looper

I have tasks completed by AsyncTask in background. At some point I need to issue a Toast that something is completed. I've tried and I failed because Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() How can I do that? onPostExecute - executes on UI thread or publishProgress() ; in your doinbackground and protected void onProgressUpdate(Integer... progress) { } http://developer.android.com/reference/android/os/AsyncTask.html you can Toast inside doInBackground add this code where you want to Toast appear runOnUiThread(new Runnable()

I have checked the official Android documentation/guide for Looper , Handler and MessageQueue . But I couldn't get it. I am new to android, and got very confused with these concepts. 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 is created, it is bound to a specific Looper (and associated thread

在日常的开发中，Android 的消息机制作为系统运行的根本机制之一，显得十分的重要。 从 Handler 发送消息开始 查看源码，Handler的post、send方法最终都会走到 代码 public final boolean sendMessageDelayed(Message msg, long delayMillis) { if (delayMillis < 0) { delayMillis = 0; } return sendMessageAtTime(msg, SystemClock.uptimeMillis() + delayMillis); } sendMessageDelayed 会走到 代码 private boolean enqueueMessage(MessageQueue queue, Message msg, long uptimeMillis) { msg.target = this; if (mAsynchronous) { msg.setAsynchronous(true); } return queue.enqueueMessage(msg, uptimeMillis); } 这里可以设置 Message 为异步消息 查看 queue 的 enqueueMessage 方法， 我们剥离出核心代码： 代码 if (p == null ||

I have the following code class OverlayTask extends AsyncTask<Void, Void, Void> { @Override public void onPreExecute() { if (sites != null) { myMapView.getOverlays().remove(sites); myMapView.invalidate(); sites = null; } } @Override public Void doInBackground(Void... unused) { grabShipsWithLocation(); return (null); } @Override public void onPostExecute(Void unused) { myMapView.getOverlays().add(sites); myMapView.invalidate(); isLoading = false; } } That seems to work fine on a few test devices but I am seeing a lot of errors appearing on the dev console. I can't seem to work out why and where

I don't understand why I'm getting this error. I'm using AsyncTask to run some processes in the background. I have: protected void onPreExecute() { connectionProgressDialog = new ProgressDialog(SetPreference.this); connectionProgressDialog.setCancelable(true); connectionProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER); connectionProgressDialog.setMessage("Connecting to site..."); connectionProgressDialog.show(); downloadSpinnerProgressDialog = new ProgressDialog(SetPreference.this); downloadSpinnerProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);