RecyclerView消失的图像 [英] RecyclerView disappearing images

问题描述

我要创建的是水平滚动图像库.我有一个RecyclerView(支持22.0.0).我遇到的问题是，当我滚动到末尾然后向后滚动时，通常一幅图像有时会丢失两幅.奇怪的是，当我不断来回滑动时，可能会丢失其他图像.这是项目的布局:

What I am trying to create is a horizontal scrolling image gallery. I have a RecyclerView (support 22.0.0). The problem I am having is that when I scroll to the end and then scroll back, usually one image will be missing sometimes two. Strangely when I keep swiping back and forth, a different image could be missing. Here is the layout for the item:

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="160dp">

<ImageView
    android:id="@+id/product_variation_image"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scaleType="centerCrop"
    android:layout_gravity="center"/>

这是Adaper:

public class TestAdapter extends RecyclerView.Adapter<TestAdapter.ViewHolder> {
private String[] mDataset;

public static class ViewHolder extends RecyclerView.ViewHolder {

    public ImageView mImageView;
    public ViewHolder(View v) {
        super(v);
        mImageView = (ImageView) v.findViewById(R.id.product_variation_image);
    }
}

public TestAdapter(String[] myDataset) {
    mDataset = myDataset;
}

@Override
public TestAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                               int viewType) {
    // create a new view
    View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.variaton_list_item, parent, false);
    ViewHolder vh = new ViewHolder(v);
    return vh;
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {

    holder.mImageView.setImageDrawable(null);
    String url = mDataset[position];
    Log.i("TEST", "position = " + position);
    ((MainActivity)MainActivity.getInstance()).imageDownloader.download(url, holder.mImageView);
}

@Override
public int getItemCount() {
    return mDataset.length;
}

download方法从URL提取图像，或者如果已将其从内存中获取，则从内存中获取.这在所有其他布局中都可以正常工作，例如ListView或GridView.这是我用来在Fragment中进行设置的代码:

The download method fetches the image, from a URL or gets it from the memory if it has been cached. This works fine in all other layouts e.g. ListView or GridView. Here is the code I use to set it up in the Fragment:

    final LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
    layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
    mRecyclerView.setLayoutManager(layoutManager);

这在onCreateView方法中.当我收到网址时，我将其填充并使用以下命令设置适配器:

This is in the onCreateView method. When I get the urls I populate them and set the adapter using:

  myDataset[i] = imageURL; // for each image       
  mAdapter = new TestAdapter(myDataset);
  mRecyclerView.setAdapter(mAdapter);

有趣的是适配器的onBindViewHolder方法中的行，我在其中记录位置.我发现没有显示图像的单元格是未调用此方法.就像出于某种原因跳过了该单元格一样.甚至更陌生，如果我握住一个单元格并保持从左向右滑动，如果一个单元格离开屏幕然后又回来，它的图像就消失了，就像没有再次调用onBindViewHolder方法一样.

The interesting thing is the line in the onBindViewHolder method in the adapter, where I log the position. What I have found is that cells where the image is not shown is that this method is not being called. It is like it is skipping that cell for some reason. Even stranger, if I hold a cell and keep swiping from left to right, if a cell goes off screen and then comes back in, its image as gone as again the onBindViewHolder method is not called.

推荐答案

我认为不重要的一个类是引起问题的那个类.我不知道是什么原因，但是它驻留在自定义ImageView类中，该类是我从BitmapFun示例中获取的用于回收利用的.

The one class that I did not think would matter was the one that was causing the issue. I am not sure what the reason is, but it resides in a custom ImageView class that I am using for recycling that I got from the BitmapFun sample.

    public class RecyclingImageView extends ImageView {

    public RecyclingImageView(Context context) {
        super(context);
    }

    public RecyclingImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    /**
     * @see android.widget.ImageView#onAttachedToWindow()
     */
    @Override
    protected void onAttachedToWindow() {}

    /**
     * @see android.widget.ImageView#onDetachedFromWindow()
     */
    @Override
    protected void onDetachedFromWindow() {
        // This has been detached from Window, so clear the drawable

        setImageDrawable(null); 

        super.onDetachedFromWindow();
    }

    /**
     * @see android.widget.ImageView#setImageDrawable(android.graphics.drawable.Drawable)
     */
    @Override
    public void setImageDrawable(Drawable drawable) {
        // Keep hold of previous Drawable
        final Drawable previousDrawable = getDrawable();

        // Call super to set new Drawable
        super.setImageDrawable(drawable);

        // Notify new Drawable that it is being displayed
        notifyDrawable(drawable, true);

        // Notify old Drawable so it is no longer being displayed
        notifyDrawable(previousDrawable, false);
    }

    /**
     * Notifies the drawable that it's displayed state has changed.
     *
     * @param drawable
     * @param isDisplayed
     */
    private static void notifyDrawable(Drawable drawable, final boolean isDisplayed) {
        if (drawable instanceof RecyclingBitmapDrawable) {
            // The drawable is a CountingBitmapDrawable, so notify it
            ((RecyclingBitmapDrawable) drawable).setIsDisplayed(isDisplayed);
        } else if (drawable instanceof LayerDrawable) {
            // The drawable is a LayerDrawable, so recurse on each layer
            LayerDrawable layerDrawable = (LayerDrawable) drawable;
            for (int i = 0, z = layerDrawable.getNumberOfLayers(); i < z; i++) {
                notifyDrawable(layerDrawable.getDrawable(i), isDisplayed);
            }
        }
    }

}

当我用普通的ImageView替换它时，我不再遇到问题.

When I replace this with a normal ImageView, I no longer get the problem.

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