启用一个JButton，当某个组件改变其边框颜色时。

huangapple
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英文:

Enable a JButton when some component changed its border color

问题

  1. public static boolean countBoards(JPanel panel){
  2.     boolean red = false;
  4.     for(Component control : panel.getComponents())
  5.     {
  6.         if(control instanceof JTextField)
  7.         {
  8.             JTextField ctrl = (JTextField) control; 
  9.             Color lineColor = ((LineBorder)ctrl.getBorder()).getLineColor();
  11.             if(lineColor.equals(Color.green))
  12.                 red = true;                
  13.         }  
  14.         else if(control instanceof JComboBox)
  15.         {
  16.             JComboBox ctr = (JComboBox) control; 
  17.             Color lineColor = ((LineBorder)ctr.getBorder()).getLineColor();
  19.             if(lineColor.equals(Color.green))
  20.                 red = true;               
  21.         }
  22.     }                 
  24.     return red;
  25. }
英文:

My goal is to enable a JButton only when some JTextFields and JComboBox change its border color from red to green.<br>
These components are included in three different JPanel.<br>
I try to create a function that reads all components in a JPanel but, when I'm going to compared the colors, the program returns me that I'm casting the variables in a bad way.<br>
Below there's my function.<br>
Can someone help me?

  1.     public static boolean countBoards(JPanel panel){
  2.         boolean red = false;
  3.         
  4.         for(Component control : panel.getComponents())
  5.         {
  6.             if(control instanceof JTextField)
  7.             {
  8.                 JTextField ctrl = (JTextField) control; 
  9.                 Color lineColor = ((LineBorder)ctrl.getBorder()).getLineColor();
  10.             
  11.                 if(lineColor.equals(Color.red))
  12.                     red = true;                
  13.             }  
  14.             else if(control instanceof JComboBox)
  15.             {
  16.                 JComboBox ctr = (JComboBox) control; 
  17.                 Color lineColor = ((LineBorder)ctr.getBorder()).getLineColor();
  18.             
  19.                 if(lineColor.equals(Color.red))
  20.                     red = true;               
  21.             }
  22.         }                 
  23.         
  24.         return red;
  25.     }

答案1

得分: 0

当您更改组件的边框时，将触发属性侦听器。您可以在组合框/文本字段上注册属性侦听器，并根据新边框启用/禁用按钮。

示例：

  1. @Test
  2. public void test() {
  3.     JButton myButton = new JButton();
  4.     JComboBox<String> combo = new JComboBox<>();
  5.     combo.addPropertyChangeListener("border", e -> {
  6.         if (e.getNewValue() != null && e.getNewValue() instanceof LineBorder) {
  7.             LineBorder border = (LineBorder) e.getNewValue();
  8.             myButton.setEnabled(border.getLineColor().equals(Color.green));
  9.         }
  10.     });
  11.     assertTrue(myButton.isEnabled(), "Button should be initially enabled.");
  13.     combo.setBorder(BorderFactory.createLineBorder(Color.red));
  14.     assertFalse(myButton.isEnabled(), "Button should be disabled when red line border occurs.");
  16.     combo.setBorder(BorderFactory.createLineBorder(Color.green));
  17.     assertTrue(myButton.isEnabled(), "Button should be enabled when green line border occurs.");
  18. }
英文:

When you change the border of a component, a property listener will be fired. You can register a property listener to the combobox/textfield and enable/disable the button according to the new border.

An example:

  1. @Test
  2. public void test() {
  3. 	JButton myButton = new JButton();
  4. 	JComboBox&lt;String&gt; combo = new JComboBox&lt;&gt;();
  5. 	combo.addPropertyChangeListener(&quot;border&quot;, e -&gt; {
  6. 		if (e.getNewValue() != null &amp;&amp; e.getNewValue() instanceof LineBorder) {
  7. 			LineBorder border = (LineBorder) e.getNewValue();
  8. 			myButton.setEnabled(border.getLineColor().equals(Color.green));
  9. 		}
  10. 	});
  11. 	assertTrue(myButton.isEnabled(), &quot;Button should be initially enabled.&quot;);
  13. 	combo.setBorder(BorderFactory.createLineBorder(Color.red));
  14. 	assertFalse(myButton.isEnabled(), &quot;Button should be disabled when red line border occurs.&quot;);
  16. 	combo.setBorder(BorderFactory.createLineBorder(Color.green));
  17. 	assertTrue(myButton.isEnabled(), &quot;Button should be enabled when green line border occurs.&quot;);
  18. }

huangapple
  • 本文由 发表于 2020年8月19日 06:53:07
  • 转载请务必保留本文链接：https://go.coder-hub.com/63477711.html
  • border
  • casting
  • java
  • jpanel
  • swing
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