Question

因此，我尝试实现一个FAB按钮，以便当我滚动回收器视图且第一项不可见（向上滚动等）时，fab按钮应可见，否则，如果第一个位置为，则应将其隐藏显示。现在我已经实现了代码，但是它根本不显示fab按钮，只是想知道我在做什么错了？

我的xml代码如下：

<Linearlayout ....


    <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        <android.support.v4.widget.SwipeRefreshLayout
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/pullToRefreshLayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

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

        </android.support.v4.widget.SwipeRefreshLayout>

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/emailFab"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="16dp"
                android:src="@android:drawable/ic_dialog_email"
                app:layout_anchor="@id/myRecyclerView"
                android:layout_gravity="bottom|end"
                app:layout_behavior="com.example.fab.ScrollAwareFABBehavior"
                app:layout_anchorGravity="bottom|end"
                />
        </FrameLayout>

</LinearLayout>

我的Kotlin代码如下：

val positionView = (myRecyclerView.getLayoutManager() as LinearLayoutManager).findFirstVisibleItemPosition()

myRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                super.onScrolled(recyclerView, dx, dy)
                if (dy >0 && positionView > 0) {
                    emailFab.show();
                } else  {
                    emailFab.hide();
                }
            }

有什么想法怎么做吗？

谢谢！

Answer 1

我认为问题在于，您应该将findFirstVisibleItemPosition()拉入OnScrollListener以在滚动更改中找到可见的位置：

myRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {

        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            super.onScrolled(recyclerView, dx, dy)

            val positionView = (myRecyclerView.getLayoutManager() as LinearLayoutManager).findFirstVisibleItemPosition()

            if (positionView > 0) {
                if(!emailFab.isShown) {
                    emailFab.show();
                }
            } else  {
                if(emailFab.isShown) {
                    emailFab.hide();
                }
            }
        }
    })

Answer 2

此代码可以100％正常工作

public class TestActivity extends AppCompatActivity {

private static final String TAG = "TestActivity";

private ArrayList<String> datas = new ArrayList<>();

private FloatingActionButton fabButton;
private RecyclerView recyclerView;
private LinearLayoutManager linearLayoutManager;
private DataAdapter dataAdapter;

private boolean isFabVisible = false;

private OnFabVisibilityCallback onFabVisibilityCallback;

public void setOnFabVisibilityCallback(OnFabVisibilityCallback onFabVisibilityCallback) {
    this.onFabVisibilityCallback = onFabVisibilityCallback;
}

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test_contacts);

    datas.add("one");
    datas.add("two");
    datas.add("three");
    datas.add("four");
    datas.add("five");
    datas.add("six");
    datas.add("seven");
    datas.add("eight");
    datas.add("nine");
    datas.add("ten");

    fabButton = (FloatingActionButton)findViewById(R.id.fabButton);
    fabButton.setVisibility(View.GONE);
    recyclerView = (RecyclerView)findViewById(R.id.recyclerView);
    linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
    recyclerView.setLayoutManager(linearLayoutManager);
    dataAdapter = new DataAdapter(this, datas);
    recyclerView.setAdapter(dataAdapter);


    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {

            if(linearLayoutManager.findFirstVisibleItemPosition() == 0){
                //hide
                if(onFabVisibilityCallback != null){
                    onFabVisibilityCallback.onChange(false);
                }
            }else{
                //show
                if(onFabVisibilityCallback != null){
                    onFabVisibilityCallback.onChange(true);
                }
            }

        }
    });

    setOnFabVisibilityCallback(new OnFabVisibilityCallback() {
        @Override
        public void onChange(boolean isVisible) {
            if(isVisible){
                if(!isFabVisible){
                    isFabVisible = true;
                    fabButton.setVisibility(View.VISIBLE);
                }
            }else{
                if(isFabVisible){
                    isFabVisible = false;
                    fabButton.setVisibility(View.GONE);
                }
            }
        }
    });

}

private class DataAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{

    private Activity activity;
    private ArrayList<String> datas;
    private LayoutInflater layoutInflater;

    public DataAdapter(Activity activity, ArrayList<String> datas) {
        this.activity = activity;
        this.datas = datas;
        this.layoutInflater = LayoutInflater.from(activity);
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new SimpleViewHolder(layoutInflater.inflate(R.layout.unit_test, parent, false));
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        ((SimpleViewHolder)holder).init(datas.get(position));
    }

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

    private class SimpleViewHolder extends RecyclerView.ViewHolder{

        private TextView text;

        public SimpleViewHolder(View itemView) {
            super(itemView);
            initViews(itemView);
        }

        private void initViews(View v){
            text = (TextView)v.findViewById(R.id.text);
        }

        public void init(String data){
            text.setText(data);
        }

    }

}

public interface OnFabVisibilityCallback{

    void onChange(boolean isVisible);

}

}

活动布局文件

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fabButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_margin="16dp"
        android:src="@drawable/ic_add_black_24dp"
        android:tint="@color/white" />

</RelativeLayout>

这是recyclerview的子布局

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:gravity="center"
    android:background="@color/yellow"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="150dp">

    <TextView
        android:text="data"
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

如果发生一些问题，leme知道:) 快乐的编码

当看不到“回收者”视图中的第一项时，如何滚动显示我的晶圆厂，但是当第一项可见时，如何隐藏我的晶圆厂？

2 个答案: