I have started looking into Android.
I have tried to build a utility class that can do Network I/O. And grasping things was little hard at first. Network I/O or other heavy-duty stuff in Android should be done on other worker thread. Because doing it in main thread (or the UI thread) can ( and will ) make your application unresponsive and may be killed as the system is persuaded to think that it has hung. For every Android developer, this is a must-read.
So you have to do the long running operations in separate thread. And to interact between threads you have to resort to Handler. A Handler is used to send message or runnable to a particular thread. The thing to remember is that a Handler is associated with the MessageQueue of the single thread which has created it. After creating a Handler, it can be used to post message or runnable to that particular thread.
Here is an example
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- public class MyActivity extends Activity {
void startHeavyDutyStuff() {
// Here is the heavy-duty thread
Thread t = new Thread() {
public void run() {
while (true) {
mResults = doSomethingExpensive();
//Send update to the main thread
messageHandler.sendMessage(Message.obtain(messageHandler, mResults)); }}};
t.start();
}
// Instantiating the Handler associated with the main thread.
private Handler messageHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch(msg.what) {
//handle update
//.....}}};}
