TL:DR;
adb shell monkey -p de.avm.android.fritzapp 1
Long Answer
How can I simply start the app as if it had been clicked on?
You can start the main activity of the app
am start -n com.package.name/.MainActivityName
Since you have decompiled the App and got the manifest file so you would have the name of the main activity. You can get this information from the App's AndroidManifest.xml by searching for the activity with intent-filter
and also contains android.intent.action.MAIN
under action
Check the activity element with skeleton as below
<activity android:name="this.is.main.activity.name you.are.looking.for">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
You can start this particular app by
am start -n app de.avm.android.fritzapp/.gui.FRITZApp
Alternatively if you do not have the source code (manifest file), you can try the more general method where knowing the package name is enough with the help of Monkey tool as below:
adb shell monkey -p package.name 1
(Simplified)
The above command works because Monkey takes a constraint -c <main-category>
which if not specified will select activities listed with the category Intent.CATEGORY_LAUNCHER
which in turn becomes
adb shell monkey -p package.name -c android.intent.category.LAUNCHER 1