Study Note 25: Event handling (i)

We must strive to survive in the competition. --Sun Yat-sen

What's in this lecture: event handling

To import a package:

Import java.awt.event.*;

The events fall into two main categories: low-level events and advanced events.

1, low-level events include the following several

Event Category	Interface Name	Describe
ComponentEvent Component Events	Componentlistener	Occurs when the component size changes, moves, displays, or hides
ContainerEvent Container Events	ContainerListener	occurs When a component is added or removed
WindowEvent Window Events	WindowListener	window is activated, masked, minimized, or closed
MouseEvent Mouse Events	Mouseeventlistener	mouse button is pressed, released, mouse moved or dragged
KeyEvent keyboard Events	KeyListener	A key on the keyboard is pressed or released
FocusEvent Focus Event	FocusEvent	Occurs when the component receives focus or loses focus

2, advanced events include the following several

Event Category	Interface Name	Describe
ActionEvent Action Events	ActionListener	Occurs when a button click, menu selection, list box selection, press Enter in a text field, and so on
AdjustmentEvent Adjustment Events	Adjustmentlistener	Occurs when the user moves the slider on the scroll bar to adjust the value
ItemEvent Project Events	ItemListener	Occurs when the user selects from a set of selection boxes or list boxes
TextEvent Text Events	TextListener	Occurs when the contents of a Text field or text box change

Example one: Two buttons to implement the corresponding event

public class Text extends JFrame implements Actionlistener{jpanel Mb=null; JButton an1,an2;public static void Main (string[] args) {text t=new text ();} Public Text () {mb=new JPanel (); Mb.setbackground (Color.yellow); An1=new JButton ("Red"); An1.addactionlistener (this);// Register the Monitor An1.setactioncommand ("rea");//Specify the action command an2=new JButton ("Blue"); An2.addactionlistener (this); An2.setactioncommand ("Blue"); This.add (An1,borderlayout.north); This.add (An2,borderlayout.south); This.add (MB);// Set the form Properties This.settitle ("Technology Daniel-Xiao Jin"); This.setlocation (+); this.setsize (400,400); this.setvisible (true); This.setdefaultcloseoperation (jframe.exit_on_close);} public void actionperformed (ActionEvent e) {if (E.getactioncommand (). Equals ("Rea")) {Mb.setbackground (color.red);} else if (E.getactioncommand (). Equals ("Blue")) {Mb.setbackground (Color.Blue);}}

Method Two (you can also get listener events)

public class Text extends JFrame {JPanel mb=null; JButton an1,an2;public static void Main (string[] args) {text t=new text ();} Public Text () {mb=new JPanel (); Mb.setbackground (Color.yellow); An1=new JButton ("Red"); An2=new JButton ("Blue"); MyListener listener=new MyListener (); An1.addactionlistener (listener);//Register for monitoring An1.setactioncommand ("red");// Specify the action command An2.addactionlistener (listener); An2.setactioncommand ("Blue"); This.add (An1,borderlayout.north); This.add (An2,borderlayout.south); This.add (MB);//Set form Properties This.settitle ("Technology Daniel-Xiao Jin"); This.setlocation (300, 300); This.setsize (400,400); this.setvisible (true); This.setdefaultcloseoperation (Jframe.exit_on_close);}} Class MyListener implements Actionlistener{public void actionperformed (ActionEvent e) {if (E.getactioncommand (). equals ("Red")) {System.out.println ("red");} else if (E.getactioncommand (). Equals ("Blue")) {System.out.println ("Blue");}}}

Example two: A rectangle will move up and down around the keyboard

public class Text extends JFrame {mypanel mb=null;public static void Main (string[] args) {text t=new text ();//each definition of a t will produce A corresponding this}public Text () {mb=new mypanel (); This.add (MB); This.addkeylistener (MB);//Add a listening keyboard to listen for objects defined by this class are monitored with MP objects Set the form Properties This.settitle ("Technology Daniel-Xiao Jin"); This.setlocation (+); this.setsize (400,400); this.setvisible (true); This.setdefaultcloseoperation (Jframe.exit_on_close);}} Class Mypanel extends JPanel implements keylistener{int x=100,y=100;public void Paint (Graphics g) {super.paint (g); G.setcolor (color.red); G.fillrect (x, Y, 10, 10);} The key is pressed public void keypressed (KeyEvent e) {//system.out.println ("1"), if (E.getkeycode () ==keyevent.vk_up) {y--;} else if (E.getkeycode () ==keyevent.vk_down) {y++;} else if (E.getkeycode () ==keyevent.vk_left) {x--;} else if (E.getkeycode () ==keyevent.vk_right) {x + +;} Call the repaint () function to redraw the interface This.repaint ();} Key is released public void keyreleased (KeyEvent e) {System.out.println ("key is Freed");} <span style= "color: #ff0000;" A value of the >//key is printed out (the next key and so on will not be executed because it is not printed) </span>public void keytyped (KeyEvent e) {System.out.println ("Other key will be executed, the next key or so will not execute, because no print out");}} 

This is where we go, take your time and enjoy it

Study Note 25: Event handling (i)