how to call a method in another Activity from Activity

Question

I'm developing an Android Application in which I have

I've two classes class A and Class B.

In class A, I tried the code Snippets like below,

How do I call a method in another Activity from Activity?

public class FirstActivity extends Activity {  

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);
    }      

    public void method() {
        // some code
    }  
}

public class SecondActivity extends Activity {  

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
         setContentView(R.layout.main2);
    
        FirstActivity fact = new FIrstActivity();
    
        fact.method();
    }
}

Answer 1

The startActivityForResult pattern is much better suited for what you're trying to achieve : http://developer.android.com/reference/android/app/Activity.html#StartingActivities

Try below code

public class MainActivity extends Activity {  

    Button button1;  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        textView1=(TextView)findViewById(R.id.textView1);  
        button1=(Button)findViewById(R.id.button1);  
        button1.setOnClickListener(new OnClickListener() {  
            @Override  
            public void onClick(View arg0) {  
                Intent intent=new Intent(MainActivity.this,SecondActivity.class);  
                startActivityForResult(intent, 2);// Activity is started with requestCode 2  
            }  
        });  
    }  
 // Call Back method  to get the Message form other Activity  
    @Override  
       protected void onActivityResult(int requestCode, int resultCode, Intent data)  
       {  
                 super.onActivityResult(requestCode, resultCode, data);  
                  // check if the request code is same as what is passed  here it is 2  
                   if(requestCode==2)  
                         {  
                          //do the things u wanted 
                         }  
     }  

} 

SecondActivity.class

public class SecondActivity extends Activity {  

    Button button1;  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_second);  

            button1=(Button)findViewById(R.id.button1);  
            button1.setOnClickListener(new OnClickListener() {  
                @Override  
                public void onClick(View arg0) {  
                    String message="hello ";  
                    Intent intent=new Intent();  
                    intent.putExtra("MESSAGE",message);  
                    setResult(2,intent);  
                    finish();//finishing activity  
                }  
            });  
    }  

}  

Let me know if it helped...

Answer 2

You should not create an instance of the activity class. It is wrong. Activity has ui and lifecycle and activity is started by startActivity(intent)

You can use startActivityForResult or you can pass the values from one activity to another using intents and do what is required. But it depends on what you intend to do in the method.

Answer 3

If you need to call the same method from both Activities why not then use a third object?

public class FirstActivity extends Activity 
{  

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);

    }      

    // Utility.method() used somewhere in FirstActivity
}

public class Utility {

    public static void method()
    {

    }  

}

public class SecondActivity extends Activity 
{  

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);

        Utility.method();

    }
}

Of course making it static depends on the use case.

Answer 4

public class ActivityB extends AppCompatActivity {

static Context mContext;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_b);

    try {

        Bundle bundle = getIntent().getExtras();
        if (bundle != null) {
            String texto = bundle.getString("message");
            if (texto != null) {
              //code....
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static void launch(String message) {
        Intent intent = new Intent(mContext, ActivityB.class);
        intent.putExtra("message", message);
        mContext.startActivity(intent);
    }
}

In ActivityA or Service.

public class Service extends Service{

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {    

        String text = "Value to send";
        ActivityB.launch(text);
        Log.d(TAG, text);
    }
}

Answer 5

Simple, use static.

In activity you have the method you want to call:

private static String name = "Robert";

...

public static String getData() {
    return name;
}

And in your activity where you make the call:

private static String name;

...

name = SplashActivity.getData();

Answer 6

Declare a SecondActivity variable in FirstActivity

Like this

public class FirstActivity extends Activity {  

SecondActivity secactivity;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main2);
  }      

  public void method() {
    // some code

  secactivity.call_method();// 'Method' is Name of the any one method in SecondActivity

  }  
}  

Using this format you can call any method from one activity to another.