自定义控件（视图）2期笔记13：View的滑动冲突之 内部拦截法

1. 内部拦截法：

父容器不拦截事件，所有的事件全部都传递给子元素，如果子元素需要此事件就直接消耗掉，否则就交给父容器进行处理。

这种方法和Android中的事件分发机制不一样，需要配合requestDisallowInterceptTouchEvent方法才能正常工作，使用起来较外部拦截法稍显负责一点。

我们需要重写子元素的dispatchTouchEvent方法。

这种方法的伪代码是：

  @Override
     public boolean dispatchTouchEvent(MotionEvent event) {
         int x = (int) event.getX();
         int y = (int) event.getY();

         switch (event.getAction()) {
         case MotionEvent.ACTION_DOWN: {
             parent.requestDisallowInterceptTouchEvent(true);
             break;
         }
         case MotionEvent.ACTION_MOVE: {
             int deltaX = x - mLastX;
             int deltaY = y - mLastY;
             if (父容器需要此类点击事件) {
                 parent.requestDisallowInterceptTouchEvent(false);
             }
             break;
         }
         case MotionEvent.ACTION_UP: {
             break;
         }
         default:
             break;
         }

         mLastX = x;
         mLastY = y;
         return super.dispatchTouchEvent(event);
     }

上面重写的子元素的dispatchTouchEvent方法，这里同时需要重写父容器的onInterceptTouchEvent方法，为什么呢？

那是因为ACTION_DOWN事件并不受FLAG_DISALLOW_INTERCEPT这个标记位的控制，所以一旦父容器拦截ACTION_DOWN事件，那么所有的事件都无法传递到子元素之中，这样内部拦截法就无法起作用了。

父容器所做的修改如下：

 @Override
     public boolean onInterceptTouchEvent(MotionEvent event) {

         int action = event.getAction();
         if (action == MotionEvent.ACTION_DOWN) {
             return false;
         } else {
             return true;
         }
     }

2. 下面通过一个Demo示例说明：

（1）首先我们创建一个Android工程，如下：

（2）首先我们来到主布局activity_main.xml，如下：

 <com.himi.viewconflict1.ui.RevealLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
     android:padding="12dp"
     tools:context="${relativePackage}.${activityClass}" >

     <Button
         android:id="@+id/button1"
         style="@style/AppTheme.Button.Green"
         android:onClick="onButtonClick"
         android:text="滑动冲突场景1-内部拦截" />

 </com.himi.viewconflict1.ui.RevealLayout>

（3）接下来来到MainActivity，如下：

 package com.himi.viewconflict;

 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.View;

 public class MainActivity extends Activity {

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

     public void onButtonClick(View view) {
          Intent intent = new Intent(this, DemoActivity_1.class);
          startActivity(intent);
     }
 }

（4）上面很自然地跳转到DemoActivity_2之中，如下：

 package com.himi.viewconflict1;

 import java.util.ArrayList;

 import com.himi.viewconflict1.ui.HorizontalScrollViewEx2;
 import com.himi.viewconflict1.ui.ListViewEx;
 import com.himi.viewconflict1.utils.MyUtils;

 import android.app.Activity;
 import android.graphics.Color;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.AdapterView;
 import android.widget.AdapterView.OnItemClickListener;
 import android.widget.ArrayAdapter;
 import android.widget.TextView;
 import android.widget.Toast;

 public class DemoActivity_2 extends Activity {
     private static final String TAG = "DemoActivity_2";

     private HorizontalScrollViewEx2 mListContainer;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.demo_2);
         Log.d(TAG, "onCreate");
         initView();
     }

     private void initView() {
         LayoutInflater inflater = getLayoutInflater();
         mListContainer = (HorizontalScrollViewEx2) findViewById(R.id.container);
         final int screenWidth = MyUtils.getScreenMetrics(this).widthPixels;
         final int screenHeight = MyUtils.getScreenMetrics(this).heightPixels;
         for (int i = 0; i < 3; i++) {
             ViewGroup layout = (ViewGroup) inflater.inflate(
                     R.layout.content_layout2, mListContainer, false);
             layout.getLayoutParams().width = screenWidth;
             TextView textView = (TextView) layout.findViewById(R.id.title);
             textView.setText("page " + (i + 1));
             layout.setBackgroundColor(Color
                     .rgb(255 / (i + 1), 255 / (i + 1), 0));
             createList(layout);
             mListContainer.addView(layout);
         }
     }

     private void createList(ViewGroup layout) {
         ListViewEx listView = (ListViewEx) layout.findViewById(R.id.list);
         ArrayList<String> datas = new ArrayList<String>();
         for (int i = 0; i < 50; i++) {
             datas.add("name " + i);
         }
         ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                 R.layout.content_list_item, R.id.name, datas);
         listView.setAdapter(adapter);
         listView.setHorizontalScrollViewEx2(mListContainer);
         listView.setOnItemClickListener(new OnItemClickListener() {
             @Override
             public void onItemClick(AdapterView<?> parent, View view,
                     int position, long id) {
                 Toast.makeText(DemoActivity_2.this, "click item "+position,
                         Toast.LENGTH_SHORT).show();

             }
         });
     }

     @Override
     public boolean dispatchTouchEvent(MotionEvent ev) {
         Log.d(TAG, "dispatchTouchEvent action:" + ev.getAction());
         return super.dispatchTouchEvent(ev);
     }

     @Override
     public boolean onTouchEvent(MotionEvent event) {
         Log.d(TAG, "onTouchEvent action:" + event.getAction());
         return super.onTouchEvent(event);
     }
 }

上面的DemoActivity_2主布局demo_2.xml，如下：

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="#ffffff"
     android:orientation="vertical" >

     <com.himi.viewconflict1.ui.HorizontalScrollViewEx2
         android:id="@+id/container"
         android:layout_width="wrap_content"
         android:layout_height="match_parent" />

 </LinearLayout>

上面使用到HorizontalScrollViewEx2是自定义控件（继承自ViewGroup），如下：

HorizontalScrollViewEx2是父容器，这里需要重写它的onInterceptTouchEvent方法，让父容器不拦截ACTION_DOWN事件。

 package com.himi.viewconflict1.ui;

 import android.content.Context;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.view.VelocityTracker;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Scroller;

 public class HorizontalScrollViewEx2 extends ViewGroup {
     private static final String TAG = "HorizontalScrollViewEx2";

     private int mChildrenSize;
     private int mChildWidth;
     private int mChildIndex;
     // 分别记录上次滑动的坐标
     private int mLastX = 0;
     private int mLastY = 0;

     // 分别记录上次滑动的坐标(onInterceptTouchEvent)
     private int mLastXIntercept = 0;
     private int mLastYIntercept = 0;

     private Scroller mScroller;
     private VelocityTracker mVelocityTracker;

     public HorizontalScrollViewEx2(Context context) {
         super(context);
         init();
     }

     public HorizontalScrollViewEx2(Context context, AttributeSet attrs) {
         super(context, attrs);
         init();
     }

     public HorizontalScrollViewEx2(Context context, AttributeSet attrs,
             int defStyle) {
         super(context, attrs, defStyle);
         init();
     }

     private void init() {
         mScroller = new Scroller(getContext());
         mVelocityTracker = VelocityTracker.obtain();
     }

     @Override
     public boolean onInterceptTouchEvent(MotionEvent event) {
         int x = (int) event.getX();
         int y = (int) event.getY();
         int action = event.getAction();
         if (action == MotionEvent.ACTION_DOWN) {
             mLastX = x;
             mLastY = y;
             if (!mScroller.isFinished()) {
                 mScroller.abortAnimation();
                 return true;
             }
             return false;
         } else {
             return true;
         }
     }

     @Override
     public boolean onTouchEvent(MotionEvent event) {
         Log.d(TAG, "onTouchEvent action:" + event.getAction());
         mVelocityTracker.addMovement(event);
         int x = (int) event.getX();
         int y = (int) event.getY();
         switch (event.getAction()) {
         case MotionEvent.ACTION_DOWN: {
             if (!mScroller.isFinished()) {
                 mScroller.abortAnimation();
             }
             break;
         }
         case MotionEvent.ACTION_MOVE: {
             int deltaX = x - mLastX;
             int deltaY = y - mLastY;
             Log.d(TAG, "move, deltaX:" + deltaX + " deltaY:" + deltaY);
             scrollBy(-deltaX, 0);
             break;
         }
         case MotionEvent.ACTION_UP: {
             int scrollX = getScrollX();
             int scrollToChildIndex = scrollX / mChildWidth;
             Log.d(TAG, "current index:" + scrollToChildIndex);
             mVelocityTracker.computeCurrentVelocity(1000);
             float xVelocity = mVelocityTracker.getXVelocity();
             if (Math.abs(xVelocity) >= 50) {
                 mChildIndex = xVelocity > 0 ? mChildIndex - 1 : mChildIndex + 1;
             } else {
                 mChildIndex = (scrollX + mChildWidth / 2) / mChildWidth;
             }
             mChildIndex = Math.max(0, Math.min(mChildIndex, mChildrenSize - 1));
             int dx = mChildIndex * mChildWidth - scrollX;
             smoothScrollBy(dx, 0);
             mVelocityTracker.clear();
             Log.d(TAG, "index:" + scrollToChildIndex + " dx:" + dx);
             break;
         }
         default:
             break;
         }

         mLastX = x;
         mLastY = y;
         return true;
     }

     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
         int measuredWidth = 0;
         int measuredHeight = 0;
         final int childCount = getChildCount();
         measureChildren(widthMeasureSpec, heightMeasureSpec);

         int widthSpaceSize = MeasureSpec.getSize(widthMeasureSpec);
         int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
         int heightSpaceSize = MeasureSpec.getSize(heightMeasureSpec);
         int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
         if (childCount == 0) {
             setMeasuredDimension(0, 0);
         } else if (heightSpecMode == MeasureSpec.AT_MOST) {
             final View childView = getChildAt(0);
             measuredHeight = childView.getMeasuredHeight();
             setMeasuredDimension(widthSpaceSize, childView.getMeasuredHeight());
         } else if (widthSpecMode == MeasureSpec.AT_MOST) {
             final View childView = getChildAt(0);
             measuredWidth = childView.getMeasuredWidth() * childCount;
             setMeasuredDimension(measuredWidth, heightSpaceSize);
         } else {
             final View childView = getChildAt(0);
             measuredWidth = childView.getMeasuredWidth() * childCount;
             measuredHeight = childView.getMeasuredHeight();
             setMeasuredDimension(measuredWidth, measuredHeight);
         }
     }

     @Override
     protected void onLayout(boolean changed, int l, int t, int r, int b) {
         Log.d(TAG, "width:" + getWidth());
         int childLeft = 0;
         final int childCount = getChildCount();
         mChildrenSize = childCount;

         for (int i = 0; i < childCount; i++) {
             final View childView = getChildAt(i);
             if (childView.getVisibility() != View.GONE) {
                 final int childWidth = childView.getMeasuredWidth();
                 mChildWidth = childWidth;
                 childView.layout(childLeft, 0, childLeft + childWidth,
                         childView.getMeasuredHeight());
                 childLeft += childWidth;
             }
         }
     }

     private void smoothScrollBy(int dx, int dy) {
         mScroller.startScroll(getScrollX(), 0, dx, 0, 500);
         invalidate();
     }

     @Override
     public void computeScroll() {
         if (mScroller.computeScrollOffset()) {
             scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
             postInvalidate();
         }
     }

     @Override
     protected void onDetachedFromWindow() {
         mVelocityTracker.recycle();
         super.onDetachedFromWindow();
     }
 }

（5）来到主布局之中，在HorizontalScrollViewEx2之中包含一个子布局content_layout2.xml，如下：

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

     <TextView
         android:id="@+id/title"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginTop="5dp"
         android:layout_marginBottom="5dp"
         android:text="TextView" />

     <com.himi.viewconflict1.ui.ListViewEx
         android:id="@+id/list"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:background="#fff4f7f9"
         android:cacheColorHint="#00000000"
         android:divider="#dddbdb"
         android:dividerHeight="1.0px"
         android:listSelector="@android:color/transparent" />

 </LinearLayout>

上面的ListViewEx是自定义的控件（继承自ListView），在ListViewEx里面实现了内部拦截法的逻辑，如下：

 package com.himi.viewconflict1.ui;

 import android.content.Context;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.widget.ListView;

 public class ListViewEx extends ListView {
     private static final String TAG = "ListViewEx";

     private HorizontalScrollViewEx2 mHorizontalScrollViewEx2;

     // 分别记录上次滑动的坐标
     private int mLastX = 0;
     private int mLastY = 0;

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

     public ListViewEx(Context context, AttributeSet attrs) {
         super(context, attrs);
     }

     public ListViewEx(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
     }

     public void setHorizontalScrollViewEx2(
             HorizontalScrollViewEx2 horizontalScrollViewEx2) {
         mHorizontalScrollViewEx2 = horizontalScrollViewEx2;
     }

     @Override
     public boolean dispatchTouchEvent(MotionEvent event) {
         int x = (int) event.getX();
         int y = (int) event.getY();

         switch (event.getAction()) {
         case MotionEvent.ACTION_DOWN: {
             mHorizontalScrollViewEx2.requestDisallowInterceptTouchEvent(true);
             break;
         }
         case MotionEvent.ACTION_MOVE: {
             int deltaX = x - mLastX;
             int deltaY = y - mLastY;
             Log.d(TAG, "dx:" + deltaX + " dy:" + deltaY);
             if (Math.abs(deltaX) > Math.abs(deltaY)) {
                 mHorizontalScrollViewEx2.requestDisallowInterceptTouchEvent(false);
             }
             break;
         }
         case MotionEvent.ACTION_UP: {
             break;
         }
         default:
             break;
         }

         mLastX = x;
         mLastY = y;
         return super.dispatchTouchEvent(event);
     }

 }

void  requestDisallowInterceptTouchEvent（boolean  disallowIntercept）：

这个方法的入参一个boolean 变量，用来表示是否需要调用onInterceptTouchEvent来判断是否拦截.

该标记如果为True，就如它的字面意思一样---不允许调用onInterceptTouchEvent()，结果就是，所有的父类方法都不会进行拦截，而把事件传递给子View. 该方法属于ViewGroup ，并且是个递归方法，也就是说一旦调用后，所有父类的disallowIntercept都会设置成True。即当前View的所有父类View，都不会调用自身的onInterceptTouchEvent()进行拦截。

该标记如果为False，就如它的字面意思一样---允许调用onInterceptTouchEvent()，结果就是，父类可以拦截事件。

接下来，来到Listview的Item布局content_list_item.xml，如下：

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="50dp"
     android:gravity="center_vertical"
     android:orientation="vertical" >

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

 </LinearLayout>

（6）最终项目如下：

（7）部署程序到手机上，如下：

3. 示例源码下载