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2015-05-29 Android

Creating a Callback to Send Data From Fragment to Activity

How to Implement a Callback Method to Send Data from a Fragment to an Activity#

  1. In the Fragment Class (MyFragment.java):

    Declare an Interface with as many abstract methods as required

    public interface Callbacks {
    public void runAbstractMethod(MyData mydata);
}

    Remember only signiture is required for an interface

  2. In the Activity Class:

    Add Code to the class declaration to Implment the Interface in the Fragment class

    public class MainActivity extends Activity
    implements MyFragment.Callbacks {

    Implement the methods (Alt + Enter) creates.

    @Override
public void runAbstractMethod(MyData mydata){
    //Get a reference to the bundle representing all of the MyData objects data
    //Uses a custom method of the MyData Class
    Bundle b = mydata.makeBundle();
    //or if your class implements serializable you can use
    b.putSerialiazble("myData", (java.io.Serializable) mydata);

    //Create an Intent to Launch the Activity
    Intent intent = new Intent(this, MyDataActivity.class);
    intent.putExtra("MY_KEY", b);
    //Want to See a Result so use
    startActivityForResult(intent, "100");
}

  3. Setup Communication from Fragment to Actviity

    In Fragment Class (MyFragment.java):

    Get a reference to the Activity Class#

    ``` //Declare a variable as an Implementation of the Callbacks Interface private Callbacks activity;

    //Override the OnAttach method public void onAttach(Activity activity){ super.onAttach(activity); this.activity = (Callbacks)activity; } ```

    Run the Method:#

    ``` //Use a Click Listener or Some event public void RuntheMethod(){ //Setup the data MyData mydata = ....

    //Run the Method
activity.onItemSelected(mydata);

    } ```

    Make sure the Activity is registered in the Manifest File

  4. Receive Bundle from MainActivity in New Activity and pass to fragment

    In MyDataActivity.java:

    MyFragment fragment = new MyFragment();
//after instantiating the fragment class
Bundle args = getIntent().getBundleExtra("MY_KEY");
fragment.setArguments(args);

//use fragement manager and send it

  5. Receive Arguments - in Fragments OnCreate

    In MyFragment.java:

    public void OnCreate(Bundle savedInstanceState){ super.onCreate(savedInstance);

    bundle b = getArguments();
if (b != null){
    MyData mydata = new Flower(b);
}

Sources#