ImageView在asynctask中无法正确刷新

Question

我从android开发者网站修改了以下类，将图像加载到imageview。输入了onPostExecute方法，但我的imageview未正确刷新。我尝试过使用imageView.refreshDrawableState，requestFocus，requestLayout，但一切都不起作用。

首先，imageview会显示一些随机颜色或显示任何内容。当我尝试下拉通知栏时，imageview仅正确显示。我很确定图像已加载，因为内存保持不变但只是没有正确显示/刷新。

我在async task方法中调用public void onWindowFocusChanged()。

任何人都可以指出我做错了什么吗？

ImageView imageView; //set in onCreate method

private class ImageViewAsyncTask extends AsyncTask<Integer, Void, Bitmap>
{
    private final WeakReference<ImageView> imageViewWeakReference;
    Activity activity;

    public ImageViewAsyncTask(Activity activity)
    {
        this.activity = activity;
        this.imageViewWeakReference = new WeakReference<>(imageView);
    }

    public int calculateInSampleSize(Options options)
    {
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;
        int reqWidth = imageView.getWidth();
        int reqHeight = imageView.getHeight();

        if (width > reqWidth || height > reqHeight)
        {
            final int halfWidth = width / 2;
            final int halfHeight = height / 2;

            while ((halfWidth / inSampleSize) > reqWidth && (halfHeight / inSampleSize) > reqHeight)
            {
                inSampleSize *= 2;
            }
        }

        return inSampleSize;
    }

    public Bitmap decodeSampledBitmapFromResource(Activity activity)
    {
        byte[] decodedImage = Base64.decode(activity.getResources().getString(R.string.cat), 0);
        final Options options = new Options();
        options.inJustDecodeBounds = true;
        decodeByteArray(decodedImage, 0, decodedImage.length, options);
        options.inSampleSize = calculateInSampleSize(options);
        options.inJustDecodeBounds = false;
        return decodeByteArray(decodedImage, 0, decodedImage.length, options);
    }

    @Override
    protected Bitmap doInBackground(Integer... params)
    {
        Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
        return decodeSampledBitmapFromResource(activity);
    }

    @Override
    protected void onPostExecute(Bitmap bitmap)
    {
        if (imageViewWeakReference != null && bitmap != null)
        {
            final ImageView imageView = imageViewWeakReference.get();
            if (imageView != null)
            {
                imageView.setImageBitmap(bitmap);
            }
        }
    }