java - FragmentStatePagerAdapter 与 Glide 一起使用会导致 NullPointerException

Question

一些背景:

我使用 FragmentStatePagerAdapter 来实现可变数量 fragment 的水平滑动 View 。需要澄清的是， fragment 的数量取决于一些外部数据。由于这种情况，并且 fragment 的数量可能非常大，因此我无法使用适配器的 setOffScreenPageLimit() 方法。

现在，解决问题:

我正在使用 Glide 从网络检索图像列表并将它们显示在我的 fragment 上。这对于第一个 fragment 和第二个 fragment 都适用(因为 setOffScreenPageLimit() 默认为 1)。

但是，第三个 fragment 超出了 setOffScreenPageLimit() 范围。当我尝试检索此 fragment 中的图像时，我从某个调用 fragment 上的 getView() 的内部 Glide 方法中收到 NullPointerException(显然为 null)。我已经确认这实际上是问题所在，例如，当我将离屏限制设置为 4 时，当我尝试检索第 5 个 fragment 上的图像时，应用程序崩溃了。

这是我的 logcat 输出:

 java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.v4.app.Fragment.getView()' on a null object reference
                                                                          at com.bumptech.glide.manager.RequestManagerRetriever.findAllSupportFragmentsWithViews(RequestManagerRetriever.java:189)
                                                                          at com.bumptech.glide.manager.RequestManagerRetriever.findSupportFragment(RequestManagerRetriever.java:200)
                                                                          at com.bumptech.glide.manager.RequestManagerRetriever.get(RequestManagerRetriever.java:167)
                                                                          at com.bumptech.glide.Glide.with(Glide.java:609)
                                                                          at com.android.miki.quickly.GIFRecyclerAdapter.onViewRecycled(GIFRecyclerAdapter.java:51)
                                                                          at com.android.miki.quickly.GIFRecyclerAdapter.onViewRecycled(GIFRecyclerAdapter.java:17)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.dispatchViewRecycled(RecyclerView.java:6056)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.addViewHolderToRecycledViewPool(RecyclerView.java:5827)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.recycleViewHolderInternal(RecyclerView.java:5792)
                                                                          at android.support.v7.widget.RecyclerView$LayoutManager.scrapOrRecycleView(RecyclerView.java:8462)
                                                                          at android.support.v7.widget.RecyclerView$LayoutManager.detachAndScrapAttachedViews(RecyclerView.java:8447)
                                                                          at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:563)
                                                                          at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3583)
                                                                          at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3312)
                                                                          at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3844)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
                                                                          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
                                                                          at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1795)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
                                                                          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
                                                                          at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
                                                                          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
                                                                          at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
                                                                          at android.view.View.layout(View.java:17637)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5575)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:261)

以下是 GIFRecyclerAdapter 类:

  public class GIFRecyclerAdapter extends RecyclerView.Adapter<GIFRecyclerAdapter.GifViewHolder>{


    private List<String> gifURLs;

    public GIFRecyclerAdapter(List<String> gifURLs) {
        this.gifURLs = gifURLs;
    }

    @Override
    public GifViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_gif, parent, false);
        GifViewHolder vh = new GifViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(GifViewHolder holder, int position) {
        holder.setGif(gifURLs.get(position));
    }

    @Override
    public int getItemCount() {
        return gifURLs.size();
    }

    public void setURLs(List<String> gifURLs) {
        this.gifURLs = gifURLs;
    }

    @Override
    public void onViewRecycled(GifViewHolder holder){
        super.onViewRecycled(holder);
        Glide.with(holder.itemView).clear(holder.mImageViewGif);
    }


    protected class GifViewHolder extends RecyclerView.ViewHolder {

        private ImageView mImageViewGif;

        private GifViewHolder(View itemView) {
            super(itemView);
            mImageViewGif = (ImageView) itemView.findViewById(R.id.gif_image_view);
        }

        private void setGif(String gifURL) {
            try{
                Glide.with(this.itemView).load(gifURL).into(mImageViewGif);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }



}

任何人都可以给我一些关于为什么会发生这种情况的提示吗？该 fragment 出现在屏幕上，并且 UI 的其余部分工作正常(可以按下按钮等)。但是，使用 Glide 加载图像会使应用程序崩溃。我有一种感觉，这是某种生命周期细节，与 FragmentStatePagerAdapter 如何创建和销毁 fragment 有关，但我不确定。

非常任何帮助。

Answer 1

我认为Glide.with(this.itemView)这一行有问题。

只需将上下文从 Activity 传递到适配器并使用它来代替 this.itemView

另一个快速解决方法可能是Glide.with(mImageView.getContext())

祝你好运

埃姆雷