Question

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，但我遇到有关VerifyInputWhenFocusTarget属性的问题。

我已制作了一个标签，以显示verify()子类的状态和覆盖的shouldYieldFocus()和InputVerifier方法，并且工作正常。

我想要做的下一步是设置按钮的VerifyInputWhenFocusTarget，以便在当前焦点所有者的验证为假的情况下不会获得焦点，但我没有注意到将VerifyInputWhenFocusTarget属性设置为true的效果，即使当前焦点所有者的验证为假，也可以按下该按钮。

也许我不理解文档 - 我认为将按钮的VerifyInputWhenFocusTarget属性设置为true会阻止按钮在文本的错误验证情况下单击时获得焦点领域。此外，我（误）了解按钮是否无法获得焦点，然后不会调用actionPerformed()方法。

然而，可以点击该按钮，然后执行其actionPerformed()方法，对文本字段进行错误验证，并保护＆＃39; javax.swing.InputVerifier。

以下是剥离的代码：

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;
        }
    }

}

以下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，另一个属性设置为false，但在此情况下单击按钮时没有任何区别假文本字段验证。可以通过输入负数或超过4位十进制数的某个数字来激发错误验证。 InputVerifier确实阻止将焦点转移到其他文本字段，但它不会阻止激活按钮。由于它没有意义（至少对我而言）按钮可以在没有首先获得焦点的情况下被激活，因此在文本字段时不应该激活 Start！按钮。验证方法verify()已返回false。

修改

我现在已更改代码以适应trashgod的建议（使用FocusListener调节 Start！按钮的启用状态），这是工作示例：< / p>

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);
        }
    }
}

我稍微改变了verify()方法的代码，以便在没有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包含某些输入，并且还检查输入是否有效明确地为每个文本字段调用verify()。

当然，代码需要一些小的调整（Tab键顺序，更新状态，......），但这超出了本主题的范围。

结论：

虽然VerifyInputWhenFocusTarget属性显然很有用（在这个例子中，？按钮可以获得焦点，即使文本字段的验证是false），我我仍然认为文档在描述所有重要的副作用时并不十分精确，这些副作用相当违反直觉，因此除了阅读文档之外，还需要进行进一步的测试和调查（可能是分析源代码）。

Answer 1

您对setVerifyInputWhenFocusTarget() 的电话会产生影响 - 确切地说是确定＆＃34; 当前焦点所有者的输入验证者的效果将在此组件请求焦点之前调用。＆＃34; [强调我的]特别是，建立以下状态：

让statusText具有初始值，或通过输入有效值来恢复初始值。
让tfFirstNum或tfSecondNum在包含无效值时具有焦点。

然后观察

点击？使statusText保持不变，这意味着焦点组件的输入验证程序不被调用，如< / p>
```
btnHelp.setVerifyInputWhenFocusTarget(false);
```
点击开始设置statusText以反映错误，这意味着已按照规定调用了焦点组件的输入验证程序由
```
btnStart.setVerifyInputWhenFocusTarget(true);
```

请注意，必须满足上述两个条件，才能在点击任一按钮时看到效果。

VerifyInputWhenFocusTarget属性无效

1 个答案: