我有一个ListView,每行上有两个图像按钮。当用户单击列表行时,它将启动一个新活动。我不得不建立我自己的标签,因为相机布局的问题。为结果启动的活动是一个映射。如果我点击我的按钮来启动图像预览(从SD卡加载图像),应用程序从活动返回到ListView活动到结果处理程序,重新启动我的新活动,这只不过是一个图像小部件。

ListView上的图像预览是用光标和ListAdapter完成的。这使得它非常简单,但我不确定我如何可以把一个调整大小的图像(即较小的位大小而不是像素作为图像按钮的src)。我只是调整了从手机摄像头拍下来的图片的大小。

问题是,当它试图返回并重新启动第二个活动时,我得到一个OutOfMemoryError。

是否有一种方法,我可以轻松地构建列表适配器行,在那里我可以调整大小的飞行(位)?

这将是可取的,因为我还需要对每行中的小部件/元素的属性做出一些更改,因为我无法选择一行与触摸屏,因为焦点问题。(我会用滚轮。)

我知道我可以做带外调整并保存我的图像,但这不是我真正想做的,但一些示例代码会很好。

当我在ListView上禁用图像时,它又可以正常工作了。

供你参考:我是这样做的:

String[] from = new String[] { DBHelper.KEY_BUSINESSNAME, DBHelper.KEY_ADDRESS,
    DBHelper.KEY_CITY, DBHelper.KEY_GPSLONG, DBHelper.KEY_GPSLAT,
    DBHelper.KEY_IMAGEFILENAME  + ""};
int[] to = new int[] { R.id.businessname, R.id.address, R.id.city, R.id.gpslong,
    R.id.gpslat, R.id.imagefilename };
notes = new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to);
setListAdapter(notes);

其中R.id.imagefilename是一个ButtonImage。

这是我的LogCat:

01-25 05:05:49.877: ERROR/dalvikvm-heap(3896): 6291456-byte external allocation too large for this process.
01-25 05:05:49.877: ERROR/(3896): VM wont let us allocate 6291456 bytes
01-25 05:05:49.877: ERROR/AndroidRuntime(3896): Uncaught handler: thread main exiting due to uncaught exception
01-25 05:05:49.917: ERROR/AndroidRuntime(3896): java.lang.OutOfMemoryError: bitmap size exceeds VM budget
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.graphics.BitmapFactory.nativeDecodeStream(Native Method)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:304)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:149)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:174)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.graphics.drawable.Drawable.createFromPath(Drawable.java:729)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.ImageView.resolveUri(ImageView.java:484)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.ImageView.setImageURI(ImageView.java:281)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.SimpleCursorAdapter.setViewImage(SimpleCursorAdapter.java:183)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.SimpleCursorAdapter.bindView(SimpleCursorAdapter.java:129)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.CursorAdapter.getView(CursorAdapter.java:150)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.AbsListView.obtainView(AbsListView.java:1057)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.ListView.makeAndAddView(ListView.java:1616)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.ListView.fillSpecific(ListView.java:1177)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.ListView.layoutChildren(ListView.java:1454)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.AbsListView.onLayout(AbsListView.java:937)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.View.layout(View.java:5611)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1108)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.LinearLayout.onLayout(LinearLayout.java:922)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.View.layout(View.java:5611)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.FrameLayout.onLayout(FrameLayout.java:294)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.View.layout(View.java:5611)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:999)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.LinearLayout.onLayout(LinearLayout.java:920)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.View.layout(View.java:5611)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.widget.FrameLayout.onLayout(FrameLayout.java:294)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.View.layout(View.java:5611)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.ViewRoot.performTraversals(ViewRoot.java:771)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1103)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.os.Handler.dispatchMessage(Handler.java:88)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.os.Looper.loop(Looper.java:123)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at android.app.ActivityThread.main(ActivityThread.java:3742)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at java.lang.reflect.Method.invoke(Method.java:515)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:497)
01-25 05:05:49.917: ERROR/AndroidRuntime(3896):     at dalvik.system.NativeStart.main(Native Method)
01-25 05:10:01.127: ERROR/AndroidRuntime(3943): ERROR: thread attach failed 

我也有一个新的错误时显示的图像:

22:13:18.594: DEBUG/skia(4204): xxxxxxxxxxx jpeg error 20 Improper call to JPEG library in state %d
22:13:18.604: INFO/System.out(4204): resolveUri failed on bad bitmap uri: 
22:13:18.694: ERROR/dalvikvm-heap(4204): 6291456-byte external allocation too large for this process.
22:13:18.694: ERROR/(4204): VM won't let us allocate 6291456 bytes
22:13:18.694: DEBUG/skia(4204): xxxxxxxxxxxxxxxxxxxx allocPixelRef failed

当前回答

我有同样的问题,并通过避免BitmapFactory.decodeStream或decodeFile函数来解决它,而是使用BitmapFactory.decodeFileDescriptor

decodeFileDescriptor看起来像调用了不同于decodeStream/decodeFile的本地方法。

不管怎样,这样做是有效的(注意,我添加了一些选项,就像上面的一些选项一样,但这并不是造成不同的原因。关键是调用BitmapFactory.decodeFileDescriptor而不是decodeStream或decodeFile):

private void showImage(String path)   {

    Log.i("showImage","loading:"+path);
    BitmapFactory.Options bfOptions=new BitmapFactory.Options();
    bfOptions.inDither=false;                     //Disable Dithering mode
    bfOptions.inPurgeable=true;                   //Tell to gc that whether it needs free memory, the Bitmap can be cleared
    bfOptions.inInputShareable=true;              //Which kind of reference will be used to recover the Bitmap data after being clear, when it will be used in the future
    bfOptions.inTempStorage=new byte[32 * 1024]; 

    File file=new File(path);
    FileInputStream fs=null;
    try {
        fs = new FileInputStream(file);
    } catch (FileNotFoundException e) {
        //TODO do something intelligent
        e.printStackTrace();
    }

    try {
        if(fs!=null) bm=BitmapFactory.decodeFileDescriptor(fs.getFD(), null, bfOptions);
    } catch (IOException e) {
        //TODO do something intelligent
        e.printStackTrace();
    } finally{ 
        if(fs!=null) {
            try {
                fs.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
    //bm=BitmapFactory.decodeFile(path, bfOptions); This one causes error: java.lang.OutOfMemoryError: bitmap size exceeds VM budget

    im.setImageBitmap(bm);
    //bm.recycle();
    bm=null;                        
}

我认为在decodeStream/decodeFile中使用的本机函数有问题。我已经确认使用decodeFileDescriptor时调用了不同的本机方法。此外,我读到的是“图像(位图)不是以标准的Java方式分配的,而是通过本机调用;分配是在虚拟堆之外完成的,但是 不算数!”

其他回答

此问题只发生在Android模拟器中。我在模拟器中也遇到过这个问题,但当我签入设备时,它工作得很好。

所以请签入设备。它可以在设备中运行。

避免内存泄漏或位图OOM的最佳实践

不要为一个Context / Activity保留长时间的位图引用。 如果你在你的应用程序中使用一个大的位图作为背景或其他东西,那么不要把完整的图像拉到主存中。您可以使用位图的insample size属性来获取屏幕所需的大小。 清洁位图引用一旦不再使用。

几分钟前我遇到了这个问题。我通过更好地管理我的listview适配器来解决这个问题。我认为这是我使用的数百个50x50px图像的问题,结果是我在每次显示一行时都试图膨胀我的自定义视图。通过简单地测试看看行是否被膨胀,我消除了这个错误,我使用了数百个位图。这实际上是用于Spinner的,但基本适配器对ListView是一样的。这个简单的修复还极大地提高了适配器的性能。

@Override
public View getView(final int position, View convertView, final ViewGroup parent) {

    if(convertView == null){
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.spinner_row, null);
    }
...

这段代码将有助于从可绘制的图中加载大的位图

public class BitmapUtilsTask extends AsyncTask<Object, Void, Bitmap> {

    Context context;

    public BitmapUtilsTask(Context context) {
        this.context = context;
    }

    /**
     * Loads a bitmap from the specified url.
     * 
     * @param url The location of the bitmap asset
     * @return The bitmap, or null if it could not be loaded
     * @throws IOException
     * @throws MalformedURLException
     */
    public Bitmap getBitmap() throws MalformedURLException, IOException {       

        // Get the source image's dimensions
        int desiredWidth = 1000;
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;

        BitmapFactory.decodeResource(context.getResources(), R.drawable.green_background , options);

        int srcWidth = options.outWidth;
        int srcHeight = options.outHeight;

        // Only scale if the source is big enough. This code is just trying
        // to fit a image into a certain width.
        if (desiredWidth > srcWidth)
            desiredWidth = srcWidth;

        // Calculate the correct inSampleSize/scale value. This helps reduce
        // memory use. It should be a power of 2
        int inSampleSize = 1;
        while (srcWidth / 2 > desiredWidth) {
            srcWidth /= 2;
            srcHeight /= 2;
            inSampleSize *= 2;
        }
        // Decode with inSampleSize
        options.inJustDecodeBounds = false;
        options.inDither = false;
        options.inSampleSize = inSampleSize;
        options.inScaled = false;
        options.inPreferredConfig = Bitmap.Config.ARGB_8888;
        options.inPurgeable = true;
        Bitmap sampledSrcBitmap;

        sampledSrcBitmap =  BitmapFactory.decodeResource(context.getResources(), R.drawable.green_background , options);

        return sampledSrcBitmap;
    }

    /**
     * The system calls this to perform work in a worker thread and delivers
     * it the parameters given to AsyncTask.execute()
     */
    @Override
    protected Bitmap doInBackground(Object... item) {
        try { 
          return getBitmap();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

最近我看到了很多关于OOM异常和缓存的问题。开发人员指南中有一篇关于这方面的非常好的文章,但有些人往往无法以合适的方式实现它。

因此,我编写了一个示例应用程序,演示了Android环境中的缓存。这个实现还没有得到一个OOM。

在答案的末尾可以找到源代码的链接。

要求:

Android API 2.1或更高版本(我根本无法在API 1.6中为应用程序获得可用内存-这是API 1.6中唯一不能工作的代码段) Android支持包

特点:

如果方向改变,使用单例保存缓存 将分配的应用程序内存的八分之一用于缓存(如果需要可以修改) 大的位图缩放(您可以定义您想要允许的最大像素) 控制在下载位图之前是否有可用的互联网连接 确保每行只实例化一个任务 如果你扔掉ListView,它就不会下载中间的位图

这不包括:

磁盘缓存。这应该很容易实现-只要指向一个不同的任务,从磁盘获取位图

示例代码:

正在下载的图像是来自Flickr的图像(75x75)。然而,不管你想处理什么图像url,如果它超过最大值,应用程序就会缩小它。在这个应用程序中,url只是一个字符串数组。

LruCache有一个处理位图的好方法。但是,在这个应用程序中,我将一个LruCache实例放在我创建的另一个缓存类中,以便使应用程序更加可行。

Cache.java的关键内容(loadBitmap()方法是最重要的):

public Cache(int size, int maxWidth, int maxHeight) {
    // Into the constructor you add the maximum pixels
    // that you want to allow in order to not scale images.
    mMaxWidth = maxWidth;
    mMaxHeight = maxHeight;

    mBitmapCache = new LruCache<String, Bitmap>(size) {
        protected int sizeOf(String key, Bitmap b) {
            // Assuming that one pixel contains four bytes.
            return b.getHeight() * b.getWidth() * 4;
        }
    };

    mCurrentTasks = new ArrayList<String>();    
}

/**
 * Gets a bitmap from cache. 
 * If it is not in cache, this method will:
 * 
 * 1: check if the bitmap url is currently being processed in the
 * BitmapLoaderTask and cancel if it is already in a task (a control to see
 * if it's inside the currentTasks list).
 * 
 * 2: check if an internet connection is available and continue if so.
 * 
 * 3: download the bitmap, scale the bitmap if necessary and put it into
 * the memory cache.
 * 
 * 4: Remove the bitmap url from the currentTasks list.
 * 
 * 5: Notify the ListAdapter.
 * 
 * @param mainActivity - Reference to activity object, in order to
 * call notifyDataSetChanged() on the ListAdapter.
 * @param imageKey - The bitmap url (will be the key).
 * @param imageView - The ImageView that should get an
 * available bitmap or a placeholder image.
 * @param isScrolling - If set to true, we skip executing more tasks since
 * the user probably has flinged away the view.
 */
public void loadBitmap(MainActivity mainActivity, 
        String imageKey, ImageView imageView,
        boolean isScrolling) {
    final Bitmap bitmap = getBitmapFromCache(imageKey); 

    if (bitmap != null) {
        imageView.setImageBitmap(bitmap);
    } else {
        imageView.setImageResource(R.drawable.ic_launcher);
        if (!isScrolling && !mCurrentTasks.contains(imageKey) && 
                mainActivity.internetIsAvailable()) {
            BitmapLoaderTask task = new BitmapLoaderTask(imageKey,
                    mainActivity.getAdapter());
            task.execute();
        }
    } 
}

您不需要在Cache.java文件中编辑任何内容,除非您想实现磁盘缓存。

java的关键部分:

public void onScrollStateChanged(AbsListView view, int scrollState) {
    if (view.getId() == android.R.id.list) {
        // Set scrolling to true only if the user has flinged the       
        // ListView away, hence we skip downloading a series
        // of unnecessary bitmaps that the user probably
        // just want to skip anyways. If we scroll slowly it
        // will still download bitmaps - that means
        // that the application won't wait for the user
        // to lift its finger off the screen in order to
        // download.
        if (scrollState == SCROLL_STATE_FLING) {
            mIsScrolling = true;
        } else {
            mIsScrolling = false;
            mListAdapter.notifyDataSetChanged();
        }
    } 
}

// Inside ListAdapter...
@Override
public View getView(final int position, View convertView, ViewGroup parent) {           
    View row = convertView;
    final ViewHolder holder;

    if (row == null) {
        LayoutInflater inflater = getLayoutInflater();
        row = inflater.inflate(R.layout.main_listview_row, parent, false);  
        holder = new ViewHolder(row);
        row.setTag(holder);
    } else {
        holder = (ViewHolder) row.getTag();
    }   

    final Row rowObject = getItem(position);

    // Look at the loadBitmap() method description...
    holder.mTextView.setText(rowObject.mText);      
    mCache.loadBitmap(MainActivity.this,
            rowObject.mBitmapUrl, holder.mImageView,
            mIsScrolling);  

    return row;
}

getView()经常被调用。如果我们没有实现检查,以确保我们不会在每行启动无限数量的线程,那么在那里下载图像通常不是一个好主意。Cache.java检查rowObject。mBitmapUrl已经在一个任务,如果它是,它不会开始另一个任务。因此,我们很可能不会超过AsyncTask池的工作队列限制。

下载:

您可以从https://www.dropbox.com/s/pvr9zyl811tfeem/ListViewImageCache.zip下载源代码。


最后一句话:

我已经测试了这个几个星期了,我还没有得到一个OOM异常。我已经在模拟器、我的Nexus One和Nexus s上测试了这个功能。我测试了包含高清图像的图像url。唯一的瓶颈是下载需要更多的时间。

只有一种可能的情况下,我可以想象OOM将会出现,那就是如果我们下载许多非常大的图像,在它们被缩放并放入缓存之前,将同时占用更多的内存并导致OOM。但无论如何,这都不是一个理想的情况,而且很可能不可能以更可行的方式解决。

在评论中报告错误!: -)