Usability features

[Eric Larsen]

Hey everybody, I've been writing a simple chat program, and I was wondering about a few features that I haven't been able to figure out just yet.

1. How do I set the scroll bar's position manually, via code.
2. How do I call a method from a keystroke?

I plan on putting a method call to whatever method number 1 entails at the end of the while loop in IncomingReader's run() method, and I'd also like the program to be able to send the user's message when they press ENTER.

The code for the client class:

package com.teslarobotics.net;

import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class SimpleChatClient {

	JTextField outgoing;
	JTextArea incoming;
	PrintWriter writer;
	BufferedReader reader;
	Socket socket;
	JTextField nameField;

	public static void main(String[] args) {

		SimpleChatClient client = new SimpleChatClient();

		client.go();

	}

	public void go () {

		JFrame frame = new JFrame("Simple Chat Client");
		JPanel mainPanel = new JPanel();
		incoming = new JTextArea(15, 50);
		incoming.setLineWrap(true);
		incoming.setWrapStyleWord(true);
		incoming.setEditable(false);
		outgoing = new JTextField(20);
		JLabel screenName = new JLabel("Screen name: ");
		nameField = new JTextField(10);

		JScrollPane scroller = new JScrollPane(incoming);
		scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
		scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

		JButton sendButton = new JButton("Send");
		sendButton.addActionListener(new SendButtonListener());

		mainPanel.add(screenName);
		mainPanel.add(nameField);
		mainPanel.add(scroller);
		mainPanel.add(outgoing);
		mainPanel.add(sendButton);

		setUpNetworking();

		Thread readerThread = new Thread(new IncomingReader());
		readerThread.start();

		frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(600,320);
		frame.setVisible(true);

	}

	public void setUpNetworking () {

		try {

			socket = new Socket("127.0.0.1", 5000);
			writer = new PrintWriter(socket.getOutputStream());
			reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			System.out.println("Connected to server.");

		} catch (Exception ex) {

			System.out.println("Failed to connect.");
			ex.printStackTrace();

		}

	}

	public class SendButtonListener implements ActionListener {

		public void actionPerformed (ActionEvent ev) {

			if (nameField.getText().trim().isEmpty()) {

				nameField.setText("Anonymous");

			}

			try {

				writer.println(nameField.getText().trim() + ": " + outgoing.getText());
				writer.flush();

			} catch (Exception ex) {

				System.out.println("Failed to send.");
				ex.printStackTrace();

			}

			outgoing.setText("");
			outgoing.requestFocus();

		}

	}

	public class IncomingReader implements Runnable {

		public void run () {

			String message;

			try {

				while((message = reader.readLine()) != null) {

					System.out.println("recieved: " + message);

					incoming.append(message + "\n");

				}

			} catch (Exception ex) {

				ex.printStackTrace();

			}

		}

	}

}

[Michael Dunn]

> 1. How do I set the scroll bar's position manually, via code.

get the scrollbar from the scrollPane and
scrollBar.setValue(someIntValue);

but this has always been a bit wonky
a lot depends on what the maximum value is (and, if I remember correctly, this 'maximum' can change)

an alternative is to get the scrollPane's viewport and
viewport.scrollRectToVisible(someRectangle);

where someRectangle could be (e.g.) textfield.getBounds()


> 2. How do I call a method from a keystroke?

keyBindings

http://java.sun.com/docs/books/tutorial/uiswing/misc/keybinding.html

[Eric Larsen]

Thanks, Michael.

I'm still having problems, though. When I try to compile my code now, it give's me an error:

com\teslarobotics\net\SimpleChatClient.java:139: com.teslarobotics.net.SimpleChatClient.SendAction is not abstract and does not override abstract method removePropertyChangeListener(java.beans.PropertyChangeListener) in javax.swing.Action

          public class SendAction implements Action {
                   ^

1 error

My revised code to bind the Enter key to my JTextField outgoing:

package com.teslarobotics.net;

import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class SimpleChatClient {

	JTextField outgoing;
	JTextArea incoming;
	PrintWriter writer;
	BufferedReader reader;
	Socket socket;
	JTextField nameField;
	SendButtonListener listener;

	public static void main(String[] args) {

		SimpleChatClient client = new SimpleChatClient();

		client.go();

	}

	public void go () {

		JFrame frame = new JFrame("Simple Chat Client");
		JPanel mainPanel = new JPanel();
		incoming = new JTextArea(15, 50);
		incoming.setLineWrap(true);
		incoming.setWrapStyleWord(true);
		incoming.setEditable(false);
		outgoing = new JTextField(20);
		JLabel screenName = new JLabel("Screen name: ");
		nameField = new JTextField(10);

		JScrollPane scroller = new JScrollPane(incoming);
		scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
		scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

		JButton sendButton = new JButton("Send");
		sendButton.addActionListener(listener = new SendButtonListener());
		outgoing.getInputMap().put(KeyStroke.getKeyStroke("ENTER"), "Enter");
		outgoing.getActionMap().put("Enter", new SendAction());

		mainPanel.add(screenName);
		mainPanel.add(nameField);
		mainPanel.add(scroller);
		mainPanel.add(outgoing);
		mainPanel.add(sendButton);

		setUpNetworking();

		Thread readerThread = new Thread(new IncomingReader());
		readerThread.start();

		frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(600,320);
		frame.setVisible(true);

	}

	public void setUpNetworking () {

		try {

			socket = new Socket("127.0.0.1", 5000);
			writer = new PrintWriter(socket.getOutputStream());
			reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			System.out.println("Connected to server.");

		} catch (Exception ex) {

			System.out.println("Failed to connect.");
			ex.printStackTrace();

		}

	}

	public class SendButtonListener implements ActionListener {

		public void actionPerformed (ActionEvent ev) {

			if (nameField.getText().trim().isEmpty()) {

				nameField.setText("Anonymous");

			}

			try {

				writer.println(nameField.getText().trim() + ": " + outgoing.getText());
				writer.flush();

			} catch (Exception ex) {

				System.out.println("Failed to send.");
				ex.printStackTrace();

			}

			outgoing.setText("");
			outgoing.requestFocus();

		}

	}

	public class IncomingReader implements Runnable {

		public void run () {

			String message;

			try {

				while((message = reader.readLine()) != null) {

					System.out.println("recieved: " + message);

					incoming.append(message + "\n");

				}

			} catch (Exception ex) {

				ex.printStackTrace();

			}

		}

	}

	public class SendAction implements Action {

		public void actionPerformed (ActionEvent ev) {

			listener.actionPerformed(ev);

		}

	}

}

[pete stein]

Rather than implement Action, I'd try having having your class extend AbstractAction. This way while it has to implement the actionPerformed method it only overrides the other Action methods that you think are necessary (or none at all).

[Rob Spoor]

You also might want to combine the SendButtonListener and SendAction classes, removing the first. Action extends ActionListener, so you can use Action where you can use ActionListener.

[Eric Larsen]

Awesome, thanks guys!!!

It works very well now! I took Rob and Pete's advice and it helped quite a bit. Thanks!
I also put in some other code to check for the presence of text in JTextField outgoing before sending.

Here's the final code:

package com.teslarobotics.net;

import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class SimpleChatClient {

	JTextField outgoing;
	JTextArea incoming;
	JScrollPane scroller;
	PrintWriter writer;
	BufferedReader reader;
	Socket socket;
	JTextField nameField;
	SendAction action;

	public static void main(String[] args) {

		SimpleChatClient client = new SimpleChatClient();

		client.go();

	}

	public void go () {

		JFrame frame = new JFrame("Eric's Simple Chat Client");
		JPanel mainPanel = new JPanel();
		incoming = new JTextArea(15, 50);
		incoming.setLineWrap(true);
		incoming.setWrapStyleWord(true);
		incoming.setEditable(false);
		outgoing = new JTextField(20);
		JLabel screenName = new JLabel("Screen name: ");
		nameField = new JTextField(10);

		scroller = new JScrollPane(incoming);
		scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
		scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

		JButton sendButton = new JButton("Send");
		sendButton.addActionListener(action = new SendAction());
		outgoing.getInputMap().put(KeyStroke.getKeyStroke("ENTER"), "Enter");
		outgoing.getActionMap().put("Enter", action);

		mainPanel.add(screenName);
		mainPanel.add(nameField);
		mainPanel.add(scroller);
		mainPanel.add(outgoing);
		mainPanel.add(sendButton);

		setUpNetworking();

		Thread readerThread = new Thread(new IncomingReader());
		readerThread.start();

		frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(600,340);
		frame.setVisible(true);

	}

	public void setUpNetworking () {

		try {

			socket = new Socket("127.0.0.1", 5000);
			writer = new PrintWriter(socket.getOutputStream());
			reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			System.out.println("Connected to server.");

		} catch (Exception ex) {

			System.out.println("Failed to connect.");
			ex.printStackTrace();

		}

	}

//	public class SendButtonListener implements ActionListener {
//
//		public void actionPerformed (ActionEvent ev) {
//
//			if (nameField.getText().trim().isEmpty()) {
//
//				nameField.setText("Anonymous");
//
//			}
//
//			try {
//
//				writer.println(nameField.getText().trim() + ": " + outgoing.getText());
//				writer.flush();
//
//			} catch (Exception ex) {
//
//				System.out.println("Failed to send.");
//				ex.printStackTrace();
//
//			}
//
//			outgoing.setText("");
//			outgoing.requestFocus();
//
//		}
//
//	}

	public class IncomingReader implements Runnable {

		public void run () {

			String message;

			try {

				while((message = reader.readLine()) != null) {

					System.out.println("recieved: " + message);

					incoming.append(message + "\n");

					JScrollBar bar = scroller.getVerticalScrollBar();

					bar.setValue(bar.getMaximum());

				}

			} catch (Exception ex) {

				ex.printStackTrace();

			}

		}

	}

	public class SendAction extends AbstractAction {

		public void actionPerformed (ActionEvent ev) {

			if (nameField.getText().trim().isEmpty()) {

				nameField.setText("Anonymous");

			}

			if (!(outgoing.getText().trim().isEmpty())) {

				try {

					writer.println(nameField.getText().trim() + ": " + outgoing.getText());
					writer.flush();

				} catch (Exception ex) {

					System.out.println("Failed to send.");
					ex.printStackTrace();

				}

			}

			outgoing.setText("");
			outgoing.requestFocus();

		}

	}

}