java 如何使用 id 在 JavaFx 中获取元素？
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how do I get an element in JavaFx using an id?
提问by Rakim
I am new to FXML and I am trying to create a handler for all of the button clicks using a switch. However, in order to do so, I need to get the elements using and id. I have tried the following but for some reason (maybe because I am doing it in the controller class and not on the main) I get a stack overflow exception.
我是 FXML 的新手，我正在尝试使用switch. 但是，为了做到这一点，我需要使用 id 获取元素。我已经尝试了以下但出于某种原因（可能是因为我在控制器类中而不是在主类中这样做）我得到了一个堆栈溢出异常。
public class ViewController {
public Button exitBtn;
public ViewController() throws IOException {
Parent root = FXMLLoader.load(getClass().getResource("mainWindow.fxml"));
Scene scene = new Scene(root);
exitBtn = (Button) scene.lookup("#exitBtn");
}
}
So how will I get an element (for example a button) using it's id as a reference?
那么我将如何使用它的 id 作为参考来获取一个元素（例如一个按钮）？
The fxml block for the button is:
按钮的 fxml 块是：
<Button fx:id="exitBtn" contentDisplay="CENTER" mnemonicParsing="false"
onAction="#handleButtonClick" text="Exit" HBox.hgrow="NEVER" HBox.margin="$x1"/>
回答by James_D
Use a controller class, so that you don't need to use a lookup. The FXMLLoaderwill inject the fields into the controller for you. The injection is guaranteed to happen before the initialize()method (if you have one) is called
使用控制器类，这样您就不需要使用查找。在FXMLLoader将注入的字段到控制器为您服务。注入保证在initialize()调用方法（如果你有的话）之前发生
public class ViewController {
@FXML
private Button exitBtn ;
@FXML
private Button openBtn ;
public void initialize() {
// initialization here, if needed...
}
@FXML
private void handleButtonClick(ActionEvent event) {
// I really don't recommend using a single handler like this,
// but it will work
if (event.getSource() == exitBtn) {
exitBtn.getScene().getWindow().hide();
} else if (event.getSource() == openBtn) {
// do open action...
}
// etc...
}
}
Specify the controller class in the root element of your FXML:
在 FXML 的根元素中指定控制器类：
<!-- imports etc... -->
<SomePane xmlns="..." fx:controller="my.package.ViewController">
<!-- ... -->
<Button fx:id="exitBtn" contentDisplay="CENTER" mnemonicParsing="false" onAction="#handleButtonClick" text="Exit" HBox.hgrow="NEVER" HBox.margin="$x1" />
<Button fx:id="openBtn" contentDisplay="CENTER" mnemonicParsing="false" onAction="#handleButtonClick" text="Open" HBox.hgrow="NEVER" HBox.margin="$x1" />
</SomePane>
Finally, load the FXML from a class other than your controller class (maybe, but not necessarily, your Applicationclass) with
最后，从控制器类以外的类（可能但不一定是您的Application类）加载 FXML
Parent root = FXMLLoader.load(getClass().getResource("path/to/fxml"));
Scene scene = new Scene(root);
// etc...
