Call A Public Method In The Activity Class From Another Class?

MAIN ACTIVITY public class MyActivity() extends Activity { onCreate() { MyClass myobj=new MyClass(); } public void Mymethod(

Solution 1:

Why not just pass the activity to the constructor like

publicclassMyActivityextendsActivity { 

   onCreate(){ 
        MyClass myobj=new MyClass(MyActivity.this);     
   } 

   publicvoidmyMethod(){

   } 
} 

//HELPER CLASS IN A SEPARATE FILE     publicclassMyClass{ 
    publicMyClass(MyActivity act) { 
        act.myMethod();
    } 
} 

Solution 2:

Make that method as static so you can call without creating the class object

publicstaticvoidMymethod()
{}

and call like this way

MainActivity.Mymethod();

Solution 3:

This is probably the best way to do it. This is how I'm doing it. It's called a Singleton Design Pattern:

publicclassMyActivityextendsActivity {
    privatestaticMainActivity instance;

    publicstaticMainActivitygetInstance() {
     if(instance==null){
          setInstance(this);
        }
        return instance;
    }

    publicstaticvoidsetInstance(MainActivity instance) {
        MainActivity.instance = instance;
    }

    @OverrideprotectedvoidonCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setInstance(this);
    }
}

Solution 4:

If I'm understanding you correctly I believe you can solve your problems using an interface as a callback.

////ACTIVITY/////////////////////////////////

publicclassMyActivity() extendsActivity {

    onCreate()
    {
        MyClass myObj=newMyClass();   

        //Set the listener on the object. Created as anonymous
        myObj.setListener(newMyClass.Listener() {
             myMethod();
        });
    }
}

publicvoidmyMethod(){

}

//////Custom Class//////////////////

publicclassMyClass {
     Listener mListener;

     publicinterfaceListener {
          publicvoidonInterestingEvent();
     }

     publicvoidsetListener(Listener listener) {
          mListener = listener;
     }

     publicvoidsomeUsefulThingTheClassDoes() {
          //Do your code here and when you're ready to call the activity's method do this
          mListener.onInterestingEvent();
     }
}

Solution 5:

I had an inner class that I wanted to pull out into a more general library "Helper" class. I had the same issue you do. I got around it by making the helper class abstract, with a single abstract method. Then in my project package I extended the helper class with a constructor call in the specific class.

publicclassMyActivityextendsActivity {
    onCreate() {
        MyHelperClass = new MyHelperClass(this, "foobar");
    }

    publicvoidmyMethod() {
        // Code...
    }
}

// In a different filepublicclassMyHelperClassextendsHelperClass {
    private MyActivity mInstance;

    publicMyHelperClass(MyActivity act, String data) {
        super();
        this.mInstance = act;
        this.mActivity = act;  // Useful for calling generic Activity methods in the HelperClassthis.mData = data;
    }

    protectedvoidcallMyActivityMethod() {
        mInstance.myMethod();
    }
}

// In a different filepublicabstractclassHelperClass {
    protected Activity  mActivity;
    protected String    mData;

    publicHelperClass() {
        // Subclass will set variables
    }

    protectedabstractvoidcallMyActivityMethod();

    // More code for all the other stuff the class does
}

In this way, I have a helper class that contains the vast majority of the "work", and all I have to do is make a subclass with the constructor and one method in order to get access to the calling activity's method of interest.