Android-practice-2-ImplicitIntents

Unlike explicit intent where we provide the current context and target component, Implicit intent needs type of action and data for that action specified. Later on Android system examines other app's intent-filters in AndroidManifest.xml file and finds activity that can handle that implicit intent, and if so, we start the Activity.

We can also think about the other way around. We can allow our app to respond to ( or receive ) an implicit intent sent from some other app by specifying it through intent-filters in the AndroidManifest.xml file.

Related methods

• The look of constructor is same as that of explicit intent, but parameters are different : Intent(String action, Uri uri) The primary pieces of implicit intent are action and data. Notice that here we don't mention target activity.

• After defining implcit intent, we ask the system to examine other apps whether they have any activity that can handle our intent : intent.resolveActivity(PackageManager pm) Above method needs an instance of PackageManager, which is provided by getPackageManager()

• If there's activity that is matching our implicit intent, the component name will be returned and we can start the activity.

  if(intent.resolveActivity(getPackageManager()) != null) {
      startAcvitity(intent)
  } else {
      Log.d(tag: "ImplicitIntents", msg: "Couldn't find any qualified activity to handle this intent")
  }
  

• ShareCompat.IntentBuilder is a helper class for constructing sharing intents. Upon getting an IntentBuilder instance via .from(Activity launchingActivity), we subsequently call setters for necessary information and finally, start a chooser.

  ShareCimpat.IntentBuilder.from(this)
                           .setType("text/plain")
                           .setCooserTitle("Choose!")
                           .setText(sharingString)
                           .startChooser();
  

Since Android 11 ( API level 30 or higher ) there is default system visibility filtering which affects the return result of methods that query for the information about the other apps on the device. In such case, we need to declare package visibility needs so our application can access other apps.

For more detail implementation of Implicit Intent for each step please refer to the attached example.