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我是JavaFX的新手，請原諒Noobishness。JavaFX：將從根視圖觸發的FileChooser中提取的圖像傳遞到嵌套視圖中的ImageView對象
所以我正在製作圖片瀏覽器。這是我第一次用MVC模式設計GUI，所以我不太確定自己在做什麼。
我正在試圖完成：
這只是一個正常的圖片瀏覽器。就像您想要查看圖片時打開的標準Windows程序一樣。
我所做的：
所以我現在有2次：
的Root.fxml觀點，這是隻是一個BorderPane一個菜單欄頂部 與菜單項「打開」這觸發FileChooser並將MainApp.java currentImage變量設置爲用戶選擇的任何值。
嵌套在（root.setCenter）裏面，我有ImageViewer.fxml視圖， 這是一個AnchorPane，它只包含一個ImageView。
我100％肯定我的FXML沒有問題，並且所有控制器和變量都被正確綁定。這在MainApp或控制器中必定是個問題。
我不知道如何將圖像從RootViewController傳遞到ImageViewerController。當我嘗試在ImageViewerController初始化程序中初始化mainApp.currentImage的偵聽器時，我得到一個NullPointerException。如果我把它放在setMainApp方法中，它什麼也不做。這裏是我的代碼：
驗證碼：
MainApp.java
import sample.model.MyImage;
import samlple.view.ImageViewerController;
import sample.view.RootController;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.FileChooser;
import javafx.stage.Stage;
import java.io.File;
import java.io.IOException;
public class MainApp extends Application {
final static File img = new File("C:\\test\\1.png"); // test initial image loading
private Stage primaryStage;
private BorderPane rootLayout;
private MyImage currentImage = new MyImage(img);
public MainApp() {
}
public MyImage getCurrentImage(){
return this.currentImage;
}
public void setCurrentImage(MyImage myImage){
currentImage = myImage;
}
public void start(Stage primaryStage) throws Exception{
this.primaryStage = primaryStage;
this.primaryStage.setTitle("Hi");
initRootLayout();
showImageViewer();
}
/**
* Initializes the root layout.
*/
public void initRootLayout() {
try {
// Load root layout from fxml file.
FXMLLoader loader = new FXMLLoader();
loader.setLocation(MainApp.class.getResource("view/Root.fxml"));
rootLayout = loader.load();
// Show the scene containing the root layout.
Scene scene = new Scene(rootLayout);
primaryStage.setScene(scene);
// Giving the controller access to the main app.
RootController controller = loader.getController();
controller.setMainApp(this);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
System.err.println("Root layout loading error.");
}
}
/**
* Shows the ImageViewer inside the root layout.
*/
public void showImageViewer() {
try {
// Load ImageViewer.
FXMLLoader loader = new FXMLLoader();
loader.setLocation(MainApp.class.getResource("view/ImageViewer.fxml"));
AnchorPane imageViewer = loader.load();
// Set the ImageViewer into the center of root layout.
rootLayout.setCenter(imageViewer);
// Giving the controller access to the main app.
ImageViewerController controller = loader.getController();
controller.setMainApp(this);
} catch (IOException e) {
e.printStackTrace();
System.err.println("ImageViewer layout loading error.");
}
}
/**
* Called when user clicks the "Open" menu item
*/
public void menuOpenImageFile() {
FileChooser fileChooser = new FileChooser();
//Set extension filter
FileChooser.ExtensionFilter extFilter = new FileChooser.ExtensionFilter("Image types (*.jpg; *.gif; *.bmp; *.png)", "*.jpg", "*.png", "*.bmp", "*.gif");
fileChooser.getExtensionFilters().add(extFilter);
//Show save file dialog
File imageFile = fileChooser.showOpenDialog(primaryStage);
MyImage myImageToSetAsCurrent = new MyImage(imageFile);
setCurrentImage(myImageToSetAsCurrent);
}
/**
* Returns the main stage.
* @return
*/
public Stage getPrimaryStage() {
return primaryStage;
}
public static void main(String[] args) { launch(args); }
}
MyImage.java（模型圖像類來保存屬性）：
package sample.model;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.scene.image.Image;
import java.io.File;
public class MyImage {
private final ObjectProperty<File> imageFile;
private final ObjectProperty<Image> image;
public MyImage(){
this(null);
}
public MyImage(File imageFile) {
this.imageFile = new SimpleObjectProperty<>(imageFile);
this.image = new SimpleObjectProperty<>(new Image("file:" + imageFile.toString()));
}
public File getImageFile() {
return imageFile.get();
}
public ObjectProperty<File> imageFileProperty() {
return imageFile;
}
public void setImageFile(File myImageFile) {
this.imageFile.set(myImageFile);
}
public Image getImage() {
return image.get();
}
public ObjectProperty<Image> imageProperty() {
return image;
}
public void setImage(Image myImage) {
this.image.set(myImage);
}
}
RootController.java
import samlple.MainApp;
import javafx.fxml.FXML;
import javafx.scene.control.MenuItem;
public class RootController {
@FXML
private MenuItem open;
// Reference to the main application.
private MainApp mainApp;
/**
* The constructor.
* The constructor is called before the initialize() method.
*/
public RootController() {
}
/**
* Initializes the controller class. This method is automatically called
* after the fxml file has been loaded.
*/
@FXML
private void initialize() {
}
@FXML
private void openImageFile() {
mainApp.menuOpenImageFile();
}
/**
* Is called by the main application to give a reference back to itself.
*
*/
public void setMainApp(MainApp mainApp) {
this.mainApp = mainApp;
}
}
ImageViewerController.java
import sample.MainApp;
import javafx.fxml.FXML;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
public class ImageViewerController {
@FXML
private ImageView imageView;
// Reference to the main application.
private MainApp mainApp;
/**
* The constructor.
* The constructor is called before the initialize() method.
*/
public ImageViewerController() {
}
/**
* Initializes the controller class. This method is automatically called
* after the fxml file has been loaded.
*/
@FXML
private void initialize() {
mainApp.getCurrentImage().imageProperty().addListener(((observable, oldValue, newValue) -> imageView.setImage(newValue))); //This keeps throwing NullPointerException!
}
/**
* Is called by the main application to give a reference back to itself.
*
*/
public void setMainApp(MainApp mainApp) {
this.mainApp = mainApp;
imageView.setImage(mainApp.getCurrentImage().imageProperty().get());
}
}