Android java.lang.OutOfMemoryError？

04-25 08:19:10.111    2431-2603/com.example.francesco.guidedautorewithtabs E/art﹕ Throwing OutOfMemoryError "Failed to allocate a 4194316 byte allocation with 1983651 free bytes and 1937KB until OOM"
04-25 08:19:10.114    2431-2603/com.example.francesco.guidedautorewithtabs E/AndroidRuntime﹕ FATAL EXCEPTION: GLThread 285
Process: com.example.francesco.guidedautorewithtabs, PID: 2431
java.lang.OutOfMemoryError: Failed to allocate a 4194316 byte allocation with 1983651 free bytes and 1937KB until OOM
        at dalvik.system.VMRuntime.newNonMovableArray(Native Method)
        at android.graphics.Bitmap.nativeCreate(Native Method)
        at android.graphics.Bitmap.createBitmap(Bitmap.java:817)
        at android.graphics.Bitmap.createBitmap(Bitmap.java:794)
        at android.graphics.Bitmap.createBitmap(Bitmap.java:761)
        at com.google.maps.api.android.lib6.gmm6.o.c.l.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.c.o.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.c.o.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.c.o.b(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.c.b.ak.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.c.b.as.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.x.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.l.a(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.l.b(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.cj.g(Unknown Source)
        at com.google.maps.api.android.lib6.gmm6.o.cj.run(Unknown Source)

在我的Android代码中，我有很多图像必须显示为不同的片段。其中一些存储在资产文件夹中，其他一些则从http请求中获取。出于这个原因，我实现了图像缓存，以便不违背java.lang.OutOfMemoryError，但是此错误似乎仍然存在。我该如何解决这个问题？下面我实现图像缓存。

图像加载器

public class ImageLoader {
MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
private Context context;

public ImageLoader(Context context){
    this.context=context;
    fileCache=new FileCache(context);
    executorService=Executors.newFixedThreadPool(5);
}

final int stub_id= R.drawable.no_image;
public void DisplayImage(String url, ImageView imageView)
{
    imageViews.put(imageView, url);
    Bitmap bitmap=memoryCache.get(url);
    if(bitmap!=null)
        imageView.setImageBitmap(bitmap);
    else
    {
        queuePhoto(url, imageView);
        imageView.setImageResource(stub_id);
    }
}

private void queuePhoto(String url, ImageView imageView)
{
    PhotoToLoad p=new PhotoToLoad(url, imageView);
    executorService.submit(new PhotosLoader(p));
}

private Bitmap getBitmapFromAsset(String strName)
{
    AssetManager assetManager = context.getAssets();
    InputStream istr = null;
    try {
        istr = assetManager.open(strName);
    } catch (IOException e) {
        e.printStackTrace();
    }
    Bitmap bitmap = BitmapFactory.decodeStream(istr);
    return bitmap;
}

private Bitmap getBitmap(String url)
{
    File f=fileCache.getFile(url);

    //from SD cache
    Bitmap b = decodeFile(f);
    if(b!=null)
        return b;

    //from assets
    Bitmap bm = getBitmapFromAsset(url);

    if(bm!=null)
        return bm;

    //from web
    try {
        Bitmap bitmap=null;
        URL imageUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
        conn.setConnectTimeout(30000);
        conn.setReadTimeout(30000);
        conn.setInstanceFollowRedirects(true);
        InputStream is=conn.getInputStream();
        OutputStream os = new FileOutputStream(f);
        Utils.CopyStream(is, os);
        os.close();
        bitmap = decodeFile(f);
        return bitmap;
    } catch (Throwable ex){
        ex.printStackTrace();
        if(ex instanceof OutOfMemoryError)
            memoryCache.clear();
        return null;
    }
}

//decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f){
    try {
        //decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(new FileInputStream(f),null,o);

        //Find the correct scale value. It should be the power of 2.
        final int REQUIRED_SIZE=70;
        int width_tmp=o.outWidth, height_tmp=o.outHeight;
        int scale=1;
        while(true){
            if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                break;
            width_tmp/=2;
            height_tmp/=2;
            scale*=2;
        }

        //decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize=scale;
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
    } catch (FileNotFoundException e) {}
    return null;
}

//Task for the queue
private class PhotoToLoad
{
    public String url;
    public ImageView imageView;
    public PhotoToLoad(String u, ImageView i){
        url=u;
        imageView=i;
    }
}

class PhotosLoader implements Runnable {
    PhotoToLoad photoToLoad;
    PhotosLoader(PhotoToLoad photoToLoad){
        this.photoToLoad=photoToLoad;
    }

    @Override
    public void run() {
        if(imageViewReused(photoToLoad))
            return;
        Bitmap bmp=getBitmap(photoToLoad.url);
        memoryCache.put(photoToLoad.url, bmp);
        if(imageViewReused(photoToLoad))
            return;
        BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
        Activity a=(Activity)photoToLoad.imageView.getContext();
        a.runOnUiThread(bd);
    }
}

boolean imageViewReused(PhotoToLoad photoToLoad){
    String tag=imageViews.get(photoToLoad.imageView);
    if(tag==null || !tag.equals(photoToLoad.url))
        return true;
    return false;
}

//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
    Bitmap bitmap;
    PhotoToLoad photoToLoad;
    public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
    public void run()
    {
        if(imageViewReused(photoToLoad))
            return;
        if(bitmap!=null)
            photoToLoad.imageView.setImageBitmap(bitmap);
        else
            photoToLoad.imageView.setImageResource(stub_id);
    }
}

public void clearCache() {
    memoryCache.clear();
    fileCache.clear();
}
}

文件缓存

public class FileCache {

private File cacheDir;

public FileCache(Context context){
    //Find the dir to save cached images
    if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
        cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"TTImages_cache");
    else
        cacheDir=context.getCacheDir();
    if(!cacheDir.exists())
        cacheDir.mkdirs();
}

public File getFile(String url){
    //I identify images by hashcode. Not a perfect solution, good for the demo.
    String filename=String.valueOf(url.hashCode());
    //Another possible solution (thanks to grantland)
    //String filename = URLEncoder.encode(url);
    File f = new File(cacheDir, filename);
    return f;

}

public void clear(){
    File[] files=cacheDir.listFiles();
    if(files==null)
        return;
    for(File f:files)
        f.delete();
}

}

内存缓存

public class MemoryCache {

private static final String TAG = "MemoryCache";
private Map<String, Bitmap> cache=Collections.synchronizedMap(
        new LinkedHashMap<String, Bitmap>(10,1.5f,true));//Last argument true for LRU ordering
private long size=0;//current allocated size
private long limit=1000000;//max memory in bytes

public MemoryCache(){
    //use 25% of available heap size
    setLimit(Runtime.getRuntime().maxMemory()/4);
}

public void setLimit(long new_limit){
    limit=new_limit;
    Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB");
}

public Bitmap get(String id){
    try{
        if(!cache.containsKey(id))
            return null;
        //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
        return cache.get(id);
    }catch(NullPointerException ex){
        ex.printStackTrace();
        return null;
    }
}

public void put(String id, Bitmap bitmap){
    try{
        if(cache.containsKey(id))
            size-=getSizeInBytes(cache.get(id));
        cache.put(id, bitmap);
        size+=getSizeInBytes(bitmap);
        checkSize();
    }catch(Throwable th){
        th.printStackTrace();
    }
}

private void checkSize() {
    Log.i(TAG, "cache size="+size+" length="+cache.size());
    if(size>limit){
        Iterator<Entry<String, Bitmap>> iter=cache.entrySet().iterator();//least recently accessed item will be the first one iterated
        while(iter.hasNext()){
            Entry<String, Bitmap> entry=iter.next();
            size-=getSizeInBytes(entry.getValue());
            iter.remove();
            if(size<=limit)
                break;
        }
        Log.i(TAG, "Clean cache. New size "+cache.size());
    }
}

public void clear() {
    try{
        //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
        cache.clear();
        size=0;
    }catch(NullPointerException ex){
        ex.printStackTrace();
    }
}

long getSizeInBytes(Bitmap bitmap) {
    if(bitmap==null)
        return 0;
    return bitmap.getRowBytes() * bitmap.getHeight();
}
}

实用程序

public class Utils {
public static void CopyStream(InputStream is, OutputStream os)
{
    final int buffer_size=1024;
    try
    {
        byte[] bytes=new byte[buffer_size];
        for(;;)
        {
            int count=is.read(bytes, 0, buffer_size);
            if(count==-1)
                break;
            os.write(bytes, 0, count);
        }
    }
    catch(Exception ex){}
}
}