Question

我在RecyclerView上向上滚动时显示一个转到顶部的按钮。如果用户向上滚动，则显示按钮。

这是嵌套在RelativeLayout中的xml代码。

<android.support.v7.widget.RecyclerView
    android:id="@+id/userFeedsRecyclerView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>

<Button
    android:id="@+id/btn_goto_top"
    android:layout_width="30dp"
    android:layout_height="30dp"
    android:text="@string/icon_up_arrow"
    android:layout_alignParentBottom="true"
    android:layout_marginBottom="20dp"
    android:visibility="gone"
    android:textSize="10sp"
    android:layout_centerHorizontal="true"
    android:background="@drawable/round_button"/>

这是java代码

btnGotoTop = (Button) findViewById(R.id.btn_goto_top);
    Const.setTypeFace(btnGotoTop, getApplication());
    btnGotoTop.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            userFeedsRecyclerView.smoothScrollToPosition(0);
            view.setVisibility(View.GONE);
        }
    });


    userFeedsRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            super.onScrollStateChanged(recyclerView, newState);
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            if(dy < 0){
                btnGotoTop.setVisibility(View.VISIBLE);
            }
            else{
                btnGotoTop.setVisibility(View.GONE);
            }
        }
    });

在onClick()的{{1}}方法中，btnGotoTop正确滚动到顶部，但按钮不会消失。我尝试将RecyclerView更改为view.setVisibility(View.GONE)，但即使滚动完成后也会显示该按钮。

Answer 1

你的病情有误。您在滚动时可以看到按钮，但只想在向下滚动时显示。改变这个

if(dy < 0){
            btnGotoTop.setVisibility(View.VISIBLE);
        }
        else{
            btnGotoTop.setVisibility(View.GONE);
        }

到

if(dy > 0){
            btnGotoTop.setVisibility(View.VISIBLE);
        }
        else{
            btnGotoTop.setVisibility(View.GONE);
        }

Answer 2

试试这个，我还建议你在这里使用浮动动作按钮。我创建了一个简单的项目，以防你需要查看带有 FloatingActionButton 的recylerView，并且需要相同的功能。 Link.

    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
           if (dy > 0 && btnGotoTop.getVisibility() == View.VISIBLE) 
           {
                    btnGotoTop.hide();

           } else if (dy < 0 && btnGotoTop.getVisibility() != View.VISIBLE) 
           {
                    btnGotoTop.show();
           }

    }
});

Answer 3

DataFrame.stack()

使用private boolean IsRecyclerViewAtTop(){ if (userFeedsRecyclerView.getChildCount() == 0) return true; return userFeedsRecyclerView.getChildAt(0).getTop() == 0; } userFeedsRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() { @Override public void onScrollStateChanged(RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); if (IsRecyclerViewAtTop()) { btnGotoTop.setVisibility(View.GONE); } } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); if (dy < 0 && btnGotoTop.getVisibility()==View.GONE) { btnGotoTop.setVisibility(View.VISIBLE); } else if (dy > 0 && btnGotoTop.getVisibility()==View.VISIBLE){ btnGotoTop.setVisibility(View.GONE); } } });方法查看回收站视图是否滚动到顶部并调用它是IsRecyclerViewAtTop方法。

Answer 4

以下是我如何解决它。在RecyclerView的onScrollListener的onScrollStateChanged（）中更改了按钮的可见性

btnGotoTop.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(final View view) {
            userFeedsRecyclerView.smoothScrollToPosition(0);
            view.setVisibility(View.GONE);
            headerAppBarLayout.setExpanded(true);
        }
    });

private boolean isUserFeedRecyclerViewAtTop(){

    int numColumns = 2;
    int pos[] = new int[numColumns];
    ((StaggeredGridLayoutManager)(userFeedsRecyclerView.getLayoutManager())).findFirstCompletelyVisibleItemPositions(pos);
    return pos[0] == 0;
}

userFeedsRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            super.onScrollStateChanged(recyclerView, newState);
            switch (newState){
                case RecyclerView.SCROLL_STATE_IDLE:
                    if(isUserFeedRecyclerViewAtTop()) {
                        btnGotoTop.setVisibility(View.GONE);
                    }
                    break;
                case RecyclerView.SCROLL_STATE_DRAGGING:
                    break;
                case RecyclerView.SCROLL_STATE_SETTLING:
                    break;
            }
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            if(dy < 0 && btnGotoTop.getVisibility() == View.GONE){
                btnGotoTop.setVisibility(View.VISIBLE);
            }
            else if (dy > 0 && btnGotoTop.getVisibility() == View.VISIBLE){
                btnGotoTop.setVisibility(View.GONE);
            }
        }
    });

按钮不会因setVisibility（View.GONE）而消失

4 个答案: