Data Sharing between Fragments and Activity in Android

Question

Ive asked a similar question before and didn't get an answer and seems many other ppl are searching for an answer. So I am posting this question to hopefully get a clear answer that everyone can benefit from.

I have an activity with 2 fragments in it. I want fragment2 to set a boolean variable in Activity when a checkbox is checked so that fragment1 can know if the checkbox was checked.

This is my Code:

Activity:

public class modestab extends Activity{
    public static Context appContext;

    public boolean lf=false;

    public void onCreate(Bundle savedInstanceState){
        appContext=this;
super.onCreate(savedInstanceState);
ActionBar tabbar= getActionBar();
        tabbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        ActionBar.Tab ModesTab =tabbar.newTab().setText("Modes");
        ActionBar.Tab CatTab =tabbar.newTab().setText("Categories");

        Fragment ModesFragment =new modes();
        Fragment CatFragment =new cats();

        ModesTab.setTabListener(new MyTabsListener(ModesFragment));
        CattTab.setTabListener(new MyTabsListener(CatFragment));

        tabbar.addTab(ModesTab);
        tabbar.addTab(CatTab);


    }

Fragment 1:(Where I want to read the boolean lf set in Acitivity above:

@TargetApi(11)
public class tabmodes extends Fragment{
@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
View V=inflater.inflate(R.layout.tab_modes, container, false);
button1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                if(lf==false) //lf here is the lf in Activity which I want to get

Fragment 2: Where I want to set lf in Activity

.....
lifecheck.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener(){
              @Override
                public void onCheckedChanged(CompoundButton buttonView,
                        boolean isChecked) {
                  if(lifecheck.isChecked())
                      getActivity().lf=true;//Where I want to set the lf flag in Activity
                  ;
              }
          });

The code doesn't compile and I am not knowing how to set lf in the Activity nor how to read it. Someone suggested I do getActivity() but I am not able to see the variable.

I tried to create a function setlf(boolean jk) but also I am not able to see it...

Any help is welcome :)

Answer 1

Many ways :

1) Activity -> Fragment

• In your Activity : create a bundle and use fragment.setArguments(bundle)
• in your Fragment : use Bundle bundle = getArguments()

2) Activity -> Fragment

• In your Fragment : create a public method

• In your Activity : call an active fragment public method :

  getSupportFragmentManager().findFragmentById(R.id.your_fragment).publicMethod(args)

3) Fragment -> Activity

• In your Fragment : create un interface with getter and setter methods (callback methods)
• In your Activity : implement the interface

4) Fragment -> Activity

• In your Activity : Create public getter and setter or other methods

• In your Fragment : called public activity getter, setter or other methods using :

  getActivity().getSomething(), getActivity().setSomething(args) or getActivity().someMethod(args)

Answer 2

You can pass data between fragments in two ways,

First, you can do it by using setArguments(...) and getArguments(....)

Second,you can do it using Call back

Answer 3

Also you can use EventBus. It's really simple. https://github.com/greenrobot/EventBus

Definitely don't use static methods like my old answer :)

Answer 4

//In fragment;
String user = MainActivity.getUserName();

Static methods are my old solution, but definitely bad solution. Don't use them like this.