Question

i want to make an android app running in background that receives a string from my bash script
the app uses the string to show a toast with a text
but i dont know how to send the string to the app and neither how to recive the string
help please

Answer 1

You could use Intent via am and send them to your service. This would look like:

adb shell am startservice -a com.yourpackage.action.name.SHOW_TOAST -e text "i did it"

And your service might look like:

....

@Override
public void onStart(Intent intent, int startId) {
    Toast.makeText(this, "Text: " + intent.getStringExtra("text"), Toast.LENGTH_LONG).show();
}
....

And add next entry to AndroidManifest.xml:

 <service  android:name="com.yourpackage.SomeService">
     <intent-filter>
            <action android:name="com.yourpackage.action.name.SHOW_TOAST" />
     </intent-filter>
 </service>