Question

我想在我的3个TextFields中添加一个关键的监听器事件：

angleText，initialVelocityText和accelerationText

我想拒绝除小数点以外的字符并保留退格，并接受数字。

提前谢谢 - 这个问题已经解决了 - 特别感谢@AliGul的回复，也感谢其他人的回复

这是我正在讨论的课程中的代码：

package projectV1;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.border.*;






public class Simulation extends JPanel {
//Initialise all the variables
private int BOX_WIDTH = 1920;
private int BOX_HEIGHT = 1080;

public String angle, distance, height , acceleration, initialVelocity, velocity, time; // Keep all as string until calc
public int x, y ,vx, vy;
private boolean isRunning; 
public JFrame simFrame;
public JPanel  inputPanel;
public Animate animatePanel;
public JButton start, apply;
public boolean validation = false;
    public static TextField accelerationText;
    public static TextField angleText;
    public static TextField initialVelocityText;
    public static TextField velocityText;
    public static TextField distanceText;
    public static TextField timeText;
    public static TextField heightText;


//FOR THE APPLY BUTTON JUST HAVE ONE OF THOSE BUT HAVE MULTIPLE BOXES WHICH YOU CAN CHANGE THE VALUE OF


// This will have my JPanel for the animatePanel, the animate panel will have the next class acting on it for the
// animation of the program.
// SO now we have the 2 panels that we need, in the bottom panel we will have the buttons and text fields, 
// will be variable holders and can be changed, we need to figure out the logic of how that will come to working.

public Simulation() {


    simFrame = new JFrame("Simulation");
     Main.setJFrame(simFrame);
     inputPanel = new JPanel(new GridLayout(2,7));
     animatePanel = new Animate();
     inputPanel.setBackground(Color.WHITE);
     animatePanel.setBackground(Color.LIGHT_GRAY);
     simFrame.add(inputPanel, BorderLayout.NORTH);
     simFrame.add(animatePanel, BorderLayout.CENTER);
     gui();

    }
  public void gui(){
    JLabel a,b,c,d,e,f,g; // These are just initialising the JLabels for the text fields

    // WHAT i attempted to do here is to make it so that adding these variables gets the things

    time = "0";
     acceleration = "9.81";
     initialVelocity = "10";
     distance = "0";
     height = "0";
     velocity = "0";
     angle = "45";
     // Place all the swing elements, I use a grid layout

     a = new JLabel("Current Velocity: ",JLabel.CENTER);
     a.setToolTipText("The velocity that the ball is currently moving at");
     inputPanel.add(a);
     velocityText = new TextField(velocity);
     inputPanel.add(velocityText);

     b = new JLabel("Current Distance:  ",JLabel.CENTER);
     b.setToolTipText("What the distance horizontally that the ball is travelling at");
     inputPanel.add(b);
     distanceText = new TextField(distance);
     inputPanel.add(distanceText);

     c = new JLabel("Current Height: ",JLabel.CENTER);
     c.setToolTipText("The current vertical height of the ball");
     inputPanel.add(c);
     heightText = new TextField(height);
     inputPanel.add(heightText);

     d = new JLabel("Current Time Elapsed: ",JLabel.CENTER);
     d.setToolTipText("The time elapsed, this relates to the motion of the ball");
     inputPanel.add(d);
     timeText = new TextField(time);
     inputPanel.add(timeText);

     e = new JLabel("Input Initial Velocity ",JLabel.CENTER);
     e.setToolTipText("How fast should the ball start as?");
     inputPanel.add(e);
     initialVelocityText = new TextField(initialVelocity);


     inputPanel.add(initialVelocityText);

     f = new JLabel("Input Acceleration",JLabel.CENTER);
     f.setToolTipText("Whats the acceleration); 9.81 is due to gravity on earth, try 1.6, its the moon's");
     inputPanel.add(f);
     accelerationText = new TextField(acceleration);
     inputPanel.add(accelerationText);

     g = new JLabel("Input angle (degrees): ",JLabel.CENTER);
     g.setToolTipText("Angle of attack? Please enter a value between 1 and 90");
     inputPanel.add(g);
     angleText = new TextField(angle);

     inputPanel.add(angleText);

     apply = new JButton("Apply Changes"); // This will apply changes put in text fields.
     inputPanel.add(apply);

     start = new JButton("Start Simulation"); // This will apply and start the timer and send all the variables.
     inputPanel.add(start);

     apply.addActionListener(new ActionListener(){
         public void actionPerformed(ActionEvent e){
             apply();
         }
     });
     start.addActionListener(new ActionListener(){
         public void actionPerformed(ActionEvent e){
             apply();
             simulate(acceleration, angle, initialVelocity);
              }
     });
      }

  private void apply(){ // ADD VALIDATION FOR THIS BEFORE THE CODE IS DONE
    int count = 0;

    angle = angleText.getText();
    if (validateAngle(angle)){
        count = count +1;
    }
    angle = convertToRadians(angle);
    acceleration = accelerationText.getText();
    if (validateAcceleration(acceleration)){
        count = count +1;
    }
    initialVelocity = initialVelocityText.getText();
    if (validateInitialVelocity(initialVelocity)){
        count = count +1;
        }
    if (count ==3){
        validation = true;
    }
    }

public void simulate(String acceleration, String angle, String initialVelocity){


    // apply();
    if (validation){

    animatePanel.start(acceleration, initialVelocity, angle);
    } else {
        JOptionPane.showMessageDialog(animatePanel, "Re-enter values");
    }
    }

public String convertToRadians(String angle){ // Does a conversion to get the angle in degrees to radians.
    double angleToRadians = 0;
    angleToRadians = Double.parseDouble(angle);
    angleToRadians = (Math.PI*angleToRadians)/180;
    angle = Double.toString(angleToRadians);
    return angle;
}

public boolean validateAcceleration(String acceleration){
    double tempAcc = Double.parseDouble(acceleration);
    if (isDouble(acceleration)){
        if (tempAcc>0){
            return true;
        } else {
            return false;
        }
    } else {
        return false;
    }

    }


public boolean validateAngle(String angle){
    double tempAngle = Double.parseDouble(angle);
    if (isDouble(angle)){
        if (tempAngle>=1 && tempAngle<= 90){
            return true;
        } else {
            return false;
        }
        } else {
        return false;
    }

}


public boolean validateInitialVelocity(String initialVelocity){
    double tempVel = Double.parseDouble(initialVelocity);
    if (isDouble(initialVelocity)){
        if (tempVel >1){
            return true;
        } else {
            return false;
        }
    } else {
        return false;
    }
}

public boolean isDouble(String str) {
    try {
        Double.parseDouble(str);
        return true;
    } catch (NumberFormatException e) {
        return false;
    }
}

}

Answer 1

我想拒绝除小数点以外的字符并保留退格，并接受数字。

KeyListener不是实现此目的的合适机制（实际上KeyListener通常不适合很多事情），而应该使用DocumentFilter

有无数的例子：

Answer 2

你试过using a focusListener吗？

简而言之，您可以检查焦点是否在任何一个文本字段中丢失，并使用特殊方法和RegExp来确认输入是否符合您的要求。

或者您可以使用FormattedTextField

Answer 3

希望这有帮助。

angleText.addKeyListener(new KeyAdapter() { //disables everything except number and dots
        public void keyTyped(KeyEvent e) {
            char input = e.getKeyChar();
            if ((input < '0' || input > '9') && input != '\b' && input != '.') {
                e.consume(); 
            }
        }
    });

然后，只需将'angleText'部分更改为'initialVelocityText'等。

如果我已经在类中实现了一个动作监听器，我该如何添加一个键监听器呢？

3 个答案: