MeasureSpec 的三中类型

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <!--  -->

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="100dp" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="100dp" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="100dp" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="100dp" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="100dp" >

        <com.example.test.MeasTestLayout
            android:layout_width="match_parent"
            android:layout_height="50dp" >
        </com.example.test.MeasTestLayout>
    </FrameLayout>

</FrameLayout>

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // TODO Auto-generated method stub
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        
        
        print(widthMeasureSpec, heightMeasureSpec);
    }
    
    private void print(int widthMeasureSpec, int heightMeasureSpec){
        int widthMode    = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode    = MeasureSpec.getMode(heightMeasureSpec);
        log("begin>>>");
        log("width    -- mode: "+getMode(widthMode) +" size: "+MeasureSpec.getSize(widthMeasureSpec));
        log("height    -- mode: "+getMode(heightMode) +" size: "+MeasureSpec.getSize(heightMeasureSpec));
        log("<<<");
    }

11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: AT_MOST size: 1599->1467
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: AT_MOST size: 1599->1467
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: EXACTLY size: 275
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: EXACTLY size: 1599->1467
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: AT_MOST size: 1599->1467
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: EXACTLY size: 275
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: EXACTLY size: 275
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: AT_MOST size: 275
11-16 15:19:27.155: D/View(8127): measure: <<<
11-16 15:19:27.155: D/View(8127): measure: begin>>>
11-16 15:19:27.155: D/View(8127): measure: width    -- mode: EXACTLY size: 1080
11-16 15:19:27.155: D/View(8127): measure: height    -- mode: EXACTLY size: 138
11-16 15:19:27.155: D/View(8127): measure: <<<

结论：1、自定义控件中的onMeasure方法接收的参数的Mode与它的父控件的w、h以及它自身的宽高有关
     2、如果自定义控件自身的高度为固定的dp值，传入的参数的mode一定是EXACTLY
     3、如果自定义控件自身的高度为wrap_content，传入的参数的mode一定是AT_MOST
     4、如果自定义控件自身的高度为match_parent,其父控件的高度为固定dp值，传入的参数的mode一定是EXACTLY
     5、如果自定义控件自身的高度为match_parent,其父控件的高度为wrap_content，传入的参数的mode一定是AT_MOST
     6、如果自定义控件自身的高度为match_parent,其父控件的高度为match_parent，传入的参数的mode依赖更上层的父控件，并且可能在多次onMeasure中变化
     7、MeasureSpec.UNSPECIFIED是未指定尺寸，这种情况不多，一般都是父控件是AdapterView，通过measure方法传入的模式。