Android开发ViewDragHelper+ListView解决事件分发滑动冲突

点击链接查看效果图：

https://s19.aconvert.com/convert/p3r68-cdx67/8ettg-eeb7q.gif

1，首先新建一个类，继承自FramLayout:

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AbsListView;
import android.widget.FrameLayout;

/**
 * Created by yly on 2019/6/29.
 */

public class VerticalDragListView extends FrameLayout {

    // 可以认为这是系统给我们写好的一个工具类
    private ViewDragHelper mDragHelper;

    private View mDragListView;
    // 后面菜单的高度
    private int mMenuHeight;
    // 菜单是否打开
    private boolean mMenuIsOpen = false;

    public VerticalDragListView(Context context) {
        this(context, null);
    }

    public VerticalDragListView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public VerticalDragListView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mDragHelper = ViewDragHelper.create(this, mDragHelperCallback);
    }

    /*@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        View menuView = getChildAt(0);
        mMenuHeight = menuView.getMeasuredHeight();
    }*/

    /*@Override
    public void addView(View child) {
        super.addView(child);
    }*/

    /*@Override
    public void setVisibility(int visibility) {
        super.setVisibility(visibility);
    }*/

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (changed) {
            View menuView = getChildAt(0);
            mMenuHeight = menuView.getMeasuredHeight();
        }
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();

        int childCount = getChildCount();
        if (childCount != 2) {
            throw new RuntimeException("VerticalDragListView 只能包含两个子布局");
        }

        mDragListView = getChildAt(1);


        /*View menuView = getChildAt(0);
        mMenuHeight = menuView.getMeasuredHeight();*/
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mDragHelper.processTouchEvent(event);
        // Log.e("TAG", "onTouchEvent -> " + event.getAction());
        return true;
    }

    // 1.拖动我们的子View
    private ViewDragHelper.Callback mDragHelperCallback = new ViewDragHelper.Callback() {
        @Override
        public boolean tryCaptureView(View child, int pointerId) {
            // 指定该子View是否可以拖动，就是 child
            // 只能是列表可以拖动
            // 2.1 后面不能拖动
            return mDragListView == child;
        }

        @Override
        public int clampViewPositionVertical(View child, int top, int dy) {
            // 垂直拖动移动的位置
            // 2.3 垂直拖动的范围只能是后面菜单 View 的高度
            if (top <= 0) {
                top = 0;
            }

            if (top >= mMenuHeight) {
                top = mMenuHeight;
            }
            return top;
        }


        // 2.2 列表只能垂直拖动
        /*@Override
        public int clampViewPositionHorizontal(View child, int left, int dx) {
            // 水平拖动移动的位置
            return left;
        }*/

        // 2.4 手指松开的时候两者选其一，要么打开要么关闭
        @Override
        public void onViewReleased(View releasedChild, float xvel, float yvel) {
            // Log.e("TAG", "yvel -> " + yvel + " mMenuHeight -> " + mMenuHeight);
            // Log.e("TAG", "top -> " + mDragListView.getTop());
            if (releasedChild == mDragListView) {
                if (mDragListView.getTop() > mMenuHeight / 2) {
                    // 滚动到菜单的高度（打开）
                    mDragHelper.settleCapturedViewAt(0, mMenuHeight);
                    mMenuIsOpen = true;
                } else {
                    // 滚动到0的位置（关闭）
                    mDragHelper.settleCapturedViewAt(0, 0);
                    mMenuIsOpen = false;
                }
                invalidate();
            }
        }
    };

    // 现象就是ListView可以滑动，但是菜单滑动没有效果了
    private float mDownY;

    // ecause ACTION_DOWN was not received for this pointer before ACTION_MOVE
    // VDLV.onInterceptTouchEvent().DOWN -> LV.onTouch() ->
    // VDLV.onInterceptTouchEvent().MOVE -> VDLV.onTouchEvent().MOVE

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        // 菜单打开要拦截
        if (mMenuIsOpen) {
            return true;
        }

        // 向下滑动拦截，不要给ListView做处理
        // 谁拦截谁 父View拦截子View ，但是子 View 可以调这个方法
        // requestDisallowInterceptTouchEvent 请求父View不要拦截，改变的其实就是 mGroupFlags 的值
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mDownY = ev.getY();
                // 让 DragHelper 拿一个完整的事件
                mDragHelper.processTouchEvent(ev);
                break;
            case MotionEvent.ACTION_MOVE:
                float moveY = ev.getY();
                if ((moveY - mDownY) > 0 && !canChildScrollUp()) {
                    // 向下滑动 && 滚动到了顶部，拦截不让ListView做处理
                    return true;
                }
                break;
        }

        return super.onInterceptTouchEvent(ev);
    }

    /**
     * @return Whether it is possible for the child view of this layout to
     * scroll up. Override this if the child view is a custom view.
     * 判断View是否滚动到了最顶部,还能不能向上滚
     */
    public boolean canChildScrollUp() {
        if (android.os.Build.VERSION.SDK_INT < 14) {
            if (mDragListView instanceof AbsListView) {
                final AbsListView absListView = (AbsListView) mDragListView;
                return absListView.getChildCount() > 0
                        && (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0)
                        .getTop() < absListView.getPaddingTop());
            } else {
                return ViewCompat.canScrollVertically(mDragListView, -1) || mDragListView.getScrollY() > 0;
            }
        } else {
            return ViewCompat.canScrollVertically(mDragListView, -1);
        }
    }

    /**
     * 响应滚动
     */
    @Override
    public void computeScroll() {
        if (mDragHelper.continueSettling(true)) {
            invalidate();
        }
    }
}

2,activity_main文件：

<?xml version="1.0" encoding="utf-8"?>
<com.example.myproject.VerticalDragListView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:text="这是内容"
        android:gravity="center"
        android:background="#e4e7a1"/>
    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:background="#0ae215"
        />

</com.example.myproject.VerticalDragListView>

3，MainActivity：

import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {

    private ListView listView;
    private List<String> mStringList;

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

        listView=findViewById(R.id.list_view);
        mStringList=new ArrayList<>();
        for (int i=0;i<30;i++){
            mStringList.add("这是内容列表");
        }
        listView.setAdapter(new BaseAdapter() {
            @Override
            public int getCount() {
                return mStringList.size();
            }

            @Override
            public Object getItem(int position) {
                return mStringList.get(position);
            }

            @Override
            public long getItemId(int position) {
                return 0;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                ViewHolder viewHolder;
                if (convertView==null){
                    viewHolder=new ViewHolder();
                    convertView= LayoutInflater.from(MainActivity.this).inflate(R.layout.item_layout,parent,false);
                    viewHolder.mTextView=convertView.findViewById(R.id.item_text);
                    convertView.setTag(viewHolder);
                }else {
                    viewHolder= (ViewHolder) convertView.getTag();
                }

                viewHolder.mTextView.setText(mStringList.get(position));
                return convertView;
            }
        });


    }

    class ViewHolder{
        private TextView mTextView;
    }
}

4.item_layout.xml文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="40dp">
    <TextView
        android:id="@+id/item_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:gravity="center"
        android:textSize="14sp"
        android:textColor="#09a"/>

</LinearLayout>