Question

这是我使用swing创建窗口的代码。

我可以看到定义大小的窗口，但窗口中没有任何组件。

为什么组件不可见？

我有单独的方法用于创建，初始化和添加组件。从构造函数调用这些方法。标题和定义大小的窗口在输出中可见。我错过了什么？

package swing_basics;

import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class MySwingDemo extends JFrame {

    JLabel lblName, lblPassword; //Declaration of variables
    JTextField txtfName;
    JPasswordField pwdfPassword;
    JButton btnSubmit, btnCancel, btnReset;

    public void createComponents(){  //method to initialise the components

        lblName = new JLabel();
        lblPassword = new JLabel();
        txtfName = new JTextField();
        pwdfPassword = new JPasswordField();
        btnSubmit = new JButton();
        btnCancel = new JButton();
        btnReset = new JButton();
    }

    public void setComponents(){  //method to set the components
        setVisible(true);
        setSize(400, 400);
        setTitle("My Swing Demo");
        setLayout(new FlowLayout());

        lblName.setText("Name");
        lblPassword.setText("Password");

        txtfName.setText("Name");// try

        pwdfPassword.setText("Password");

        btnSubmit.setText("Submit");
        btnCancel.setText("Cancel");
        btnReset.setText("Reset");
    }

    public void addComponents(JFrame frame){  //method to add the components
        frame.add(lblName);
        frame.add(txtfName);

        frame.add(lblPassword);
        frame.add(pwdfPassword);

        frame.add(btnSubmit);
        frame.add(btnCancel);
        frame.add(btnReset);
    }

    public static void main(String[] args) {
        new MySwingDemo();
    }

    public MySwingDemo() {  //Constructor
        createComponents();
        setComponents();
        addComponents(this);
    }

}

Answer 1

按照操作顺序，您可以在添加（和设置）组件之前设置frame可见。而是在之后将setVisible(true);移至，然后设置组件。，请务必在致电addComponents(this); 之前致电setComponents(); 。

像

public MySwingDemo() { // Constructor createComponents(); addComponents(this); setComponents(); }

和我还会添加默认的frame关闭操作

public void setComponents() { // method to set the components setSize(400, 400); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setTitle("My Swing Demo"); setLayout(new FlowLayout()); lblName.setText("Name"); lblPassword.setText("Password"); txtfName.setText("Name");// try pwdfPassword.setText("Password"); btnSubmit.setText("Submit"); btnCancel.setText("Cancel"); btnReset.setText("Reset"); setVisible(true); }

为什么我的组件不可见？

1 个答案: