Start an Android Activity

Many Android APIs want you to communicate with other apps and services via an Intent. Creating these is easy, but receiving the results requires adding code to your apps Activity which is ugly in terms of code separation.

To make this a little nicer to work with from Uno, we have an API you can use. It is used in the following fashion:

  • First add Android.ActivityUtils to the 'Packages' section of your unoproj file.
  • Then make an Android intent object you wish to start. This is best done via foreign code.
  • Finally call ActivityUtils.StartActivity with the intent object and method to call on completion

For example the code to take a picture on Android looks like this:

using Uno;
using Uno.Graphics;
using Uno.Platform;
using Uno.Collections;
using Fuse;
using Fuse.Controls;
using Fuse.Triggers;
using Fuse.Resources;
using Android;
using Uno.Compiler.ExportTargetInterop;

public partial class MainView
    void ClickPlay(object a1, EventArgs a2)
        var intent = MakeMyIntent(); // [0]
        if (intent!=null)
            ActivityUtils.StartActivity(intent, OnResult);  // [1]
        } else {
            debug_log "Failed to make intent.";

    extern(android) void OnResult(int resultCode, Java.Object intent, object info)  // [2]
        debug_log "Success!: " + resultCode + " - " + intent + "\n";

    static extern(android) Java.Object MakeMyIntent()
        try {
            String fileName = "JPEG_TEST";
            String ext = ".jpg";
            File storageDir = com.fuse.Activity.getRootActivity().getExternalFilesDir(null);
            File photoFile = File.createTempFile(fileName, ext, storageDir);
            Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            Bundle bdl = new Bundle();
            bdl.putParcelable(MediaStore.EXTRA_OUTPUT, Uri.fromFile((File)photoFile));
            return takePictureIntent;
        } catch (Exception ex) {
            return null;

    extern(!android) void OnResult(int resultCode, object intent)

    static extern(!android) object MakeMyIntent()
        return null;

[0] - First we call a foreign method to create the Intent object in the usual Android fashion. [1] - Here we call StartActivity with our intent and the method to call on completion. [2] - Lastly we have the method that gets called when the result is received.

The info object allows us to associate some Uno data with the request. This data is not passed to the Activity being started but is stored and passed to the Uno callback when the result arrives.

Can I start an Activity which doesn't have a result?

Certainly! Simply call StartActivity and only pass in the intent object without supplying a callback.