Develop Reference

How to use threads and services. Android

I have three classes. "actone", "acttwo" and "actthree". I have a button in "actone". When I click that button, I want to be able to run "acttwo" on a different thread in the background, while my UI takes me to "actthree" and I can do whatever I want there while the code in "acttwo" keeps executing(I'll be doing uploading to a server in "acttwo" that is why I want it to keep running in the background).
if(v.getId() == R.id.button1){
//Start "acttwo" in background on another thread.
Intent i= new Intent(actone.this, actthree.class);
startActivity(i);
}
How do I do that? Do I use a service? If yes, then what's the procedure? How to do that? I'm a newbie at Android. Please help. Thanks!

There are two ways to do this, use a Singleton or use a Service (as you mentioned). Personally I don't like the singleton patterns very much and a service follows the Android patter much better. You will want to use a bound Service which is bound to your Applications context (actone.getActivityContext()). I have written a similar answer to this question however you will want to do something like:
public class BoundService extends Service {
private final BackgroundBinder _binder = new BackgroundBinder();
//Binding to the Application context means that it will be destroyed (unbound) with the app
public IBinder onBind(Intent intent) {
return _binder;
}
//TODO: create your methods that you need here (or link actTwo)
// Making sure to call it on a separate thread with AsyncTask or Thread
public class BackgroundBinder extends Binder {
public BoundService getService() {
return BoundService.this;
}
}
}
Then from your actone (I'm assuming Activity)
public class actone extends Activity {
...
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
Intent intent = new Intent(this, BoundService.class);
bindService(intent, _serviceConnection, Context.BIND_AUTO_CREATE);
}
private ServiceConnection _serviceConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className, IBinder service) {
BoundService.BackgroundBinder binder = (BoundService.BackgroundBinder)service;
_boundService = binder.getService();
_isBound = true;
//Any other setup you want to call. ex.
//_boundService.methodName();
}
#Override
public void onServiceDisconnected(ComponentName arg0) {
_isBound = false;
}
};
}
Then from ActOne and ActThree (Activities?) you can get the bound service and call methods from actTwo.

You can use a AsyncTask for that. Services are not really useful (much more to code).

Keep record of launched activities in Android

I was wondering how to keep a record of launched activites for logging purposes. what broadcast receiver I have to subscribe to intercept this intent? or what intent-filter to use? I figure that I must use some type of long-running service in the background.
My first objetive is to track main-focus applications, some sort of history.
Want to get finally some similar to:
- Launched app com.android.xxx
- Launched app xx.yy.zz
- App xx.yy.zz lost focus
Thanks in advance
EDIT - Just see that app MyAppRank , that does exactly what i mean

What i'm able to figure out from your question is that you want to keep track of all the activities when they are launched in your application. If that is correct, the solution may work for you:
Crate a BaseActivity which all of your Activities should extend
public class BaseActivity extends Activity
{
private Activity activity;
public static final String INTENTFILTER_TRACK_MY_ACTIVITIES="INTENTFILTER_TRACK_MY_ACTIVITIES";
public static final String INTENTFILTER_REMOVE_MY_ACTIVITIES="INTENTFILTER_REMOVE_MY_ACTIVITIES";
public void setActivity(Activity act)
{
activity = act;
}
public Activity getActivity()
{
return activity;
}
#Override protected void onCreate(Bundle savedInstanceState)
{
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
Intent intent = new Intent();
intent.setAction(INTENTFILTER_TRACK_MY_ACTIVITIES);
intent.putExtra("activityName", activity.getClass().getSimpleName());
sendBroadcast(intent);
}
#Override protected void onDestroy()
{
// TODO Auto-generated method stub
super.onDestroy();
Intent intent = new Intent();
intent.setAction(INTENTFILTER_REMOVE_MY_ACTIVITIES);
intent.putExtra("activityName", activity.getClass().getSimpleName());
sendBroadcast(intent);
setActivity(null);
}
}
Now extend above BaseActivity for all your activities. i.e instead of extending your Activities should extend BaseActivity and call setActivity(this); in onCreate like below:
public class MyActivity extends Activity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setActivity(this);
//write your other code form here
}
}
3.Then write a BroadcastReceiver like below:
class TrackActivitiesReceiver extends BroadcastReceiver
{
private static final Object SEPERATOR = ",";// use , as seperator
String sb="";
#Override
public void onReceive(Context context, Intent intent)
{
if(intent.getAction().equalsIgnoreCase(BaseActivity.INTENTFILTER_TRACK_MY_ACTIVITIES))
{
sb+=intent.getStringExtra("activityName");
sb+=SEPERATOR;
}
else if(intent.getAction().equalsIgnoreCase(BaseActivity.INTENTFILTER_REMOVE_MY_ACTIVITIES))
{
sb=sb.replace(intent.getStringExtra("activityName")+SEPERATOR, "");
}
}}
4Finally, Register above Receiver in your AndroidManifest.xml
<receiver
android:name="TrackActivitiesReceiver"
android:exported="false" >
<intent-filter>
<action android:name="INTENTFILTER_TRACK_MY_ACTIVITIES" />
</intent-filter>
</receiver>
Hope this solves your problem. cheers!

There are no Intents broadcast when applications are started or when applications come to the foreground. There isn't anything that you can hook into as a listener to get these events.
The way you can do this (which is the way apps like MyAppRank do it) is to use the methods of the ActivityManager:
getRunningTasks()
getRunningAppProcesses()
getRecentTasks()
You create a Service which runs all the time and at regular intervals calls methods of the ActvityManager to determine which task is in the foreground and you can "infer" what the user has done (or is doing). It isn't an exact science.
Note: You will need android.permission.GET_TASKS and none of this works anymore as of API 21 (Android 5, Lollipop). As of API 21 the security has been tightened and an application can only get information about its own tasks, not other tasks in the system.

Android MediaPlayer On Stop Event, or similar, exists?

I have several activities which use several audio features. For that, I have a MediaPlayer in a singleton java class, so the activities interact with that class and just exist on the media player.
One of the features is to stop automatically the media player after X minutes. So I created a timer in the singleton class and stops perfectly the radio streaming. the problem is that there is no feedback or callback to the running activity. There is a play/stop button wich has to change the image and I do not know how can I capture that onStop event or whatever....or can be called from a single java class the current activity class running, so I could call a function of the activity in order to change the image?

You probably want to use a broadcast receiver for this.
From your singlton class which does the stopping, when your timer stops the music, call this method:
public void broadcastMusicPaused(View v){
Intent broadcast = new Intent();
broadcast.setAction("MUSIC_STOPPED");
sendBroadcast(broadcast);
}
Then, from your controlling activity, set up your receiver like this:
private BroadcastReceiver receiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
Toast.makeText(getApplicationContext(), "Music Paused", Toast.LENGTH_SHORT).show();
displayMusicStopped(); //switches images
}
};
#Override
protected void onResume() {
IntentFilter filter = new IntentFilter();
filter.addAction("MUSIC_STOPPED");
registerReceiver(receiver, filter);
super.onResume();
}
#Override
protected void onPause() {
unregisterReceiver(receiver);
super.onPause();
}

First of all, thanks jameo for his answer, sounds pretty good, but i do not know if i will have time to try, i promise i will if i can this week or next time i have a similar issue.
Finally i did the trick this way:
1 - Create a Interface with Method onStopMediaPlayer(); //For example call MediaPlayerStopInterface
public interface MediaPlayerStopInterface {
/**
* Called when the player timer ends
*/
public void onStopMediaPlayer();
}
2 - My activities classes implements the interface switching images.
public class PortadaActivity extends Activity implements MediaPlayerStopInterface{
public void onStopMediaPlayer(){
//Switch images or whatever
}
}
3 - My singletton class has an object of the type of the interface MediaPlayerStopInterface
public class AudioControllerClass { //The Singletton Java Class
private MediaPlayerStopInterface currentActivity;
public void setCurrentActivity(MediaPlayerStopInterface mpsi){
currentActivity=mpsi;
}
}
4 - My activities classes in onResume() do a Singlettonclass.setStoppedPlayerInterface(this), so i always have a reference of the running activitie.
public class PortadaActivity extends Activity implements MediaPlayerStopInterface{
public void onResume() {
AudioControllerClass.getInstance(getApplicationContext()).setCurrentActivity(this); //In every resume the singletton class knows who was the last one in being active
}
}
5 - when timer execute, as i have the activitie class reference, i just call object_StoppedPlayerInterface.stoppedPlayer();
public class AudioControllerClass { //The Singletton Java Class
class TimerRadio extends TimerTask {
public void run() {
if(whatever==true){
currentActivity.onStopMediaPlayer();
}
}
}
}
Finally, i didn't code it, but the callback to onStopMediaplayer in activities must be done with a Handler, if you do not want a "Only UI thread can touch his views" exception :P
It works perfectly :). But i don't know if it is a really bad practice or is not so horrible xD
Anyway thanks Jameo. Yours sound much more elegant :P

Android, start service using thread and warn activity when it's done

I have a service which has a method that downloads an image from an URL and returns an Uri.
That service will get more complex when it has all the intended features. Therefore,
I'm invoking its methods within a thread.
My problem is how to warn the activity that the service has done it's work.
I could change a class isFinished variable but the activity had to be constantly checking
for its value.
I just want the service to tell the activity that it's work is done and the resources are
available for use.
I thought something in the lines of the service calling stopSelf() and the activity was
warned through "onServiceDisconnected" but that didn't seem very "political correct".
Thanks in advance

There are two ways to do it.
1. You can start your activity using by firing an intent.
2. You can Broadcast an intent and write receiver for it in your app when your receiver receives intent and onreceive method is called in this method you can start your activity using intent.
cheers...

public class MyActivity extends Activity{
public MyActivity() {
...
MyThread thread = new MyThread(this);
thread.start();
}
public void onFinishedThread(...) {
}
}
class MyThread extends Thread {
MyActivity activity;
public MyThread(MyActivity activity) {
this.activity = activity;
}
public void run() {
// do work
...
this.activity.onFinishedThread(...);
}
}

easy android unit test fail

I have a simple activity with only one edittext which was set to "http://" in xml. Based on google tutorial, I wrote some unit tests for status check. I want to practice unit test and pass all tests. But I cannot pass testStateDestroy() and testStatePause() (log shows mUrlView=="changed"). The code below is very easy, did I miss something? Thank you in advance.
public class MainActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public class MainActivityTest extends ActivityInstrumentationTestCase2<MainActivity> {
private Activity mActivity;
private EditText mUrlView;
public MainActivityTest() {
super("au.com.crystalfish.safeshare.activity", MainActivity.class);
}
protected void setUp() throws Exception {
super.setUp();
mActivity = this.getActivity();
mUrlView = (EditText) mActivity.findViewById(au.com.crystalfish.safeshare.R.id.url);
}
public void testPreconditions() {
assertNotNull(mActivity);
assertEquals(mUrlView.getText().toString(), "http://");
}
#UiThreadTest
public void testRotate() {
mUrlView.setText("changed");
mActivity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
mActivity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
assertEquals(mUrlView.getText().toString(), "changed");
}
#UiThreadTest
public void testStateDestroy() {
mUrlView.setText("changed");
assertEquals(mUrlView.getText().toString(), "changed");
mActivity.finish();
mActivity = this.getActivity();
assertEquals(mUrlView.getText().toString(), "http://"); <===========should be "http://" since it is a new activity
}
#UiThreadTest
public void testStatePause() {
Instrumentation mInstr = this.getInstrumentation();
mInstr.callActivityOnPause(mActivity);
mUrlView.setText("changed");
mInstr.callActivityOnResume(mActivity);
assertEquals(mUrlView.getText().toString(), "http://");<======should be "http://" since the text should bot be changed when the activity was paused
}
}

Well, for your testStatePause() test I think that may be valid. Even if the activity is paused you are still free to modify it however you want since you still have a reference to it (or one of its textViews at least. In a test like this, you should change the value of the textView in the actual activity's onPause method, then use your testStatePause test to verify that onPause was called and did its job correctly, then do the same for onResume().
I'm not really familiar with Android's testing framework but maybe a similar issue is happening with your testStateDestroy() test. Your mUrlView could still be pointing to the old, finished Activity. The old activity is no longer valid but its widgets might be.