1.介绍
(1)常识
(2)特点
2.实例演示
<1>新建drawable文件
app--->src---->main---->res---->drawable ,选中drawable文件夹，右击new--->drawable resource file
<2>xml文件代码
(1)layer1代码
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@android:id/background"
android:drawable="@drawable/grow"></item>
<item android:id="@android:id/progress"
android:drawable="@drawable/ok"></item>
</layer-list>
(2)layer2代码
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<bitmap android:src="@drawable/img1" android:gravity="center"></bitmap>
</item>
<!--注意：第二个item与第一个item有一定的间距（左边14dp,上边14dp）-->
<item android:left="14dp" android:top="14dp" >
<bitmap android:src="@drawable/img2" android:gravity="center"></bitmap>
</item>
<item android:left="28dp" android:top="28dp" >
<bitmap android:src="@drawable/img3" android:gravity="center"></bitmap>
</item>
</layer-list>
(3)主屏幕XML代码
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<SeekBar
android:id="@+id/seekBar"
android:progressDrawable="@drawable/layer1"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<ImageView
android:id="@+id/imageView"
android:layout_width="188dp"
android:layout_height="188dp"
app:srcCompat="@drawable/layer2" />
</LinearLayout>