Question

当我尝试在初始化时将我的阶段设置为变量时，我不断收到null引用异常。

我的代码。

public class ListController implements Initializable {
        private Stage thisStage;

        @Override
        public void initialize(URL location, ResourceBundle resources) {
            lblCount.setText("Hey"); //This works

            thisStage = (Stage) lblCount.getScene().getWindow(); //this doesn't
        }

        public ListController()
        {
            thisStage = (Stage) lblCount.getScene().getWindow(); //this doesn't
        }
}

我尝试使用构造函数，但两者都不起作用。

Answer 1

获取舞台引用的一种方法是在控制器上创建一个方法并进行设置：

        FXMLLoader loader = new FXMLLoader();
        Parent node = loader.load(getClass().getResource("view.fxml").openStream());
        Scene scene = new Scene(node);

        Stage stage = new Stage();
        Controller controller = (Controller)loader.getController();

        controller.setPrimaryStage(stage);

        stage.show();

然后在你的方法中你有一个有效的参考。

Answer 2

当您调用舞台时，您可以通过类似

的方法传递舞台参考

  Stage primaryStage = new Stage(); 
  FXMLLoader loader = new FXMLLoader();
  loader.setLocation(YourClass.class.getResource("yourpaht.fxml"));
  //here you change AnchorPane for your root Node
  rootLayout = (AnchorPane) loader.load();
  // Show scene.
  Scene scene = new Scene(rootLayout);
  primaryStage.setScene(scene);
  // Da acceso al programa principal.
  ListController controller = loader.getController();
  //method for passing the stage to the controller 
  controller.controlerPassing(this, primaryStage);
  // Show stage,
  primaryStage.show();

现在控制器类看起来像这样

public class ListController implements Initializable {
      private Stage stage;
      pivate YourClass classs;

      public controlerPassing(YourClass classs, Stage stage){
        this.stage = stage;
        this.classs = classs;
      }

     @Override
     public void initialize(URL location, ResourceBundle resources) {
          lblCount.setText("Hey"); //This works
          //now you can do whatever you want whit the stage
          stage. do stuff........
     }
}

Answer 3

如果我们在Stage类中找到数据类型并相应地使用这样的初始化，就可以解决这个空引用。

例如，

Stage myStage = null ; // this will raise a null pointer reference exception the possible solution can be to say:

Stage myStage = {" ", 0, ' ', etc } ; // as long as the class Stage has data members like String, int, char, etc

JavaFX - 在初始化时需要帮助设置Stage

3 个答案: