java - 按 JButton 时将光标转移到 JTextField

Question

当我单击“预览页面”按钮时，光标应移动到开始位置 (txtStartPosition)。下面是我编写的代码，但不知何故它不起作用。

    btnPreviewPage = new JButton("Preview Single");
    btnPreviewPage.setFocusable(false);
    btnPreviewPage.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            txtStartPosition.setCaretPosition(txtStartPosition.getCaretPosition() - 1);
            new UIPreviewPage().execute();
        }
    });
    panel.add(btnPreviewPage, "cell 1 18,alignx right");

Answer 1

您需要执行JTextField.requestFocus();或者，更首选的JTextField.requestFocusInWindow();

https://docs.oracle.com/javase/7/docs/api/javax/swing/JComponent.html#requestFocus()

public void requestFocus() Requests that this Component gets the input focus. Refer to Component.requestFocus() for a complete description of this method. Note that the use of this method is discouraged because its behavior is platform dependent. Instead we recommend the use of requestFocusInWindow(). If you would like more information on focus, see How to Use the Focus Subsystem, a section in The Java Tutorial.

Overrides:
    requestFocus in class Component
    Since:
    1.4
    See Also:

    Component.requestFocusInWindow(), Component.requestFocusInWindow(boolean)

<小时/>

使用你的代码应该是

    tnPreviewPage = new JButton("Preview Single");
    btnPreviewPage.setFocusable(false);
    btnPreviewPage.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {

//Add YourJTextField.requestFocusInWindow() here, but not sure if the other information is needed
txtStartPosition.setCaretPosition(txtStartPosition.getCaretPosition() - 1);
            new UIPreviewPage().execute();
        }
    });
    panel.add(btnPreviewPage, "cell 1 18,alignx right");