Develop Reference

I'm developing in Android Studio, When I run my app on my S4 2 copies are created on my phone

My project currently has just two classes and when I run the project on my phone two apps are created. The first app runs the entire project and the second app only runs one class(The class that isn't my Main). Has anyone encountered this bug before?

Maybe you have multiple activities defined as launcher activities in your manifest, like so:
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name">
<activity
android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".AnotherActivity">
<!-- creates a second "app" when deploying -->
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
That would create two apps on your phone.

Yes, 'Jaap Van Hengstum' is correct.
If you want only one entry point for your application, then only one activity should have below intent filter.
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
Remove if you have multiple entry of it in your manifest file.

Having a single application name, and not separate activity names

I have an android application with three activities: Loading, Main, Credits.
But when I try to run and look into the emulator, I have three icons: Loading, Main, Credits.
How can I just have a single Application name? And where do I set it?

Set in android manifest file in application level.
android:label="#string/app_name"
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".Loading"
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=".Main" />
<activity android:name=".Credits" />

In your AndroidManifest.xml, you just need to set <intent-filter> for only one Activity other Activities don't need this tag.

What does it mean "No Launcher activity found!"

I am writing a simple program of Android, and getting these no errors, I don't know what they are. My program is right, but showing not output.
I think it is because of these two lines:
[2005-01-06 19:56:38 - my_Android] No Launcher activity found!
[2005-01-06 19:56:38 - my_Android] The launch will only sync the application package on the device!

Here's an example from AndroidManifest.xml. You need to specify the MAIN and LAUNCHER in the intent filter for the activity you want to start on launch
<application android:label="#string/app_name" android:icon="#drawable/icon">
<activity android:name="ExampleActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

Multiple action tags in a single intent-filter tag will also cause the same error.

Like Gusdor said above, "Multiple action tags in a single intent-filter tag will also cause the same error." (Give him the credit! I could just kiss Gusdor for this!)
I didn't find any docs for this fact!
I had added a new (USB) action and being clever, I lumped it in the same intent-filter. And it broke the launch.
Like Gusdor said, one intent filter, one action!
Apparently each action should go in its own intent filter.
It should look like this...
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
<action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
</intent-filter>
When I did this, WAZOO! it worked!

Do you have an activity set up the be the launched activity when the application starts?
This is done in your Manifest.xml file, something like:
<activity android:name=".Main" android:label="#string/app_name"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

Check your manifest.xml. Make sure you have the category LAUNCHER there.
<activity android:name=".myActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

It means you didn't specify an Activity for Android to launch as the default when the app opens from the launcher. You have to add an Intent Filter in the Manifest for the Activity you would like to act as the default when the app is being launched.
Read http://developer.android.com/guide/topics/intents/intents-filters.html#ccases for more details.

I fixed the problem by adding activity block in the application tag. I created the project using wizard, I don't know why my AdroidManifest.xml file was not containing application block? I added the application block:
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name" >
<activity
android:name=".ToDoListActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
And I get the desired output on the emulator.

As has been pointed out, this error is likely caused by a missing or incorrect intent-filter.
I would just like to add that this error also shows up if you set android:exported="false" on your launcher activity (in the manifest).

I had this same problem and it turns out I had a '\' instead of a '/' in the xml tag. It still gave the same error but just due to a syntax problem.

If you are using the standard eclipse IDE provided by google for Android development, you can check the "Launcher Activity" check-box while creating a new Activity. Please find below:

In Eclipse when can do this:
But it is preferable make the corresponding changes inside the Android manifest file.

You missed in specifying the intent filter elements in your manifest file.Manifest file is:
<application android:label="#string/app_name" android:icon="#drawable/icon">
<activity android:name="Your Activity Name"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
Add and check this correctly. Hope this will help..

Manifest is case sensitive, so please compare this lines for any case mismatch especially the word MAIN in:
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />

You can add launcher to activity in eclipse manifest visual editor:

MAIN will decide the first activity that will used when the application will start.
Launcher will add application in the application dashboard.
If you have them already and you are still getting the error message but maybe its because you might be using more than more category or action in an intent-filter. In an intent filter there can only be one such tag. To add another category, put it in another intent filter, like the following
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<!--
TODO - Add necessary intent filter information so that this
Activity will accept Intents with the
action "android.intent.action.VIEW" and with an "http"
schemed URL
-->
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<data android:scheme="http" />
<category android:name="android.intent.category.BROWSABLE" />
</intent-filter>

just add this to your aplication tag in AndroidManifest.xml file
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
and also edit the uses-sdk tag from android:targetSdkVersion="16" to 17
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />

You have not included Launcher intent filter in activity you want to appear first, so it does not know which activity to start when application launches, for this tell the system by including launcher filter intent in manifest.xml

Issue with launching Android application via Intents

My problem is thus; I am new to programming on the ANDROID platform and have a 'working' application that piggy-backs on the API-Docs example. I wish it to launch three tabs one containing a list of reports, one a form to file a report and the last to show the geo-located reports. It doesn't appear as a separate application, it instead appears as a list to be launched by the API-Docs example. Below is my manifest code...
<activity android:name=".HelloFlamingos">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.SAMPLE_CODE" />
</intent-filter>
</activity>
<activity android:name=".Controls2" android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.TAB" />
</intent-filter>
</activity>
<activity android:name=".List1" android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.TAB" />
</intent-filter>
</activity>
<activity android:name=".ReviewTab" android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.TAB" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="3" />
HelloFlamingos is the initial page that I wish to be displayed, I realise that the intents for this are wrong, have thought about using category: VIEWS, action: DEFAULT, however is seemingly unwilling to work. Thanks!

In what context is the activity started? If you're looking to have the HelloFlamingos activity the first displayed from the Android OS, you should change its category in the manifest to category.LAUNCHER.
If you're looking to start the activity from elsewhere in your app, create an Intent which matches what you've specified (category.SAMPLE_CODE) and use startActivity or startActivityForResult.

Too many Activities being started when launching an Android Application

I am confirming about creating activity.
My Manifest.xml is like this :
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".FirstActivity"
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=".SecondActivity"
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=".ThirdActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
You can see property action android:name= property is "android.intent.action.MAIN" and
category android:name= is "android.intent.category.LAUNCHER" for all activities.
When the application starts up, it calls FirstActivity.
Then calls useless Activity such as ThirdActivity or SecondActivity.
In this case, is my manifest.xml correct?
Or, do I need to set another property to Second and Third activity?
If so, what is that?
I wonder manifest.xml file is right for my case.
Please advise.

Try this config:
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".FirstActivity" 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=".SecondActivity" android:label="#string/app_name">
<intent-filter>
</intent-filter>
</activity>
<activity android:name=".ThirdActivity" android:label="#string/app_name">
<intent-filter>
</intent-filter>
</activity>

Think of an Intent as message used to start an Activity to do something. So I can create an Intent to view a web page and an application with an Activity which knows how to view a web page - most likely the browser - can intercept his Intent as act on it.
You tell Android which Activities can act on which Intents using the <intent-filter> part of your Manifest.
The MAIN Intent is a special one. This is sent to an application when it is launched and basically it says "Go!" So the Activity which shoud be displayed first needs to intercept this by having a correctly defined <intent-filter>.
As you had all three Activities with MAIN in their filter they all responded to the request to start your application. So you should have that <intent-filter> only for FirstActivity.

One of the other problems with using
<category android:name="android.intent.category.LAUNCHER" /> for more than one activity is that the Phone's launcher menu will display more than one icon...
From the docs:
CATEGORY_LAUNCHER The activity can
be the initial activity of a task and
is listed in the top-level application
launcher.