AndroidManifest.xml 中的两个主要活动

Question

I would like to have two main activities in my app. So in my manifest I put:

<activity
    android:name="mypackage1.MainActivity"
    android:label="@string/title_activity_main">

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

<activity
    android:name="mypackage2.MainActivity2"
    android:label="@string/title_activity_main2">

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />

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

</activity>

Two icons are created in my apps menu. But when I click on each of them the first activity MainActivity is always launched. Is it possible to have two main activities? If so, what's wrong with what I did? Thanks

Answer 1

The LAUNCHER intent filter is what determines what shows up in the app drawer/launcher. That is why you get two icons shown up.

However, you also set the DEFAULT intent filter, which sets the default Activity for the whole package. Since you set it twice, you get the problem of precedence of the first/latest registered. When you remove the DEFAULT filter, you will be able to start whatever you click on in the launcher.

In short, remove the following line from both Activities:

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

Answer 2

Yes, just mark two or more of your <activity> s as LAUNCHER within your manifest. In addition you have to set the android:taskAffinity attribute on both of your Launcher-Activities which specify the exact package and Activity to be started.

<activity android:label="MyApp" android:name=".MyApp" android:taskAffinity="com.example.MainActivity">
        <intent-filter>
            <action android:name=".MyApp"/>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
</activity>


<activity android:label="Settings" android:name=".Settings" android:taskAffinity="com.example.SettingsActivity" >
    <intent-filter>
        <action android:name=".Settings"/>
        <action android:name="android.intent.action.MAIN"/>
        <category android:name="android.intent.category.LAUNCHER"/>
    </intent-filter>
</activity>

Answer 3

Use android:documentLaunchMode="intoExisting" , to launch a separate task based on the intent's Component name and data URI. Without this (by default), the activity will share all the same activities, as android:documentLaunchMode default to none .

intoExisting: The system searches for a task whose base intent's ComponentName and data URI match those of the launching intent. If the system finds such a task, the system clears the task, and restarts with the root activity receiving a call to onNewIntent(android.content.Intent). If the system does not find such a task, the system creates a new task. source

    <activity
        android:name=".CameraActivity"
        android:exported="true"
        android:documentLaunchMode="intoExisting"
        android:label="@string/app_1_label">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity
        android:name=".ProfilePoseNetActivity"
        android:exported="true"
        android:documentLaunchMode="intoExisting"
        android:label="@string/app_2_label">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

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The intention of potroae using task affinities to prevent your 2 activities from sharing the same task. However, it is annoying to have to select a task name, ie com.example/SettingsActivity for every task you want to launch separately.