java - 使用方法添加 JTextField 时从 JTextField 检索文本

Question

我目前正在学习如何在 Java 中使用 Swing。将 JTextFields、JLabels 或 JButtons 添加到 JPanel 时，我通常用 4 行来完成，如下所示:

gbc.gridx = 0;
gbc.gridy = 0;
JTextField example = new JTextField("", 6);
p.add(example, gbc);

但是我试图通过创建这样的方法来压缩我的代码:

public static void addTextField (JPanel p, GridBagConstraints gbc, String str, int x, int y, int len) {
gbc.gridx = x;
gbc.gridy = y;
JTextField tempTF = new JTextField(str, len);
p.add(tempTF, gbc);
}

并在主方法中调用addTextField()，如下所示:

ClassName.addTextField(p2, gbc, "", 1, 1, 6);

我遇到的问题是如何检索 JTextField 中的文本。比如，

String str = example.getText();

或

String str2 = tempTF.getText();

通常有效，但不再有效。

关于如何解决这个问题有什么想法吗？

这是我在给出任何答案之前正在使用的完整代码:

/**
* This program creates two windows.
* Window #1 displays Hello World
* WIndow #2 prompts users to input information
*/

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class MessingWithSwing extends JFrame{

  //Main Method
  public static void main(String[] args) { 
    //makes the first window
    MessingWithSwing window1 = new MessingWithSwing("Window #1", 300, 300);
    //makes the second window with minimum dimensions
    MessingWithSwing window2 = new MessingWithSwing("Window #2", 450, 300, 300, 300);

    //GridBagConstraints allows the objects in each panel to be positioned in grid cordinates
    GridBagConstraints gbc = new GridBagConstraints();
    //sets the spaces between each grid position
    gbc.insets = new Insets(10, 10, 10, 10);

    //creates a JPanel that uses a grid layout
    JPanel p1 = new JPanel(new GridBagLayout());
    //adds the panel in the center of window1
    window1.add(p1, BorderLayout.CENTER);
    //sets the panel visible so it can correctly display the labels, textfields, and buttons
    p1.setVisible(false);

    //uses the method created below to add JLabels to p1
    MessingWithSwing.addLabel(p1, gbc, "Hello", 0, 0);
    MessingWithSwing.addLabel(p1, gbc, "World", 0, 1);

    p1.setVisible(true);

    //creates a second JPanel that also uses a grid layout
    JPanel p2 = new JPanel(new GridBagLayout());
    //adds the panel at the top of window2
    window2.add(p2, BorderLayout.NORTH);
    //sets the panel visible so it can correctly display the labels, textfields, and buttons
    p2.setVisible(false);

    //uses the method created below to add JLabels to p2
    MessingWithSwing.addLabel(p2, gbc, "Please Enter The Following", 0, 0);
    MessingWithSwing.addLabel(p2, gbc, "Name: ", 0, 1);
    MessingWithSwing.addLabel(p2, gbc, "Age: ", 0, 2);

    //uses the method created below to add JTextFields to p2
    MessingWithSwing.addTextField(p2, gbc, "", 1, 1, 6);
    MessingWithSwing.addTextField(p2, gbc, "<age>", 1, 2, 6);

    //uses the method created below to add a JButton to p2
    MessingWithSwing.addButton(p2, gbc, "Enter", 0, 3);

    p2.setVisible(true);

    /* Issue:
     * The someting like the line below would not work
     * How would you access the text inputted into each JTextField?
     */
//    String str = tempTF.getText();

  } //end of Main Method

  //first constructor makes a window that is completely resizable
  public MessingWithSwing(String title, int sizeX, int sizeY) {
    super(title);
    setSize(sizeX, sizeY);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setVisible(true);
  }

  //second constructor makes a window that is resizable but has minimum dimensions
  public MessingWithSwing(String title, int sizeX, int sizeY, int minSizeX, int minSizeY) { 
    super(title);
    setSize(sizeX, sizeY);
    setMinimumSize(new Dimension(minSizeX, minSizeY));
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setVisible(true);
  }

  //This method adds a JLabel with an indicated text, at an indicated GridBagConstraints location, to an indicated JPanel
  public static void addLabel(JPanel p, GridBagConstraints gbc, String str, int x, int y) {
    gbc.gridx = x;
    gbc.gridy = y;
    JLabel tempLabel = new JLabel(str);
    p.add(tempLabel, gbc);
  }

  //This method adds a JTextField with an indicated length and text, at an indicated GridBagConstraints location, to an indicated JPanel
  public static void addTextField (JPanel p, GridBagConstraints gbc, String str, int x, int y, int len) {
    gbc.gridx = x;
    gbc.gridy = y;
    JTextField tempTF = new JTextField(str, len);
    p.add(tempTF, gbc);
  }

  //This method adds a JButton with an indicated text, at an indicated GridBagConstraints location, to an indicated JPanel
  public static void addButton (JPanel p, GridBagConstraints gbc, String str, int x, int y) {
    gbc.gridx = x;
    gbc.gridy = y;
    JButton tempB = new JButton(str);
    p.add(tempB, gbc);
  }

}

所以，如果我正确理解 Kequiang Li，它看起来会是这样的:

public static JTextField addTextField (JPanel p, GridBagConstraints gbc, String str, int x, int y, int len) {
    gbc.gridx = x;
    gbc.gridy = y;
    JTextField tempTF = new JTextField(str, len);
    p.add(tempTF, gbc);
    return tempTF;
  }

然后:

ArrayList<JTextField> tfList = new ArrayList<JTextField>();
tfList.add(ClassName.addTextField(p1,gbc,text,0,0,8));
String str = tfList.get(0).getText();

Answer 1

如何获取文本字段中的文本完全取决于您想要获取文本的位置和时间。

假设您想随时检索文本，那么您可以使 addTextField 返回它已添加的文本字段。这样，您就可以跟踪列表、数组甚至 map 中的所有文本字段，并且只需对这些文本字段调用 getText 即可。

在另一种情况下，您可能只需要当用户在文本字段中按下回车键时才需要文本，然后您可以将监听器绑定(bind)到文本字段。当事件发生时，您可以访问事件源(即文本字段)，然后检索文本。