用Java生成jLabel代码

Question

Can anyone explain me why my code doesn't seem to work? Result of this code is an empty screen.

Altough my labels array contains all and right labels. I probably miss something but can't find out what.... thanks in advance!

 //create the array
private static JLabel[] labels = new JLabel[135];

private  void setup(){

  for(int i = 0; i < labels.length; i++){
    int x; 
    int y = 0;
    int z = 0;
    int r;
    z++;
      if (z == 16) {
          z=0;
          y += 40;
      }
    x = 40*z+40;

    labels[i] = new JLabel("foo");
    labels[i].setText("test");
    labels[i].setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0,0,0)));
    labels[i].setMaximumSize(new java.awt.Dimension(32, 32));
    labels[i].setMinimumSize(new java.awt.Dimension(32, 32));
    labels[i].setPreferredSize(new java.awt.Dimension(32, 32)); 
    labels[i].setLocation(x, y);

    this.add(labels[i]);
    //this.setVisible(true);

  } 
  //this.pack();
  //this.rootPane.add(this);

}

Answer 1

The answer depends on what layout manager you use for your content pane (which you didn't post).

You add your labels to your JFrame like this:

this.add(labels[i]);

JFrame.add() redirects to the add() method of the content pane which by default is a JPanel with BorderLayout layout manager. Calling add() on this will add the component to the center. Adding another component will replace the previously added component.

So you end up with a Jrame which only has 1 JLabel added to its center. Since the panel has a layout manager, you should not call setLocation() on its children.

You may use a null layout (position components absolutely) which you may or may not do corrently as you did not post all your code.

Or use a proper layout manager which allows you to add many components to the Container like GridLayout or use Container s like Box .

Answer 2

This tutorial explains how to add JLabels to a JFrame.

The following snippet from the tutorial is where your problem might lie:

Now that we have created the JLabel, it needs to be added to the JFrame:

frame.getContentPane().add(textLabel, BorderLayout.CENTER);