将文件路径拖放到 Java Swing JTextField
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Drag and Drop file path to Java Swing JTextField
提问by ewok
Using this question, I created the class below, which handles drag and drop of files to a JTextField. The point of the application is to be able to drag a file into the text field, and have the text field's text set to the file's path (you can see the goal in the code pretty clearly).
使用这个问题，我创建了下面的类，它处理文件到 JTextField 的拖放。应用程序的重点是能够将文件拖入文本字段，并将文本字段的文本设置为文件的路径（您可以很清楚地看到代码中的目标）。
My problem is the below code does not compile. The compilation error states Cannot refer to non-final variable myPanel inside an inner class defined in a different method. I haven't worked much with inner classes, so can seomeone show me how to resolve the error and get the code to behave as designed?
我的问题是以下代码无法编译。编译错误状态Cannot refer to non-final variable myPanel inside an inner class defined in a different method。我对内部类的工作不多，所以有人可以告诉我如何解决错误并使代码按设计运行吗？
Code:
代码：
import java.awt.datatransfer.DataFlavor;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDropEvent;
import java.io.File;
import java.util.List;
import javax.swing.*;
public class Test {
public static void main(String[] args) {
JTextArea myPanel = new JTextArea();
myPanel.setDropTarget(new DropTarget() {
public synchronized void drop(DropTargetDropEvent evt) {
try {
evt.acceptDrop(DnDConstants.ACTION_COPY);
List<File> droppedFiles = (List<File>) evt
.getTransferable().getTransferData(
DataFlavor.javaFileListFlavor);
for (File file : droppedFiles) {
/*
* NOTE:
* When I change this to a println,
* it prints the correct path
*/
myPanel.setText(file.getAbsolutePath());
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
});
JFrame frame = new JFrame();
frame.add(myPanel);
frame.setVisible(true);
}
}
采纳答案by unholysampler
As the error message says, myPanelneeds to be defined as final.
正如错误消息所说，myPanel需要定义为final。
final JTextArea myPanel = new JTextArea();
This way the inner class can be given one reference pointer to the variable instance without concern that the variable might be changed to point to something else later during execution.
通过这种方式，可以为内部类提供一个指向变量实例的引用指针，而不必担心在执行期间变量可能会更改为指向其他内容。
回答by no one
Another option is to declare the variable static.
另一种选择是将变量声明为静态。
static JTextArea myPanel = new JTextArea();
