如何从一个类到另一个类访问JTextArea

Question

I want to access status so I can append values to it but my code doesn't seem to work. Please help me.

public class NewClient extends JFrame implements ActionListener{


private static final int WIDTH = 600;
private static final int HEIGHT = 400;
public static JTextArea chat, event, cwindow, c2window, type, status;

public NewClient(){

    status = new JTextArea(30,10);
    status.setEditable(false);
}

Here's the other class

public class NewServer{


public static NewClient client;

public static void main(String args[]){
       client.status.append("Online");
}

Answer 1

There two things to note here:

You have to create object to invoke its constructor, otherwise you will hit NullPointerException in the following line

client.status.append("Online");

So, the fix is to create an object and assign value:

client = new NewClient();
client.status.append("Online");

Static variables like status need not be invoked through object. So, instead of assigning value like the following:

client.status.append("Online");

You can directly invoke the variable using class name:

client = new NewClient();   
NewClient.status.append("Online");

If you note above, we created new object for NewClient so that the value for status text area is initialized as part of NewClient 's constructor.