I have an initial activity O and one more activity A in which i can select to go to activities A1,A2,A3 and for example fill in a form in each of them. So i follow this path:
O>A>A1>A>A2>A>A3
While i am at A3 i want to press the back button and go to O again but i will have to pass from every instance of A (let's assume i use finish() or no history in the manifest for A1,A2,A3 so they will be not present in the stack)
how can i declare that A will only have one instance (the last one) in the stack, so that if i press back button twice i will go to O again?
#Override
public void onBackPressed() {
Intent intent = new Intent(this,O.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
}
Change the launchMode of activity A to singleTop. As it states in the documentation:
If an instance of the activity already exists at the top of the target
task, the system routes the intent to that instance through a call to
its onNewIntent() method, rather than creating a new instance of the
activity.
Now, instead of going from A -> A1 -> A, you can just finish() activity A1 (or use the up button), which will return you to the instance of activity A.
Related
I want to go back to an already launched activity without recreating again.
#Override
public void onBackPressed() {
Intent i = new Intent(SecondActivity.this, FirstActivity.class);
this.startActivity(i);
}
Instead of doing is there any other way to go back to another activity which is already created, which I get back with " Back button "
Add android:launchMode="singleTop" in the FirstActivity declaration in your AndroidManifest.xml like so
<activity
android:name=".FirstActivity"
android:launchMode="singleTop"/>
You could also try the following if SecondActivity was started from FirstActivity
#Override
public void onBackPressed() {
this.finish();
}
Whenever you start a new activity with an intent you can specify an intent flag like this:
// this flag will cause the launched activity to be brought to the front
// of its task's history stack if it is already running.
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
or
// If set and this intent is being used to launch a new activity from an
// existing one, the current activity will not be counted as the top activity
// for deciding whether the new intent should be delivered to the top instead
// of starting a new one.
intent.addFlags(Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP);
When starting SecondActivity do not finish the first activity so when you go back , you will be taken to the first activity.
Intent i = new Intent(FirstActivity.this,SecondActivity.class);
startActivity(i);
On your second Activity, close the Activity calling finish() instead of creating a Intent for the other screen.
By calling finish() the Application will go back in the Activity stack and show the previous Activity (if its not finished()).
Don't call finish() on 1st Activity, when you start 2nd Activity. When back is pressed on 2nd Activity, it finishes itself and goes back to 1st Activity by default. onCreate() is not called for 1st Activity in this case. No need to override onBackPressed() in 2nd Activity.
However, Android can destroy 1st Activity when you are using 2nd Activity, to reclaim resources, or, if you have checked Don't keep activities in Developer options. In such case you can use onSaveInstanceState() to save data and onRestoreInstanceState() to use it again in 1st Activity. You can also get the saved data in onCreate(). Here is how it works. Also, onSaveInstanceState() is called only if android decides to kill the Activity and not when user kills the Activity(e.g. using back button).
In My application there are three activities A, B and C and i have kept two buttons in every activity (Previous and Next button) so that user can move from one activity to another. Suppose User is in activity B and user wants to navigate to Activity A.
Here my problem is.. I need to load the old activity instead of creating new instance of Activity A.
Just call finish on the current activity and the previous one will be shown automatically.
Try to call your intent with the flag "BROUGHT TO FRONT"
Intent i = new Intent(...);
i.setFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
startActivity(i);
I am new to android, I am using the TabActivity. From the TabActivity I am starting the activity from intent. Order of Activity A - B - C - D then from the activity D, How can I create the same new Activity A (destroy the previous A). If i use the FLAG_ACTIVITY_REORDER_TO_FRONT its does not create the activity, instead open the last Activity A, If I use the Clear_top then it destroy the B and C Activity.
Please help to achieve this.
When you are calling Activity B from within activity A, call finish() after creating the new activity B using Intent. This will end the Activity A there. Then again from witin Activity D you can create a new Activity A using intent. Hope this helps.
You might want to consider destroying the previous activity before calling the next activity
so when you are going to call the activity B from A you might want to destroy the activity A using the keyword finish()
and likewise when you move from B to C and C to D and in the D activity destroy the activity of C and call the new activity A that way the A activity will get restarted.
finish(); //finish the current class
Intent intent = new Intent();
intent.setClass(getApplicationcontext(), nextclass.class); //specify the next class
startActivity(intent); //start the next class.
http://developer.android.com/guide/topics/manifest/activity-element.html#lmode
android:launchMode might be the answer you are looking for. From documentation:
Every time there's a new intent for a "standard" activity, a new instance of the class is created to respond to that intent. Each instance handles a single intent.
Means the existing the activity (if exist) will remain in the current stack untouched and new instance will be created at the top of the current stack. So when user back buttons, the user will see your activity A at the bottom of the stack as well.
When I am starting a new activity do I need to explicitly finish the current activity or does android take care this ?
This is what I write in activity A to start activity B:
Intent intent = new Intent(this, BActivity.class);
startActivity(intent);
Should I end A by calling next line after above mentioned two lines ?
this.finish()
In General no you shouldn't.
The difference will be if you call finish in Activity A, While the user is in Activity B if they press the back button they will go back to whatever they were doing before opening your application. If you instead do not call finish in Activity A they will go back to Activity A
If you DO call finish:
Activity A -> Activity B -> [user press back] -> Homescreen (or whatever activity is on the stack below activity A)
if you DO NOT call finish:
Activity A -> Activity B -> [user press back] -> Activity A
No it is not compulsory.
finish()
finish method state that "Call this when your activity is done and should be closed. The ActivityResult is propagated back to whoever launched you via onActivityResult()."
reference link >> link
explicitly finish the current activity or does android take care this ?
It depends on your requirement if you wants activity A while coming back form activity B still there so you need not to call finish but if you does not want activity A when coming back form activity B then you should call finish ....
Example: I have an android app with 3 activities that has the following behaviors:
A (Home) -> B -> C
Activity A launches Activity B
Activity B launches Activity C
When user is on Activity B and they hit the Back button, it takes them Activity A
When user is on Activity C and they hit the Back button, it takes them Activity B
What I would like is when user is on Activity C, if they hit the "My Root Activity" button, it will take them to Activity A without adding a new instance of Activity A to the back stack.
So I don't want to have:
1) A
2) A-B
3) A-B-C
4) A-B-C-A
What I would like is:
1) A
2) A-B
3) A-B-C
4) A
How can I do this?
Check out the intent stack machinery!
http://developer.android.com/guide/topics/fundamentals/tasks-and-back-stack.html
EDIT:
You can add "singleTaks" or "singleInstance" to your activity in the manifest file and implement the onNewIntent() method.
"singleTaks"
The system creates the activity at the root of a new task and routes the intent to it. However, if an instance of the activity already exists, the system routes the intent to existing instance through a call to its onNewIntent() method, rather than creating a new one.
"singleInstance"
Same as "singleTask", except that the system doesn't launch any other activities into the task holding the instance. The activity is always the single and only member of its task.
Check out this link
I have each child activity extend a base activity. In the base activity, I defined an onActivityResult() which will impose a finish() if the activity at the top of the stack set a specific resultCode. So if they hit the "My Root Activity" button on Activity C, it will recursively roll up to Activity A. The Back button maintains it's functionality.
This is a rare scenario as I would have used "singleTask" but launching Activity A involves reloading it's dependencies which I don't want to couple of Activity C.