How do I call a Java methods from one class to another class in Android development?

Question

I have two classes which extend Activity and need to call another class method on main class on android development. I did something like subclass sub = new subclass() . It did not work.

In 1st activity class

package org.me.intent_testing;

import android.app.Activity;
import android.os.Bundle;
import android.widget.*;
import android.view.*;
import android.content.Intent;

public class FirstActivity extends Activity {

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

   // Button orderButton = (Button)findViewById(R.id.order);
    Button orderButton = new Button(this);
    orderButton.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View view) {
        Intent intent = new Intent(FirstActivity.this, secondActivity.class);
        startActivity(intent);
      }

    });
  }
}

In secondActivity class

package org.me.intent_testing;

import android.app.Activity;
import android.os.Bundle;
import android.widget.*;
import android.view.*;
import android.content.Intent;

public class secondActivity extends Activity {

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
          setContentView(R.layout.main);
       // setContentView(R.layout.order);


   // Button orderButton = (Button) findViewById(R.id.end);
    Button orderButton =  new Button(this);
    orderButton.setOnClickListener(new View.OnClickListener() {

     @Override
      public void onClick(View view) {
        finish();
      }

    });
  }
}

In AndroidManifest.xml

<?xml version="1.0" encoding="UTF-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.me.intent_testing">
    <application>
         <activity android:name=".FirstActivity" android:label="FirstActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
         <activity android:name=".secondActivity" />
    </application>

</manifest>

In R.java

package org.me.intent_testing;

public final class R {
    public static final class attr {
    }
    public static final class layout {
        public static final int main=0x7f020000;
    }
    public static final class string {
        public static final int app_name=0x7f030000;
    }
}

I have a problem linking between two classes.

Answer 1

SubClass sub=new SubClass(); is creating an object of class SubClass .

It is not a method calling.

enter code here

If the method is defined in class SubClass then you can call it by using its object and dot operator.

sub.MethodName();

Answer 2

May i know why you would want to do so? If that method is so important to both of the classes, then create it inside a helper class (Which doesn't extend Activity) and create an object of it in both the classes, then with that object access that method.

Answer 3

Try just to label the required method as static. But remember that in that case the called method should not depends on any non-static member variables of methods of the class.