RGB JTextfields - 在需要3个值时即使其他框为空也会更改颜色

Question

如果在蓝色文本框（tblue）中输入了任何内容（即使其他内容为空），则会将文本更改为该颜色（如果框为空或包含字母，它应该会产生一个错误信息。这个错误不会发生在其他盒子上，尽管它是相同的代码，它仍然可以正常工作。

package FirstCE203Project; 

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

class CE203_2016_Ex1 extends JFrame { 

    JTextField tred, tgreen, tblue; 
    JLabel message;        //to reference later on 
    JButton goButton, reset; 


    public CE203_2016_Ex1() { 

     JPanel panel1 = new JPanel();  //creates panels for the boxes that will hold the rgb values 
     JPanel panel2 = new JPanel(); 
     JPanel panel3 = new JPanel(); 

     tred = new JTextField("Red", 10); 
     tgreen = new JTextField("Green", 10);    //creates boxes for rgb values 
     tblue = new JTextField("Blue", 10); 

     panel2.setLayout(new GridBagLayout());   //sets text to the centre of the panel 

     panel1.add(tred); 
     panel1.add(tgreen);       //adding panels to frame 
     panel1.add(tblue); 


     add(panel1, BorderLayout.SOUTH); //adding panels to frame    //location of panels on frame 
     add(panel2, BorderLayout.CENTER); 
     add(panel3, BorderLayout.NORTH); 


     message = new JLabel("hello"); //text 
     message.setForeground(new Color(255, 0, 0));  //original text set to red 

     JButton goButton = new JButton("Change"); //adds button to change colour 
     JButton reset = new JButton("Reset"); 


     panel1.add(goButton); 
     panel2.add(message); 
     panel3.add(reset);     //adding buttons to panels 

     goButton.addActionListener(new ButtonHandler(this)); 
     reset.addActionListener(new ButtonHandler1(this));     //creating action listener 

    } 


    class ButtonHandler implements ActionListener { 

     private CE203_2016_Ex1 theApp; 

     public ButtonHandler(CE203_2016_Ex1 theApp) { 
      this.theApp = theApp; 
     } 

     @Override 
     public void actionPerformed(ActionEvent e) { 
      int a=0, b=0, c=0; 

      try { 
       a = Integer.parseInt(theApp.tred.getText()); 

       if (a < 0) { 
        a = 200;           //if statements for values above and below the targets set 
        tred.setText("200"); 
       } 

       if (a > 255) { 
        a = 255; 
        tred.setText("255"); 
       } 
       message.setText("CE203 Assignment submitted by: Steven Beresford - 1404398"); 
       message.setForeground(new Color(a, b, c)); //changes colour to desired input 
      } 

      catch(NumberFormatException ex) { 

       message.setText("invalid input! please enter numbers only"); //text 
       message.setForeground(new Color(0, 0, 0));  //error message set to black 
       tred.setText(""); 
      } 

      try { 
       b = Integer.parseInt(theApp.tgreen.getText()); 

       if (b < 0) { 
        b = 200; 
        tgreen.setText("200"); 
       } 

       if (b > 255) { 
        b = 255; 
        tgreen.setText("255"); 
       } 
       message.setText("CE203 Assignment submitted by: Steven Beresford - 1404398"); 
       message.setForeground(new Color(a, b, c)); //changes colour to desired input 
      } 
      catch(NumberFormatException ey) { 

       message.setText("invalid input! please enter numbers only"); //text 
       message.setForeground(new Color(0, 0, 0));  //original text set to red 
       tgreen.setText(""); 

      } 

      try { 
       c = Integer.parseInt(theApp.tblue.getText()); 

       if (c < 0) { 
        c = 200; 
        tblue.setText("200"); 
       } 

       if (c > 255) { 
        c = 255; 
        tblue.setText("255"); 
       } 
       message.setText("CE203 Assignment submitted by: Steven Beresford - 1404398"); 
       message.setForeground(new Color(a, b, c)); //changes colour to desired input 
      } 
      catch(NumberFormatException ez) { 

       message.setText("invalid input! please enter numbers only"); //text 
       message.setForeground(new Color(0, 0, 0));  //original text set to red 
       tblue.setText(""); 
      } 

     } 
    } 


    class ButtonHandler1 implements ActionListener { 

     private CE203_2016_Ex1 theApp; 

     public ButtonHandler1(CE203_2016_Ex1 theApp) { 
      this.theApp = theApp; 
     } 

     @Override 
     public void actionPerformed(ActionEvent e) { 
      message.setText("CE203 Assignment submitted by: Steven Beresford - 1404398"); 
      message.setForeground(new Color(255, 0, 0));     //resets message back to red 
      tred.setText("Red"); 
      tgreen.setText("Green"); 
      tblue.setText("Blue"); 
     } 
    } 

    public static void main(String[] args) { 
     JFrame app = new CE203_2016_Ex1(); 
     app.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); 
     app.setSize(700, 700); 
     app.setVisible(true); 
    } 
} 

Answer 1

它实际上是你想要做什么，但文本然后立即覆盖（这就是为什么你不能看到的变化）。

假设您为绿色输入无效值（b）。

该消息将被设置为“无效输入...”。

try { 
    b = Integer.parseInt(theApp.tgreen.getText()); 
    ... 
} catch (NumberFormatException ey) { 
    message.setText("invalid input! please enter numbers only"); 
    ... 
} 

但你必须为蓝色（c）有效输入：

try { 
    c = Integer.parseInt(theApp.tblue.getText()); 
    ... 
    message.setText("CE203 Assignment submitted by: Steven Beresford - 1404398"); 
    ... 
} 

，这将覆盖“无效的输入。”与价值“CE203分配......”。

---

一个可能的解决方案：

@Override 
    public void actionPerformed(ActionEvent e) { 
     int a = 0, b = 0, c = 0; 
     boolean isValidA = true, isValidB = true, isValidC = true; 

     try { 
      a = Integer.parseInt(theApp.tred.getText()); 
     } catch (NumberFormatException ex) { 
      isValidA = false; 
     } 

     try { 
      b = Integer.parseInt(theApp.tgreen.getText()); 
     } catch (NumberFormatException ex) { 
      isValidB = false; 
     } 

     try { 
      c = Integer.parseInt(theApp.tblue.getText()); 
     } catch (NumberFormatException ex) { 
      isValidC = false; 
     } 

     if (!isValidA) { 
      tred.setText(""); 
     } else { 
      if (a < 0) { 
       a = 200; 
       tred.setText("200"); 
      } else if (a > 255) { 
       a = 255; 
       tred.setText("255"); 
      } 
     } 

     if (!isValidB) { 
      tgreen.setText(""); 
     } else { 
      if (b < 0) { 
       b = 200; 
       tgreen.setText("200"); 
      } else if (b > 255) { 
       b = 255; 
       tgreen.setText("255"); 
      } 
     } 

     if (!isValidC) { 
      tblue.setText(""); 
     } else { 
      if (c < 0) { 
       c = 200; 
       tblue.setText("200"); 
      } else if (c > 255) { 
       c = 255; 
       tblue.setText("255"); 
      } 
     } 
     if (isValidA && isValidB && isValidC) { 
      message.setText("CE203 Assignment submitted by: Steven Beresford - 1404398"); 
      message.setForeground(new Color(a, b, c)); 
     } else { 
      message.setText("invalid input! please enter numbers only"); 
      message.setForeground(new Color(0, 0, 0)); 
     } 

    }