Show a dialog in `Thread.setDefaultUncaughtExceptionHandler`

Question

When my android application throw an exception, I want to show a custom dialog to tell user there is something wrong happened, so I use Thread.setDefaultUncaughtExceptionHandler to set a global exception handler:

public class MyApplication extends Application {

    @Override
    public void onCreate() {
        super.onCreate();

        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
            @Override
            public void uncaughtException(Thread thread, final Throwable ex) {
                AlertDialog.Builder builder = new AlertDialog.Builder(getApplicationContext());
                builder.setTitle("There is something wrong")
                        .setMessage("Application will exit：" + ex.toString())
                        .setPositiveButton("OK", new DialogInterface.OnClickListener() {

                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                // throw it again
                                throw (RuntimeException) ex;
                            }
                        })
                        .show();
            }
        });
    }

}

But I found it there is any exception thrown, the AlertDialog won't show, instead, the application blocks and after a while, it will show a system dialog:

X app is not responding. Would you like to close it?
Wait  |  OK

What should I do now?

---

UPDATE

The log:

11-16 12:54:16.017: WARN/WindowManager(90): Attempted to add window with non-application token WindowToken{b38bb6a8 token=null}.  Aborting.

It seems the error is coming from new AlertDialog.Builder(getApplicationContext());

But this is an exception handler in Application subclass, how can I set an activity instance to it?

Answer 1

You cannot do any UI operation from here. Just start another activity/ splash screen. Pass an intent extra to denote crash and show dialog in that activity.

    /*
     * (non-Javadoc)
     * 
     * @see
     * java.lang.Thread.UncaughtExceptionHandler#uncaughtException(java.
     * lang.Thread, java.lang.Throwable)
     */
    @Override
    public void uncaughtException(Thread t, final Throwable e) {
        StackTraceElement[] arr = e.getStackTrace();
        final StringBuffer report = new StringBuffer(e.toString());
        final String lineSeperator = "-------------------------------\n\n";
        report.append(DOUBLE_LINE_SEP);
        report.append("--------- Stack trace ---------\n\n");
        for (int i = 0; i < arr.length; i++) {
            report.append( "    ");
            report.append(arr[i].toString());
            report.append(SINGLE_LINE_SEP);
        }
        report.append(lineSeperator);
        // If the exception was thrown in a background thread inside
        // AsyncTask, then the actual exception can be found with getCause
        report.append("--------- Cause ---------\n\n");
        Throwable cause = e.getCause();
        if (cause != null) {
            report.append(cause.toString());
            report.append(DOUBLE_LINE_SEP);
            arr = cause.getStackTrace();
            for (int i = 0; i < arr.length; i++) {
                report.append("    ");
                report.append(arr[i].toString());
                report.append(SINGLE_LINE_SEP);
            }
        }
        // Getting the Device brand,model and sdk verion details.
        report.append(lineSeperator);
        report.append("--------- Device ---------\n\n");
        report.append("Brand: ");
        report.append(Build.BRAND);
        report.append(SINGLE_LINE_SEP);
        report.append("Device: ");
        report.append(Build.DEVICE);
        report.append(SINGLE_LINE_SEP);
        report.append("Model: ");
        report.append(Build.MODEL);
        report.append(SINGLE_LINE_SEP);
        report.append("Id: ");
        report.append(Build.ID);
        report.append(SINGLE_LINE_SEP);
        report.append("Product: ");
        report.append(Build.PRODUCT);
        report.append(SINGLE_LINE_SEP);
        report.append(lineSeperator);
        report.append("--------- Firmware ---------\n\n");
        report.append("SDK: ");
        report.append(Build.VERSION.SDK);
        report.append(SINGLE_LINE_SEP);
        report.append("Release: ");
        report.append(Build.VERSION.RELEASE);
        report.append(SINGLE_LINE_SEP);
        report.append("Incremental: ");
        report.append(Build.VERSION.INCREMENTAL);
        report.append(SINGLE_LINE_SEP);
        report.append(lineSeperator);

        Log.e("Report ::", report.toString());
        Intent crashedIntent = new Intent(BaseActivity.this, SplashActivity.class);
        crashedIntent.putExtra(EXTRA_CRASHED_FLAG,  "Unexpected Error occurred.");
        crashedIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
        crashedIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(crashedIntent);

        System.exit(0);
        // If you don't kill the VM here the app goes into limbo

    }

Also see:

Android UncaughtExceptionHandler that instantiates an AlertDialog breaks

Toast not showing up in UnCaughtExceptionHandler

How to start activity from UncaughtExceptionHandler if this is main thread crashed?

How i do it:

I have a BaseActivity which extends Activity, and in onCreate of the activity I set the UncaughtExceptionHandler. All my activities extend the BaseActivity instead of Activity.

Keys

1. You can't set the exception handler in Application.onCreate, instead, you should create a BaseActivity and set it on the onCreate method of it.
2. After starting the SplashActivity, we should call System.exit(0)
3. We can't hold the error instance to share it to SplashActivity, since it will be destroyed, instead, we can pass some error message or persist it in file.