What does it mean "No Launcher activity found!"

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.

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>

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>

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.

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.

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!

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" />

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).

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 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..

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:

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

In Eclipse when can do this:

But it is preferable make the corresponding changes inside the Android manifest file.

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>

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