如何在JFrame中显示JButtons和jlabel ?

Question

我尝试使用这段代码来显示一个有标签的窗口，但它只显示一个空白窗口。

    JFrame window = new JFrame("My Window");
    window.setVisible(true);
    window.setResizable(true);
    window.setSize(680,420);
    window.setContentPane(new Container());
    window.getContentPane().setLayout(new FlowLayout());
    JPanel panel = new JPanel();
    JLabel label = new JLabel("LABEL");
    label.setBackground(Color.BLACK);
    panel.add(label);
    window.add(panel);

Answer 1

尝试呼叫setVisible last

JFrame window = new JFrame("My Window");
//window.setVisible(true);
//window.setResizable(true);
//window.setSize(680,420);
//window.setContentPane(new Container());
window.setLayout(new FlowLayout());
JPanel panel = new JPanel();
JLabel label = new JLabel("LABEL");
label.setBackground(Color.BLACK);
panel.add(label);
window.add(panel);
window.setResizable(true);
// Pack will size the window to fit the content, 
// tacking into account the preferred size of the
// content...
window.pack();
window.setVisible(true);

还要注意，JLabel默认是透明的，所以设置它的背景颜色将没有效果，除非你改变它的opaque属性为true

Answer 2

将所有component, set加到frame的visibility。

    JFrame window = new JFrame("My Window");
    window.setResizable(true);
    window.setSize(680,420);
    window.setContentPane(new Container());
    window.getContentPane().setLayout(new FlowLayout());
    JPanel panel = new JPanel();
    JLabel label = new JLabel("LABEL");
    label.setBackground(Color.BLACK);
    panel.add(label);
    window.add(panel);     
    window.setVisible(true);

Answer 3

(当你在开始时调用setvisible()方法时)..您还可以使用update()方法，以便更新或重新绘制jframe上的组件。