Use intent to start an activity

Basically we can start an activity with this:

void startApp(Context ctx, String packageName, String activityName) throws ClassNotFoundException {
        Intent intent = new Intent();
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setClassName(packageName, activityName);
        ctx.startActivity(intent);
}

private Context mContext = InstrumentationRegistry.getTargetContext();
...
private String activityName02 = "com.google.android.finsky.activities.TvMainActivity";
private String packageName02 = "com.android.vending";
...
startApp(mContext, packageName02, activityName02);

But meanwhile, when the activity is named with a ".", it will throw an exception.

android:name
The name of the class that implements the activity, a subclass of Activity. The attribute value should be a fully qualified class name (such as, "com.example.project.ExtracurricularActivity"). However, as a shorthand, if the first character of the name is a period (for example, ".ExtracurricularActivity"), it is appended to the package name specified in the <manifest>.

So the following code will work:

private String settingsPackageName = "com.android.tv.settings";
private String activityName = settingsPackageName + ".accessories.AddAccessoryActivity";
startApp(mContext, settingsPackageName, activityName);

We need to add the package name before the ., and treat the whole as the activity name.