Java 如何解除JTextField的焦点
当我的应用程序加载(使用netbeans创建)时,第一个JTextField会自动聚焦,在这个JTextField中,我写了“输入你的用户名”,当用户点击这个字段时,它会消失,但当应用程序加载时,这个字段聚焦,意味着我看不到“输入你的用户名”,如何在启动时解除焦点?用于将焦点设置在其他组件上,而不是首先设置您的Java 如何解除JTextField的焦点,java,swing,netbeans,focus,jtextfield,Java,Swing,Netbeans,Focus,Jtextfield,当我的应用程序加载(使用netbeans创建)时,第一个JTextField会自动聚焦,在这个JTextField中,我写了“输入你的用户名”,当用户点击这个字段时,它会消失,但当应用程序加载时,这个字段聚焦,意味着我看不到“输入你的用户名”,如何在启动时解除焦点?用于将焦点设置在其他组件上,而不是首先设置您的JTextfield 但是我建议不要改变本机焦点系统,而是在initComponents()调用constructor(假定在netbeans中)之后在JTextField上更改setTe
JTextfield
但是我建议不要改变本机焦点系统,而是在initComponents()
调用constructor
(假定在netbeans中)之后在JTextField
上更改setText(String s)
进一步的可选阅读:登录最好在模式对话框中完成,但这会带来问题,因为在组件可见后必须调用方法
requestFocusInWindow()
,但由于对话框是模式对话框,这会被阻止
此示例使用Rob Camick的RequestFocusListener
(如中所示)在对话框可见后管理焦点
注意:这就是它在用户执行任何操作之前的显示方式。默认情况下,密码字段是聚焦的
import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
public class LoginRequired {
LoginRequired() {
JFrame f = new JFrame("Login Required");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setResizable(false);
f.setSize(400, 300); // not recommended, but used here for convenience
f.setLocationByPlatform(true);
f.setVisible(true);
showLogin(f);
}
private void showLogin(JFrame frame) {
JPanel p = new JPanel(new BorderLayout(5,5));
JPanel labels = new JPanel(new GridLayout(0,1,2,2));
labels.add(new JLabel("User Name", SwingConstants.TRAILING));
labels.add(new JLabel("Password", SwingConstants.TRAILING));
p.add(labels, BorderLayout.LINE_START);
JPanel controls = new JPanel(new GridLayout(0,1,2,2));
JTextField username = new JTextField("Joe Blogs");
controls.add(username);
JPasswordField password = new JPasswordField();
password.addAncestorListener(new RequestFocusListener(false));
controls.add(password);
p.add(controls, BorderLayout.CENTER);
JOptionPane.showMessageDialog(
frame, p, "Log In", JOptionPane.QUESTION_MESSAGE);
System.out.println("User Name: " + username.getText());
System.out.println("Password: " + new String(password.getPassword()));
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
new LoginRequired();
});
}
}
/**
* Convenience class to request focus on a component.
*
* When the component is added to a realized Window then component will
* request focus immediately, since the ancestorAdded event is fired
* immediately.
*
* When the component is added to a non realized Window, then the focus
* request will be made once the window is realized, since the
* ancestorAdded event will not be fired until then.
*
* Using the default constructor will cause the listener to be removed
* from the component once the AncestorEvent is generated. A second constructor
* allows you to specify a boolean value of false to prevent the
* AncestorListener from being removed when the event is generated. This will
* allow you to reuse the listener each time the event is generated.
*/
class RequestFocusListener implements AncestorListener
{
private boolean removeListener;
/*
* Convenience constructor. The listener is only used once and then it is
* removed from the component.
*/
public RequestFocusListener()
{
this(true);
}
/*
* Constructor that controls whether this listen can be used once or
* multiple times.
*
* @param removeListener when true this listener is only invoked once
* otherwise it can be invoked multiple times.
*/
public RequestFocusListener(boolean removeListener)
{
this.removeListener = removeListener;
}
@Override
public void ancestorAdded(AncestorEvent e)
{
JComponent component = e.getComponent();
component.requestFocusInWindow();
if (removeListener)
component.removeAncestorListener( this );
}
@Override
public void ancestorMoved(AncestorEvent e) {}
@Override
public void ancestorRemoved(AncestorEvent e) {}
}
我认为将键盘焦点放在用户名字段是正确的行为,假设这是用户首先需要做的。与其在焦点上清除,为什么不在用户键入内容后才清除
import java.awt.*;
import javax.swing.*;
import javax.swing.text.Document;
public class PlaceholderTextField extends JTextField {
public static void main(final String[] args) {
final PlaceholderTextField tf = new PlaceholderTextField("");
tf.setColumns(20);
tf.setPlaceholder("All your base are belong to us!");
final Font f = tf.getFont();
tf.setFont(new Font(f.getName(), f.getStyle(), 30));
JOptionPane.showMessageDialog(null, tf);
}
private String placeholder;
public PlaceholderTextField() {
}
public PlaceholderTextField(
final Document pDoc,
final String pText,
final int pColumns)
{
super(pDoc, pText, pColumns);
}
public PlaceholderTextField(final int pColumns) {
super(pColumns);
}
public PlaceholderTextField(final String pText) {
super(pText);
}
public PlaceholderTextField(final String pText, final int pColumns) {
super(pText, pColumns);
}
public String getPlaceholder() {
return placeholder;
}
@Override
protected void paintComponent(final Graphics pG) {
super.paintComponent(pG);
if (placeholder.length() == 0 || getText().length() > 0) {
return;
}
final Graphics2D g = (Graphics2D) pG;
g.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g.setColor(getDisabledTextColor());
g.drawString(placeholder, getInsets().left, pG.getFontMetrics()
.getMaxAscent() + getInsets().top);
}
public void setPlaceholder(final String s) {
placeholder = s;
}
}
如果您真的只想移除焦点,请选择以下选项:
component.setFocusable(false)代码>
KeyboardFocusManager.getCurrentKeyboardFocusManager().FocusNext组件()代码>
KeyboardFocusManager.getCurrentKeyboardFocusManager().clearGlobalFocusOwner()代码>
(没有在只有一个可聚焦组件的GUI中测试:)如果我必须单击一个JMenuItem才能登录怎么办?我在另一个元素上使用了requestFocusInWindow(),但当我单击该JMenuItem时,JTextField被聚焦,当我第二次单击该JMenuItem时,JTextField没有聚焦,它会稍后工作,但是第一次尝试在NetBeans属性编辑器中为您的
JMenuItem
创建nextFocusableComponent
属性时,我修复了它,在启动时,我使用了两次您的代码,当我点击JMenuItem时,感谢它们的两个JTextFields,第一个是用户名,第二个是密码,还有一个叫登录的JMenuItem,在我运行应用程序的那一刻,第一个JTextField是焦点,我不希望看到,顺便说一句,如果每个应用程序的用户名。安装应该是固定的,只需使用默认值填充用户名字段&如果正确,让用户选项卡转到下一个字段。如果保证为常量,则填充该字段并禁用它。它将不可聚焦,默认情况下焦点将转到第二个字段。@AloneInTheDark这是一个单独的问题,应该在单独的问题上提问。
textField.setFocusable(false);
textField.setFocusable(true);