dispatchDraw()和onDraw()的区别

onDraw()先于dispatchDraw()执行,用于本身控件的绘制,dispatchDraw()用于子控件的绘制

onDraw()绘制的内容可能会被子控件覆盖而dispatchDraw()是子控件的绘制,所以是覆盖在onDraw()上的

布局:

    <? version=\"1.0\" encoding=\"utf-8\"?>
    <LinearLayout ns:android=\"http://schemas.android.com/apk/res/android\"
        ns:tools=\"http://schemas.android.com/tools\"
        android:layout_width=\"match_parent\"
        android:layout_height=\"match_parent\"
        android:orientation=\"vertical\"
        tools:context=\".MainActivity\">
        <com.example.myviewpage.ViewPagerIndicator
            android:layout_width=\"match_parent\"
            android:layout_height=\"50dp\"
            android:background=\"#999999\"
            android:id=\"@+id/main_vpi\">
            <TextView
                android:layout_width=\"0dp\"
                android:layout_height=\"match_parent\"
                android:layout_weight=\"1\"
                android:text=\"标题1\"
                android:background=\"#f00\"
                android:gravity=\"center\"/>
            <TextView
                android:layout_width=\"0dp\"
                android:layout_height=\"match_parent\"
                android:layout_weight=\"1\"
                android:text=\"标题2\"
                android:gravity=\"center\"/>
            <TextView
                android:layout_width=\"0dp\"
                android:layout_height=\"match_parent\"
                android:layout_weight=\"1\"
                android:text=\"标题3\"
                android:gravity=\"center\"/>
        </com.example.myviewpage.ViewPagerIndicator>
        <android.support.v4.view.ViewPager
            android:layout_width=\"match_parent\"
            android:layout_height=\"match_parent\"
            android:id=\"@+id/mian_vp\"/>
    </LinearLayout>

ViwPagerIndicator是继承自LinearLayout的自定义控件目的是绘制一个三角形的指示器

ViwPagerIndicator使用dispatchDraw():

@Override
protected void dispatchDraw(Canvas canvas) {
    super.dispatchDraw(canvas);
    canvas.save();
    canvas.translate(minitTrianslationX+mTrianslationX,getHeight());
    canvas.drawPath(path,paint);
    canvas.restore();
    Log.i(TAG, \"dispatchDraw: \");
}

效果:

ViwPagerIndicator使用onDraw():

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.save();
    canvas.translate(minitTrianslationX+mTrianslationX,getHeight());
    canvas.drawPath(path,paint);
    canvas.restore();
    Log.i(TAG, \"onDraw: \");
}

效果:

可以看出,这种情况是应该使用dispatchDraw()保证绘制的内容不被子控件覆盖
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作者：久不见天晴  
来源：CSDN  
原文：https://blog.csdn.net/qq_34888942/article/details/80192848  
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