Toast from FileObserver

问题

I have a problem. I'm using a FileObserver, which moves new files from the watched directories to another, former specified directory. In my thoughts there should be shown a toast message that says 'File xy has been moved', as long as the observer watches the directory, also if the applications is only in the background. But I didn't get it working. It always tells me, that there is a RuntimeException, and that it cannot been done without calling Looper.prepare().

05-11 13:21:28.484: WARN/System.err(3397): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

I tried the way with using an handler too, but I also didn't get it to work.

Has someone else an idea? Thanks in advance.

Best regards, Tobi

回答1:

Obviously, your FileObserver runs(or is) another thread. You can not modify the UI from non-UI thread. Pass a Handler to your FileObserver and send messages from it. Read about Handlers.

回答2:

Before your Toast statement add the following :

runOnUiThread(new Runnable() {
            public void run()
            {
                Toast.makeText(getApplicationContext(), text, Toast.LENGTH_SHORT).show();
            }
        });

This will make it run on UI thread. Hope this helps.

回答3:

What are you using for the context of the Toast message? That will have to have a way to display something on the screen.

回答4:

Put the following code in your class:

// Need handler for callbacks to UI Threads
    // For background operations
    final Handler mHandler = new Handler();

    // Create Runnable for posting results
    final Runnable mUpdateResults = new Runnable() {
        public void run() {
            // Show the toast here.
        }
    };

and in your fileobserver's thread call place following fragment of code:

mHandler.post(mUpdateResults);

and don't use the getApplicationContext() instead try YourClassPhysicalName.java for the context of the Toast.

来源：https://stackoverflow.com/questions/5963438/toast-from-fileobserver

标签

android

toast