java - VerifyInputWhenFocusTarget属性无效

我正在尝试使用javax.swing.InputVerifier验证文本字段用户输入，并且输入验证按预期工作，但是我对VerifyInputWhenFocusTarget属性有问题。

我制作了一个标签来显示verify()子类的状态和重写的shouldYieldFocus()和InputVerifier方法，并且效果很好。

我下一步要做的是设置按钮的VerifyInputWhenFocusTarget，以便在当前焦点所有者的验证为false的情况下不会获得焦点，但是我没有注意到将VerifyInputWhenFocusTarget属性设置为true和即使当前焦点所有者的验证为假，也可以按下该按钮。

也许我听不懂文档-我认为将按钮的VerifyInputWhenFocusTarget属性设置为true会在错误验证文本字段的情况下阻止按钮在单击时获得焦点。此外，我(错误)理解了如果按钮无法获得焦点，则不会调用其actionPerformed()方法。

但是，可以单击按钮并执行其actionPerformed()方法，尽管对javax.swing.InputVerifier“保护”的文本字段进行了错误的验证。

这是剥离的代码:

package verifiertest;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;

import javax.swing.UIManager;
import java.awt.GridLayout;
import java.math.BigDecimal;

import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.SwingConstants;
import javax.swing.JTextField;
import javax.swing.InputVerifier;
import javax.swing.JButton;
import javax.swing.JComponent;

import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class TestVerifier {

    private JFrame frmInputverifierTest;
    private JTextField tfFirstNum;
    private JTextField tfSecondNum;
    private JLabel lblStatus;
    private String statusText = "Input the numbers and press the \"Start!\" button...";

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    TestVerifier window = new TestVerifier();
                    window.frmInputverifierTest.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public TestVerifier() {
        initialize();
    }

    private void initialize() {
        frmInputverifierTest = new JFrame();
        frmInputverifierTest.setTitle("InputVerifier Test");
        frmInputverifierTest.setBounds(100, 100, 500, 450);
        frmInputverifierTest.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panelContainer = new JPanel();
        panelContainer.setBorder(new EmptyBorder(5, 5, 5, 5));
        frmInputverifierTest.getContentPane().add(panelContainer, BorderLayout.CENTER);
        panelContainer.setLayout(new BorderLayout(0, 0));

        JPanel panelInput = new JPanel();
        panelInput.setBorder(new TitledBorder(null, "Input", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        panelContainer.add(panelInput, BorderLayout.NORTH);
        panelInput.setLayout(new GridLayout(2, 2, 10, 4));

        JLabel lblFirstNum = new JLabel("Number #1:");
        lblFirstNum.setHorizontalAlignment(SwingConstants.TRAILING);
        panelInput.add(lblFirstNum);

        tfFirstNum = new JTextField();
        panelInput.add(tfFirstNum);
        tfFirstNum.setColumns(10);
        // setup the verifier
        MyTxtVerifier txtVerifier = new MyTxtVerifier();
        tfFirstNum.setInputVerifier(txtVerifier);

        JLabel lblSecondNum = new JLabel("Number #2:");
        lblSecondNum.setHorizontalAlignment(SwingConstants.TRAILING);
        panelInput.add(lblSecondNum);

        tfSecondNum = new JTextField();
        panelInput.add(tfSecondNum);
        tfSecondNum.setColumns(10);
        // setup the verifier
        tfSecondNum.setInputVerifier(txtVerifier);

        JPanel panelOutput = new JPanel();
        panelOutput.setBorder(new TitledBorder(UIManager.getBorder("TitledBorder.border"), "Output (not used at the moment)", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        panelContainer.add(panelOutput, BorderLayout.CENTER);

        JPanel panelSouth = new JPanel();
        panelSouth.setBorder(null);
        panelContainer.add(panelSouth, BorderLayout.SOUTH);
        panelSouth.setLayout(new GridLayout(0, 1, 0, 0));

        JPanel panelStatus = new JPanel();
        FlowLayout flowLayout_1 = (FlowLayout) panelStatus.getLayout();
        flowLayout_1.setAlignment(FlowLayout.LEFT);
        panelStatus.setBorder(new TitledBorder(null, "Status", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        panelSouth.add(panelStatus);

        lblStatus = new JLabel(statusText);
        panelStatus.add(lblStatus);

        JPanel panelActions = new JPanel();
        panelActions.setBorder(new TitledBorder(null, "Actions", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        FlowLayout flowLayout = (FlowLayout) panelActions.getLayout();
        flowLayout.setAlignment(FlowLayout.RIGHT);
        panelSouth.add(panelActions);

        JButton btnHelp = new JButton("?");
        btnHelp.setVerifyInputWhenFocusTarget(false);   // <-- NO EFFECT!?
        btnHelp.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frmInputverifierTest, "Help button pressed...", "Help", JOptionPane.PLAIN_MESSAGE);
            }
        });
        panelActions.add(btnHelp);

        JButton btnStart = new JButton("Start!");
        btnStart.setVerifyInputWhenFocusTarget(true);   // <-- NO EFFECT!?
        btnStart.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frmInputverifierTest, "Start button pressed...", "Start", JOptionPane.PLAIN_MESSAGE);
            }
        });
        panelActions.add(btnStart);
        btnHelp.setPreferredSize(btnStart.getPreferredSize());  // make buttons equal in size
    }

    // an inner class so it can access parent fields
    public class MyTxtVerifier extends InputVerifier {
        // This method should have no side effects
        @Override
        public boolean verify(JComponent input) {
            String text = ((JTextField)input).getText();
            try {
                BigDecimal value = new BigDecimal(text);
                if(value.floatValue() <= 0.0)
                    return false;
                return (value.scale() <= Math.abs(4));  // why not 4 instead of Math.abs(4)??
            } catch (Exception e) {
                return false;
            }
        }

        // This method can have side effects
        @Override
        public boolean shouldYieldFocus(JComponent input) {
            String statusOld, status;

            statusOld = statusText;         // remember the original text
            boolean isOK = verify(input);   // call overridden method
            if(isOK)
                status = statusOld;
            else
                status = "Error: The parameter should be a positive number up to 4 decimal places";
            lblStatus.setText(status);
            // return super.shouldYieldFocus(input);
            return isOK;
        }
    }

}

这是测试应用程序的屏幕截图:



可以看出，有两个按钮。其中一个将VerifyInputWhenFocusTarget属性设置为true，另一个将相同的属性设置为false，但是在错误文本字段验证的情况下单击按钮时没有任何区别。可以通过输入负数或带有4个以上十进制数字的数字来引发错误验证。 InputVerifier确实阻止了将焦点转移到其他文本字段，但是并没有阻止激活按钮。由于没有任何意义(至少对我来说不是)，可以在没有先获得焦点的情况下激活按钮，因此不应激活“开始”按钮!当文本字段验证方法verify()返回false时，单击。

编辑:

现在，我更改了代码以适应垃圾桶的建议(使用FocusListener调节Start!按钮的启用状态)，这是工作示例:

package verifiertest;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;
import javax.swing.text.JTextComponent;
import javax.swing.UIManager;
import java.awt.GridLayout;
import java.math.BigDecimal;

import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.SwingConstants;
import javax.swing.JTextField;
import javax.swing.InputVerifier;
import javax.swing.JButton;
import javax.swing.JComponent;

import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.ActionEvent;

public class TestVerifier implements FocusListener {

    private JFrame frmInputverifierTest;
    private JTextField tfFirstNum;
    private JTextField tfSecondNum;
    private JLabel lblStatus;
    private JButton btnStart;
    private String statusText = "Input the numbers and press the \"Start!\" button...";

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    TestVerifier window = new TestVerifier();
                    window.frmInputverifierTest.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public TestVerifier() {
        initialize();
    }

    private void initialize() {
        frmInputverifierTest = new JFrame();
        frmInputverifierTest.setTitle("InputVerifier Test");
        frmInputverifierTest.setBounds(100, 100, 500, 450);
        frmInputverifierTest.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panelContainer = new JPanel();
        panelContainer.setBorder(new EmptyBorder(5, 5, 5, 5));
        frmInputverifierTest.getContentPane().add(panelContainer, BorderLayout.CENTER);
        panelContainer.setLayout(new BorderLayout(0, 0));

        JPanel panelInput = new JPanel();
        panelInput.setBorder(new TitledBorder(null, "Input", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        panelContainer.add(panelInput, BorderLayout.NORTH);
        panelInput.setLayout(new GridLayout(2, 2, 10, 4));

        JLabel lblFirstNum = new JLabel("Number #1:");
        lblFirstNum.setHorizontalAlignment(SwingConstants.TRAILING);
        panelInput.add(lblFirstNum);

        tfFirstNum = new JTextField();
        panelInput.add(tfFirstNum);
        tfFirstNum.setColumns(10);
        // setup the verifier
        MyTxtVerifier txtVerifier = new MyTxtVerifier();
        tfFirstNum.setInputVerifier(txtVerifier);
        // add focus listener
        tfFirstNum.addFocusListener(this);

        JLabel lblSecondNum = new JLabel("Number #2:");
        lblSecondNum.setHorizontalAlignment(SwingConstants.TRAILING);
        panelInput.add(lblSecondNum);

        tfSecondNum = new JTextField();
        panelInput.add(tfSecondNum);
        tfSecondNum.setColumns(10);
        // setup the verifier
        tfSecondNum.setInputVerifier(txtVerifier);
        // add focus listener
        tfSecondNum.addFocusListener(this);

        JPanel panelOutput = new JPanel();
        panelOutput.setBorder(new TitledBorder(UIManager.getBorder("TitledBorder.border"), "Output (not used at the moment)", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        panelContainer.add(panelOutput, BorderLayout.CENTER);

        JPanel panelSouth = new JPanel();
        panelSouth.setBorder(null);
        panelContainer.add(panelSouth, BorderLayout.SOUTH);
        panelSouth.setLayout(new GridLayout(0, 1, 0, 0));

        JPanel panelStatus = new JPanel();
        FlowLayout flowLayout_1 = (FlowLayout) panelStatus.getLayout();
        flowLayout_1.setAlignment(FlowLayout.LEFT);
        panelStatus.setBorder(new TitledBorder(null, "Status", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        panelSouth.add(panelStatus);

        lblStatus = new JLabel(statusText);
        panelStatus.add(lblStatus);

        JPanel panelActions = new JPanel();
        panelActions.setBorder(new TitledBorder(null, "Actions", TitledBorder.LEADING, TitledBorder.TOP, null, null));
        FlowLayout flowLayout = (FlowLayout) panelActions.getLayout();
        flowLayout.setAlignment(FlowLayout.RIGHT);
        panelSouth.add(panelActions);

        JButton btnHelp = new JButton("?");
        btnHelp.setVerifyInputWhenFocusTarget(false);   // <-- NO EFFECT!?
        btnHelp.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frmInputverifierTest, "Help button pressed...", "Help", JOptionPane.PLAIN_MESSAGE);
            }
        });
        panelActions.add(btnHelp);

        btnStart = new JButton("Start!");
        btnStart.setEnabled(false);
        btnStart.setVerifyInputWhenFocusTarget(true);   // <-- NO EFFECT!?
        btnStart.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frmInputverifierTest, "Start button pressed...", "Start", JOptionPane.PLAIN_MESSAGE);
            }
        });
        panelActions.add(btnStart);
        btnHelp.setPreferredSize(btnStart.getPreferredSize());  // make buttons equal in size
    }

    // an inner class so it can access parent fields
    public class MyTxtVerifier extends InputVerifier {
        // This method should have no side effects
        @Override
        public boolean verify(JComponent input) {
            String text = ((JTextField)input).getText();
            // to allow changing focus when nothing is entered
            if(text.isEmpty())
                return true;
            try {
                BigDecimal value = new BigDecimal(text);
                if(value.floatValue() <= 0.0)
                    return false;
                return (value.scale() <= Math.abs(4));  // why not 4 instead of Math.abs(4)??
            } catch (Exception e) {
                return false;
            }
        }

        // This method can have side effects
        @Override
        public boolean shouldYieldFocus(JComponent input) {
            String statusOld, status;

            statusOld = statusText;         // remember the original text
            boolean isOK = verify(input);   // call overridden method
            if(isOK)
                status = statusOld;
            else {
                btnStart.setEnabled(false);
                status = "Error: The parameter should be a positive number up to 4 decimal places";
            }
            lblStatus.setText(status);
            // return super.shouldYieldFocus(input);
            return isOK;
        }
    }

    @Override
    public void focusGained(FocusEvent e) {
        // nothing to do on focus gained
    }

    @Override
    public void focusLost(FocusEvent e) {
        // in case we want to show a message box inside focusLost() - not to be fired twice
        if(e.isTemporary())
            return;
        final JTextComponent c = (JTextComponent)e.getSource();
        // in case there are more text fields but
        // we are validating only some of them
        if(c.equals(tfFirstNum) || c.equals(tfSecondNum)) {
            // are all text fields valid?
            if(c.getInputVerifier().verify(tfFirstNum) && c.getInputVerifier().verify(tfSecondNum) &&
                    !tfFirstNum.getText().isEmpty() && !tfSecondNum.getText().isEmpty())
                btnStart.setEnabled(true);
            else
                btnStart.setEnabled(false);
        }
    }
}

我略微更改了verify()方法的代码，以允许在未输入任何内容的情况下更改焦点(focusLost()方法检查所有文本字段是否都包含某些输入，并且还通过为每个文本字段显式调用verify()来检查输入是否有效)。

当然，该代码需要进行一些细微的调整(制表顺序，更新状态等)，但这超出了本主题的范围。

结论:

尽管VerifyInputWhenFocusTarget属性显然有用(在此示例中，即使在文本字段验证为false的情况下，？按钮也可以获得焦点)，但我仍然认为我的文档在描述所有重要副作用方面不够精确这非常违反直觉，因此除了阅读文档外，还需要进行进一步的测试和研究(也许是分析源代码)。

最佳答案

您对 setVerifyInputWhenFocusTarget() 的调用确实具有效果-确切地确定“确定是否在此组件请求焦点之前调用当前焦点所有者的输入验证程序”的效果。 [强调我的]特别要建立以下状态:

让statusText具有其初始值，或通过输入有效值来恢复初始值。

包含无效值时让tfFirstNum或tfSecondNum成为焦点。

然后观察

点击？保留statusText不变，这意味着未调用焦点组件的输入验证程序，具体说明如下

btnHelp.setVerifyInputWhenFocusTarget(false);

单击“开始”将设置statusText以反映错误，这表示已调用了焦点组件的输入验证程序，具体说明如下

btnStart.setVerifyInputWhenFocusTarget(true);

请注意，单击任一按钮时必须同时满足以上两个条件才能看到效果。

关于java - VerifyInputWhenFocusTarget属性无效，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/38680552/