Java 使用设备管理时应用程序中的Android实例化异常

我快到了

日志：

07-29 19:15:05.509: D/libEGL(31021): loaded /system/lib/egl/libEGL_mali.so
07-29 19:15:05.544: D/libEGL(31021): loaded /system/lib/egl/libGLESv1_CM_mali.so
07-29 19:15:05.549: D/libEGL(31021): loaded /system/lib/egl/libGLESv2_mali.so
07-29 19:15:05.549: D/(31021): Device driver API match
07-29 19:15:05.549: D/(31021): Device driver API version: 10
07-29 19:15:05.549: D/(31021): User space API version: 10 
07-29 19:15:05.549: D/(31021): mali: REVISION=Linux-r2p4-02rel0 BUILD_DATE=Mon Mar  5 09:47:55 KST 2012 
07-29 19:15:05.574: D/OpenGLRenderer(31021): Enabling debug mode 0
07-29 19:15:07.509: W/IInputConnectionWrapper(31021): showStatusIcon on inactive InputConnection
07-29 19:15:08.444: D/dalvikvm(31021): newInstance failed: no <init>()
07-29 19:15:08.444: D/AndroidRuntime(31021): Shutting down VM
07-29 19:15:08.444: W/dalvikvm(31021): threadid=1: thread exiting with uncaught exception (group=0x41443300)
07-29 19:15:08.549: E/AndroidRuntime(31021): FATAL EXCEPTION: main
07-29 19:15:08.549: E/AndroidRuntime(31021): java.lang.RuntimeException: Unable to instantiate receiver com.liamwli.parent.trap.ParentTrap$Controller: java.lang.InstantiationException: can't instantiate class com.liamwli.parent.trap.ParentTrap$Controller; no empty constructor
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2333)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.app.ActivityThread.access$1500(ActivityThread.java:139)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1281)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.os.Handler.dispatchMessage(Handler.java:99)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.os.Looper.loop(Looper.java:137)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.app.ActivityThread.main(ActivityThread.java:4896)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at java.lang.reflect.Method.invokeNative(Native Method)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at java.lang.reflect.Method.invoke(Method.java:511)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:788)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at dalvik.system.NativeStart.main(Native Method)
07-29 19:15:08.549: E/AndroidRuntime(31021): Caused by: java.lang.InstantiationException: can't instantiate class com.liamwli.parent.trap.ParentTrap$Controller; no empty constructor
07-29 19:15:08.549: E/AndroidRuntime(31021):    at java.lang.Class.newInstanceImpl(Native Method)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at java.lang.Class.newInstance(Class.java:1319)
07-29 19:15:08.549: E/AndroidRuntime(31021):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2328)
07-29 19:15:08.549: E/AndroidRuntime(31021):    ... 10 more
07-29 19:15:09.719: I/Process(31021): Sending signal. PID: 31021 SIG: 9

请帮我回答这个问题，我保证明天之前不会打扰你：）

这表明Controller需要一个默认构造函数，如下所示：

public class Controller extends DeviceAdminReceiver {
    public Controller() {
        super();
    }

    void showToast(Context context, String msg) {
        String status = "Status";
        Toast.makeText(context, status, Toast.LENGTH_SHORT).show();

        //Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
    }
    ...
}

---

你做过调试吗？你认为错误在哪里？我不理解错误。我知道我没有空的构造函数——但我如何创建一个空构造函数，以及将它放在哪里？

Caused by: java.lang.InstantiationException: can't instantiate class com.liamwli.parent.trap.ParentTrap$Controller; no empty constructor

public class Controller extends DeviceAdminReceiver {
    public Controller() {
        super();
    }

    void showToast(Context context, String msg) {
        String status = "Status";
        Toast.makeText(context, status, Toast.LENGTH_SHORT).show();

        //Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
    }
    ...
}