Android如何设置两个view的Z order？

有的时候想让一个view出现在另一个view的上面，可以这样：

You can't use a LinearLayout for this, but you can use a FrameLayout. In a FrameLayout, the z-index is defined by the order in which the items are added, for example:

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    >
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/my_drawable"
        android:scaleType="fitCenter"
        />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|center"
        android:padding="5dp"
        android:text="My Label"
        />
</FrameLayout>

In this instance, the TextView would be drawn on top of the ImageView, along the bottom center of the image.