Java Swing - JLabel位置

Question

I have problem while setting the Jlabel location.
I set the content pane to some JPanel, I created and tried to add my JLabel.

    JLabel mainTitle = new JLabel("SomeApp");
    mainTitle.setFont(new Font("Arial",2 , 28));
    mainTitle.setBounds(0,0, 115, 130);
    getContentPane().add(mainTitle);

I want that my JPanel will be on the top left corner on my application and what I am getting is "SomeApp" on the top center.(and not top left).

btw I tried to add JButton the and the I can`t change the width,height,x,y of the JButton.

Answer 1

Swing uses Layout Managers to place the components.

You have to understand how they work to use them effectively. You can set the layout manager to null, and do the layout your self, but is not recommendable because you'll have to keep track of new components each time, and perform layout computation your self when the window moves shrink etc.

Layout managers are a bit hard to grasp at first.

Your windows could be like this:

Using this code:

import javax.swing.*;
import java.awt.Font;
import java.awt.FlowLayout;

class JLabelLocation  {

    public static void main( String [] args ) {

        JLabel mainTitle = new JLabel("SomeApp");
        mainTitle.setFont(new Font("Arial",2 , 28));
        //mainTitle.setBounds(0,0, 115, 130); //let the layout do the work

        JFrame frame = new JFrame();
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.LEFT));// places at the left
        panel.add( mainTitle );

        frame.add( panel );// no need to call getContentPane
        frame.pack();
        frame.setVisible( true );

    }
}

Answer 2

Where a particular widget ends up in its container depends on the layout manager that it's using. The layout manager determines how to resize and arrange the widgets to make them fit appropriately. Obviously, the default layout for the content pane decided that the top center was the best place to put the JLabel.

If you want to get to not use a layout manager and just place everything yourself (which generally isn't the best way to lay things out btw), then add:

getContentPane().setLayout(null);

Answer 3

Using layouts is usually a better idea since they allow for dynamic resizing of components. Here's how you'd do it with a BorderLayout:

this.getContentPane().setLayout(new BorderLayout());
this.getContentPane().add (new JLabel ("Main title"), BorderLayout.NORTH);

If you want to add something to the right of the label you could create an additionnal panel with it's own layout :

// Create a panel at the top for the title and anything else you might need   
JPanel titlePanel = new JPanel (new BorderLayout());
titlePanel.add(new JLabel ("Main title"), BorderLayout.WEST);

// Add the title panel to the frame
this.getContentPane().setLayout(new BorderLayout());
this.getContentPane().add(titlePanel, BorderLayout.CENTER);

Here are some usefull links to get started with layouts:

http://download.oracle.com/docs/cd/E17409_01/javase/tutorial/uiswing/layout/visual.html http://download.oracle.com/docs/cd/E17409_01/javase/tutorial/uiswing/layout/using.html