looper

How to create a Looper thread, then send it a message immediately?

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Eventual solution (minus error checking), thanks to CommonsWare: class Worker extends HandlerThread { // … public synchronized void waitUntilReady() { d_handler = new Handler(getLooper(), d_messageHandler); } } And from the main thread: Worker worker = new Worker(); worker.start(); worker.waitUntilReady(); // <- ADDED worker.handler.sendMessage(…); This works thanks to the semantics of HandlerThread.getLooper() which blocks until the … Read more

Can’t create handler inside thread that has not called Looper.prepare() inside AsyncTask for ProgressDialog

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The method show() must be called from the User-Interface (UI) thread, while doInBackground() runs on different thread which is the main reason why AsyncTask was designed. You have to call show() either in onProgressUpdate() or in onPostExecute(). For example: class ExampleTask extends AsyncTask<String, String, String> { // Your onPreExecute method. @Override protected String doInBackground(String… params) … Read more

What is the relationship between Looper, Handler and MessageQueue in Android?

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A Looper is a message handling loop: it reads and processes items from a MessageQueue. The Looper class is usually used in conjunction with a HandlerThread (a subclass of Thread). A Handler is a utility class that facilitates interacting with a Looper—mainly by posting messages and Runnable objects to the thread’s MessageQueue. When a Handler … Read more

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