Support lazy loading through DeviceApps.streamInstalledApplications()

[alexrintt]

Lazy loading through new API streamInstalledApplications

With this PR there's an way to use this package to list all packages individually; how and why was explained on #89.

Take this for instance:

final apps = <Application>[];
final appsStream = DeviceApps.streamInstalledApplications(
  includeAppIcons: true,
  includeSystemApps: true,
);

appsStream.listen(
  (app) {
    apps.add(app);
    setState(() {});
  },
  onDone: () {
    isLoading = false;
    setState(() {});
  },
);

The example above will updated the Flutter UI every time a new package is loaded in the native side, instead of:

// This call takes 5~10 seconds in real devices with large apps data set
// Meanwhile a boring loading spinner should be shown
final apps = await DeviceApps.getInstalledApplications(
  includeAppIcons: true,
  includeSystemApps: true,
);
setState(() {}); 

getInstalledApplications propose

We can also re-implement the getInstalledApplications API since the Stream<T>s can be converted to Future<T>s (but not vice-versa).

static Future<List<Application>> getInstalledApplications({
  bool includeSystemApps: false,
  bool includeAppIcons: false,
  bool onlyAppsWithLaunchIntent: false,
}) async {
  return streamInstalledApplications().toList(); // Re-use the logic here and convert as Future<T>
}

This PR is a scratch, I would to know what we can change here to improve even more this feature.

[Djihanegh]

Hello, i need this feature to improve my app performance, any updates @g123k @alexrintt ?

[alexrintt]

i think this repository is no longer maintained, i am using this feature directly from my fork:

dependencies:
  # ...
  device_apps:
    git:
      url: https://github.com/alexrintt/flutter_plugin_device_apps
      ref: 6051e51fd78778f848eca870ec51a0367b5d2fd9 # use this hash instead 'master' because i can push a new commit in the future maybe, and i don't wanna break anyone else app.

there are no docs for this feature, but you can see how i am using this at:

https://github.com/alexrintt/kanade/blob/f149d373a214d59804b26a50fee703eeb28404ca/lib/stores/device_apps.dart#L187-L214

class Store {
  // ...
  Future<void> loadPackages() async {
    isLoading = true;

    notifyListeners();

    totalPackagesCount = await DeviceApps.getInstalledPackagesCount();

    final appsStream = DeviceApps.streamInstalledApplications(
      includeAppIcons: true,
      includeSystemApps: true,
    );

    appsStream.listen(
      (app) {
        apps.add(app);

        throttle(() {
          if (!isDisposed) {
            notifyListeners();
          }
        });
      },
      onDone: () {
        isLoading = false;
        notifyListeners();
      },
    );
  // ...
}

[Djihanegh]

Thank you, it works !