Android Studio could not find class

一个CheckBox 多选按钮实现程序，layout预览没有问题,启动APK不能运行。

build.gradle

logcat：

08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.os.PersistableBundle', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.os.PersistableBundle', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.media.session.MediaController', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.widget.Toolbar', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.app.ActivityManager$TaskDescription', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.app.SharedElementCallback', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.820 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.os.PersistableBundle', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.840 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.app.SharedElementCallback', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.840 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.app.assist.AssistContent', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.840 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.view.SearchEvent', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.840 3020-3020/com.example.administrator.myapplication12 E/dalvikvm: Could not find class 'android.os.PersistableBundle', referenced from method com.example.administrator.myapplication12.MainActivity.access$super
08-18 05:15:38.900 3020-3020/com.example.administrator.myapplication12 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.administrator.myapplication12, PID: 3020
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.administrator.myapplication12/com.example.administrator.myapplication12.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.administrator.myapplication12.MainActivity.onCreate(MainActivity.java:39)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
at android.app.ActivityThread.access$800(ActivityThread.java:135) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5017) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
at dalvik.system.NativeStart.main(Native Method) 

你的Activity中是否有以下的方法
onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState)
onPostCreate(Bundle savedInstanceState, PersistableBundle persistentState)

PersistableBundle是API 21引入的，如果你的app运行在低于API21的设备中，有可能就会报错。
可以改为对低版本也适用的方法：
onSaveInstanceState(Bundle outState)
onPostCreate(Bundle savedInstanceState)

没有导入PersistableBundle，和MediaController这两个类

少导入或者引入什么类或者jar包了？