对JTextField进行效验，有两个途径：
（1）是使用javax.swing.InputVerifier在获取焦点时进行校验
（2）在点击“确定”按钮的监听事件中对控件的值进行校验
鉴于涉及的业务比较多，代码结构已经确定，如果在“确定”按钮的监听事件中进行效验，需要增加一个步骤，并且并不是所有的业务都需要这个效验，
就倾向于使用javax.swing.InputVerifier进行，这样做有两个好处，（1）分离业务逻辑与前端 （2）代码更优雅
javax.swing.InputVerifier用的不多，用了之后发现这个控件的特性和以前UE的不同：
“校验器并非问题很安全。如果点击了某个按钮，而这个按钮在无效构件再次获得焦点之前通知了它的动作监听器，那么这个动作监听器就会未通过校验的构件中得到一个无效的结果。这种行为的原因在于：用户可能希望点击Cancel按钮，而无需订正无效输入”
还有个问题，如果控件JTextField在java.awt.Container中没有获得焦点，则相关校验就不起作用
（Abstract）java.awt.FocusTraversalPolicy调整焦点顺序(没有生效)
或在Container上增加监听，在Container执行setVisile(true)后
addWindowFocusListener(new WindowAdapter() {
public void windowGainedFocus(WindowEvent e) {
textField.requestFocusInWindow();
}
});
进行这样的处理后，在win7上程序出现一些意外的异常情况，并且由于增加监听，也增加了程序的处理逻辑，进行了结构的调整
鉴于以上的情况，最终在“确定”按钮的监听中的处理流程中增加constraintCheck的逻辑
查找最小可用ID的一个算法：
package algorithm;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/*2015-6-26*/
public class FindMinUsefulValue {
private static final int MIN = 1;
public static void main(String[] args) {
List<Integer> list = new ArrayList<Integer>() {
private static final long serialVersionUID = 1L;
{
add(1);
add(2);
add(5);
add(3);
add(10);
add(100);
add(9);
}
};
Collections.sort(list);
for (Integer item : list) {
System.out.print(item + " ");
}
System.out.println("Result:" + search(list));
}
private static int search(List<Integer> list) {
int max = list.get(list.size() - 1);
if (max == list.size() + MIN - 1) {
return max + 1;
}
int targetNum = MIN;
for (int i = 0; i < list.size(); i++) {
targetNum = MIN + i;
if (list.get(i) == MIN + i) {
continue;
}
break;
}
return targetNum;
}
/**
* 查找最接近目标值的数，并返回
*
* @param array
* @param targetNum
* @return
*/
public static Integer binarysearchKey(Object[] array, int targetNum) {
Arrays.sort(array);
int targetindex = 0;
int left = 0, right = 0;
for (right = array.length - 1; left != right;) {
int midIndex = (right + left) / 2;
int mid = (right - left);
int midValue = (Integer) array[midIndex];
if (targetNum == midValue) {
return midIndex;
}
if (targetNum > midValue) {
left = midIndex;
} else {
right = midIndex;
}
if (mid <= 2) {
break;
}
}
System.out.println("和要查找的数：" + targetNum + "最接近的数："
+ array[targetindex]);
return (Integer) (((Integer) array[right] - (Integer) array[left]) / 2 > targetNum ? array[right]
: array[left]);
}
}
Output:
1 2 3 5 9 10 100 Result:4
Tutorials上的一个Sample:
package misc; import java.awt.*; import java.awt.event.*; import java.util.Vector; import javax.swing.*; /* * FocusTraversalDemo.java requires no other files. */ public class FocusTraversalDemo extends JPanel implements ActionListener { static JFrame frame; JLabel label; JCheckBox togglePolicy; static MyOwnFocusTraversalPolicy newPolicy; public FocusTraversalDemo() { super(new BorderLayout()); JTextField tf1 = new JTextField("Field 1"); JTextField tf2 = new JTextField("A Bigger Field 2"); JTextField tf3 = new JTextField("Field 3"); JTextField tf4 = new JTextField("A Bigger Field 4"); JTextField tf5 = new JTextField("Field 5"); JTextField tf6 = new JTextField("A Bigger Field 6"); JTable table = new JTable(4,3); togglePolicy = new JCheckBox("Custom FocusTraversalPolicy"); togglePolicy.setActionCommand("toggle"); togglePolicy.addActionListener(this); togglePolicy.setFocusable(false); //Remove it from the focus cycle. //Note that HTML is allowed and will break this run of text //across two lines. label = new JLabel("<html>Use Tab (or Shift-Tab) to navigate from component to component.<p>Control-Tab (or Control-Shift-Tab) allows you to break out of the JTable.</html>"); JPanel leftTextPanel = new JPanel(new GridLayout(3,2)); leftTextPanel.add(tf1, BorderLayout.PAGE_START); leftTextPanel.add(tf3, BorderLayout.CENTER); leftTextPanel.add(tf5, BorderLayout.PAGE_END); leftTextPanel.setBorder(BorderFactory.createEmptyBorder(0,0,5,5)); JPanel rightTextPanel = new JPanel(new GridLayout(3,2)); rightTextPanel.add(tf2, BorderLayout.PAGE_START); rightTextPanel.add(tf4, BorderLayout.CENTER); rightTextPanel.add(tf6, BorderLayout.PAGE_END); rightTextPanel.setBorder(BorderFactory.createEmptyBorder(0,0,5,5)); JPanel tablePanel = new JPanel(new GridLayout(0,1)); tablePanel.add(table, BorderLayout.CENTER); tablePanel.setBorder(BorderFactory.createEtchedBorder()); JPanel bottomPanel = new JPanel(new GridLayout(2,1)); bottomPanel.add(togglePolicy, BorderLayout.PAGE_START); bottomPanel.add(label, BorderLayout.PAGE_END); add(leftTextPanel, BorderLayout.LINE_START); add(rightTextPanel, BorderLayout.CENTER); add(tablePanel, BorderLayout.LINE_END); add(bottomPanel, BorderLayout.PAGE_END); setBorder(BorderFactory.createEmptyBorder(20,20,20,20)); Vector<Component> order = new Vector<Component>(7); order.add(tf1); order.add(tf2); order.add(tf3); order.add(tf4); order.add(tf5); order.add(tf6); order.add(table); newPolicy = new MyOwnFocusTraversalPolicy(order); } //Turn the custom focus traversal policy on/off, //according to the checkbox public void actionPerformed(ActionEvent e) { if ("toggle".equals(e.getActionCommand())) { frame.setFocusTraversalPolicy(togglePolicy.isSelected() ? newPolicy : null); } } /** * Create the GUI and show it. For thread safety, * this method should be invoked from the * event-dispatching thread. */ private static void createAndShowGUI() { //Create and set up the window. frame = new JFrame("FocusTraversalDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. JComponent newContentPane = new FocusTraversalDemo(); newContentPane.setOpaque(true); //content panes must be opaque frame.setContentPane(newContentPane); //Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { /* Use an appropriate Look and Feel */ try { //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); //UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel"); UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel"); } catch (UnsupportedLookAndFeelException ex) { ex.printStackTrace(); } catch (IllegalAccessException ex) { ex.printStackTrace(); } catch (InstantiationException ex) { ex.printStackTrace(); } catch (ClassNotFoundException ex) { ex.printStackTrace(); } /* Turn off metal's use of bold fonts */ UIManager.put("swing.boldMetal", Boolean.FALSE); //Schedule a job for the event-dispatching thread: //creating and showing this application's GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } public static class MyOwnFocusTraversalPolicy extends FocusTraversalPolicy { Vector<Component> order; public MyOwnFocusTraversalPolicy(Vector<Component> order) { this.order = new Vector<Component>(order.size()); this.order.addAll(order); } public Component getComponentAfter(Container focusCycleRoot, Component aComponent) { int idx = (order.indexOf(aComponent) + 1) % order.size(); return order.get(idx); } public Component getComponentBefore(Container focusCycleRoot, Component aComponent) { int idx = order.indexOf(aComponent) - 1; if (idx < 0) { idx = order.size() - 1; } return order.get(idx); } public Component getDefaultComponent(Container focusCycleRoot) { return order.get(0); } public Component getLastComponent(Container focusCycleRoot) { return order.lastElement(); } public Component getFirstComponent(Container focusCycleRoot) { return order.get(0); } } }
public abstract class InputVerifier extends Object
此类的用途是通过带文本字段的 GUI 帮助客户端支持流畅的焦点导航。在允许用户导航到文本字段以外之前，这类 GUI 常常需要确保用户输入的文本是有效的（例如，文本具有正确的格式）。为做到这一点，客户端要使用 JComponent 的 setInputVerifier 方法创建 InputVerifier 的子类，并将其子类的实例附加到想要验证其输入的 JComponent 中。在将焦点转移到另一个请求它的 Swing 组件之前，要调用输入验证器的 shouldYieldFocus 方法。只在该方法返回 true 时才转移焦点。
以下示例有两个文本字段，其中第一个字段期望用户输入字符串 "pass"。如果在第一个文本字段中输入该字符串，那么用户可以通过在第二个文本字段上单击或按下 TAB 前进到第二个文本字段。不过，如果将其他字符串输入到第一个文本字段中，则用户无法将焦点转移到第二个文本字段。
import java.awt.*; import java.util.*; import java.awt.event.*; import javax.swing.*; // This program demonstrates the use of the Swing InputVerifier class. // It creates two text fields; the first of the text fields expects the // string "pass" as input, and will allow focus to advance out of it // only after that string is typed in by the user. public class VerifierTest extends JFrame { public VerifierTest() { JTextField tf1 = new JTextField ("Type "pass" here"); getContentPane().add (tf1, BorderLayout.NORTH); tf1.setInputVerifier(new PassVerifier()); JTextField tf2 = new JTextField ("TextField2"); getContentPane().add (tf2, BorderLayout.SOUTH); WindowListener l = new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }; addWindowListener(l); } class PassVerifier extends InputVerifier { public boolean verify(JComponent input) { JTextField tf = (JTextField) input; return "pass".equals(tf.getText()); } } public static void main(String[] args) { Frame f = new VerifierTest(); f.pack(); f.setVisible(true); } }