開發一個Swing功能時的一點總結

時間 2019-11-11

標籤開發一個 swing 功能一點 1點總結简体版

原文原文鏈接

對JTextField進行效驗，有兩個途徑：
（1）是使用javax.swing.InputVerifier在獲取焦點時進行校驗
（2）在點擊「肯定」按鈕的監聽事件中對控件的值進行校驗

鑑於涉及的業務比較多，代碼結構已經肯定，若是在「肯定」按鈕的監聽事件中進行效驗，須要增長一個步驟，而且並非全部的業務都須要這個效驗，
就傾向於使用javax.swing.InputVerifier進行，這樣作有兩個好處，（1）分離業務邏輯與前端（2）代碼更優雅

javax.swing.InputVerifier用的很少，用了以後發現這個控件的特性和之前UE的不一樣：
「校驗器並不是問題很安全。若是點擊了某個按鈕，而這個按鈕在無效構件再次得到焦點以前通知了它的動做監聽器，那麼這個動做監聽器就會未經過校驗的構件中獲得一個無效的結果。這種行爲的緣由在於：用戶可能但願點擊Cancel按鈕，而無需訂正無效輸入」html

還有個問題，若是控件JTextField在java.awt.Container中沒有得到焦點，則相關校驗就不起做用前端

（Abstract）java.awt.FocusTraversalPolicy調整焦點順序(沒有生效)
或在Container上增長監聽，在Container執行setVisile(true)後
addWindowFocusListener(new WindowAdapter() {
    public void windowGainedFocus(WindowEvent e) {
        textField.requestFocusInWindow();
    }
});

進行這樣的處理後，在win7上程序出現一些意外的異常狀況，而且因爲增長監聽，也增長了程序的處理邏輯，進行告終構的調整

鑑於以上的狀況，最終在「肯定」按鈕的監聽中的處理流程中增長constraintCheck的邏輯

查找最小可用ID的一個算法：

java

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;
	}

	/**
	 * 查找最接近目標值的數，並返回
	 * 
	 * @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("和要查找的數：" + targetNum + "最接近的數："
		        + array[targetindex]);
		return (Integer) (((Integer) array[right] - (Integer) array[left]) / 2 > targetNum ? array[right]
		        : array[left]);

	}
}

Output:算法

1 2 3 5 9 10 100 Result:4

Tutorials上的一個Sample:windows

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
此類的用途是經過帶文本字段的 GUI 幫助客戶端支持流暢的焦點導航。在容許用戶導航到文本字段之外以前，這類 GUI 經常須要確保用戶輸入的文本是有效的（例如，文本具備正確的格式）。爲作到這一點，客戶端要使用 JComponent 的 setInputVerifier 方法建立 InputVerifier 的子類，並將其子類的實例附加到想要驗證其輸入的 JComponent 中。在將焦點轉移到另外一個請求它的 Swing 組件以前，要調用輸入驗證器的 shouldYieldFocus 方法。只在該方法返回 true 時才轉移焦點。安全

如下示例有兩個文本字段，其中第一個字段指望用戶輸入字符串 "pass"。若是在第一個文本字段中輸入該字符串，那麼用戶能夠經過在第二個文本字段上單擊或按下 TAB 前進到第二個文本字段。不過，若是將其餘字符串輸入到第一個文本字段中，則用戶沒法將焦點轉移到第二個文本字段。

app

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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