }
    }
};

//oncreateview里面的代码

iv = (ImageView) findViewById(R.id.iv);
//实例化对象
ImagesUtils in=new ImagesUtils(this,handler);
//调用方法   urlBitmap为URI链接
Bitmap bitMap = in.getBitMap(urlBitmap);
//给控件赋值
iv.setImageBitmap(bitMap);