CODEWITHSUNDEEP
javainheritanceoverriding
Ponmalar
Ponmalar

Reputation: 7031

Create Custom Override method issue

I have created the class like below. But Override method is not called. Is anything I missed? Otherwise i need to add any key word(like Virtual) to use as Override?

MyWebView.java

package com.example.stackoverflow;    

import android.content.Context;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.LinearLayout;

public class MyWebView extends WebView 
{
    WebView localView;
    static Context localcontext;
    A aclass;

    public MyWebView(Context context)
    {
        super(context);     
        localcontext=context;
    }

    public LinearLayout init()
    {
        LinearLayout layout=new LinearLayout(localcontext);
        localView=new WebView(localcontext);
        localView.setWebViewClient(new MyClient());
        aclass=new A();
        layout.addView(localView);
        return layout;
    }

    class MyClient extends WebViewClient
    {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            aclass.startMyMethod();
            return super.shouldOverrideUrlLoading(view, url);
        }
    }

}

A.java

package com.example.stackoverflow;

import android.os.Bundle;
import android.widget.LinearLayout;
import android.app.Activity;

public class A extends Activity 
{

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        MyWebView view=new MyWebView(this);
        LinearLayout layout = view.init();
        view.loadUrl("https://www.google.co.in/");
        setContentView(layout);
     }

    public void startMyMethod() 
    {       
        System.out.println("ParentMethod");
    }
}

B.java(MainActivity)

package com.example.stackoverflow;

import android.os.Bundle;

public class B extends A {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
     }

    @Override
    public void startMyMethod() {
        System.out.println("ChildMethod");
        super.startMyMethod();
    }

}

Note: class B is client side class. others two in jar file. how can i use new B() inside jar file(library source). name B may be changed. If parent method is overridden, then parent content should not be executed

Upvotes: 0

Views: 3413

Answers (3)

swemon
swemon

Reputation: 5946

In your init() method of MyWebView.java you initialize variable aclass variable as aclass=new A();

In shouldOverrideUrlLoading() method, you call

aclass.startMyMethod();

Since A is parent class, it will only called startMyMethod() of A class.

In order to get advantage of inheritance and override, you can initialize aclass variable as aclass=new B(); This will call startMyMethod() of B class and then call startMyMethod() of A class because of using super.startMyMethod();

http://docs.oracle.com/javase/tutorial/java/javaOO/annotations.html said that

@Override—the @Override annotation informs the compiler that the element is meant to override an element declared in a superclass (overriding methods will be discussed in the the lesson titled "Interfaces and Inheritance").

Not for program execution sequence. I hope it may be your want.

Upvotes: 1

Nandkumar Tekale
Nandkumar Tekale

Reputation: 16158

Java does not have any keyword like virtual, by default all java non-static methods are virtual. See http://en.wikipedia.org/wiki/Virtual_function#Java.

@Override annotation is used to instruct compiler that you are overriding super class method. See here

A a =new A();
a.startMyMethod(); // calls A.startMyMethod()

A b = new B(); // Object reference of type A and Object of B
a.startMyMethod(); // calls B.startMyMethod()

Upvotes: 2

aviad
aviad

Reputation: 8278

It should work if you create an instance of ClassB and call the overridden method like below:

ClassB b = new ClassB();
b.strartMyMehtod();

Put some prints inside the ClassB method before the call to the parent to see the difference.

class A
{
     public void startMyMethod()
     {
         System.out.println("A.startMyMethod() called");
     }
 }    

class B extends A
 {
    @Override
     public void startMyMethod() {
         System.out.println("B.startMyMethod() called");
        // TODO Auto-generated method stub
        super.startMyMethod();
     }
 }

Upvotes: 1

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