Develop Reference

How to detect if activity stack is empty and activity stack size?

One method is to pass a bundle/store in sharedpreference through which this information is obtained. Is there a method other than such to achieve this? In fragments you can do a getBackStackEntryCount.

In your Application class, register a listener for Activity life cycle events:
public class MyApplication extends Application {
#Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
// add to stack
}
#Override
public void onActivityStarted(Activity activity) {
}
#Override
public void onActivityResumed(Activity activity) {
}
#Override
public void onActivityPaused(Activity activity) {
}
#Override
public void onActivityStopped(Activity activity) {
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
#Override
public void onActivityDestroyed(Activity activity) {
// remomve from stack
}
});
}
}
Then you just need to keep track of your activities in a list (do not put the Activity itself, put the name or a weak reference to it). You can monitor other events as needed.

Android, How do I know if the application has closed

I need to know when the user close the App, not when the user press on the "home" button, but when the user close the App at the "recent applications menu".
At those two cases the App go to the onPause method. Is there any way to tell them apart?
I`m asking because, I want to delete the user from my database on one situation, and not at the other.

you can try combining multiple callbacks from the activity lifecycle.
onUserLeaveHint() can be realy usefull to get know if the activity is in background or foreground
isFinishing(): can bu used to know if the activity is been closed by a finish() call or if is the system shutting down the activity to free resources

you can try using a Service for that, in this service override onTrimMemory method
#Override
public void onTrimMemory(int level) {
super.onTrimMemory(level);
switch (level) {
case ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN:
//app was closed
break;
}
}
check more about services

I'm not sure, but maybe ActivityLifecycleCallbacks can help you. It need to test.
Example:
public class YourApplication extends Application {
#Override
public void onCreate() {
lifecycleListener = new ActivityLifecycleListener();
registerActivityLifecycleCallbacks(lifecycleListener);
}
public class ActivityLifecycleListener implements Application.ActivityLifecycleCallbacks {
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
#Override
public void onActivityStarted(Activity activity) {
}
#Override
public void onActivityResumed(Activity activity) {
}
#Override
public void onActivityPaused(Activity activity) {
}
#Override
public void onActivityStopped(Activity activity) {
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
#Override
public void onActivityDestroyed(Activity activity) {
}
}
}

Application Level onResume Android

Problem
The idea is very simple. Whenever an user comes back to my app from the Recents I want to show a simple dialog prompting with the password.
I know how to prompt the dialog with password, but my problem is how do I understand that the user has entered my app from the recents. If I put the prompt in the onResume in every activity, then it will get triggered everytime even if the user doesn't enter from the Recents menu.
There are lots of activities and fragments in my app. So, I would love to have a more generic or application level solution.

Implement Application.ActivityLifecycleCallbacks, that will provide all activity callback in your application class.
public class AppController extends Application implements
Application.ActivityLifecycleCallbacks
{
#Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(this);
}
#Override
public void onActivityCreated(Activity activity, Bundle bundle) {
}
#Override
public void onActivityStarted(Activity activity) {
}
#Override
public void onActivityResumed(Activity activity) {
}
#Override
public void onActivityPaused(Activity activity) {
}
#Override
public void onActivityStopped(Activity activity) {
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle bundle) {
}
#Override
public void onActivityDestroyed(Activity activity) {
}
}

You could try with this flag FLAG_ACTIVITY_LAUNCHER_FROM _HISTORY:
if((getIntent().getFlags() & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY )!=0){
Log.d(TAG, "Called from history");
//clear flag from history
Intent intent = getIntent().setFlags( getIntent().getFlags() & (~ Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY));
setIntent(intent);
}
Source : Android - detecting application launch from home or history
When "A" Activity is start from recent, this flag is present.
Now this flag will be also present if "A" activity call "B" activity and on "B" user press back.
So you have to check flag and when you detect it you have clear intent by removing this flag, source: Remove a Paint Flag in Android

Try below sample
/**
* TODO : After update to API level 14 (Android 4.0),
* We should implement Application.ActivityLifecycleCallbacks
*/
public class GlobalApplication extends android.app.Application
{
private boolean inForeground = true;
private int resumed = 0;
private int paused = 0;
public void onActivityResumed( Activity activity )
{
++resumed;
if( !inForeground )
{
// Don't check for foreground or background right away
// finishing an activity and starting a new one will trigger to many
// foreground <---> background switches
//
// In half a second call foregroundOrBackground
}
}
public void onActivityPaused( Activity activity )
{
++paused;
if( inForeground )
{
// Don't check for foreground or background right away
// finishing an activity and starting a new one will trigger to many
// foreground <---> background switches
//
// In half a second call foregroundOrBackground
}
}
public void foregroundOrBackground()
{
if( paused >= resumed && inForeground )
{
inForeground = false;
}
else if( resumed > paused && !inForeground )
{
inForeground = true;
}
}
}
Put below code in your all activities.
public class BaseActivity extends android.app.Activity
{
private GlobalApplication globalApplication;
#Override
protected void onCreate()
{
globalApplication = (GlobalApplication) getApplication();
}
#Override
protected void onResume()
{
super.onResume();
globalApplication.onActivityResumed(this);
}
#Override
protected void onPause()
{
super.onPause();
globalApplication.onActivityPaused(this);
}
#Override
public void onDestroy()
{
super.onDestroy();
}
}

I would suggest using LifecycleObserver. If your Application class implements this interface it marks a class as a LifecycleObserver, it does not have any methods, instead, it relies on OnLifecycleEvent annotated methods. The usage is simple:
public class AndroidApplication extends Application implements LifecycleObserver {
#OnLifecycleEvent(Lifecycle.Event.ON_START)
public void onAppStart() {
//enter code here
}
#OnLifecycleEvent(Lifecycle.Event.ON_STOP)
public void onAppStop() {
//enter code here
}
...etc
}
With Lifecycle.Event you can access all lifecycle states through Enum. It is part of androidx.

How does automatic activity tracking work for google analytics android

I've implemented something similar for iOS using a quick swizzle of viewDidAppear to allow my company to track flow around the app in our own internal systems.
Now, ideally I'd like to avoid having to implement appear & disappear tracking in every activity for our internal use, so was hoping someone could shed some light into how the GA library achieves this.
I had a good google around and couldn't find any kind of internal event that's posted when an activity comes into the foreground so am at a bit of a loss at the moment.
Cheers!

I know the following is not a direct answer to your question but why not applying a basic OOP principle? Inheritance.
import android.app.Activity;
public class BaseActivity extends Activity {
#Override
protected void onResume() {
super.onResume();
// hit when activity appears. Tell Appserver!
}
#Override
protected void onPause() {
super.onPause();
// hit when activity hides. Tell Appserver!
}
}
and then have your other Acivities extend this instead of android.app.Activity?

You can use ActivityLifecycleCallback. Example below:
public class MordorApplication extends Application {
#Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(new ActivityLifecycleLogger());
}
}
public class ActivityLifecycleLogger implements Application.ActivityLifecycleCallbacks {
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
createActivityStateLog(activity, "created");
}
#Override
public void onActivityStarted(Activity activity) {
createActivityStateLog(activity, "started");
}
#Override
public void onActivityResumed(Activity activity) {
createActivityStateLog(activity, "resumed");
}
#Override
public void onActivityPaused(Activity activity) {
createActivityStateLog(activity, "paused");
}
#Override
public void onActivityStopped(Activity activity) {
createActivityStateLog(activity, "stopped");
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
createActivityStateLog(activity, "savingStateInstance");
}
#Override
public void onActivityDestroyed(Activity activity) {
createActivityStateLog(activity, "destroyed");
}
private void createActivityStateLog(Activity activity, String state) {
String log = String.format("Activity %s - %s", activity.getClass().getName(), state);
LOG.debug(log);
}
private static final Logger LOG = LoggerFactory.getLogger(ActivityLifecycleLogger.class);
}

Google Analytics has automatic Activity tracking feature.
See
https://developers.google.com/analytics/devguides/collection/android/v4/?hl=en#analytics-xml
or do John's answer :)
You can create delegate class (suppose GaUtils) then call that on resume/pause. Just one line, don't you?
#Override
protected void onPause() {
super.onPause();
GaUtils.onPause(screenName); // track pause
}

Android AsyncTask re-runs when activity is opened

In my App the user has to login.
They open the app on the login page
They enter email/password and hit login
A LoadingScreenActivity is opened that has a swirly circle and is running an AsyncTask that goes to my database and retrieves all the users info
After the AsyncTask is completed it starts an intent to launch MainPageActivity.
There are two problems with this at the moment:
If the user logs in and then goes to the home screen while the app loads the MainPageActivity will open as soon as it is ready (on top of the existing home page) even though the app has been minimised
If the user logs in and then goes to the home screen while the app loads and then returns to the loading screen the AsyncTask will complete twice over
For problem 1. At the moment my onPostExecute() method in LoadingScreenActivity looks like this:
#Override
public void onPostExecute() {
//open the main page
Intent mainPage = new Intent(getApplicationContext(), MainPageActivity.class);
mainPage.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
mainPage.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK );
startActivity(mainPage);
}
Is there a way I could detect in this method if the main page activity should be opened yet?
For problem 2. I've hit a complete road block on this, is there a way to detect if the activity has simply been re opened rather than started for the first time? I'd really appreciate any tips on this, I'm quite new to android so I'm not even convinced an Async task is the way to go with this.
Thanks for your time
LoadingScreenActivity.java
public class LoadingScreenActivity extends Activity implements TaskFragment.TaskCallbacks {
private static final String TAG_TASK_FRAGMENT = "task_fragment";
private TaskFragment mTaskFragment;
#Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
FragmentManager fm = getFragmentManager();
mTaskFragment = (TaskFragment) fm.findFragmentByTag(TAG_TASK_FRAGMENT);
// If the Fragment is non-null, then it is currently being
// retained across a configuration change.
if (mTaskFragment == null) {
mTaskFragment = new TaskFragment();
fm.beginTransaction().add(mTaskFragment, TAG_TASK_FRAGMENT).commit();
}
setContentView(R.layout.loading_screen);
ActionBar actionBar = getActionBar();
actionBar.hide();
TextView title = (TextView) findViewById(R.id.loading_title);
TextView progress = (TextView) findViewById(R.id.loading_progress);
title.setText(R.string.app_name);
progress.setText("Loading your info");
}
#Override
public Context onPreExecute() {
return getApplicationContext();
}
#Override
public void onProgressUpdate(int percent) {
}
#Override
public void onCancelled() {
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
finish();
}
#Override
public void onPostExecute() {
//open the main page
Intent mainPage = new Intent(getApplicationContext(), MainPageActivity.class);
mainPage.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
mainPage.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK );
startActivity(mainPage);
}
}
and TaskFragment.java
public class TaskFragment extends Fragment {
static interface TaskCallbacks {
Context onPreExecute();
void onProgressUpdate(int percent);
void onCancelled();
void onPostExecute();
}
private TaskCallbacks mCallbacks;
private DummyTask mTask;
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
mCallbacks = (TaskCallbacks) activity;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Retain this fragment across configuration changes.
setRetainInstance(true);
// Create and execute the background task.
mTask = new DummyTask();
mTask.execute();
}
#Override
public void onDetach() {
super.onDetach();
mCallbacks = null;
}
private class DummyTask extends AsyncTask<Void, Integer, Void> {
Context context;
boolean running = true;
#Override
protected void onPreExecute() {
if (mCallbacks != null) {
context = mCallbacks.onPreExecute();
}
}
#Override
protected Void doInBackground(Void... ignore) {
//Get the current thread's token
synchronized (this)
{
if(running){
DatabaseHandler dbHandler = new DatabaseHandler(context);
dbHandler.populateSQLiteDatabase();
}
}
return null;
}
#Override
protected void onProgressUpdate(Integer... percent) {
if (mCallbacks != null) {
mCallbacks.onProgressUpdate(percent[0]);
}
}
#Override
protected void onCancelled() {
if (mCallbacks != null) {
mCallbacks.onCancelled();
}
}
#Override
protected void onPostExecute(Void ignore) {
if (mCallbacks != null) {
mCallbacks.onPostExecute();
}
}
}
}

in your activity in the manifest just add android:configChanges="keyboardHidden|orientation|screenSize"
and in the activity implement this
#Override
public void onConfigurationChanged(Configuration newConfig) {
};

I'm afraid, i don't really understand your first problem.
About the second one, there are a couple of ways depending on your minimum API level. Starting from API 14 you may register ActivityLifecycle Callbacks inside an Android Application. To do this, i would recommend:
Inherit Android application with a custom one
Replace the Android application in your manifest
inside your custom application register itself as activity lifecycle listener
inside the abstract methods you get the instance of the currently applying activity (may safe object.name() in a String)
depending on your handling you may safe a boolean value or whatever to identify the behaviour
methods inside your custom application are accessible by casting (MyCustomApplication)getApplication()
Heres a snippet:
package com.example.preferencestest;
import android.app.Activity;
import android.app.Application;
import android.app.Application.ActivityLifecycleCallbacks;
import android.os.Bundle;
public class MyCustomApplication extends Application implements ActivityLifecycleCallbacks {
private String storedActivity;
private Boolean doOrNot = false;
public MyCustomApplication() {}
public Boolean getDoOrNot() { return doOrNot;}
public void setDoOrNot(Boolean doOrNot) { this.doOrNot = doOrNot; }
#Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(this);
}
// these two are the most important ones since they will be fired everytime
#Override
public void onActivityResumed(Activity activity) {
if (activity.getClass().getName().equals(storedActivity)) {
doOrNot = true;
}
}
#Override
public void onActivityPaused(Activity activity) {
storedActivity = activity.getClass().getName();
}
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) { }
#Override
public void onActivityStarted(Activity activity) { }
#Override
public void onActivityStopped(Activity activity) { }
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) { }
#Override
public void onActivityDestroyed(Activity activity) { }
}
inside your Manifest you MUST declare this new Applicationclass like this:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.preferencestest"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="16"
android:targetSdkVersion="21" />
<application
android:name="com.example.preferencestest.MyCustomApplication"
{...}
Then inside your Activity you may do this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Boolean whatToDo = ((MyCustomApplication)getApplication()).getDoOrNot();
}
Using onConfigurationChanged has a couple of disadvantages. There are a couple of actions (placing device in dock, turning display and so on) which restart the Activity. You should rather save the current state of the Activity with
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
#Override
protected void onRestoreInstanceState(Bundle state) {
super.onRestoreInstanceState(state);
}