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![](/i/favi32.png) Pro Android with Kotlin@de android telegram Pro Android with Kotlin Developing Modern Mobile15
CHAPTER 3: Activities
This is an arbitrary name-value pair in the form
android:name="..." android:resource="..." android:value="..." />
.
You can have several of them, and they go into an
android.os.Bundle
element available as
PackageItemInfo.metaData
.
Caution
Writing an app without any activity is possible. The app can still provide services,
broadcast receivers, and data content as a content provider. One thing you as an app developer
need to bear in mind is that users do not necessarily understand what such components without
user interfaces actually do. In most cases, providing a simple main activity just to give information
is recommended and improves the user experience. In a corporate environment, though, providing
apps without activities is acceptable.
Starting Activities
Activities can be started in one of two ways. First, if the activity is marked as the launchable
main activity of an app, the activity can be started from the app launcher. To declare an
activity as a launchable main activity, inside the
AndroidManifest.xml
file you’d write the
following:
"com.example.myapp.ExampleActivity">
"android.intent.action.MAIN" />
"android.intent.category.LAUNCHER" />
android.intent.action.MAIN
tells Android that it is the main activity and will go to the
bottom of a task, and the
android.intent.category.LAUNCHER
specifies that it must be listed
inside the launcher.
Second, an activity can be started by an intent from the same app or any other app. For this
to be possible, inside the manifest you declare an intent filter, as shown here:
"com.example.myapp.ExampleActivity">
"com.example.myapp.ExampleActivity.START_ME" />
"android.intent.category.DEFAULT"/>
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