LevelListDrawable 用于管理一组 Drawable

可以为里面的 drawable 设置不同的 level，当它们绘制的时候，会根据 level 属性值获取对应的 drawable 绘制到画布上

根节点为 <level-list>，它并没有可以设置的属性，能做的只是设置每个 <item> 的属性

<item> 属性

范例

1. 创建一个 空的 Android 项目 cn.twle.android.LevelListDrawable

2. 使用 shapeDrawable 画圆，一式五份，不同点在于大小

   res/drawable/shape_circle_1.xml

   <?xml version="1.0" encoding="utf-8"?>
   <shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">
       <solid android:color="#2C96ED"/>
       <size android:height="20dp" android:width="20dp"/>
   </shape>
   

   res/drawable/shape_circle_2.xml

   <?xml version="1.0" encoding="utf-8"?>
   <shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">
       <solid android:color="#2C96ED"/>
       <size android:height="40dp" android:width="40dp"/>
   </shape>
   

   res/drawable/shape_circle_3.xml

   <?xml version="1.0" encoding="utf-8"?>
   <shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">
       <solid android:color="#2C96ED"/>
       <size android:height="80dp" android:width="80dp"/>
   </shape>
   

   res/drawable/shape_circle_4.xml

   <?xml version="1.0" encoding="utf-8"?>
   <shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">
       <solid android:color="#2C96ED"/>
       <size android:height="160dp" android:width="160dp"/>
   </shape>
   

   res/drawable/shape_circle_5.xml

   <?xml version="1.0" encoding="utf-8"?>
   <shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">
       <solid android:color="#2C96ED"/>
       <size android:height="320dp" android:width="320dp"/>
   </shape>
   

3. 使用 LevelListDrawable ，设置五层

   res/drawable/level_circle.xml

   <?xml version="1.0" encoding="utf-8"?>
   <level-list xmlns:android="http://schemas.android.com/apk/res/android" >
       <item android:drawable="@drawable/shape_circle_1" android:maxLevel="2000"/>
       <item android:drawable="@drawable/shape_circle_2" android:maxLevel="4000"/>
       <item android:drawable="@drawable/shape_circle_3" android:maxLevel="6000"/>
       <item android:drawable="@drawable/shape_circle_4" android:maxLevel="8000"/>
       <item android:drawable="@drawable/shape_circle_5" android:maxLevel="10000"/>
   </level-list>
   

4. 修改 activity_main.xml

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
   
       <ImageView 
           android:id="@+id/img_show"
           android:layout_width="match_parent"
           android:layout_height="match_parent"
           android:scaleType="center"
           android:src="@drawable/level_circle" />
   
   </LinearLayout>
   

5. 最后修改 MainActivity

   package cn.twle.android.levellistdrawable;
   
   import android.graphics.drawable.LevelListDrawable;
   import android.os.Handler;
   import android.os.Message;
   import android.support.v7.app.AppCompatActivity;
   import android.os.Bundle;
   import android.widget.ImageView;
   
   import java.util.Timer;
   import java.util.TimerTask;
   
   public class MainActivity extends AppCompatActivity {
   
       private ImageView img_show;
   
       private LevelListDrawable ld;
       private Handler handler = new Handler() {
           public void handleMessage(Message msg) {
               if (msg.what == 0x123) {
                   if (ld.getLevel() > 10000) ld.setLevel(0);
                   img_show.setImageLevel(ld.getLevel() + 2000);
               }
           }
       };
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           img_show = (ImageView) findViewById(R.id.img_show);
           ld = (LevelListDrawable) img_show.getDrawable();
           img_show.setImageLevel(0);
           new Timer().schedule(new TimerTask() {
               @Override
               public void run() {
                   handler.sendEmptyMessage(0x123);
               }
           }, 0, 200);
       }
   }