Posting Toast message from a Thread

Question

My application launches a thread to query the web for some data. I want to display a Toast message when nothing is found, but my application always crashes.

I've tried using the application Context from within the thread, like so:

Toast.makeText(getApplicationContext(), "testttt", Toast.LENGTH_LONG).show();

I've also tried creating a Runnable with the Toast call and calling runOnUiThread(runnable) from the Thread (the Toast call in this runnable uses the Activity as the first parameter).

Does anyone have any ideas on how to accomplish this?

Are you using `Thread` as an inner class or are you extending `AsyncTask` in a totally separate class? — Octavian Helm, Nov 17 '10 at 22:37
At the moment I'm using a class I extended from Thread. It's likely I'll move this into an AsyncTask at some point. I just haven't gotten around to it yet. — Andrew, Nov 17 '10 at 22:53

score 22 · Accepted Answer · answered Nov 18 '10 at 00:05

Try to post inside to a Handler object.

final Handler mHandler = new Handler();
final Runnable mUpdateResults = new Runnable() {
    public void run() {
        Toast(this, message, duration).show();
    }

new Thread() {
    public void run() {
        mHandler.post(mUpdateResults);
    }
}.start();

score 4 · Answer 2 · answered Nov 17 '10 at 22:47

4

Toast.makeText().show() definitely needs to be run on the UI thread.

You should probably use an AsyncTask like Octavian Damiean mentioned, but here's some code using runOnUiThread if you're set on using that:

    public void showToastFromBackground(final String message) {
    runOnUiThread(new Runnable() {

        @Override
        public void run() {
            Toast.makeText(this, message, Toast.LENGTH_LONG).show();
        }
    });
}

answered Nov 17 '10 at 22:47

Brandon O'Rourke

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As I stated in my original post, I've tried this and it crashes – Andrew Nov 17 '10 at 22:53
2

Post the stack trace in your original post. – Brandon O'Rourke Nov 17 '10 at 22:55
in the code above the first parameter "this" is likely incorrect, you need to pass a valid context explicitly, f.i. your ProgressDialog.getContent() – Eric Grange Apr 22 '11 at 09:45

score 3 · Answer 3 · answered Nov 17 '10 at 22:47

Try implementing a class extending "Handler" in your Activity class and send a Message to it from the other thread. Explained more in detail here:

http://www.anddev.org/the_pizza_timer_-_threading-drawing_on_canvas-t126.html

And please, when asking a question like this, include the stack trace you are getting.

score 1 · Answer 4 · answered Jul 22 '11 at 17:30

If you're running the Handler from your Activity class, you can set the context by just referencing the .this of your Activity like so:

final Runnable showToastMessage = new Runnable() {
    public void run() {
        Toast.makeText(YourActivity.this, "Message", Toast.LENGTH_SHORT).show();
    }
};

Posting Toast message from a Thread

4 Answers4

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