Java uses the clipboard to implement data exchange between programs

The example of this article describes the implementation method of Java using the clipboard to exchange data between programs. In graphical systems, the system clipboard is very important. It is difficult to imagine how a graphical operating system without a clipboard function would be used. This example realizes the data exchange between the Java program and the clipboard of the system. When the "Paste" button is clicked, the Java program obtains the data from the system clipboard and displays it in a JTextArea component; when the "Copy" button is clicked After that, the selected text in the text area will be transferred to the system clipboard.

First you must get an instance reference to the system clipboard. The java.awt.Toolkit class provides the getSystemClipboard() method to return a Clipboard instance; and the Toolkit class provides the static method getDefaultToolkit() to return a Toolkit instance. , so there is no need to create a new Toolkit object. The specific implementation code is as follows:

Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();

Here the Clipboard class provides getContents() and setContents() methods to implement data exchange.

Transferable getContents(Object requester);
Void setContents(Transferable contents, ClipboardOwner owner);

The getContents() method here obtains a Transferable object from the system clipboard. The parameter requester represents the data applicant. Generally, this is enough. It is the instance object of this class that requires data. If the required data is text, you can call getTransferData(DataFlavor.stringFlavor) of the Transferable object to obtain it. The implementation code is as follows:

Transferable tr = cb.getContents(this);
String s = (String) tr.getTransferData(DataFlavor.stringFlavor);

setContents() method from the program Pass data to the system clipboard, the parameter contents represents the data, and the parameter owner represents the owner of the clipboard.

StringSelection ss = new StringSelection(this.jTextArea1.getText());
cb.setContents(ss,ss);

The StringSelection class in the above statement represents the selected text.
From the above analysis, in fact, the system clipboard stores a collection of Transferable objects, and the data exchange between the program and the system clipboard is the transfer of Transferable objects. Program code:

1. Create a new Project and name it JClipDemo.
2. Create a new Application and name it JClipDemo; name the main window MainFrame and title it JClipDemo.
3. Add a JTextArea component, two JButtons, and a JPanel component to the design window of the MainFrame class, and place the two JButton components on the JPanel component. Add new property Clipboard cb. The specific code is as follows:

public class MainFrame extends JFrame {
private JPanel contentPane;
private BorderLayout borderLayout1 = new BorderLayout();
//创建新的组件
private JTextArea jTextArea1 = new JTextArea();
private JPanel jPanel1 = new JPanel();
private JButton jButton1 = new JButton();
private JButton jButton2 = new JButton();
//剪贴板实例
Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
……
}

4. Write the initialization method jbInit() of the MainFrame class, complete the initial property settings of each component, and add event listeners for the button components. The specific code is as follows:

private void jbInit() throws Exception {
//setIconImage(Toolkit.getDefaultToolkit().createImage(MainFrame.class.getResource("[Your Icon]")));
contentPane = (JPanel) this.getContentPane();
contentPane.setLayout(borderLayout1);
this.setSize(new Dimension(396, 203));
this.setTitle("JClipboardDemo");
jButton1.setFont(new java.awt.Font("Dialog", 0, 14));
jButton1.setText("Copy");
jButton1.addActionListener(new java.awt.event.ActionListener() { //添加事件监听器
public void actionPerformed(ActionEvent e) {
jButton1_actionPerformed(e);
}
});
jButton2.setFont(new java.awt.Font("Dialog", 0, 14));
jButton2.setText("Paste");
jButton2.addActionListener(new java.awt.event.ActionListener() {//添加事件监听器
public void actionPerformed(ActionEvent e) {
jButton2_actionPerformed(e);
}
});
contentPane.add(jTextArea1, BorderLayout.CENTER);
contentPane.add(jPanel1, BorderLayout.SOUTH);
jPanel1.add(jButton1, null);
jPanel1.add(jButton2, null);
}

5. Write the event handling method of the "Copy" button to send data to the system clipboard.

void jButton1_actionPerformed(ActionEvent e) {
StringSelection ss = new StringSelection(this.jTextArea1.getText()); //发送选中文本到系统剪贴板
cb.setContents(ss,ss);
}

6． Write the event handling method of the "Paste" button to obtain data from the system clipboard.

void jButton2_actionPerformed(ActionEvent e) {
try{
Transferable tr = cb.getContents(this); //从系统剪贴板得到一个Transferable 对象
if (tr != null){
String s = (String) tr.getTransferData(DataFlavor.stringFlavor); //从Transferable 对象中得到文本数据
if (s!=null)
this.jTextArea1.insert(s,this.jTextArea1.getCaretPosition()); //在JTextArea 组件中的光标所在处插入文本
}
}catch(Exception err){
err.printStackTrace();
}
}

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