Detailed explanation of common APIs for component and container containers: frame, panel, scrollpane

Recommended reading ：Java Detailed explanation of graphical interface (AWT、Swing) special column

Container Inheritance system

1.Window It is a top-level window that can exist independently , By default BorderLayout Manage its internal component layout ;
2.Panel Can accommodate other components , But it can't exist independently , It must be embedded in other containers for use , By default FlowLayout Manage its internal component layout ;
3. ScrollPane yes A container with scroll bars , Nor can it exist independently , By default BorderLayout Manage its internal component layout ;

Commonly used API

Component As the base class , The following common methods are provided to set the size of components 、 Location 、 Visibility, etc .

Method signature	Method function
setLocation(int x, int y)	Set the location of the component
setSize(int width, int height)	Set the size of the component
setBounds(int x, int y, int width, int height)	At the same time, set the position of the components 、 size
setVisible(Boolean b)	Set the visibility of the component

Container As the root class of the container , The following methods are provided to access the components in the container .

Method signature	Method function
Component add(Component comp)	Add other components to the container ( This component can be either a normal component , It can also be a container ) , And return the added component
Component getComponentAt(int x, int y)	Returns the component of the specified point
int getComponentCount()	Returns the number of components in the container
Component[] getComponents()	Return all components in the container

Container demonstration

window

import java.awt.*;

public class FrameDemo {
    

    public static void main(String[] args) {
    
        //1. Create window objects 
        Frame frame = new Frame(" This is the first window container ");

        // Set the position and size of the window 

        frame.setBounds(100,100,500,300);

        // Set window visible 
        frame.setVisible(true);
    }
}

Panel

because IDEA By default utf-8 Encoding , But at present, the code we execute is windows On the system , and windows The default encoding for the operating system is gbk, So it's messy , If there's a garbled code , Then just before running the current code , Set up a jvm Parameters -Dfile.encoding=gbk that will do .

public class PanelDemo {
    
    public static void main(String[] args) {
    
        //1. establish Frame Container object 
        Frame frame = new Frame(" Here we are testing Panel");
        //2. establish Panel Container object 
        Panel panel = new Panel();

        //3. Go to Panel Add components to the container 
        panel.add(new TextField(" This is a test text "));
        panel.add(new Button(" This is a test button "));

        //4. hold Panel Add to Frame in 
        frame.add(panel);

        //5. Set up Frame Location and size of 
        frame.setBounds(30,30,500,300);

        //6. Set up Frame so 
        frame.setVisible(true);
    }
}

ScrollPane

The program is clearly directed to ScrollPane Added... To the container A text box and a button , But you can only see A button , But I can't see the text box , Why is that Well ? This is because ScrollPane Use BorderLayout Layout manager , and BorderLayout As a result, only one component in the container is displayed .

import java.awt.*;

public class ScrollPaneDemo {
    

    public static void main(String[] args) {
    
        //1. establish Frame Window object 
        Frame frame = new Frame(" Test here ScrollPane");

        //2. establish ScrollPane object , And specify that there is a scroll bar by default 
        ScrollPane scrollPane = new ScrollPane(ScrollPane.SCROLLBARS_ALWAYS);

        //3. Go to ScrollPane Add components to 
        scrollPane.add(new TextField(" This is the test text "));
        scrollPane.add(new Button(" This is the test button "));

        //4. hold ScrollPane Add to Frame in 
        frame.add(scrollPane);

        //5. Set up Frame The location and size of 
        frame.setBounds(30,30,500,300);

        //6. Set up Frame so 
        frame.setVisible(true);

    }
}

Recommended reading ：Java Detailed explanation of graphical interface (AWT、Swing) special column