android leaked window force close

Question

I have integrated zxing barcode scanner in my app. When the scanner gets a scan it takes the result and searches an external online database via a async task then opens a new activity based on the results. I am getting a force close that is not consistent, it does not happen every scan, only sometimes so I am having trouble figuring out why I am getting a leaked window error, and only sometimes:

09-25 21:02:48.105  24371-24371/com.beerportfolio.beerportfoliopro E/WindowManager﹕ Activity com.example.beerportfoliopro.BeerPage2 has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@424b7198 that was originally added here
        android.view.WindowLeaked: Activity com.example.beerportfoliopro.BeerPage2 has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@424b7198 that was originally added here
        at android.view.ViewRootImpl.<init>(ViewRootImpl.java:468)
        at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:419)
        at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:351)
        at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:171)
        at android.view.Window$LocalWindowManager.addView(Window.java:558)
        at android.app.Dialog.show(Dialog.java:282)
        at com.example.beerportfoliopro.GetBeerRateJSON.onPreExecute(GetBeerRateJSON.java:52)
        at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
        at android.os.AsyncTask.execute(AsyncTask.java:534)
        at com.example.beerportfoliopro.GetBeerDataJSON.onPostExecute(GetBeerDataJSON.java:111)
        at com.example.beerportfoliopro.GetBeerDataJSON.onPostExecute(GetBeerDataJSON.java:34)
        at android.os.AsyncTask.finish(AsyncTask.java:631)
        at android.os.AsyncTask.access$600(AsyncTask.java:177)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:155)
        at android.app.ActivityThread.main(ActivityThread.java:5536)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1074)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:841)
        at dalvik.system.NativeStart.main(Native Method)
09-25 21:02:48.265  24371-24371/com.beerportfolio.beerportfoliopro E/AndroidRuntime﹕ FATAL EXCEPTION: main
        java.lang.IllegalArgumentException: View not attached to window manager
        at android.view.WindowManagerImpl.findViewLocked(WindowManagerImpl.java:784)
        at android.view.WindowManagerImpl.removeView(WindowManagerImpl.java:476)
        at android.view.WindowManagerImpl$CompatModeWrapper.removeView(WindowManagerImpl.java:182)
        at android.app.Dialog.dismissDialog(Dialog.java:328)
        at android.app.Dialog.dismiss(Dialog.java:311)
        at com.example.beerportfoliopro.GetBeerRateJSON.onPostExecute(GetBeerRateJSON.java:74)
        at com.example.beerportfoliopro.GetBeerRateJSON.onPostExecute(GetBeerRateJSON.java:27)
        at android.os.AsyncTask.finish(AsyncTask.java:631)
        at android.os.AsyncTask.access$600(AsyncTask.java:177)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:155)
        at android.app.ActivityThread.main(ActivityThread.java:5536)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1074)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:841)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

From the stack trace, it looks like your Dialog isn't visible when the AsyncTask finishes its work. In that case, the call to dismiss() will crash the app.

You might try using Dialog.isShowing() to avoid the crash:

protected void onPostExecute(...) {
    ...
    if (dialog.isShowing()) {
        dialog.dismiss(); // or .cancel()
    }
    ...
}