From my MainActivity (Launcher Activity) I press a button to start my GameActivity. I have it so when I hit the Back button in Game Activity, I don't return to my MainActivity and instead return to my home screen. Now when I resume my app it goes to MainActivity instead of returning to GameActivity despite being shown.
Goal
Main Activity -> Game Activity -> Home -> Game Activity
Current Result
Main Activity -> Game Activity -> Home -> Home Activity
A couple things..
It works perfectly when I navigate with my home and menu buttons.
I have no launchMode in my Manifest
So let us see what I have done!
Main Activity Button Click
Button startButton = findViewById(R.id.buttonStart);
startButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, GameActivity.class);
//stops back button to return to add player screen
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
});
Manifest Simplified
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainPage.MainActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar"
android:screenOrientation="portrait"
>
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".GamePage.GameActivity"
android:label="#string/title_activity_game"
android:theme="#style/AppTheme.NoActionBar"
android:screenOrientation="portrait" />
</application>
In that case, just call finish() right after launching you GameActivity.
Button startButton = findViewById(R.id.buttonStart);
startButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, GameActivity.class);
startActivity(intent);
finish();
}
});
Edit: Update launchMode for your GameActivity also:
<activity android:name=".GameActivity" android:launchMode="singleInstance">
when you tap on the back button of device the method onBackPress is called, you can override him to redirect user according your necessity, which mean you can change the action for the Back Button, Code:
//When Back Button on click, it will come to this method.
#Override
public void onBackPressed() {
//Do anything you want here,
}
It doesn't seem like this is possible to do using the conventional back-stack mechanism. You can't return to the home screen using the back button without popping off all the Activities in your back-stack first (hence destroying them, if you have no memory leaks).
Then, when you click the menu button, a screenshot of your last displayed Activity should be shown, but since all of your Activities are destroyed your launcher Activity is loaded.
One way you can handle re-entering the app at the point of your choosing is by implementing a navigation Activity (in many cases this is a splash screen) as the launcher Activity. In this Activity, you would determine (using persistent storage i.e. SharedPreferences) which Activity/back-stack state the app should be set to.
For this example, you could store a boolean with key isInGame in SharedPreferences when you enter GameActivity. Then in the navigation activity, you can retrieve the value and launch GameActivity if true. Obviously, for handling game/app state you will have to store a lot more, but this demonstrates simple navigation.
When I press the arrow back I want to navigate to my previous screen(where I came from). So if I'm in MainActivity and go to setting I want the arrow to point back to MainActivity, but if I'm in another Activity I want it to go back to that activity.
<activity
android:name=".SettingsActivity"
android:label="#string/action_settings"
android:parentActivityName=".MainActivity" >
</activity>
How do you start settings activity?
Just use startActivity(intent) in main activity and don't call finish() method. It should be handled automatically.
sample code:
Intent intent = new Intent(MainActivity.this, SettingsActivity.class);
startActivity(intent);
just comment what's your problem exactly and I'll edit my answer.
I am developing simple application with only two activities.
Activity C configures application
Activity A for interaction with user when some event occur
It is not possible for user to navigate from the one to the other - this is why I call them independent activities. Further more activity A is being invoked only form event, there is no way for user to do it manually.
Problem. Let's assume that application is properly configured. Some event occurs in the system, so application A is being shown to the user. The user interact with it and activity goes to background. Then the user decides to launch configuration activity C. Activity C is shown to the user. The user uses back button to "close" activity, but instead of android launcher or desktop the user is being shown activity A (taken from history).
Similar scenario might happen the other way. C is being used by user, then taken to background. Some event shows activity A and user using back button goes to C instead of closing activity A.
I have solved the problem, but the solution is pretty dirty. Is there any clean or standard way of solving such problem?
Part of my solution includes what was suggested in one answer:
snippet from AndroidManifest.xml:
<activity
android:name=".C"
android:clearTaskOnLaunch="true"
android:excludeFromRecents="false"
android:launchMode="singleTask"
...
>
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:exported="false"
android:name=".A"
android:excludeFromRecents="true"
android:noHistory="true"
android:launchMode="singleInstance"
android:clearTaskOnLaunch="true"
....
>
</activity>
snippet from activity A:
public boolean onKeyUp(final int p_keyCode, final KeyEvent p_event) {
switch(p_keyCode) {
case KeyEvent.KEYCODE_ENDCALL:
case KeyEvent.KEYCODE_HOME:
case KeyEvent.KEYCODE_BACK:
case KeyEvent.KEYCODE_MUTE:
case KeyEvent.KEYCODE_POWER:
this.finish();
break;
....
}
return super.onKeyUp(p_keyCode, p_event);
}
snipped from event handler:
public class H extends BroadcastReceiver {
...
Intent intent = new Intent(p_context, A.class);
intent.addFlags(Intent.FLAG_FROM_BACKGROUND);
intent.addFlags(Intent.FLAG_ACTIVITY_NO_USER_ACTION);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
p_context.startActivity(intent);
...
}
It works for my application. However I want application (activity C) to appear in Recent application. But once activity A is invoked application is removed from Recent.
I don't know if this is the cleanest way to do this, but you can override the void onBackPressed() activity method. This way you can mannually move your activity to the background, like this, and prevent the previous activity from popping in:
public void onBackPressed () {
moveTaskToBack (true);
}
Edit: Turns out there's a better way to do this:
Open your AndroidManifest.xml, and inside each declaration put the following: `android:noHistory="true"``. Doing so will tell Android that your activity does not leave a history, and therefore, when the user hits back Android will quit the application, since there's no other activity for it to return to.
I've an app with 3 activities
LoginActivity
ActivityA
ActivityB
User starts with LoginActivity. After successful login, he goes to ActivityA. ActivityA invokes ActivityB using startActivityForResult and processes the response using onActivityResult.
If user presses 'Home' button from ActivityA or ActivityB and relaunches the application, I want to take user back to LoginActivity
I tried playing around with onRestart and onResume. Both of these are called when ActivityA is reinitialized via home screen or onActivityResult (when user comes back from ActivityB).
How can I implement this requirement?
PS: I checked similar questions on SO and did not find something that matches my requirement.
Thanks.
I will redirect you to this question here. I think it should answer your question.
When you declare your intents to start activity A and activity B, try using the nohistory flag e.g.
Intent intent = new Intent(this, ActivityA.class);
// do not keep this intent in history
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
startActivity(intent);
Then when you relaunch, it will go back to the login activity.
Try writing this in your AndroidManifest file for each activity
<activity android:launchMode="singleTask"
android:name=".LoginActivity" />
<activity android:launchMode="singleTask"
android:name=".ActivityA" />
<activity android:launchMode="singleTask"
android:name=".ActivityB" />
My main activity A has as set android:launchMode="singleTask" in the manifest. Now, whenever I start another activity from there, e.g. B and press the HOME BUTTON on the phone to return to the home screen and then again go back to my app, either via pressing the app's button or pressing the HOME BUTTONlong to show my most recent apps it doesn't preserve my activity stack and returns straight to A instead of the expected activity B.
Here the two behaviors:
Expected: A > B > HOME > B
Actual: A > B > HOME > A (bad!)
Is there a setting I'm missing or is this a bug? If the latter, is there a workaround for this until the bug is fixed?
FYI: This question has already been discussed here. However, it doesn't seem that there is any real solution to this, yet.
This is not a bug. When an existing singleTask activity is launched, all other activities above it in the stack will be destroyed.
When you press HOME and launch the activity again, ActivityManger calls an intent
{act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER]flag=FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_IF_NEEDED cmp=A}
So the result is A > B > HOME > A.
It's different when A's launchMode is "Standard". The task which contains A will come to the foreground and keep the state the same as before.
You can create a "Standard" activity eg. C as the launcher and startActivity(A) in the onCreate method of C
OR
Just remove the launchMode="singleTask" and set FLAG_ACTIVITY_CLEAR_TOP|FLAG_ACTIVITY_SINGLE_TOP flag whenever call an intent to A
From http://developer.android.com/guide/topics/manifest/activity-element.html on singleTask
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.
This means when the action.MAIN and category.LAUNCHER flags targets your application from the Launcher, the system would rather route the intent to the existing ActivityA as opposed to creating a new task and setting a new ActivityA as the root. It would rather tear down all activities above existing task ActivityA lives in, and invoke it's onNewIntent().
If you want to capture both the behavior of singleTop and singleTask, create a separate "delegate" activity named SingleTaskActivity with the singleTask launchMode which simply invokes the singleTop activity in its onCreate() and then finishes itself. The singleTop activity would still have the MAIN/LAUNCHER intent-filters to continue acting as the application's main Launcher activity, but when other activities desire calling this singleTop activity it must instead invoke the SingleTaskActivity as to preserve the singleTask behavior. The intent being passed to the singleTask activity should also be carried over to the singleTop Activity, so something like the following has worked for me since I wanted to have both singleTask and singleTop launch modes.
<activity android:name=".activities.SingleTaskActivity"
android:launchMode="singleTask"
android:noHistory="true"/>
public class SingleTaskActivity extends Activity{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
intent.setClass(this, SingleTop.class);
startActivity(intent);
}
}
And your singleTop activity would continue having its singleTop launch mode.
<activity
android:name=".activities.SingleTopActivity"
android:launchMode="singleTop"
android:noHistory="true"/>
Good luck.
Stefan, you ever find an answer to this? I put together a testcase for this and am seeing the same (perplexing) behavior...I'll paste the code below in case anyone comes along and sees something obvious:
AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example" >
<uses-sdk android:minSdkVersion="3"/>
<application android:icon="#drawable/icon" android:label="testSingleTask">
<activity android:name=".ActivityA"
android:launchMode="singleTask">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<activity android:name=".ActivityB"/>
</application>
</manifest>
ActivityA.java:
public class ActivityA extends Activity implements View.OnClickListener
{
#Override
public void onCreate( Bundle savedInstanceState )
{
super.onCreate( savedInstanceState );
setContentView( R.layout.main );
View button = findViewById( R.id.tacos );
button.setOnClickListener( this );
}
public void onClick( View view )
{
//Intent i = new Intent( this, ActivityB.class );
Intent i = new Intent();
i.setComponent( new ComponentName( this, ActivityB.class ) );
startActivity( i );
}
}
ActivityB.java:
public class ActivityB extends Activity
{
#Override
public void onCreate( Bundle savedInstanceState )
{
super.onCreate( savedInstanceState );
setContentView( R.layout.layout_b );
}
}
I tried changing minSdkVersion to no avail. This just seems to be a bug, at least according to the documentation, which states the following:
As noted above, there's never more than one instance of a "singleTask" or "singleInstance" activity, so that instance is expected to handle all new intents. A "singleInstance" activity is always at the top of the stack (since it is the only activity in the task), so it is always in position to handle the intent. However, a "singleTask" activity may or may not have other activities above it in the stack. If it does, it is not in position to handle the intent, and the intent is dropped. (Even though the intent is dropped, its arrival would have caused the task to come to the foreground, where it would remain.)
I think this is the behaviour you want:
singleTask resets the stack on home press for some retarded reason that I don't understand.
The solution is instead to not use singleTask and use standard or singleTop for launcher activity instead (I've only tried with singleTop to date though).
Because apps have an affinity for each other, launching an activity like this:
Intent launchIntent = context.getPackageManager().getLaunchIntentForPackage(packageName);
if(launchIntent!=null) {
launchIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
}
will cause your activty stack to reappear as it was, without it starting a new activity upon the old one (which was my main problem before). The flags are the important ones:
FLAG_ACTIVITY_NEW_TASK Added in API level 1
If set, this activity will become the start of a new task on this
history stack. A task (from the activity that started it to the next
task activity) defines an atomic group of activities that the user can
move to. Tasks can be moved to the foreground and background; all of
the activities inside of a particular task always remain in the same
order. See Tasks and Back Stack for more information about tasks.
This flag is generally used by activities that want to present a
"launcher" style behavior: they give the user a list of separate
things that can be done, which otherwise run completely independently
of the activity launching them.
When using this flag, if a task is already running for the activity
you are now starting, then a new activity will not be started;
instead, the current task will simply be brought to the front of the
screen with the state it was last in. See FLAG_ACTIVITY_MULTIPLE_TASK
for a flag to disable this behavior.
This flag can not be used when the caller is requesting a result from
the activity being launched.
And:
FLAG_ACTIVITY_RESET_TASK_IF_NEEDED Added in API level 1
If set, and this activity is either being started in a new task or
bringing to the top an existing task, then it will be launched as the
front door of the task. This will result in the application of any
affinities needed to have that task in the proper state (either moving
activities to or from it), or simply resetting that task to its
initial state if needed.
Without them the launched activity will just be pushed ontop of the old stack or some other undesirable behaviour (in this case of course)
I believe the problem with not receiving the latest Intent can be solved like this (out of my head):
#Override
public void onActivityReenter (int resultCode, Intent data) {
onNewIntent(data);
}
Try it out!
I've found this issue happens only if the launcher activity's launch mode is set to singleTask or singleInstance.
So, I've created a new launcher activity whose launch mode is standard or singleTop. And made this launcher activity to call my old main activity whose launch mode is single task.
LauncherActivity (standard/no history) -> MainActivity (singleTask).
Set splash screen to launcher activity. And killed launcher activity right after I call the main activity.
public LauncherActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = new Intent(this, HomeActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_TASK_ON_HOME);
startActivity(intent);
finish();
}
}
<activity
android:name=".LauncherActivity"
android:noHistory="true"
android:theme="#style/Theme.LauncherScreen">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.DEFAULT"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<!-- Launcher screen theme should be set for the case that app is restarting after the process is killed. -->
<activity
android:name=".MainActivity"
android:launchMode="singleTask"
android:theme="#style/Theme.LauncherScreen"/>
Pros: Can keep the MainActivity's launch mode as singleTask to make sure there always is no more than one MainActivity.
If both A and B belong to the same Application, try removing
android:launchMode="singleTask"
from your Activities and test because I think the default behavior is what you described as expected.
Whenever you press the home button to go back to your home screen the activity stack kills some of the previously launched and running apps.
To verify this fact try to launch an app from the notification panel after going from A to B in your app and come back using the back button ..........you will find your app in the same state as you left it.
When using launch mode as singleTop make sure to call finish() (on current activity say A) when starting the next activity (using startActivity(Intent) method say B). This way the current activity gets destroyed.
A -> B -> Pause the app and click on launcher Icon, Starts A
In oncreate method of A, you need to have a check,
if(!TaskRoot()) {
finish();
return;
}
This way when launching app we are checking for root task and previously root task is B but not A. So this check destroys the activity A and takes us to activity B which is currently top of the stack.
Hope it works for you!.
This is how I finally solved this weird behavior. In AndroidManifest, this is what I added:
Application & Root activity
android:launchMode="singleTop"
android:alwaysRetainTaskState="true"
android:taskAffinity="<name of package>"
Child Activity
android:parentActivityName=".<name of parent activity>"
android:taskAffinity="<name of package>"
Add below in android manifest activity, it will add new task to top of the view destroying earlier tasks.
android:launchMode="singleTop" as below
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:launchMode="singleTop"
android:theme="#style/AppTheme.NoActionBar">
</activity>
In child activity or in B activity
#Override
public void onBackPressed() {
Intent intent = new Intent(getApplicationContext(), Parent.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
startActivity(intent);
finish();
}
<activity android:name=".MainActivity"
android:launchMode="singleTop">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
//Try to use launchMode="singleTop" in your main activity to maintain single instance of your application. Go to manifest and change.