What are intent-filters in Android?

Question

In my android app, I wanted to start an activity \'B\' from initial activity \'A\'. I have created classes for both of these. However when using following code to start B, I

Answer 1

An intent filter is an expression in an app's manifest file that specifies the type of intents that the component would like to receive.

When you create an implicit intent, the Android system finds the appropriate component to start by comparing the contents of the intent to the intent filters declared in the manifest file of other apps on the device. If the intent matches an intent filter, the system starts that component and delivers it the Intent object.

AndroidManifest.xml

<activity android:name=".HelloWorld"
    android:label="@string/app_name">
    <intent-filter>
        <action android:name="android.intent.action.VIEW"/>
        <category android:name="android.intent.category.DEFAULT"/>
        <category android:name="android.intent.category.BROWSABLE"/>
        <data android:scheme="http" android:host="androidium.org"/>
    </intent-filter>
</activity>

Launch HelloWorld

Intent intent = new Intent (Intent.ACTION_VIEW, Uri.parse("http://androidium.org"));
startActivity(intent);

Answer 2

There can be no two Lancher AFAIK. Logcat is a usefull tool to debug and check application/machine status in the behind. it will be automatic while switching from one activity to another activity.

Answer 3

The Activity which you want it to be the very first screen if your app is opened, then mention it as LAUNCHER in the intent category and remaining activities mention Default in intent category.

For example :- There is 2 activity A and B
The activity A is LAUNCHER so make it as LAUNCHER in the intent Category and B is child for Activity A so make it as DEFAULT.

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".ListAllActivity"
              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=".AddNewActivity" android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>
</application>

Answer 4

intent filter is expression which present in manifest in your app that specify the type of intents that the component is to receive. If component does not have any intent filter it can receive explicit intent. If component with filter then receive both implicit and explicit intent

Answer 5

When there are multiple activities set as main and launcher with an intent filter in the manifest. Then first activity considers as Launcher activity, and android launch or open the first activity.

<category android:name="android.intent.category.LAUNCHER" />  

The above code makes an app icon available in the device menu, so if we declare 2 launcher activity in the manifest, there will be 2 app icons get created in the device app menu.

So there will be 2 app icons, on click of the first icon, first declared activity in manifest will be launch, and click of another second declared activity gets launch

Answer 6

Keep the first intent filter with keys MAIN and LAUNCHER and add another as ANY_NAME and DEFAULT.

Your LAUNCHER will be activity A and DEFAULT will be your activity B.