android.view.WindowManager$BadTokenException error while creating dialog box

I am trying to create a Dialog Box from an Non activity Class.

This is my Code

  public static void ShowDialogBox(final Context con, final Listener list) {
        AlertDialog.Builder dlgAlert = new AlertDialog.Builder(con);
        dlgAlert.setMessage("TEXT");
        dlgAlert.setTitle("TEXT");
        dlgAlert.setPositiveButton("TEXT"),
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {

                    }
                });
        dlgAlert.setCancelable(false);
        dlgAlert.create().show(); // THIS LINE GIVES ME AN ERROR
    }

This is the error which I am getting

android.view.WindowManager$BadTokenException: at android.view.ViewRootImpl.setView (ViewRootImpl.java:574) at android.view.WindowManagerGlobal.addView (WindowManagerGlobal.java:282) at android.view.WindowManagerImpl.addView (WindowManagerImpl.java:85)
at android.app.Dialog.show (Dialog.java:298) at PACKAGE NAME AND CLASS PACKAGE NAME AND CLASS at PACKAGE NAME AND CLASS PACKAGE NAME AND CLASS at PACKAGE NAME AND CLASS.onBackPressed (Class.java:95) at android.app.Activity.onKeyUp (Activity.java:2465) at android.view.KeyEvent.dispatch (KeyEvent.java:2646) at android.app.Activity.dispatchKeyEvent (Activity.java:2716) at android.support.v7.internal.view.WindowCallbackWrapper.dispatchKeyEvent (WindowCallbackWrapper.java:50) at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent (AppCompatDelegateImplBase.java:224) at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent (PhoneWindow.java:2280) at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent (ViewRootImpl.java:4038) at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess (ViewRootImpl.java:4000) at android.view.ViewRootImpl$InputStage.deliver (ViewRootImpl.java:3562) at android.view.ViewRootImpl$InputStage.onDeliverToNext (ViewRootImpl.java:3615) at android.view.ViewRootImpl$InputStage.forward (ViewRootImpl.java:3581) at android.view.ViewRootImpl$AsyncInputStage.forward (ViewRootImpl.java:3698) at android.view.ViewRootImpl$InputStage.apply (ViewRootImpl.java:3589)
at android.view.ViewRootImpl$AsyncInputStage.apply (ViewRootImpl.java:3755) at android.view.ViewRootImpl$InputStage.deliver (ViewRootImpl.java:3562) at android.view.ViewRootImpl$InputStage.onDeliverToNext (ViewRootImpl.java:3615) at android.view.ViewRootImpl$InputStage.forward (ViewRootImpl.java:3581) at android.view.ViewRootImpl$InputStage.apply (ViewRootImpl.java:3589) at android.view.ViewRootImpl$InputStage.deliver (ViewRootImpl.java:3562) at android.view.ViewRootImpl$InputStage.onDeliverToNext (ViewRootImpl.java:3615) at android.view.ViewRootImpl$InputStage.forward (ViewRootImpl.java:3581) at android.view.ViewRootImpl$AsyncInputStage.forward (ViewRootImpl.java:3731) at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent (ViewRootImpl.java:3892) at android.view.inputmethod.InputMethodManager$PendingEvent.run (InputMethodManager.java:2208) at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback (InputMethodManager.java:1849) at android.view.inputmethod.InputMethodManager.finishedInputEvent (InputMethodManager.java:1840) at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished (InputMethodManager.java:2185) at android.view.InputEventSender.dispatchInputEventFinished (InputEventSender.java:141) at android.os.MessageQueue.nativePollOnce (Native Method) at android.os.MessageQueue.next (MessageQueue.java:143) at android.os.Looper.loop (Looper.java:122) at android.app.ActivityThread.main (ActivityThread.java:5254) at java.lang.reflect.Method.invoke (Native Method) at java.lang.reflect.Method.invoke (Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:902) at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:697)

Here is the scenario of the user

Activity A -->Opens Activity B-->User presses Back button in Activity B--> On Back button pressed a listener is sent to Activity A --> And then the Dialog Box shown is called.

The issue you are having with the attempt to build your AlertDialog in a separate class is you are passing the AlertDialog the Context of your Activity. You get the error because the AlertDialog requires the WindowManager from the Activity which has the layout--not the Context. This is because Activit extends Context... not the other way around.

In order to make your code work you need to provide the AlertDialog.Builder access to the Activity. So change your code to something like this:

public class TestDialog {

    private static final String TAG = TestDialog.class.getSimpleName();

    Activity mActivity;

    public TestDialog(Activity activity){
        mActivity = activity;
    }


    public void showDialog(){
        AlertDialog.Builder b = new AlertDialog.Builder(mActivity);
        b.setTitle("Title");
        b.setMessage("message");
        b.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Log.e(TAG, "showDialog : onClick");
            }
        });
        b.create().show();
    }
}

Now you can call the AlertDialog from an Activity lets say in this case MainActivity like this:

TestDialog testDialog = new TestDialog(MainActivity.this);
testDialog.showDialog();

I have not tried this from a Fragment, so I do not know whether this works from a Fragment or whether you will continue to have issues with certain devices. For those reasons, I (and Google!) still strongly suggest that you use the DialogFragment instead, because is has been especially designed for this scenario. Take a look at the Google Docs.:

https://developer.android.com/guide/topics/ui/dialogs