检查 smoothScrollToPosition 何时完成

Question

我想检查

smoothScrollToPosition

何时完成滚动回

recyclerview

的第一项。我尝试这样做，只有当 smoothScrollToPosition 仍在滚动时才有效：

recyclerView.getLayoutManager().smoothScrollToPosition(recyclerView,new RecyclerView.State(), 0);
if (!recyclerView.getLayoutManager().isSmoothScrolling()) {
    Log.d(TAG, "Scrolling has ended.");
} 

Answer 1

我使用

onScrollStateChanged(RecyclerView recyclerView, int newState)

方法来跟踪滚动状态。启动滚动的方法如下所示：

private void scrollToPosition(int position){
    recyclerView.removeOnScrollListener(onScrollListener);
    recyclerView.addOnScrollListener(onScrollListener);
    recyclerView.smoothScrollToPosition(position);
}

这是听众：

RecyclerView.OnScrollListener onScrollListener = new RecyclerView.OnScrollListener() {
       @Override
       public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
           switch (newState) {
               case SCROLL_STATE_IDLE:
                   //we reached the target position
                   recyclerView.removeOnScrollListener(this);
                   break;
           }
       }
   };

所以，当recyclerView达到SCROLL_STATE_IDLE时，就意味着它已经完成滚动。不要忘记在这种状态下删除侦听器，这样它就不会在下一次滚动时触发。

Answer 2

您可以自定义

LinearLayoutManager

来实现

onStop

回调

public class XLinearLayoutManager extends LinearLayoutManager {
    private OnLayoutManagerListener mListener;

    public interface OnLayoutManagerListener {
        void onSmoothScrollStopped();
    }

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

    public void setLayoutManagerListener(OnLayoutManagerListener listener) {
        mListener = listener;
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        // super.smoothScrollToPosition(recyclerView, state, position);
        // clone super.smoothScrollToPosition and add onStop callback
        final LinearSmoothScroller linearSmoothScroller = new LinearSmoothScroller(recyclerView.getContext()) {
            @Override
            protected void onStop() {
                super.onStop();
                if (mListener != null) {
                    mListener.onSmoothScrollStopped();
                }
            }
        };
        linearSmoothScroller.setTargetPosition(position);
        startSmoothScroll(linearSmoothScroller);
    }
}

并在调用平滑滚动之前实现监听器

// setup LayoutManager for RecyclerView
final XLinearLayoutManager layoutManager = new XLinearLayoutManager(context);
recyclerView.setLayoutManager(layoutManager);

// call smoothScrollToPosition
layoutManager.setLayoutManagerListener(new OnLayoutManagerListener() {
    @Override
    public void onSmoothScrollStopped() {
        //TODO: smoothScrollToPosition finished
    }
});
recyclerView.smoothScrollToPosition(position);

Answer 3

有一个监听器：

https://developer.android.com/reference/android/support/v7/widget/RecyclerView.OnScrollListener

void onScrolled (RecyclerView recyclerView, 
                int dx, 
                int dy)

RecyclerView 滚动时调用的回调方法。 滚动完成后将调用此函数。