How to pass data both ways between different android applications?

Question

What's the easiest way to pass string variables from one application to another and also return values back? I have access to the source code of both apps, but it has to be two different applications.

I tried with startActivityForResult, but this only seems to work between activies of the same application. When calling an activity from a different package, startActivityForResult returns immediately with RESULT_CANCELED. There seems to be the possibility to solve this with a Service, but isn't that a bit oversized for just some string vars?

Is there an easy and clean way to do this?

Here the code i tried to use for startActivityForResult:

//App A:
            Intent intent = new Intent();
            intent.setAction("com.example.testapp.MESSAGE");
            Bundle b = new Bundle();
            b.putString("loginToken", "263bhqw3jhf6as4yf8j0agtz8h2hj2z9j3hg3g3ggh34uzh2h2ui78h3i9wdnj89x");
            intent.putExtra("MyData", b);

            startActivityForResult(intent, TEST_REQUEST);

    @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    Log.d("pairing", "onActivityResult called");
    // Check which request we're responding to
    if (requestCode == TEST_REQUEST) {
        // Make sure the request was successful
        Log.d("pairing", "got result, resultCode: " + resultCode);
        if (resultCode == RESULT_OK) {
            // The Intent's data Uri identifies which contact was selected.
            if (data.hasExtra("returnMessage")) {
                Toast.makeText(this, data.getExtras().getString("returnMessage"), Toast.LENGTH_LONG).show();
            }

        }
    }
}


            // App B:
        Intent result = new Intent();
        Bundle b = new Bundle();
        b.putString("returnValue", "this is the returned value");
        result.putExtra("MyData", b);
        setResult(Activity.RESULT_OK, result);
        Log.d("pairing", "RESULT_OK set");
        finish();


//App B Manifest
        <activity
        android:name="com.example.testapp"
        android:launchMode="singleTop"
        android:screenOrientation="portrait"
        android:windowSoftInputMode="adjustPan" >
        <intent-filter>
            <action android:name="com.example.testapp.MESSAGE" />

            <category android:name="android.intent.category.DEFAULT" />

            <data android:mimeType="text/plain" />
        </intent-filter></activity>

Anybody seeing the mistake? App B always returns immediately with RESULT_CANCELED

EDIT: Right now I'm getting a android.content.activitynotfoundexception no activity found to handle intent { act=com.example.testapp.MESSAGE (has extras) } error. What am I doing wrong?

Answer 1

AIDL is one means of communication between two different applications using Interfaces

http://developer.android.com/guide/components/aidl.html

You can find a working sample in the below tutorial http://manishkpr.webheavens.com/android-aidl-example/

Answer 2

you can use ContentProvider.This is a better way than others.