Develop Reference

Proper way to start activity in background

I need to do a logout after some time, so I'm opening the login window in my app using.
startActivity(intent);
Problem is that, if the user has my app in the background, my activity will pop up.
Is there a way to easily open an activity but keep my app in the background?

It can be done with Android appliaction component Service.
you can read about it in official documentation by links below.
https://developer.android.com/training/run-background-service/create-service#java
https://developer.android.com/guide/components/services?hl=en
Initialize your Service
public class MyBackgroundService extends Service {
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
//onCreate - Service created
}
#Override
public void onDestroy() {
//onDestroy - Service destroyed (Stopped)
}
#Override
public void onStart(Intent intent, int startid) {
//onStart - Service started
}
}
Then call Service in your Main Activity
startService(new Intent(this, MyBackgroundService.class));
And don't forget about declare in Manifest.
<service android:enabled="true"
android:name=".MyBackgroundService" />

You can implement "local logout" after some time and when user returns to activity you can detect it. More: https://developer.android.com/guide/components/activities/activity-lifecycle

Detect if the application is manually closed or not

I've written an android app which checks the network status by using a BroadcastReceiver inherited class:
public class NetworkChangeReceiver extends BroadcastReceiver {
#Override
public void onReceive(final Context context, final Intent intent) {
Log.d("mylog", "NetworkChangeReceiver Hit");
}
}
which is registered in the manifest file like this:
<receiver
android:name="foo.NetworkChangeReceiver"
android:label="NetworkChangeReceiver" >
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
<action android:name="android.net.wifi.WIFI_STATE_CHANGED" />
</intent-filter>
</receiver>
I needed to handle the internet connection whenever it connects or disconnects. Actually, it works perfectly in normal situations.
But the problem is that when the application is closed manually (by minimizing the app and then closing it by swiping out the app icon in the Recents button menu), it still receives the network status changes. This sometimes causes some exceptions.
Even I have included all the code in receiver function in try/catch block, but still sometimes a toast message containing an error message is shown. This sometimes happen even after some days after the closure of the app.
Please note that the code in the receiver function is more complicated than the code that is shown here and has some access to internal classes and variables.

Your app will still receive events, even if it isn't running. Before you do anything in onReceive(), you can check if the activity is running by:
Option 1: Use a static variable in your activity to check it's state for access from the receiver :
public class YourActivity extends Activity {
public static boolean isRunning = false;
#Overrride
public void onCreate(Bundle savedInstanceState){
isRunning = true;
....
}
//We need receiver to work when app is minimized
/*
#Override
public void onStart() {
super.onStart();
isRunning = true;
}
#Override
public void onStop() {
super.onStop();
isRunning = false;
}
*/
}
And in the receiver:
public class NetworkChangeReceiver extends BroadcastReceiver {
#Override
public void onReceive(final Context context, final Intent intent) {
Log.d("mylog", "NetworkChangeReceiver Hit");
if(!YourActivity.isRunning)
return;
}
}
Option 2 : Using the ActivityManager
public class NetworkChangeReceiver extends BroadcastReceiver {
#Override
public void onReceive(final Context context, final Intent intent) {
if (isAppForground(context))
return;
}
public boolean isAppForground(Context mContext) {
ActivityManager am = (ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE);
List<RunningTaskInfo> tasks = am.getRunningTasks(1);
if (!tasks.isEmpty()) {
ComponentName topActivity = tasks.get(0).topActivity;
if (!topActivity.getPackageName().equals(mContext.getPackageName())) {
return false;
}
}
return true;
}
}
You'll need the permission:
<uses-permission android:name="android.permission.GET_TASKS" />

If you define receivers in your manifest, the app will receive events, even if it is not started.
http://developer.android.com/guide/topics/manifest/receiver-element.html
Broadcast receivers enable applications to receive intents that are broadcast by the system or by other applications, even when other components of the application are not running.
To fix this, just don't define the Receiver in the manifest, but do it programatically in onStart and unregister it again in onStop. The problem with this solution is, that you won't get messages if your app is in the background.
private BroadcastReceiver receiver;
#Overrride
public void onStart(){
super.onStart();
IntentFilter filter = new IntentFilter();
filter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
filter.addAction("android.net.wifi.WIFI_STATE_CHANGED");
receiver = new NetworkChangeReceiver();
registerReceiver(receiver, filter);
}
#Override
protected void onStop() {
super.onStop();
//don't forget to unregister the receiver again
unregisterReceiver(receiver);
}
EDIT: onCreate and onDestroy won't work, as onDestroy will not be called in every instance the app is closed (e.g. if it is closed with the task manager)

Solution Found:
I found a perfect solution to my problem. Thanks to the correct answer in Android service crashes after app is swiped out of the recent apps list, I found out that when an app is closed via Recents list, the whole process will be created again and all the static variables will be freshed to their default values, and the onCreate and all other methods will not be called.
So the solution is something like:
public static boolean appStarted = false;
protected void onCreate(Bundle savedInstanceState) {
appStarted = true;
...
}
public class NetworkChangeReceiver extends BroadcastReceiver {
#Override
public void onReceive(final Context context, final Intent intent) {
if (!MyActivity.appStarted)
return;
...
}
}
The key is to just keep track of when the app starts, and not when the app is closed (because the closing event of app is not dependable and in some situations doesn't work properly)

Can't get embedded BroadcastReceiver to work

This is for a GPS. I have a parent class with an embedded receiver class, and a separate LocationTrackingService class that handles the GPS stuff. I need to Broadcast the mileage traveled to update the UI, but the broadcast is never received. This is the only BroadcastReceiver in the project. I guess I could set a timer to have my ServiceConnection check every couple of seconds and grab the new mileage, but that's bad coding.
Nothing is in the Manifest because I'm registering and unregistering dynamically.
public class Parent
{
GPSReceiver gpsreceiver;
public class EmbeddedReceiver extends BroadcastReceiver
{
#Override
public void onReceive(Context arg0, Intent intent)
{
Bundle extras = intent.getExtras();
if (extras != null) {
distance = extras.getDouble(LocationTrackingService.UPDATE_MILEAGE_MESSAGE);
}
}
}
#Override
public void onCreate(Bundle savedInstanceState)
{
gpsReceiver = new EmbeddedReceiver();
}
private void gpsStart()
{
if (gpsReceiver != null) {
intentFilter = new IntentFilter();
intentFilter.addAction("don't know what goes here");
LocalBroadcastManager.getInstance(this).registerReceiver(gpsReceiver, intentFilter);
}
}
private void gpsStop()
{
if (gpsReceiver != null) {
LocalBroadcastManager.getInstance(this).unregisterReceiver(gpsReceiver);
}
}
}
public class LocationTrackingService extends Service
{
private LocalBroadcastManager broadcaster;
#Override
public int onStartCommand(Intent intent, int flags, int startId)
{
super.onStartCommand(intent, flags, startId);
broadcaster = LocalBroadcastManager.getInstance(this);
return START_STICKY;
}
.... code
private void sendResult(String message)
{
Intent i = new Intent("ParentActivity");
i.setAction("ParentActivity");
if (message != null) {
i.putExtra(message, mileageRunningTotal);
}
broadcaster.sendBroadcast(i);
}
}
When I follow the code into LocalBroadcastManager, on line 215 it does mActions.get(intent.getAction() to get an ArrayList<ReceiverRecord>, and it's null, but I don't know why.
I appreciate any help you can give.

Broadcasts work in such a way that the action acts as a trigger for the receiver. In other words, there are tons of broadcasts being sent around throughout your phone at any given time, the goal of the receiver is to catch the broadcast with the corresponding action when it flies by. It will let all other broadcasts continue through without interruption. Once it finds the one it is looking for, it will receive it and perform the onReceive() functionality.
Though an action can be any string key you care for it to be, it is advised to add in your package name. This gives specificity to your broadcast and allows your broadcast to be more easily managed in the barrage of broadcasts that your phone is sending. This is important as broadcasts can be sent between applications. It makes it so you avoid the following scenario
Application A sends out a system broadcast with action "SOME_ACTION" which we have no interest in. Application B will also be sending out a local broadcast with action "SOME_ACTION" which we are awnt to receive. We will setup Receiver 1 to look for and receive the action "SOME_ACTION" from Application B. However, because of conflicting actions, when Application A sends out a broadcast of "SOME_ACTION", we will inappropriately receive it in Receiver 1 and perform our onReceive() functionality as though we had just received a local broadcast from Application B.
Following recommended convention, you avoid the above situation by doing the following
Instead of setting your action as "SOME_ACTION", it would be set to "com.app_b.package.SOME_ACTION". That way when the broadcast action "com.app_a.package.SOME_ACTION" passes by, it won't be confused for our action and will be allowed to pass.
There may be other reasons for using package name, and this may not be the best of them, but to the best of my knowledge this is the reasoning behind the convention.

I cant see the declaration for the broadcaster object.
broadcaster.sendBroadcast(i);
Is it a Local Broadcast Manager instance?
If not it won't work.

Discovering if Android activity is running

I'm using C2DM, my BroadcastReceivers propagate the C2DM events to a local service. the service complete the registration by sending the id to my webserver pus it's responsible for letting the device know about new messages, however if the application (one of the activities) is up we want to send an intent to that activity with the new data so it can be updated, if not than the NotificationManager is used to notify the user.
The issue is, how to know the activity is running ? the Application object is not an option since the Service is part of the application it's obviously going to be present. unregister in the onDesroy of each application is also not an option since it may occur in orientation change...
Any standard way to get it done ?

Solution 1:
You can use ActivityManager for Checking if Activity is Running or not:
public boolean isActivityRunning() {
ActivityManager activityManager = (ActivityManager)Monitor.this.getSystemService (Context.ACTIVITY_SERVICE);
List<RunningTaskInfo> activitys = activityManager.getRunningTasks(Integer.MAX_VALUE);
isActivityFound = false;
for (int i = 0; i < activitys.size(); i++) {
if (activitys.get(i).topActivity.toString().equalsIgnoreCase("ComponentInfo{com.example.testapp/com.example.testapp.Your_Activity_Name}")) {
isActivityFound = true;
}
}
return isActivityFound;
}
need to add the permission to your manifest..
<uses-permission android:name="android.permission.GET_TASKS"/>
Solution 2:
Your can use an static variable in your activity for which you want to check it's running or not and store it some where for access from your service or broadcast receiver as:
static boolean CurrentlyRunning= false;
public void onStart() {
CurrentlyRunning= true; //Store status of Activity somewhere like in shared //preference
}
public void onStop() {
CurrentlyRunning= false;//Store status of Activity somewhere like in shared //preference
}
I hope this was helpful!

The next approach would work well if you want to handle incoming Google Cloud message (C2DM) by your activity (if any is running) or issue a notification if no activities are running.
Register one BroadcastReceiver in the manifest file. This receiver will handle C2D messages whenever application not running. Register another BroadcastReceiver programmatically in your activity. This receiver will handle C2D messages whenever activity is running.
AndoroidManifest.xml
<receiver
android:name=".StaticReceiver"
android:permission="com.google.android.c2dm.permission.SEND" >
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<category android:name="com.mypackage" />
</intent-filter>
</receiver>
MyReceiver.java
public class StaticReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
// TODO Trigger a Notification
}
}
MyActivity.java
public class MyActivity extends ActionBarActivity {
#Override
protected void onResume() {
super.onResume();
final IntentFilter filter = new
IntentFilter("com.google.android.c2dm.intent.RECEIVE");
filter.addCategory("com.mypackage");
filter.setPriority(1);
registerReceiver(dynamicReceiver, filter,
"com.google.android.c2dm.permission.SEND", null);
}
#Override
protected void onPause() {
super.onPause();
unregisterReceiver(dynamicReceiver);
}
private final BroadcastReceiver dynamicReceiver
= new BroadcastReceiver()
{
#Override
public void onReceive(Context context, Intent intent) {
// TODO Handle C2DM
// blocks passing broadcast to StaticReceiver instance
abortBroadcast();
}
};
}
Note! To catch broadcasts first, the priority of dynamicReceiver IntentFilter must be higher than priority of StaticReceiver instance IntentFilter (default priority is '0').
PS. It looks like broadcasts issued by Google Cloud Messaging Service are ordered broadcasts. Original idea author: CommonsWare

Copied from here.
you can use a static variable within the activity.
class MyActivity extends Activity {
static boolean active = false;
public void onStart() {
active = true;
}
public void onStop() {
active = false;
}
}

Easiest way to check that whether an Activity is running or not is:
Context context = MyActivity.this;
if (! ((Activity) context).isFinishing()) {
// Activity is running
} else {
// Activity has been finished
}
Note: If activity is not running you should not perform any UI related operation.

How do I cancel all pending intents that are qued for intent Service

I have an intentservice that gets qued by the user and by my app automatically. I need to be able to kill all pending intents that are qued when the user logs out of my application, but I cannot seem to get that to work. I have tried stopService() and stopself(), but the intents continue to fire off the intentservice after the user has logged out. I would try to get the id of the intent but that is difficult as everytime the intentservice starts, the variable holding the intent id's is empty. Here is my intentservice code:
public class MainUploadIntentService extends IntentService {
private final String TAG = "MAINUPLOADINTSER";
private GMLHandsetApplication app = null;
private SimpleDateFormat sdf = null;
public boolean recStops = true;
public MainUploadIntentService() {
super("Main Upload Intent Service");
GMLHandsetApplication.writeToLogs(TAG,
"GMLMainUploadIntentService Constructor");
}
#Override
protected void onHandleIntent(Intent intent) {
GMLHandsetApplication.writeToLogs(TAG, "onHandleIntent Started");
if (app == null) {
app = (GMLHandsetApplication) getApplication();
}
uploadData(app);
GMLHandsetApplication.writeToLogs(TAG, "onHandleIntent Finished");
}
#Override
public void onDestroy() {
GMLHandsetApplication.writeToLogs(TAG, "onDestroy Started");
app = null;
stopSelf();
GMLHandsetApplication.writeToLogs(TAG, "onDestroy completed");
}
public void uploadData(GMLHandsetApplication appl) {
//All of my code that needs to be ran
}

Unfortunately, I don't think it's possible to accomplish that with the standard IntentService methods since it doesn't offer a way to interrupt it while it's already going.
There are a few options I can think of that you can try to see if they fit your need.
Copy the IntentService code to make your own modifications to it that would allow you to remove pending messages. Looks like someone had some success with that here: Android: intentservice, how abort or skip a task in the handleintent queue
Instead of copying all the IntentService code, you might also be able to Bind to it like a normal Service (since IntentService extends Service) so you can write your own function to remove pending messages. This one is also mentioned in that link.
Rewrite the IntentService as a regular Service instead. With this option, you'd have more control over adding and removing messages.
I had what sounds like a similar situation where I was using an IntentService, and I eventually just converted it to a Service instead. That let me run the tasks concurrently and also cancel them when I needed to clear them.

Here
When should I free the native (Android NDK) handles? is the HangAroundIntentService class that has the method cancelQueue().
The class also has the method
public static Intent markedAsCancelIntent(Intent intent)
that converts an intent into a cancel intent, and
public static boolean isCancelIntent(Intent intent).
The class is based on the open-sourced Google's code.

Just a thought but inside of your onhandleintent can you have an argument that checks to see if app is running if not then don't run the code? example. In the start of your app you could have a static var
boolean appRunning;
Next in your onhandle of the intent, when you set the appRunning to false, after an onPause or onDestroy of activity, you could wrap the onhandleintent code in a boolean:
protected void onHandleIntent(final Intent intent) {
if(MainActivity.appRunning){
...
}
}
Just a thought