Java 使用 for 循环时向 JButton 添加动作
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Adding action to a JButton when using a for loop
提问by Wbcreators Crea
I'm trying to dynamically add buttons (JButtons), which changes names everytime. I doing it with a for loop and is not really problematic. but when adding an action listener or identifying which button got pressed, that is when things don't work so good.
我正在尝试动态添加按钮（JButtons），它每次都会更改名称。我用 for 循环来做，并没有真正的问题。但是当添加一个动作侦听器或识别哪个按钮被按下时，事情就不太好了。
MyFrame.java
我的框架
import javax.swing.*;
import java.awt.event.*;
import java.awt.GridLayout;
public class MyFrame extends JFrame implements ActionListener
{
private JPanel panel;
private static JButton[] buttons = new JButton[18];
// set all static calculate JButtons
private static JButton equalsBtn, addBtn, subBtn, multiBtn, divBtn, clearBtn, plusMinusBtn, decimalBtn;
// set all static number JBtuttons
private static JButton zeroBtn, oneBtn, twoBtn, threeBtn, fourBtn, fiveBtn, sixBtn, sevenBtn, eightBtn, nineBtn;
private static JTextField resultField;
// numOne is the first row of figures en the second numSecond is the second row
private static double numOne, numSecond, result;
private static double plusMinus;
private static int addClick = 0, subClick = 0, multiClick = 0, divClick = 0;
private static int clearField;
public MyFrame() {
// configure the JFrame
super("Rekennen maar!");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
setSize(230, 370);
setLocationRelativeTo(null);
// confugure the JPanel
panel = new JPanel();
panel.setSize(230, 370);
panel.setLayout(new GridLayout(5, 0));
// array string whit all the button names
String a_btnNames[] = {"clearBtn", "plusMinusBtn", "divBtn", "multiBtn", "sevenBtn", "eightBtn", "nineBtn", "subBtn", "fourBtn", "fiveBtn", "sixBtn", "addBtn", "oneBtn", "twoBtn", "threeBtn", "equalsBtn", "zeroBtn", "decimalBtn"};
// array String whit all button characters
String a_btnCharts[] = {"C", "+/-", "/", "*", "7", "8", "9", "-", "4", "5", "6", "+", "1", "2", "3", "=", "0", "."};
for(int i = 0; i < buttons.length; i++)
{
// make new button name
buttons[i] = new JButton(a_btnNames[i]);
// add button to panel
panel.add(new JButton(a_btnCharts[i]));
//System.out.println(buttons[i]);
}
// add panel when he's filled
add(panel);
setVisible(true);
}
public void actionPerformed(ActionEvent e) {
// press the button
if ( e.getSource() == ...... ) {
System.out.println("123");
}
}
}
Main.java
主程序
public class Main {
public static void main(String[] arg) {
MyFrame mf = new MyFrame();
}
}
采纳答案by Mike M
There is nothing listening for when the buttons are pressed. When you create each button, you must give them action listeners.
按下按钮时没有任何声音。创建每个按钮时，必须为它们提供动作侦听器。
Also, you should be adding the same button that you create.
此外，您应该添加与您创建的按钮相同的按钮。
buttons[i] = new JButton("" + a_btnNames[i]);
//buttons[i] should now be added to the panel
New for loop should be...
新的 for 循环应该是...
for(int i = 0; i < buttons.length; i++){
buttons[i] = new JButton("" + a_btnNames[i]); //create button & add to array
buttons[i].addActionListener(this); //add an action listener to the current button
panel.add(buttons[i]); //add that same button to the panel
}
回答by Rayf
Alter the loop, to something like this.
改变循环，像这样。
for(int i = 0; i < buttons.length; i++)
{
// make new button name
JButton btn = new JButton("" + a_btnNames[i]);
buttons[i] = btn;
btn.addActionListener(this);
// add button to panel
panel.add(btn);
//System.out.println(buttons[i]);
}
And then have an actionPerformed() like this.
然后有一个这样的 actionPerformed()。
public void actionPerformed(ActionEvent evt) {
Object src = evt.getSource();
if (src == buttons[0]) {
//First button actions
} else if (src == buttons[1]) {
//Second button actions
}
}
Should work.
应该管用。
回答by Sage
Well i don't see any problem when you know that
evt.getSource()return the source Component of theActionEvent.To register an action listener to a component like
JButton, we usually do this:jButton.addActionListener(anActionListener);For your context you can pass
ActionListenerusing the help ofthis.Do not implement
ActionListenerinterface to some class which doesn't listen to such Event or have them. If required declare a new class by implementing it and use instance of that class to register the listener.class MyActionListener implements ActionListener { public void actionPerformed(ActionEvent e) { // press the button } } MyActionListener actionListener = new MyActionListener(); jButton1.addActionListener(actionListener); jButton2.addActionListener(actionListener); jButton3.addActionListener(actionListener);
好吧，当您知道
evt.getSource()返回ActionEvent.要将动作侦听器注册到像 那样的组件
JButton，我们通常这样做：jButton.addActionListener(anActionListener);对于您的上下文，您可以
ActionListener使用this.不要
ActionListener为某些不侦听此类事件或拥有它们的类实现接口。如果需要，通过实现它来声明一个新类并使用该类的实例来注册侦听器。class MyActionListener implements ActionListener { public void actionPerformed(ActionEvent e) { // press the button } } MyActionListener actionListener = new MyActionListener(); jButton1.addActionListener(actionListener); jButton2.addActionListener(actionListener); jButton3.addActionListener(actionListener);
I'm trying to dynamically add buttons (JButtons), which changes names everytime.
我正在尝试动态添加按钮（JButtons），它每次都会更改名称。
But you are probably having misconception about setting name with new JButton("some text").
This doesn't set name of the Button, rather it's text content. You need to use button.setName("aName")instead.
但是您可能对使用new JButton("some text"). 这不会设置按钮的名称，而是文本内容。你需要button.setName("aName")改用。
However, You can always use the either of the getNameor getTextmethod to identify your specific button.
但是，您始终可以使用getName或getText方法中的任一个来标识您的特定按钮。
public void actionPerformed(ActionEvent e) {
// press the button
JButton button = (JButton)e.getSource();
Syestem.out.println(button.getName()); // get the name
System.out.println(button.getText()) // get the text content
if(button.getText().equals("clearBtn"))
// clear things for me
}
回答by vels4j
Few changes
变化不大
for(int i = 0; i < buttons.length; i++)
{
// make new button name
buttons[i] = new JButton(a_btnCharts[i]);
buttons[i].setName(a_btnNames[i]); // assign button name
buttons[i].addActionListener(this); // assign action listener
// add button to panel
panel.add(buttons[i]);
}
and
和
@Override
public void actionPerformed(ActionEvent e) {
// press the button
System.out.println(e.getActionCommand());
JButton btn=(JButton)e.getSource();
System.out.println(btn.getName()); // use name or action command in if statment
}
Your main method should be
你的主要方法应该是
public static void main(String[] arg) {
SwingUtilities.invokeLater( new Runnable() {
@Override
public void run() {
MyFrame mf = new MyFrame();
}
});
}
Read The Event Dispatch Thread
阅读事件调度线程
回答by Dario
Remember to add the ActionListener to JButtons first. Then, using getSource() this way doesn't help in your case because you are not keeping references to the JButtons you are adding to the panel. You can use getActionCommand() instead - Default behavior is it returns the label of the button but you can override it with setActionCommand(...):
请记住首先将 ActionListener 添加到 JButtons。然后，以这种方式使用 getSource() 对您的情况没有帮助，因为您没有保留对要添加到面板的 JButton 的引用。您可以改用 getActionCommand() - 默认行为是它返回按钮的标签，但您可以使用 setActionCommand(...) 覆盖它：
if ( e.getActionCommand().equals(a_btnCharts[0] ) {
回答by Larois
loop over the JButton array:
循环 JButton 数组：
for (int i = 0; i < buttons.length; ++i) {
if (e.getSource()==buttons[i]){
System.out.println("Button name: " + a_btnNames[i] +"<> Char:"+ a_btnCharts[i] + " pressed");
}
}
}
