java - 除非刷新，否则 RecyclerAdapter 不会加载数据

Question

这是我在主 FeedActivity 中初始化适配器的方式:

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setHasFixedSize(true);
FeedAdapter adapter = new FeedAdapter(FeedActivity.this, retrieveYeets());
recyclerView.setAdapter(adapter);

这是我的错误:

java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
    at com.yitter.feed.FeedAdapter.getItemCount(FeedAdapter.java:478)
    at android.support.v7.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:3170)
    at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3067)
    at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3518)
    at android.view.View.layout(View.java:16636)
    at android.view.ViewGroup.layout(ViewGroup.java:5437)
    at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:598)
    at android.view.View.layout(View.java:16636)
    at android.view.ViewGroup.layout(ViewGroup.java:5437)
    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:107

它提示我的 FeedAdapter 中的以下代码:

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

我不知道为什么我的列表是空的。显然，我的列表中有一个 NullPointerException ，但它并不明显。这可能与我的列表中元素的位置有关。有人有建议吗？

Answer 1

我认为问题就出在这里

public FeedAdapter(Context context, List<ParseObject> yeets) {
        super();

        mYeets = yeets;
        mContext = context;
        this.adapter = this;

        profilePictureImageLoader = new ImageLoader(new ProfilePictureFileCache(mContext));
    }

你忘记在开头附加“this”

public FeedAdapter(Context context, List<ParseObject> yeets) {
        super();

        this.mYeets = yeets;
        this.mContext = context;
        this.adapter = this;

        profilePictureImageLoader = new ImageLoader(new ProfilePictureFileCache(mContext));
    }