从另一个类作为主要活动调用时，Android Alertdialog崩溃并显示“无法添加窗口”异常

Question

I have a problem with an AlertDialog in Android. In a class "Misc" there is a method which creates an alertdialog.

public static void getAlert (Context context)
{
Builder builder = new AlertDialog.Builder(context);
builder.setTitle("Notruf absenden?");
builder.setMessage("automatischer Notruf in 60 sec.");
builder.setCancelable(true);
builder.setPositiveButton("Ja", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               callEmergency(context);
           }
       });
builder.setNegativeButton("Abbrechen", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
              countdown.cancel();
           }
       });

 final AlertDialog alertBox = builder.create();
 alertBox.show();

 countdown = new CountDownTimer(60000, 1000) 
 {
   public void onTick(long millisUntilFinished) 
   {
     alertBox.setMessage("automatischer Notruf in "+ (millisUntilFinished/1000) + " sec.");
   }
   public void onFinish()
   {
   alertBox.cancel();
   callEmergency(context);
   }
}.start();

When I call the method in the main activity by typing:

Misc.getAlert(this)

it works, but in another class named Algorithm I call it in the same way:

Misc.getAlert(context)

But then there is this exception:

09-16 17:15:32.304: E/AndroidRuntime(19797): FATAL EXCEPTION: main
09-16 17:15:32.304: E/AndroidRuntime(19797): android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
09-16 17:15:32.304: E/AndroidRuntime(19797):    at android.view.ViewRoot.setView(ViewRoot.java:536)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:177)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at android.app.Dialog.show(Dialog.java:241)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at de.smehner.Sturzerkennung.Misc.getAlert(Misc.java:220)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at de.smehner.Sturzerkennung.Algorithm.fall(Algorithm.java:203)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at de.smehner.Sturzerkennung.Algorithm.performNonGraphical(Algorithm.java:68)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at de.smehner.Sturzerkennung.SensorValueReceiver.onSensorChanged(SensorValueReceiver.java:66)
09-16 17:15:32.304: E/AndroidRuntime(19797):    at android.hardware.SensorManager$ListenerDelegate$1.handleMessage(SensorManager.java:538)

I tried to set in getAlert

Builder builder = new AlertDialog.Builder(Sturzerkennung.this); // Sturzerkenung is the main activity

But then there is the error: "No enclosing instance of the type Sturzerkennung is accessible in scope"

context.getApplicationContext instead of Sturzerkennung.this didn't solve the problem either. Has anybody an idea for this problem?

Answer 1

Problem solved.. The context in the Algorithm class was not from the Activity Sturzerkennung...

In Sturzerkennung I put

public static Context context;
...
context = this;

and then in Algorithm the parameter for getAlert is

Misc.getAlert(Sturzerkennung.context)

Now it works..