java 启动时 JTextField 未显示在 JPanel 中
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JTextField not showing up in JPanel on launch
提问by tazboy
The JTextFieldis there because when I move the mouse over where it's supposed to be the mouse icon changes to a cursor, then when I click it shows up. But it's invisible at launch. What am I missing?
这JTextField是因为当我将鼠标移到它应该是鼠标图标的位置时，它会变成一个光标，然后当我点击它时就会显示出来。但它在启动时是不可见的。我错过了什么？
public class JavaSwingTextfield extends JFrame {
private static final long serialVersionUID = 1L;
JTextField myTextField;
public JavaSwingTextfield(){
/***** JFrame setup *****/
// Set the size of the window
setSize(600,600);
// Make the application close when the X is clicked on the window
setDefaultCloseOperation(EXIT_ON_CLOSE);
// Makes the JFrame visible to the user
setVisible(true);
/***** JFrame setup END *****/
/***** JButton setup *****/
// Create a JLabel and set its label to "Start"
myTextField = new JTextField("Start");
// Set the label's size
myTextField.setSize(100, 50);
// Put the label in a certain spot
myTextField.setLocation(200, 50);
// Set a font type for the label
//Font myFont = new Font("Serif", Font.BOLD, 24);
//myTextField.setFont(myFont);
// Add the label to the JFrame
add(myTextField);
/***** JButton setup END *****/
}
/***** The main method *****/
public static void main(String[] args){
new JavaSwingTextfield();
}
}
回答by David Kroukamp
- Use
Event Dispatch Threadfor creating GUI components - Do not call
setVisible(..)before all components have been added to theJFrame( this is the above code snippets actual error +1 to @Clark) - Do not unnecessarily extend
JFrameclass - Do not call
setSize(..), rather simply callJFrame#pack()before setting theJFramevisible - Do not call
setSize()onJTextFieldrather look at its constructor:JTextField(String text,int columns) - Use appropriate
LayoutManagers, see here for some examples: A Visual Guide to Layout Managers
- 使用
Event Dispatch Thread用于创建GUI组件 setVisible(..)在将所有组件添加到JFrame（这是上面的代码片段实际错误 +1 到 @Clark）之前不要调用- 不要不必要地扩展
JFrame类 - 不要调用
setSize(..)，而只是JFrame#pack()在设置JFrame可见之前调用 - 不要叫
setSize()上JTextField，而看它的构造函数：JTextField(String text,int columns) - 使用适当的
LayoutManagers，请参见此处的一些示例：布局管理器的可视化指南
Here is an example I made (basically your code with fixes):
这是我制作的示例（基本上是您的修复代码）：
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class JavaSwingTextfield {
private JTextField myTextField;
? ? public JavaSwingTextfield() {
? ? ? ? JFrame frame = new JFrame();
? ? ? ? frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
? ? ? ??
? ? ? ? myTextField = new JTextField("Start");
? ? ? ??
? ? ? ? // Add the label to the JFrame
? ? ? ? frame.add(myTextField);
? ? ? ??
? ? ? ? //pack frame to component preferred sizes
? ? ? ? frame.pack();
? ? ? ? frame.setVisible(true);
? ? }
? ? public static void main(String[] args) {
? ? ? ? //Create UI on EDT
? ? ? ? SwingUtilities.invokeLater(new Runnable() {
? ? ? ? ? ? @Override
? ? ? ? ? ? public void run() {
? ? ? ? ? ? ? ? new JavaSwingTextfield();
? ? ? ? ? ? }
? ? ? ? });
? ? }
}
回答by Clark
You're adding the JTextfieldto the JFrameAFTERyou've made the JFramevisible. Just add the JTextFieldbefore hand.
您正在将 加入JTextfield到使可见的JFrameAFTER 中。只需添加前手。JFrameJTextField
