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开发一个Swing功能时的一点总结
阅读量:7247 次
发布时间:2019-06-29

本文共 10095 字,大约阅读时间需要 33 分钟。

 

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
list = new ArrayList
() { 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
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("Use Tab (or Shift-Tab) to navigate from component to component.

Control-Tab (or Control-Shift-Tab) allows you to break out of the JTable."); 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

order = new Vector
(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
order; public MyOwnFocusTraversalPolicy(Vector
order) { this.order = new Vector
(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);     } }

 

 

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