Develop Reference

Running android apps particular activity independently than rest of activities

THIS QUESTION IS SOLVED, PROVIDING ANSWER FOR FUTURE SO VISITORS BELOW
Context :
I am developing a default phone app. Which handles action.DIAL and action.CALL from My application as well as it handles these both intents from other apps too.
What is problem :
If my CallActivity is running ( if any call is ongoing ) then -
When i again try to open my app, it is presenting me CallActivity only.
And because of this i am unable to make another call by opening my app.
What manifest.xml looks like :
<application
android:allowBackup="true"
android:directBootAware="true"
android:fullBackupContent="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=".MainActivity"
android:label="#string/app_name"
android:screenOrientation="portrait"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.CALL_BUTTON" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
</intent-filter>
</activity>
<activity
android:name=".CallActivity"
android:label="#string/title_activity_call"
android:process=":CallManager"
android:screenOrientation="portrait"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter android:priority="800">
<action android:name="android.intent.action.ACTION_CALL" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
</intent-filter>
</activity>
</application>
What i found when searched for the said problem :
How can I launch an independent activity to my application as well as the application of phone launches the activity to make calls?
https://stackoverflow.com/questions/9458300/how-to-create-an-android-activity-and-service-that-use-separate-processes
What are my efforts taken :
You can note i tried android:process=":CallManager" attribute in manifest for my CallActivity
Did that solved the issue :
Nope. I am still unable to open my MainActivity, whenever CallActivity is running. But is caused the problem that now my call is not getting ended as this is completely another process it is unable to reference other calls which remain there in older process.
ANSWER
Did android:process was correct :
No not at all in this case, as it is used when our app memory usage increases over particular limit android starts caching its services and resources in order to avoid it developers generally use android:process which allows them another heap memory available with same heap size.
** What was problem :**
It was related to task and its affinities
Both activities needed to be separated for tasks and their affinities
like :
<activity
android:name="com.example.ActivityA"
android:label="Activity A"
android:launchMode="singleInstance"
android:taskAffinity="com.example.AffinityA" >
</activity>
<activity
android:name="com.example.ActivityB"
android:label="Activity B"
android:launchMode="singleInstance"
android:taskAffinity="com.example.AffinityB" >
</activity>
I must thanks #JayWozz for his answer over SO https://stackoverflow.com/a/45488126/9810130 and must appreciate #gabe-sechan for his sincere help and efforts and for giving his value-able time for this thread.

I think you're basically asking for a new stack of activities. Try launching the intent with FLAG_ACTIVITY_NEW_DOCUMENT| FLAG_ACTIVITY_MULTIPLE_TASKS That will launch the activity as if its a new set of activities, with its own separate listing in the recent apps list. See the definiton of these flags at https://developer.android.com/reference/android/content/Intent

How to run a certain activity in Android Studio?

For instance, I have a few activities within one app, and in order to see a certain activity's UI or whatever, I need to run a certain activity that is not the launcher of the app.
One stupid way is to build a "door" for that activity in the launcher and go inside the activity from the door. However, Is there any better way to run a certain activity alone?

Very easy. Start by exporting the activity you need to run:
Add android:exported="true" in the Activity declaration in the Manifest. This is because am is an external application, and you need to export Activities to allow external application to start them.
Go to "Edit Configurations..." in the "Run" menu.
In the left pane, select your application. In the right pane, in the "General" tab, in the "Launch Options" section, there is a "Launch:" dropdown.
Select "Specified Activity", and enter the name of your activity as it appears in your Manifest.
You can create as many Configurations as you like, and name them according however you like, for example to indicate which activity is being started.

I am using Android Studio stable version 2.1.2 and there is one shortcut to do so. Just open the activity class you wish to run and right click on coding area, There is options to run and debug the particular activity as shown in below screen shot.
For windows use shortcut ctrl+shift+F10 and for mac use ctrl+shift+R. I have tested this in emulator and its working fine, didn't test in actual device.Works only for activity class and don't forget to put cursor in coding area by clicking on it. Also I am not aware whether this option available in older Android studio versions less than 2.1.2.

As mentioned in this answer, you can easily achieve that by giving the activity an action name in the manifest.xml of the app:
<activity android:name="Activity3" ... >
<intent-filter>
<action android:name="com.company.package.FOO"/>
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
then create the following intent from anywhere in order to run this activity specifically:
startActivity(new Intent("com.company.package.FOO"));
After your clarification that the activity has to be run firstly when running the app instead of the launcher, you can achieve that by not setting the content of the launcher activity and instead create an intent that runs the wanted activity:
MainActivity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_layout); // remove this line
Intent intent = new Intent(ThisActivity.this, WantedActivity.class);
intent.putExtra("EXIT", false);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
}

Add exported true Manifest declaration of that activity.
Go to that activity, right click anywhere, go will get certain option with a 'Run XYZ Activity' option too. just run it

<activity android:name=".phoneVideo">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

First you need to have two or more activities in your app to start with. Let's say you want to go to a certain activity in your app to display first. May be for testing purposes or any other. Let's see how it can be done,
First you need to find the AndroidManifest.xml file. Its there under the manifests folder.
According to this first dispaly activity is MainActivity
Lets's say I want to make the home activity display first. So what I have to do is simply cut the intent-filter.../intent-filter and paste it within home activity. Like this
First Displaying Acivity is MainActivity according to this,
<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=".home">
</activity>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
When we want to make the home acivity display first simplay change it as this,
<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=".home">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MainActivity">
</activity>
</application>
This should work. Hope this will help

For my example, the specific activity was called Activity2 and the project was called ScreenSizes
1- Open the Android Manifest: app>manifests>AndroidManifest.xml
2- Change the activity section for the specific activity to include android:exported="true" like this:
<activity android:name=".Activity2"
android:exported="true">
</activity>
3- Open the java class of the specific activity: app>java>com.example.(your app name)>(specific activity)
in my case it was: app>java>com.example.screensizes>Activity2
4- Right click anywhere in the blank/white area of the Java file and select the option Run '(activity name)'
in my case it was: Run 'Activity2'

android app running multiple instances

When i download my app from store.
its installed on main screen, and on apps menu ( when i click the circle with 6 dots on it )
when i click from main screen it opens an app, and when i click from the other place..it opens a second app as well.
i need one app running only..
how can this be fixed?
my manifest
<application
android:name="dfsfsdp"
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".StartupActivity"
android:screenOrientation="portrait" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

I think you aren't running multiples instances (if you are running multiple instances if fail of the mobile), or you see two applications open in the menu what you use to close the running apps (the recent applications menu)?
If you only see one maybe your are restarting the same instance. Look at your StartupActivity or post here to try help you.
If this don't help you, take a look at to read about the lifecycle of an Activity:
http://developer.android.com/training/basics/activity-lifecycle/index.html
Best regards.

Android: Bug when changing the default activity

I'm having a problem with my app after changing the default activity in the manifest. This is the manifest after i changed it. As far as i can see it's syntactically correct.
<application android:icon="#drawable/icon" android:label="#string/app_name">
<uses-library android:name="com.google.android.maps" />
<activity android:name=".loginActivity"
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="CouncilPlannerActivity"></activity>
<activity android:name="MainTabActivity"></activity>
<activity android:name="MapTabActivity" android:theme="#android:style/Theme.NoTitleBar"></activity>
<activity android:name="NodeFormActivity"></activity>
<activity android:name="viewNewsActivity"></activity>
</application>
The problem is when i deploy the app to my device it works fine first time. However, when i close the app with the home button it refuses to open again. Clicking the icon in the devices app list doesn't do anything.
If i change the default activity to the one it was at originally it works fine. Is this a bug or is there another reference to a default activity that i'm missing?
I'm developing on Android 2.2 if that makes a difference.
I just noticed the logcat spits out an error when i try to open the app : "Permission Denied: checkComponentPermission() reqUID10064"

You probably need to post the loginActivity in question here so we can see if there are any problems in the activity. Otherwise double check that the loginActivity is in the same package as the other activities, if its not you need to change the ".loginActivity" part of the manifest to its relative location to the main package, aka "somename.loginActivity"

I think the problem is in loginActivity class. May be you check for already loggined user and finish activity in this case?

How do I close my application when it goes to background (via Home key)?

I want to close my application when it goes background.
My current method is to call finish() in the OnPause() of one of the main activity.
However, in my application there are several activities. When it jump to another activity from my main activity, my main activity will be closed.
It's not what I excepted. I want my applications closed only when the entire applications goes to background (e.g. via Home key)
Thanks.

You don't have to do that.. Android does it by itself when you press Home key.. and when it needs Resources... read this for more http://developer.android.com/reference/android/app/Activity.html

You can kill your own app's process using Process.killProcess(Process.myPid()). If you can't rely on a callback to you activity to tell you when your app has lost focus, and given that you can't rely on onPause (as noted above), you could in principle post yourself a suicide note during onPause:
_runnable = new Runnable() {
#Override
public void run() {
Process.killProcess(Process.myPid());
};
_handler = new Handler().postDelayed(_runnable, 3000);
and then have one your other activities intercept and cancel it during onResume:
_handler.removeCallbacks(_runnable);
(You'll need a way to provide access to the variables across multiple activities.) If the cancelation never comes, then your app will eventually be killed.
Kludgy, but possible, I think.

Now lets consider this is how ur manifest looks like. Main activity Hello starts Hello2 which starts Hello3 and so on.
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".Hello" 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="Hello2"></activity>
<activity android:name="Hello3"></activity>
<activity android:name="Hello4"></activity>
</application>
Now create dummy Launcher activity(HelloStarter) which starts ur Hello activity.
See updated manifest.
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".HelloStarter" android:label="#string/app_name"
android:clearTaskOnLaunch="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="Hello"></activity>
<activity android:name="Hello2"></activity>
<activity android:name="Hello3"></activity>
<activity android:name="Hello4"></activity>
</application>
In ur Hello activity's onDestroy() add this:
System.exit(0);
This works....!!!!