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what will happen if add screenOrientation=behind into launch Activity element

what will happen if add screenOrientation=behind into launch Activity element
<activity
android:name=".ui.activity.SplashActivity"
android:screenOrientation="behind"
android:configChanges="screenSize|orientation|keyboard"
android:noHistory="true">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
I want to know what will happen if I write this , and want to know the details.

If you are set all activity of your project in the same screenOrientation. you can start your application with a splash screen activity, set the orientation like in your current code and forward to your CoreActivity or any other activity in your App.
In your AndroidManifest.xml set
<activity
android:name=".CoreActivity"
android:screenOrientation="behind"/>
This will use the same orientation as the activity that's immediately beneath it in the activity stack.
Explicitly it's used to Keep the screen in the same orientation as whatever is behind this activity.

singleTask activity not loading properly

I have an activity 'A' defined in Manifest like below:
<activity
android:name=".A"
android:launchMode="singleTask"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
When I launch my APP, that activity is always loaded from the start. It wont start from my prev activity.
When I remove android:launchMode, then it works as I expect.

Since you set android:launchMode="singleTask", the activity A will always be the root of your activities.
From DOCS:
In contrast, "singleTask" and "singleInstance" activities can only begin a task. They are always at the root of the activity stack. Moreover, the device can hold only one instance of the activity at a time — only one such task.
Default mode is standard. So, when you remove android:launchMode="singleTask", your APP returns to standard launch mode.
That's why if you app is always starting Activity A.

If you would like to start a different Activity on launch replace that in the xml name attribute that contains LAUNCHER
<activity
android:name=".ActivityB"
android:launchMode="singleTask"
android:screenOrientation="portrait"
>
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
Where Activity B is an alternate activity.

How to make an activity above the MainActivity.java?

My current MainActivity is a navigation drawer.
I want to make another activity on top of the navigation drawer.
Lets make that activity StartActivity.
On StartActivity there is a start button.
What i want to do is make the StartActivity opens up first when the app runs.
And when the user presses the START button on the StartActivity, it will direct him/her to the navigation drawer.
is this possible?

Create the StartActivity.
somewhere call "startActivity(intentforMainactivity);
go to the manifest and move
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
from the
<activity
android:name="sehtestapp.MainActivity"
into
<activity
android:name="sehtestapp.StartActivity"
Your Application will then start the StartActivity first

1) Create another Activity, that you'll call StartActivity
2) Set up a layout that you'll use in your StartActivity with a
button in it.
3)Create the onClickListener to launch a new Intent when clicked.
Make it launch the MainActivity.
4) Change your AndroidManifest as follow :
<activity
android:name="XXX.StartActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="XXX.MainActivity"
android:parentActivityName="XXX.StartActivity" />

You can try changing the Launcher activity and send intent having a boolean bundled in it when START button is pressed, in MainActivity fetch the intent, read that boolean value and open the drawer programmatically.

How open not main activity from Notification

In my app I have a Activity that is opened from a Notification, but is not declared has main activity or launcher activity·
Also, this activity is declared has "singleTop".
Works fine for most users, but some are a little problem.
In some occassions when click the Notification the Activity is opened and, when click back, the app Main Activity is shown.
How to don't show the main activity when click back?
Also, if the users are in this activity and click home, and later it clicks into the app icon in order to open the Main activity, the previously opened activity, that is not main activity is opened. This can change?
Thanks.
-- The structure of the manifest is:
<activity android:name=".MainActivity" android:label="#string/app_name" android:exported="true" android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".ShowAlarmsActivity" android:launchMode="singleTop" android:exported="true" android:theme="#style/AppThemeWithoutActionBar" />

you may do this my either overriding on back press and starting the parent activity using this code
or if you are using action bar you may use parent activity tag
Intent intent = new Intent(getApplicationContext(), ParentActivity.class);
startActivity(intent);
also if you want to distinguish that if the user is coming from notification or from app launch you may use intent to pass some key value and cater it
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="parentActivity" />

Open only one activity, without the main activity

I have an application that has one service and 2 activities.One activity (the main one) is a preferences activity and the other one is a dialog themed activity. The service from time to time needs to open only the dialog themed activity (using FLAG_ACTIVITY_NEW_TASK).
The problem is that when the preferences activity is opened in background (for example the user pressed HOME key instead of BACK, so the activity is OnPause) and the service tries to open the dialog themed activity, also the main activity is opened (comes in foreground).
I don't want this. So, how can I open only the themed activity from the service, without the main activity pop up ?
Android Manifest .xml
<service android:name=".SimpleService"> </service>
<activity
android:name=".Preferences" android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".popup_activity" android:theme="#android:style/Theme.Dialog" android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.SAMPLE_CODE" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="screenon.popup.activity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
And from the service :
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.addCategory("screenon.popup.activity");
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

I believe you're looking for the android:launchMode attribute.

Alex , I believe that all you want is to display preferences activity just once & then it must die(or lets say finish()) .
In that case you can override onResume of the preferences activity
to finish your preferences activity after it is resumed after pause
#Override
public void onResume()
{
//if activity is resumed after onPause then only run it
this.finish(); //simply kill your activity if it is resumed after pause
}
EDIT-To know whether the activity was paused you need to override onPause().I think you can dig out the rest.
Hope it helps!