android 控件绘图和触摸事件分发

布局文件：GroupView继承了FrameLayout，其中层叠了两个View

<com.example.textdemo.view.DTGroupView
        android:id="@+id/dTGroupView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <com.example.textdemo.view.DTView
            android:id="@+id/dTView1"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

        <com.example.textdemo.view.DTView1
            android:id="@+id/dTView2"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </com.example.textdemo.view.DTGroupView>

public class DTGroupView extends FrameLayout{
	
	public DTGroupView(Context context) {
		super(context);
	}
	
	public DTGroupView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public DTGroupView(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
	}
	
	@Override
	public boolean dispatchTouchEvent(MotionEvent ev) {
		Log.i("dt", "group+++dispatchTouchEvent");
		return super.dispatchTouchEvent(ev);
	}
	
	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		Log.i("dt", "group+++onInterceptTouchEvent");
		return super.onInterceptTouchEvent(ev);
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		Log.i("dt", "group+++onTouchEvent");
		return super.onTouchEvent(event);
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		Log.i("dt", "group+++onLayout");
		getChildAt(0).layout(l, t, r, b);
		getChildAt(1).layout(l, t, r, b);
	}
	
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		Log.i("dt", "group+++onMeasure");
		getChildAt(0).measure(widthMeasureSpec, heightMeasureSpec);
		getChildAt(1).measure(widthMeasureSpec, heightMeasureSpec);
	}
	
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		Log.i("dt", "group+++onDraw");
	}

}

先研究一下绘图方法，日志如下：

03-07 11:15:41.032 4975 4975 I dt : DTView+++onMeasure

03-07 11:15:41.032 4975 4975 I dt : DTView1+++onMeasure

03-07 11:15:41.032 4975 4975 I dt : group+++onMeasure

03-07 11:15:41.032 4975 4975 I dt : DTView+++onMeasure

03-07 11:15:41.032 4975 4975 I dt : DTView1+++onMeasure

03-07 11:15:41.035 4975 4975 I dt : group+++onLayout

03-07 11:15:41.035 4975 4975 I dt : DTView+++onLayout

03-07 11:15:41.035 4975 4975 I dt : DTView1+++onLayout

03-07 11:15:41.054 4975 4975 I dt : DTView+++onDraw

03-07 11:15:41.055 4975 4975 I dt : DTView1+++onDraw

对比代码我们很好理解，Measure测量方法，从ViewGroup中getChildAt(0)开始测量，然后测量完控件之后，测量ViewGroup本身（多出的测量方法是由于我在代码中调用了一次），Layout布局方法是从最下层空间逐级往上执行。

03-07 11:16:38.609 4975 4975 I dt : group+++dispatchTouchEvent

03-07 11:16:38.611 4975 4975 I dt : group+++onInterceptTouchEvent

03-07 11:16:38.614 4975 4975 I dt : DTView1+++dispatchTouchEvent

03-07 11:16:38.615 4975 4975 I dt : DTView1+++onTouchEvent

03-07 11:16:38.615 4975 4975 I dt : DTView+++dispatchTouchEvent

03-07 11:16:38.615 4975 4975 I dt : DTView+++onTouchEvent

03-07 11:16:38.616 4975 4975 I dt : group+++onTouchEvent

触摸事件分发机制：首先理解ViewGroup包含dispatch/intercept/onTouchEvent，而View只包含dispatch/onTouchEvent；看日志，dispatch最先执行，然后是onIntercept,如果没有被打断，才继续派发给子控件，子控件最上层首先接收事件，执行dispatch然后onTouch，然后如果返回false则继续派发给下层控件，

android 控件绘图和触摸事件分发

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