Question

我正在写一个画廊应用程序。它适用于列表片段的androidstudio模板，带有AbsList。

我重写getView以使用任务和lrucache来缓存一些位图。

listview中的每个视图都是一个RelativeLayout，在TextView上方有一个ImageView。如果缓存中没有Bitmap，则AsyncTask会加载它并将其放入缓存中，getView会在ImageView上绘制资源。加载后，onPostExecute将位图放入ImageView。

如果缓存上有相应的Bitmap，则将其设置为ImageView

我将一个持有TextView和ImageView的对象以及一个id放入getView的convertView参数标记中，以跟踪要绘制的正确位图。

但我有这两个问题：

当我第一次向下滚动时，在任务完成设置正确的位图之前，新的图像视图会显示前一个位图（即使我在适配器的getView上绘制了资源位图）不明白为什么。
当我向后滚动时，大多数时候应用程序崩溃，因为缓存上的位图最终会被回收，但我不知道是谁回收它。

任何人都可以帮我理解这里发生的事情吗？

public View getView(int position, View convertView, ViewGroup parent) {
            Log.i(TAG, "getView: Asking for view " + position);
            GalleryItemViewHolder lViewHolder;
            if (convertView == null) {
                convertView = getActivity().getLayoutInflater().inflate(R.layout
                        .gallery_item, null);
                lViewHolder = new GalleryItemViewHolder();
                convertView.setTag(lViewHolder);

            } else {
                lViewHolder = (GalleryItemViewHolder) convertView.getTag();
            }
            lViewHolder.setId(position);
            lViewHolder.setTextView((TextView) convertView.findViewById(R.id.gallery_infoTextView));
            lViewHolder.setImageView((ImageView) convertView.findViewById(R.id.gallery_imageView));

            lViewHolder.getTextView().setText(getItem(position).getName() + ": (" + getItem
                    (position).getCount() + ")");
            if (!getItem(position).paintCover(lViewHolder.getImageView())) {
                Log.i(TAG,"getView: task");
                new GalleryItemTask(position, lViewHolder)
                        .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, null);
            }
            Log.i(TAG,"getView: return");
            return convertView;
        }

Cover类有这个paintCover方法，其中mId是图像的uri / stream

public boolean paintCover(ImageView imageView) {
    Bitmap lBitmap;
    if (mId == null || (lBitmap = BitmapCacheManager.getInstance().get(mId)) == null) {
        i(TAG, "paintCover: Sin Cache ");
        imageView.getHeight();
        imageView.getWidth();
        imageView.setImageResource(android.R.drawable.alert_dark_frame);
        return false;

    } else

    {
        i(TAG, "paintCover: En Cache "+lBitmap.isRecycled());
        imageView.setImageBitmap(lBitmap);
        return true;
    }

}

更多细节。在Fragment的onCreate，我运行这个方法：

private void prepareGalleryLoaders() {
    LoaderManager lm = getLoaderManager();
    Log.i(TAG, "prepareGalleryLoaders: Iniciando loader");
    lm.initLoader(IdConstants.GALLERY_LOADER, null, new GalleryLoaderCallbacks());
}



/**
 * Callbacks para cargar los datos de las galerías
 * Al terminar de cargarlas, se crea el nuevo arreglo
 */
private class GalleryLoaderCallbacks implements LoaderManager.LoaderCallbacks<List<Gallery>> {
    @Override
    public Loader<List<Gallery>> onCreateLoader(int id, Bundle args) {

        return new GalleriesLoader(getActivity());
    }private class GalleryItemTask extends AsyncTask<Void, Void, Gallery> {
    private static final String TAG = "GalleryItemTask";
    private int mId;
    private String mCoverId;
    private GalleryItemViewHolder mViewHolder;
    private Bitmap mBitmap;

    GalleryItemTask(int id, GalleryItemViewHolder galleryItemViewHolder) {
        mViewHolder = galleryItemViewHolder;
        mId = id;
    }



    @Override
    protected void onPostExecute(Gallery galleries) {

        if (mId != mViewHolder.getId()) {
            Log.i(TAG, "onPostExecute: IDs difieren!!! "+mId+" - "+mViewHolder.getId());
            mBitmap.recycle();
            mBitmap=null;
            return;
        }
        // Validar y actualizar bitmap


        mViewHolder.getImageView().setImageBitmap(mBitmap);
        //mGalleries.get(mId).setBitmap(mBitmap);

        super.onPostExecute(galleries);
    }

    @Override
    protected Gallery doInBackground(Void... params) {
        // generar bitmap (y posiblemente agregarlo a algún cache)


        String[] queryProjection = {
                MediaStore.Images.ImageColumns.DATA, MediaStore.Images.ImageColumns.TITLE};
        String[] selectionArgs = new String[]{String.valueOf(mGalleries.get(mId).getId())};
        Cursor lCursor = getView().getContext().getContentResolver().query(
                MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                queryProjection, MediaStore.Images.ImageColumns.BUCKET_ID + "= ?",
                selectionArgs, MediaStore.Images.ImageColumns.TITLE);
        lCursor.moveToFirst();
        while (!lCursor.isAfterLast()) {
            //Log.i(TAG,"doInBackground: "+mGalleries.get(mId).getName()+" - "+lCursor.getString
            //        (1)+" - "+ lCursor.getString(0));
            lCursor.moveToNext();
        }
        lCursor.moveToFirst();
        Log.i(TAG, "doInBackground: " + mId + " - " + mViewHolder.getId());

        BitmapFactory.Options lOptions = new BitmapFactory.Options();
        lOptions.inJustDecodeBounds = true;
        mBitmap = BitmapFactory.decodeFile(lCursor.getString(0), lOptions);
        lOptions.inSampleSize = ImageUtils.calculateInSampleSize(lOptions, 256, 256);
        lOptions.inJustDecodeBounds = false;
        mBitmap = BitmapFactory.decodeFile(lCursor.getString(0), lOptions);

        BitmapCacheManager.getInstance().put(lCursor.getString(0), mBitmap);


        //if(mGalleries.get(mId).getBitmap()!=null)
        //    mGalleries.get(mId).getBitmap().recycle();
        //mGalleries.get(mId).setBitmap(mBitmap);



        if(!mGalleries.get(mId).hasCover()) {
            SimpleCover lSimpleCover=new SimpleCover(getActivity(),lCursor.getString(0));
            mGalleries.get(mId).setCover(lSimpleCover);
        }
        lCursor.close();
        return null;
    }
}


    @Override
    public void onLoadFinished(Loader<List<Gallery>> loader, List<Gallery> data) {
        if (mGalleries != null) {
            mGalleries.clear();

        } else
            mGalleries = new ArrayList<Gallery>();
        mGalleries.addAll(data);
        for (Gallery lGallery : data) {
            Log.i(TAG, "onLoadFinished: " + lGallery.getName());
        }

        mAdapter.notifyDataSetChanged();
    }

此时，没有定义封面，库列表只是加载了标题和总内容以及id数据。图像（封面）从列表适配器的getView加载。

GalleryItemTask类：

 private class GalleryItemTask extends AsyncTask<Void, Void, Gallery> {
    private static final String TAG = "GalleryItemTask";
    private int mId;
    private String mCoverId;
    private GalleryItemViewHolder mViewHolder;
    private Bitmap mBitmap;

    GalleryItemTask(int id, GalleryItemViewHolder galleryItemViewHolder) {
        mViewHolder = galleryItemViewHolder;
        mId = id;
    }



    @Override
    protected void onPostExecute(Gallery galleries) {

        if (mId != mViewHolder.getId()) {
            Log.i(TAG, "onPostExecute: IDs difieren!!! "+mId+" - "+mViewHolder.getId());
            mBitmap.recycle();
            mBitmap=null;
            return;
        }
        // Validar y actualizar bitmap


        mViewHolder.getImageView().setImageBitmap(mBitmap);
        //mGalleries.get(mId).setBitmap(mBitmap);

        super.onPostExecute(galleries);
    }

    @Override
    protected Gallery doInBackground(Void... params) {
        // generar bitmap (y posiblemente agregarlo a algún cache)


        String[] queryProjection = {
                MediaStore.Images.ImageColumns.DATA, MediaStore.Images.ImageColumns.TITLE};
        String[] selectionArgs = new String[]{String.valueOf(mGalleries.get(mId).getId())};
        Cursor lCursor = getView().getContext().getContentResolver().query(
                MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                queryProjection, MediaStore.Images.ImageColumns.BUCKET_ID + "= ?",
                selectionArgs, MediaStore.Images.ImageColumns.TITLE);
        lCursor.moveToFirst();
        while (!lCursor.isAfterLast()) {
            //Log.i(TAG,"doInBackground: "+mGalleries.get(mId).getName()+" - "+lCursor.getString
            //        (1)+" - "+ lCursor.getString(0));
            lCursor.moveToNext();
        }
        lCursor.moveToFirst();
        Log.i(TAG, "doInBackground: " + mId + " - " + mViewHolder.getId());

        BitmapFactory.Options lOptions = new BitmapFactory.Options();
        lOptions.inJustDecodeBounds = true;
        mBitmap = BitmapFactory.decodeFile(lCursor.getString(0), lOptions);
        lOptions.inSampleSize = ImageUtils.calculateInSampleSize(lOptions, 256, 256);
        lOptions.inJustDecodeBounds = false;
        mBitmap = BitmapFactory.decodeFile(lCursor.getString(0), lOptions);

        BitmapCacheManager.getInstance().put(lCursor.getString(0), mBitmap);


        //if(mGalleries.get(mId).getBitmap()!=null)
        //    mGalleries.get(mId).getBitmap().recycle();
        //mGalleries.get(mId).setBitmap(mBitmap);



        if(!mGalleries.get(mId).hasCover()) {
            SimpleCover lSimpleCover=new SimpleCover(getActivity(),lCursor.getString(0));
            mGalleries.get(mId).setCover(lSimpleCover);
        }
        lCursor.close();
        return null;
    }
}

Answer 1

第一次向下滚动时，新的图像视图显示为在任务完成设置之前的瞬间的前一个位图正确的位图（即使我在适配器上绘制资源Bitmap） getView）我不明白为什么。

应该是因为你把notifyDataSetChanged()放在了错误的地方。请将代码发布到您的位置。

当我向后滚动时，大多数时候应用程序崩溃，因为Bitmap打开了缓存最终被回收，但我不知道谁回收它

我认为是因为如果paintCover为true，您没有说明该怎么做：

if (!getItem(position).paintCover(lViewHolder.getImageView())) {
       Log.i(TAG,"getView: task");
       new GalleryItemTask(position, lViewHolder)
               .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, null);
}
else
{
   //what should the adapter do if paintCover is true?
}

如果错误仍然存在，请发布您的GalleryItemTask代码。

ListView在lrucache中回收了Bitmap而没有注意到

1 个答案: