We Keep Coding

How to exit onBackPressed method in android studio?

I have developed an android apps that have a splash screen and a login page. The problem is when a user give credential and pressed log in button it open controlActivity. but when I pressed back button, I navigate to login page again If I pressed back button again I navigate to splash screen. How can I stop navigating to previous page, when user press back button then app should exit?

Why does it happen ?
This is happening because whenever you open another activity from intent, it creates it over it.
How to solve the problem?
You can add a flag like this
Intent intent = new Intent(this, SecondActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
OR
You can finish it.
Intent intent = new Intent(this, SecondActivity.class);
startActivity(intent);
finish();
If you want to close the app onBackPressed, you can override the method. Add this to your activity.
#Override
public void onBackPressed(){
finish();
System.exit(0);
}
Doing this, the app will be closed on back pressed!

You need to put a flag in the activity you want to be forgotten.
Intent intent = new Intent(this, Main2Activity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);

Answer by #Sambhav Khandelwal should solve your problem. In your splash screen you need to do add flags with intent like:
Intent intent = new Intent(SplashScreenActivity.this, LoginActivity.class); //assuming your splash screen name as SplashScreenActivity and login as LoginActivity
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
Or you can do without flags like below:
Intent intent = new Intent(SplashScreenActivity.this, LoginActivity.class);
startActivity(intent);
finish();

Redirect to activity with preserving/creating activity stack

I want to start activity from notification. I want to open an activity, which is successor of some other activities.
Example activities: IntroActivity -> Photos -> SpecificPhoto. What I want to achieve: In case user clicks on notification, I want to open SpecificPhoto activity. Keep in mind, that app can be running (for example PhotosActivity is displayed), or it can be shut down.
I want to preserve back button functionality (move to PhotosActivity on back pressed).
On notification click, I need to launch IntroActivity, because user needs to login here in case he is not.
I tried following (using constants in activities, code):
On PhotosActivity onCreate:
redirectToActivity();
RedirectToActivity method:
private void redirectToActivity() {
Intent intent = getIntent();
int activityCode = intent.getIntExtra("code", 0);
switch (activityCode) {
case SpecificPhotoActivity.CODE:
startActivity(new Intent(this, SpecificPhotoActivity.class));
break;
default:
return;
}
}
By applying this approach, I can traverse the whole activity stack and go to the activity I want. However, this approach is not working in every case. Sometimes, the activity_code is not set (don't know why) and therefore we end in the first activity.
Is there any more professional approach to solve this issue? I believe this must be solved somehow in many apps.

What you want is called TaskStackBuilder.
Here's how you should construct the intent, that would navigate to SpecificPhotoActivity:
Intent action = new Intent(context, SpecificPhotoActivity.class);
PendingIntent pendingIntent = TaskStackBuilder.create(context)
.addNextIntentWithParentStack(action)
.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
In order to correctly specify stack of activities, you should provide android:parentActivityName inside manifest file:
<application ...>
<activity android:name=".SpecificPhotoActivity"
android:parentActivityName=".PhotosActivity"/>
</application>
With this parameter you have specified, that the parent of SpecificPhotoActivity is PhotoActivity, thus TaskStackBuilder would understand where to navigate as soon as back button is clicked inside SpecificPhotoActivity.
Construction of the notification should be as follows:
NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
Notification notification = new NotificationCompat.Builder(this)
.setContentTitle(...)
.setContentText(...)
.setSmallIcon(...)
.setContentIntent(pendingIntent)
.build();
manager.notify(NOTIFICATION_ID, notification);
Now notification click would open SpecificPhotoActivity. A click on back button would navigate to PhotosActivity.
What's left is authorization handling. I suppose you are able to apprehend whether user is authorized or no during the construction of the notification. Hence, following approach should work:
PendingIntent pendingIntent = null;
if (authorized) {
Intent action = new Intent(context, SpecificPhotoActivity.class);
pendingIntent = TaskStackBuilder.create(context)
.addNextIntentWithParentStack(action)
.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
} else {
Intent action = new Intent(context, IntroActivity.class);
action.putExtra("photos_flow", true);
pendingIntent = PendingIntent.getActivity(context, 0, action, 0);
}
Now, inside IntroActivity after successful authorization:
void onAuthorized() {
if(getIntent().getBooleanExtra("photos_flow", false)) {
// most possibly you should pass some id into SpecificPhotoActivity's intent
Intent[] intents = new Intent[]{new Intent(this, PhotosActivity.class), new Intent(this, SpecificPhotoActivity.class)};
startActivities(intents);
finish();
}
}

build a "fake" stake using startActivity()

I need to build a fake back stack in my application. I am starting an activity using aContext.startActivity(aIntent) and would like to build a stack to allow the user to go to the HomeActivity instead of exiting the application.
Now I know about the TaskStackBuilder but I am not sure on how to implement it when it comes to startActivity method.
This is what I got so far when building the stack but I am not sure how to use it in startActivity method
Intent detailActivity = new Intent(aContext, DetailsActivity.class);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(aContext);
stackBuilder.addNextIntentWithParentStack(detailActivity);
PendingIntent pendingIntent = stackBuilder
.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);

Why don't you just use onBackPressed
Context context = this;
#Override
public void onBackPressed()
{
Intent intent = new Intent(context,YourActivity.class);
startActivity(intent);
}

You need to start activity without adding to back stack, then override the onBackpressed
//Start activity without adding to history stack
Intent i = new Intent(...); // Your list's Intent
i.setFlags(i.getFlags() | Intent.FLAG_ACTIVITY_NO_HISTORY); // Adds the FLAG_ACTIVITY_NO_HISTORY flag
startActivity(i);
//Override the newly open activity onBackPressed()
#Override
public void onBackPressed()
{
Intent i= new Intent(getApplicationContext(),HomeActivity.class);
startActivity(i);
}

The fix that i found to work without having to use onBackPressed was to add a flag to the intent
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

For building fake stack use TaskStackBuilder.This will help you to create back stack.
Suppose you activities are 'ActivityA', ActivityB, ActivityC, ActivityD. Now you are in ActivityB and from ActivityB you want launch ActivityD and want a back stack like this:
ActivityA -> ActivityC -> ActivityD
That means back press from ActivityD will go to ActivityC and back press from ActivityC wil go to ActivityA
In ActivityB you can use this
TaskStackBuilder.create(this)
.addParentStack(ActivityA.class)
.addNextIntent(new Intent(this, ActivityA.class))
.addNextIntent(new Intent(this, ActivityC.class))
.addNextIntent(new Intent(this, ActivityD.class))
.startActivities();
To use TaskStackBuilder you min sdk version should be 16 or higher.
For sdk less than 16 you can manually check in onBackPressed and start Activity.
In Activity D:
#Override
public void onBackPressed(){
Bundle extras = getIntent().getExtras();
if (extras.containsKey("FROM_ACTIVITY_B_FOR_STACK")){
// start Activity C
}else{
super.onBackPressed();
}
}
Do this for other activities where you want to add back stack

How do I implement a Button that will return to "Home" after it is clicked?

I have created a "Button" in android studio to send emails. When I click it, it sends an email as intended, but does not then return to the "Home" activity.

You can use finish(); method, but it's not recommended.
See: How to finish current activity in Android
http://developer.android.com/guide/components/processes-and-threads.html#Threads
But, this is my suggestion, you should be able to after clicking the Button, then clear the activity and restart it(or you can do something like Gmail App and doing some stuffs after clicking):
Intent i = getBaseContext().getPackageManager().getLaunchIntentForPackage(getBaseContext().getPackageName());
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
Also you can use:
Intent m = new Intent(FirstActivity.this, SecondActivity.class);
startActivity(m);
Or:
startActivity(new Intent(FirstActivity.this, SecondActivity.class));

Intent intent = new Intent(context, HomeActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
finish();

How to close all running activities from another one?

I've got some activities which I execute one after another without closing (1->2->3->4). I want to close 1,2,3 activities from 4 and execute a new one; the code:
Intent intent = new Intent(UserpickActivity.this, CommunicationActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
UserpickActivity - 4th activity, CommunicationActivity - the next activity. But after this code all previous activities still worked. How can I close all running activities and execute some new activity?

Try this:
When you want to launch CommunicationActivity from Activity4, do this instead:
Intent intent = new Intent(this, Activity1.class); // Your root activity
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); // Will remove all other activities from the task
intent.putExtra("foo", true); // This is to tell Activity1 to launch Activity4
startActivity(intent);
In Activity1.onCreate() do the following:
super.onCreate();
if (getIntent().hasExtra("foo")) {
// We should now launch CommunicationActivity and finish ourselves
Intent intent = new Intent(this, CommunicationActivity.class);
startActivity(intent);
finish();
return; // Don't continue the rest of onCreate()
}
// The rest of your onCreate() goes here
You can only use CLEAR_TOP to clear down to an existing activity in the activity stack. That's why your use of CLEAR_TOP isn't working (because CommunicationActivity doesn't exist in the activity stack).
This method clears all activities and launches the root activity again. When the root activity's onCreate() is called, it checks the Intent for the extra "foo", which it uses as a signal that it needs to launch CommunicationActivity and finish itself. This should do what you want.

Call activity.finish(); after you switch to other activity. This way no activity will remain on stack.
Intent intent = new Intent(UserpickActivity.this, CommunicationActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
//YOUR_ACTIVITY.finish();
Uncomment the above line if you want this activity to be removed from activity stack.

// This will clear all activity and start new task.
Intent intent = new Intent(UserpickActivity.this, CommunicationActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);

Use android:nohistory=true in manifest for Activities.
<activity
android:name=".A"
android:label="#string/app_name"
android:noHistory="true" >