Develop Reference

Check if activity onStop is called while starting a new activity

I am trying to solve a problem. In my application I need to determine if onStop method was called because of starting a new activity or it was called after user had clicked on the home button or had switched to another app.
I have BaseActivity class, and I need to check it here.
I have tried to find a way to do this, but unfortunately still no solution is found.
Maybe there is a workaround for that.
The idea is to differentiate the initiator of onStop method call.
I would be grateful for any help.

A possible solution would be to register an ActivityLifecycleCallbacks and save the reference name of the last activity that called onResume:
public class ActivityChecker implements Application.ActivityLifecycleCallbacks {
private static ActivityChecker mChecker;
private String mCurrentResumedActivity = "";
public static ActivityChecker getInstance() {
return mChecker = mChecker == null ? new ActivityChecker() : mChecker;
}
// If you press the home button or navigate to another app, the onStop callback will be called without touching the mCurrentResumedActivity property.
// When a new activity is open, its onResume method will be called before the onStop from the current activity.
#Override
public void onActivityResumed(Activity activity) {
// I prefer to save the toString() instead of the activity to avoid complications with memory leaks.
mCurrentResumedActivity = activity.toString();
}
public boolean isTheLastResumedActivity(#NonNull Activity activity) {
return activity.toString().equals(mCurrentResumedActivity);
}
// [...] All other lifecycle callbacks were left empty
}
The ActivityLifecycleCallbacks can be registered in your Application class:
public class App extends Application {
public App() {
registerActivityLifecycleCallbacks(ActivityChecker.getInstance());
}
}
Don't forget to register it in your manifest:
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="your.package.name">
<application
...
android:name=".App"
> ...
</application>
</manifest>
Then, you can use it in your base Activity.
public class MyBaseActivity {
#Override protected void onStop() {
if(ActivityChecker.getInstance().isTheLastResumedActivity(this)) {
// Home button touched or other application is being open.
}
}
}
References:
Registering your custom Application class and the ActivityLifecycleCallbacks: https://developer.android.com/reference/android/app/Application.html
After writing this I found this link with some other options to retrieve the current resumed activity: How to get current foreground activity context in android?.

You can use SharedPreferences to check it:
#Override
protected void onStop() {
super.onStop();
SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);
pref.edit().putBoolean("IfOnStopCalled", true).apply();
}
Check in your BaseActivity:
SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);
Boolean IfOnStopCalled = pref.getBoolean("IfOnStopCalled",false);
if(IfOnStopCalled){
//Do your action
}
else{
//Do your action
}

How to check activity has been destroyed or no more running

I am working on an android app and have an activity. I have written a code in my activity that will start a new activity after getting response from server, this code is getting executed even after I press back button on my activity.
So, I want to check that if my current activity is not active anymore, then the code should not run.
How can I check that activity is not running or in existence any more.
Please help me if anyone know how to do this.
Thanks a lot in advanced.

Activity is still in memory that's why your code is executed to finish it completed call finish() after starting another activity.
To check if current activity is there or not you have to override onDestroy() method which is called everytime when your activity is completely destroyed.
For checking activity is running or not follow this question

just call finish() method when you starts a new Activity
like
Intent intent = new Intent(this, NextActivity.class);
startActivity(intent);
finish();//this activity has been finish and the code will not execute
you can check if Activity is destroyed or not.
override this method
public void onDestroy() {
super.onDestroy();
Log.d("Activity name,"destroyed");
}

Try like this
class MyActivity extends Activity {
static boolean isActive = false;
#Override
public void onStart() {
super.onStart();
isActive = true;
}
#Override
public void onStop() {
super.onStop();
isActive = false;
}
}

Check here : Proper way to know whether an Activity has been destroyed
The question have your answer and as the solution provided just use the SharedPrefrence to store the variable.

Android - How to know when app has been resumed after being in background

I'm trying to determine when my app is being resumed after the user closed it, in any way, pressing home button, back button or switching to another app.
What I need to do is to set a boolean when the app goes in background, so, when it is resumed, I know that it was in background before and I can act accordingly.
I tried to use onResume and onPause methods in activities to know when the app goes in background and it is then resumed, but as only one activity can be alive at at time, I had no success. When an activity is paused, this doesn't mean that the app went to background, because another activity could have been launched, but the onResume event of that activity will trigger only after the previous one has paused.
I've also tried to list all the apps in foreground, but with no success, if I put my app in background resuming another app, my app always results to be in the foreground.
I read that since Android 4 there is a new method to know when the app is in foreground, but I need my app to be compatible with Android 3.0 devices too.
Here is the code I tried putting in every single activity (MyApp is my Application name):
#Override
protected void onResume() {
super.onResume();
MyApp.isPaused = false;
}
#Override
protected void onPause() {
super.onPause();
MyApp.isPaused = true;
}
This is also my attempt to list all the apps in foreground:
ActivityManager activityManager = (ActivityManager)((Activity) currentContext).getSystemService( ACTIVITY_SERVICE );
List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
for(RunningAppProcessInfo appProcess : appProcesses){
if(appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND){
if(appProcess.processName.equals("com.xxx.myapp")) {
Log.i("MyApp", "it's in foreground");
}
Log.i("MyApp", appProcess.processName);
}
}

This class provides a singleton to determine "the activity in background" status. It uses a timer with a threshold(i.e. 0.3s) to determine the activity is went to background or not.
One thing has to point out is that if the user resumes to the activity within the threshold (i.e. 0.3s), this test will be failed.
If you have a better solution, please share with us :)
Ref: https://gist.github.com/steveliles/11116937

You are absolutely correct :) Because only one activity can be alive at a time so you need something which remains alive through out the application life cycle :) like Application instance itself or you can also make use of shared preference for that matter. But seriously using shared prefference for checking lifecycle is wrong choice if you ask me.
If I was in your position I would have gone for Application class :) Here is code if you want to do the same :)
import android.app.Application;
/**
* Created by sandeepbhandari on 3/3/16.
*/
public class AppService extends Application{
private static AppService sInstance;
public static boolean isGoingToBackGround=false;
#Override
public void onCreate() {
super.onCreate();
sInstance = this;
}
public static AppService getInstance() {
return sInstance;
}
}
In all your activities onPause just set
AppService service = AppService.getInstance();
service.isGoingToBackGround =true;
And in onResume check the same variablethats all :) and yeah if you want to use your application class rather than default Application you have to make change to manifest.xml
<application
android:name=".AppService"
Thats all :)

Override onTrimMemory(int level) in your Application. Might not be the prettiest way, but it has worked for me.
You will get
TRIM_MEMORY_BACKGROUND = 40;
when your application went into the Background.

You can make Application class inside your project to save state of your project. When any activity goes to pause call on pause respectively while on resume call on resume method and save state of the inside this class. Even if one activity goes on pause another on resume your class will know exact state of the application. Or another way you can save applicaton state in shared preference in each activity can change its value.

i trust there is no need for u to post a code... that being said...
start by logging every implemented methods onCreate(), onPause(), onDestroy(), and other well reputed Activity methods...
but back button does not just pause it kills, thus onCreate is called most
and check onStart() too.

public class CustomApplication extends Application {
private static boolean activityVisible;
#Override
public void onCreate() {
super.onCreate();
}
public static boolean isActivityVisible() {
return activityVisible;
}
public static void activityResumed() {
activityVisible = true;
}
public static void activityPaused() {
activityVisible = false;
}
}
and in your all activities set
#Override
protected void onResume() {
super.onResume();
CustomApplication.activityResumed();
}
#Override
protected void onPause() {
super.onPause();
CustomApplication.activityPaused();
}
and in your manifest
<application
android:name=".CustomApplication"

Check if activity that used intent still alive

I have two activities: MainActivity and EventActivity.
Whenever I open my app (in MainActivity by default) and it has a certain flag in SharedPreferences, it intents to EventActivity and finishes itself. Otherwise, it only intents.
In EventActivity I have a button that, when clicked, calls finish() and goes back to EventActivity.
The problem is, when I re-open my application, it will finish the MainActivity and, when I press my custom back button, it will close the app (because the intent handle has finished).
How do I check if MainActivity didn't used finish()?
If I can do that, checking if it is finished I can intent to it.
Thanks.

Override the onDestroy method of MainActivity in that set a public static Boolean field of MainActivity. In that method set that public static field as true. Check for its value in EventActivity before you finish it i.e. when you are coming back from EventActivity to MainActivity. And fire an intent to start MainActivity from EventActivity if it's value is true. And set it's value as false in onCreate of MainActivity.
As follows:
In MainActivity.java
public class MainActivity extends Activity {
public static boolean isMainActivityDestroyed = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
isMainActivityDestroyed = false;
.
.
.//Do something here
}
#Override
protected void onDestroy() {
super.onDestroy();
isMainActivityDestroyed = true;
.
.
.//Do something here
}
}
In EventActivity.java
public class EventActivity extends Activity {
.
.
.//Some methods
//Method which finishes EventActivity & starts MainActivity if destroyed
public void buttonOnClick()
{
if(MainActivity.isMainActivityDestroyed)
{
Intent i = new Intent(this, MainActivity.class);
startActivity(i);
finish();
}
}
}
If isMainActivityDestroyed becomes true then it is an indication that MainActivity used finish().

You could create your own Application class extending Application and launch the needed activity from your Application's onCreate. In manifest you would then remove the default intent filter for your MainActivity.

how to know if an activity has started already

I'm working in a app ,where I filter if screen is on or off and launch an activity when the screen is on, but sometime it launch the activity but the activity was started already , i would like to ask you if it was any way to know inside my app if an activity is already launched.
When i start the activity i added this code
intent11.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
Thank you so much.

I think that you can set variable with activity life cycle
class IAMActivity extends Activity {
static boolean isStart = false;
public void onStart() {
super.onStart();
isStart = true;
}
public void onStop() {
super.onStop();
isStart = false;
}
}

Here is what you are looking for:
class MyActivity extends Activity {
static boolean alreadyLaunched = false;
#Override
public void onStart() {
super.onStart();
alreadyLaunched = true;
}
#Override
public void onStop() {
super.onStop();
alreadyLaunched = false;
}
}

If you want to restrict your activity to one instance, you can set the launchMode in the manifest file to either singleTask or singleInstance, depending on your requirements.
<activity
android:launchMode="singleTask"
...>
...
</activity>
With singleTask a new intent is delivered via onNewIntent() instead of onCreate().
See <activity> for more details.