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);
}
}
