Java FXML setText空指针异常
我对编程相当陌生,经常遇到空指针异常,需要帮助。我试图从另一个类发送一个变量来设置标签的文本。当用户通过DB.DBcomm(条形码)单击Enter键时,会启动另一个类,如下所示:Java FXML setText空指针异常,java,netbeans,nullpointerexception,controller,fxml,Java,Netbeans,Nullpointerexception,Controller,Fxml,我对编程相当陌生,经常遇到空指针异常,需要帮助。我试图从另一个类发送一个变量来设置标签的文本。当用户通过DB.DBcomm(条形码)单击Enter键时,会启动另一个类,如下所示: public void keyEnter(javafx.scene.input.KeyEvent event) { if (event.getCode() == KeyCode.ENTER) { Barcode = textField.getText(); textField.s
public void keyEnter(javafx.scene.input.KeyEvent event) {
if (event.getCode() == KeyCode.ENTER) {
Barcode = textField.getText();
textField.setText("");
System.out.println("Enter Key Was Pressed");
CommController DB = new CommController();
DB.DBcomm(Barcode);
}
}
keyListen call = new keyListen();
call.setlabelText(labeltext);
@FXML
public void setlabelText(String text) {
// set text from another class
System.out.println("text received: " + text);
label.setText(text);
}
在另一个类的代码末尾,还有另一个调用方法,如下所示:
public void keyEnter(javafx.scene.input.KeyEvent event) {
if (event.getCode() == KeyCode.ENTER) {
Barcode = textField.getText();
textField.setText("");
System.out.println("Enter Key Was Pressed");
CommController DB = new CommController();
DB.DBcomm(Barcode);
}
}
keyListen call = new keyListen();
call.setlabelText(labeltext);
@FXML
public void setlabelText(String text) {
// set text from another class
System.out.println("text received: " + text);
label.setText(text);
}
然后在第一个类中启动一个方法,如下所示:
public void keyEnter(javafx.scene.input.KeyEvent event) {
if (event.getCode() == KeyCode.ENTER) {
Barcode = textField.getText();
textField.setText("");
System.out.println("Enter Key Was Pressed");
CommController DB = new CommController();
DB.DBcomm(Barcode);
}
}
keyListen call = new keyListen();
call.setlabelText(labeltext);
@FXML
public void setlabelText(String text) {
// set text from another class
System.out.println("text received: " + text);
label.setText(text);
}
控制台成功地打印了该行
"text received: " + text
然而,当它到达
label.setText(text);
我收到空指针异常。您似乎从未创建标签对象。尝试更新不存在的对象的属性将抛出NPE。您创建过标签对象吗?谢谢!这删除了空指针异常;但是,现在我的标签文本在FXML文档上没有更改。它与初始化时的方式相同。