Android处理网络和图片的工具类

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import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import java.util.concurrent.RejectedExecutionException;


import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.methods.HttpGet;


import xiaogang.enif.utils.HttpManager;
import xiaogang.enif.utils.IOUtils;
import xiaogang.enif.utils.LogUtils;
import xiaogang.enif.utils.LruCache;
import android.app.ActivityManager;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.os.AsyncTask;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.widget.ImageView;


public class CacheView extends ImageView {
    private static final int DEFAULT_RES_ID = 0;
    private int mDefaultImage = DEFAULT_RES_ID;


    private static LruCache<String,Bitmap> mLruCache;
    private static HashMap<Integer,SoftReference<Bitmap>> mResImage;


    private Context mContext;
    private LogUtils mLog = LogUtils.getLog(CacheView.class);


    public CacheView(Context context,AttributeSet attrs,int defStyle) {
        super(context,attrs,defStyle);
        init(context);
    }


    public CacheView(Context context,AttributeSet attrs) {
        super(context,attrs);
        init(context);


    }


    public CacheView(Context context) {
        super(context);
        init(context);
    }


    private void init(Context context) {
        mContext = context;


        if (mLruCache == null) {
            final int cacheSize = getCacheSize(context);
            mLruCache = new LruCache<String,Bitmap>(cacheSize) {
                @Override
                protected int sizeOf(String key,Bitmap bitmap) {
                    // The cache size will be measured in bytes rather than
                    // number of items.
                    return bitmap.getRowBytes() * bitmap.getHeight();
                }


                @Override
                protected void entryRemoved(boolean evicted,String key,Bitmap oldValue,Bitmap newValue) {
                    if (evicted && oldValue != null && !oldValue.isRecycled()) {
                        oldValue.recycle();
                        oldValue = null;
                    }
                }
            };
        }


        if (mResImage == null) {
            mResImage = new HashMap<Integer,SoftReference<Bitmap>>();
        }
    }


    @Override
    protected void onDraw(Canvas canvas) {
        BitmapDrawable drawable = (BitmapDrawable)getDrawable();
        if (drawable == null) {
            setDefaultImage();
        } else {
            if (drawable.getBitmap() == null || drawable.getBitmap().isRecycled()) {
                setDefaultImage();
            }
        }
        try {
            super.onDraw(canvas);
        } catch(RuntimeException ex) {


        }
    }


    public void setImageUrl(String url,int resId) {
        setTag(url);
        Bitmap bitmap = getBitmapFromCache(url);
        if (bitmap == null || bitmap.isRecycled()) {
            mDefaultImage = resId;
            setDefaultImage();
            try {
                new DownloadTask().execute(url);
            } catch (RejectedExecutionException e) {
                // do nothing,just keep not crash
            }
        } else {
            setImageBitmap(bitmap);
        }
    }


    private void setDefaultImage() {
        if (mDefaultImage != DEFAULT_RES_ID) {
            setImageBitmap(getDefaultBitmap(mContext));
        }
    }


    private Bitmap getDefaultBitmap(Context context) {
        SoftReference<Bitmap> loading = mResImage.get(mDefaultImage);
        if (loading == null || loading.get() == null || loading.get().isRecycled()) {
            loading = new SoftReference<Bitmap>(BitmapFactory.decodeResource(
                    context.getResources(),mDefaultImage));
            mResImage.put(mDefaultImage,loading);
        }
        return loading.get();
    }


    private class DownloadTask extends AsyncTask<String,Void,Bitmap> {
        private String mParams;


        @Override
        public Bitmap doInBackground(String... params) {
            mParams = params[0];
            final Bitmap bm = download(mParams);
            addBitmapToCache(mParams,bm);
            return bm;
        }


        @Override
        public void onPostExecute(Bitmap bitmap) {
            String tag = (String)getTag();
            if (!TextUtils.isEmpty(tag) && tag.equals(mParams)) {
                if (bitmap != null) {
                    setImageBitmap(bitmap);
                }
            }
        }
    };


    /*
     * An InputStream that skips the exact number of bytes provided,unless it
     * reaches EOF.
     */
    static class FlushedInputStream extends FilterInputStream {
        public FlushedInputStream(InputStream inputStream) {
            super(inputStream);
        }


        @Override
        public long skip(long n) throws IOException {
            long totalBytesSkipped = 0L;
            while (totalBytesSkipped < n) {
                long bytesSkipped = in.skip(n - totalBytesSkipped);
                if (bytesSkipped == 0L) {
                    int b = read();
                    if (b < 0) {
                        break; // we reached EOF
                    } else {
                        bytesSkipped = 1; // we read one byte
                    }
                }
                totalBytesSkipped += bytesSkipped;
            }
            return totalBytesSkipped;
        }
    }


    private Bitmap download(String url) {
        InputStream in = null;
        HttpEntity entity = null;
        Bitmap bmp = null;
        try {
            final HttpGet get = new HttpGet(url);
            final HttpResponse response = HttpManager.execute(mContext,get);
            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                entity = response.getEntity();
                in = entity.getContent();
                try {
                    bmp = getDecodeBitmap(in,url);
                } catch (OutOfMemoryError err) {
                    Runtime.getRuntime().gc();
                    bmp = getDecodeBitmap(in,url);
                }
            } else {
                get.abort();
                return bmp;
            }
            addBitmapToCache(url,bmp);
        } catch (IOException e) {
            return bmp;
        } finally {
            IOUtils.closeStream(in);
        }
        return bmp;
    }


    private final Bitmap getDecodeBitmap(InputStream in,String url) {
        Options options = new Options();
        options.inPurgeable = true;
        options.inInputShareable = true;
        return BitmapFactory.decodeStream(new FlushedInputStream(in),null,options);
    }


    private final void addBitmapToCache(String url,Bitmap bitmap) {
        if (bitmap != null) {
            mLruCache.put(url,bitmap);
            Runtime.getRuntime().gc();
        }
    }


    private final Bitmap getBitmapFromCache(String url) {
        return mLruCache.get(url);
    }


    private int getCacheSize(Context context) {
        // According to the phone memory,set a proper cache size for LRU cache
        // dynamically.
        final ActivityManager am = (ActivityManager)context
                .getSystemService(Context.ACTIVITY_SERVICE);
        final int memClass = am.getMemoryClass();


        int cacheSize;
        if (memClass <= 24) {
            cacheSize = (memClass << 20) / 24;
        } else if (memClass <= 36) {
            cacheSize = (memClass << 20) / 18;
        } else if (memClass <= 48) {
            cacheSize = (memClass << 20) / 12;
        } else {
            cacheSize = (memClass << 20) >> 3;
        }
        mLog.debug("cacheSize == "+cacheSize);
        System.out.println("cacheSize == "+cacheSize);
        return cacheSize;
    }


    public static void recycle() {
        if (mLruCache != null && !mLruCache.isEmpty()) {
            mLruCache.evictAll();
            mLruCache = null;
        }


        if (mResImage != null) {
            for (SoftReference<Bitmap> reference : mResImage.values()) {
                Bitmap bitmap = reference.get();
                if (bitmap != null && !bitmap.isRecycled()) {
                    bitmap.recycle();
                    bitmap = null;
                }
            }
            mResImage = null;
        }
    }
}




说明：

1）entryRemoved 在做Bitmap recyle 的时候的三个条件缺一不可

2）onDraw 里面判断图片是否被回收，如果回收  需要设置默认的图片

3）add bitmap 到cache 的时候 Runtime.getRuntime().gc 的调用

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