如何在安卓回收器视图中检测过度滚动

Question

我试图覆盖OverScrolled((，但它没有被触发：

public class MyRecyclerView extends RecyclerView {
    public MyRecyclerView(@NonNull Context context) {
        super(context);
    }
    public MyRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }
    public MyRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }
    @Override
    protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
        super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);
        Toast.makeText(getContext(), "overScrolled", Toast.LENGTH_SHORT).show();
    }
}

我的回收器视图已recyclerView.setOverScrollMode(View.OVER_SCROLL_ALWAYS);

Answer 1

试试这个来找到bottom overscroll和top overscroll

使用布局管理器查找bottom overscroll和top overscroll

import android.os.Bundle;
import java.util.ArrayList;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
public class MainActivity extends AppCompatActivity {
    RecyclerView myRecyclerView;
    ArrayList<String> arrayList = new ArrayList<>();
    DataAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myRecyclerView = findViewById(R.id.myRecyclerView);
        LinearLayoutManager linearLayoutManager= new LinearLayoutManager(this){
            @Override
            public int scrollVerticallyBy ( int dx, RecyclerView.Recycler recycler, RecyclerView.State state ) {
                int scrollRange = super.scrollVerticallyBy(dx, recycler, state);
                int overScroll = dx - scrollRange;
                if (overScroll > 0) {
                    Utils.printLog("NILU_PILU :-> BOTTOM OVERSCROLL");
                } else if (overScroll < 0) {
                    Utils.printLog("NILU_PILU :-> TOP OVERSCROLL");
                }
                return scrollRange;
            }
        };
        myRecyclerView.setLayoutManager(linearLayoutManager);
        myRecyclerView.setHasFixedSize(true);
        addDataToList();
        adapter = new DataAdapter(this, arrayList);
        myRecyclerView.setAdapter(adapter);
    }
    private void addDataToList() {
        for (int i = 0; i < 50; i++) {
            arrayList.add("NILU_PILU :-> " + i);
        }
    }
}

使用RecyclerView.addOnScrollListener()查找bottom overscroll

 myRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            if (dy > 0) {
                int pos = linearLayoutManager.findLastVisibleItemPosition();
                int numItems = myRecyclerView.getAdapter().getItemCount();
                if (pos >= numItems - 1 ) {
                    Utils.printLog("NILU_PILU :-> BOTTOM OVERSCROLL");
                }
            }
        }
    });

Answer 2

这是我在reddit上找到的解决方案：

而不是自定义回收器视图，您创建自定义 LinearLayoutManager 并覆盖布局管理器scrollVerticallyBy()方法并检查 dx/dy 减去超级实现返回的值是否为 ！= 0。然后发生了过度滚动。

@Override
public int scrollVerticallyBy ( int dx, RecyclerView.Recycler recycler, 
RecyclerView.State state ) {
    int scrollRange = super.scrollVerticallyBy(dx, recycler, state);
    int overscroll = dx - scrollRange;
    if (overscroll > 0) {
        // bottom overscroll
    } else if (overscroll < 0) {
        // top overscroll
    }
    return scrollRange;
}