GUI programming in Java

1. Definition

The full name of GUI is Graphical User Interface, that is, graphical user interface. JDK provides two packages, AWT and Swing, for the design and development of GUI programs.

1.java .awt abstract Window Toolkit (Abstract Window Toolkit), which is an early version of java, has limited types of components and needs to call local system methods to implement functions. It is heavyweight and somewhat platform-dependent.

2.javax.SWing is a graphical user interface system established by Sun Company on the basis of AWT. It provides more components and is completely implemented in Java, which enhances portability and is lightweight. magnitude.

SWing is equivalent to an upgraded version of AWT, which solves the problem of cross-platform operation. However, it does not mean that AWT has been completely eliminated. It is the foundation, and it is still important to understand its performance.

2. AWT class hierarchy

##Container: is the container, It is a special component into which other components can be added through the add method.

Simple code example:

import java.awt.Frame;public class Test19 {public static void main(String[] args) {
        demo();
    }static void demo() {
        Frame f = new Frame("这是我做的第一个窗口");
        f.setSize(400, 400);
        f.setLocation(40, 60);// 左上角的坐标System.out.println("運行成功");// 验证程序是否被执行了    }
}

If you do the above code, judging from the console results, the program has not hung up and has been executed. The desired dialog box just doesn't appear.

The above program is missing a piece of code:

f.setVisible(true);

import java.awt.Frame;public class Test19 {public static void main(String[] args) {
        demo();
    }static void demo() {
        Frame f = new Frame("这是我做的第一个窗口");
        f.setSize(400, 400);
        f.setLocation(40, 60);// 左上角的坐标        
        f.setVisible(true);//使得窗口可见        
        System.out.println("運行成功");// 验证程序是否被执行了    }
}

Execution results: (It is worth noting that clicking the X in the upper right corner of this small window will not close the window. We need to set it ourselves)

The following demonstrates the operation of adding a button:

import java.awt.Button;import java.awt.Frame;public class Test19 {public static void main(String[] args) {
        demo();
    }static void demo() {
        Frame f = new Frame("这是我做的第一个窗口");
        f.setSize(400, 400);
        f.setLocation(40, 60);// 左上角的坐标f.setVisible(true);// 使得窗口可见Button b = new Button("按钮");// 需要导包f.add(b);// 添加该按钮System.out.println("運行成功");// 验证程序是否被执行了    }
}

Execution results: (Note that if there is a button, the button will fill the border by default when the size and position are not set)

Summary:

Many GUI components can be divided into two major categories according to their functions, basic components and containers .

Basic components: buttons, text boxes, etc., cannot accommodate other components.

Container: can accommodate other components, such as windows, dialog boxes, etc. All containers are direct or indirect subclasses of java.awt.Container (the Frame above is a container)

Attachment, thoughts:

The above program ends when it is executed to System.out.println("Run successfully"); In fact, the main function ends at this time. But the window is still there. We can even do it. Then there must be other foreground threads running. It can be understood that when Frame is created, another thread is started.

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