JavaFX访问控制器给出nullpointerexception
我想要实现的是从主要方法获取控制器实例,所以我可以从另一个类调用控制器的方法并更新fxml。反正这里是我的代码:JavaFX访问控制器给出nullpointerexception
主要类:
public class Main extends Application {
Controller controller;
@Override
public void start(Stage primaryStage) throws Exception{
FXMLLoader fxmlLoader = new FXMLLoader();
Parent root = fxmlLoader.load(getClass().getResource("sample.fxml"));
controller = fxmlLoader.getController();
primaryStage.setTitle("uPick Smart Service");
primaryStage.setScene(new Scene(root, 1600, 600));
primaryStage.show();
ConnectionHandling connectionHandling = new ConnectionHandling();
Thread X = new Thread (connectionHandling);
X.start();
}
public static void main(String args[]){
launch(args);
}
public Controller getController(){
return controller;
}
}
我的控制器类:
public class Controller {
public HBox billbox;
public int childnr;
public void createBill() {
System.out.println("Creating");
TableView<Item> bill = new TableView<>();
DropShadow dropShadow = new DropShadow();
dropShadow.setRadius(5.0);
dropShadow.setOffsetX(3.0);
dropShadow.setOffsetY(3.0);
dropShadow.setColor(Color.color(0.4, 0.5, 0.5));
VBox fullbill = new VBox();
fullbill.setPadding(new Insets(1, 1, 1, 1));
fullbill.getStyleClass().add("fullbill");
TableColumn<Item, String> nameColumn = new TableColumn<>("Emri");
nameColumn.setMinWidth(200);
nameColumn.setCellValueFactory(new PropertyValueFactory<>("name"));
TableColumn<Item, String> quantsColumn = new TableColumn<>("Sasia");
quantsColumn.setMinWidth(50);
quantsColumn.setCellValueFactory(new PropertyValueFactory<>("quants"));
double tablewidth = nameColumn.getWidth() + quantsColumn.getWidth();
Label tablenrlabel = new Label("Table 5");
tablenrlabel.getStyleClass().add("tablenr-label");
tablenrlabel.setMinWidth(tablewidth);
Button closebutton = new Button("Mbyll");
closebutton.setMinWidth(tablewidth);
closebutton.getStyleClass().add("red-tint");
bill.setItems(getItem());
bill.setMinWidth(256);
bill.setColumnResizePolicy(TableView.CONSTRAINED_RESIZE_POLICY);
bill.getColumns().addAll(nameColumn, quantsColumn);
fullbill.setEffect(dropShadow);
fullbill.getChildren().addAll(tablenrlabel, bill, closebutton);
billbox.getChildren().addAll(fullbill);
childnr += 1;
//Loops over every button in every vbox and gives it a seperate listener (the index of the button is hardcoded so it can cause problems if you add more items)
for (int i = 0; i < childnr; i++) {
VBox box = (VBox) billbox.getChildren().get(i);
Button btn = (Button) box.getChildren().get(2); //if sudden issues change this
btn.setId(Integer.valueOf(i).toString());
btn.setOnAction(new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
int index = billbox.getChildren().indexOf(btn.getParent());
billbox.getChildren().remove(index);
childnr -= 1;
System.out.println(btn.getId());
}
});
}
System.out.println("done");
}
}
和阶级试图调用控制器的方法:
public class TakeOrder implements Runnable {
Socket SOCK;
Controller controller;
//OrderIndexes: "Order","Waiter","Payment"
private int NonConnectedDatas = 2;
public TakeOrder(Socket X){
this.SOCK = X;
}
public void CheckConnection() throws IOException{
System.out.println("Checking connection");
if(!SOCK.isConnected()){
System.out.println("Dissconectiong");
for(int i = 0; i < ConnectionHandling.ConnectionArray.size(); i++){
if(ConnectionHandling.ConnectionArray.get(i) == SOCK){
ConnectionHandling.ConnectionArray.remove(i);
}
}
}
}
public void run(){
try{
try{
CheckConnection();
ObjectInputStream ob = new ObjectInputStream(SOCK.getInputStream());
String[] structuredArray = (String[])ob.readObject();
String tablenr = structuredArray[0];
String index = structuredArray[1];
ArrayList<String> names = new ArrayList<>();
ArrayList<String> quants = new ArrayList<>();
int a = 0;
int b = 0;
switch (index) {
case "Order":
for (int i = NonConnectedDatas; i < structuredArray.length; i++) {
if (i % 2 == 0) {
names.add(a, structuredArray[i]);
System.out.println(names.get(a));
a++;
} else {
quants.add(b, structuredArray[i]);
System.out.println(quants.get(b));
b++;
}
}
break;
}
Platform.runLater(new Runnable() {
@Override
public void run() {
}
});
}finally{
SOCK.close();
}
}catch(Exception X){
System.out.print(X);
}
}
}
这是我的错误消息:
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at sample.TakeOrder$1.run(TakeOrder.java:80)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
的ConnectionHandling类:
public class ConnectionHandling implements Runnable{
public static ArrayList<Socket> ConnectionArray = new ArrayList<Socket>();
public void run(){
System.out.println("Starting");
try{
final int PORT = 60123;
ServerSocket SERVER = new ServerSocket(PORT);
System.out.println("Waiting for clients");
while(true){
Socket SOCK = SERVER.accept();
ConnectionArray.add(SOCK);
TakeOrder ORDER = new TakeOrder(SOCK);
Thread X = new Thread(ORDER);
X.setDaemon(true);
X.start();
}
}catch(Exception x){
System.out.print(x);
}
}
首先,您使用的是static
FXMLLoader.load(URL)
方法。因为它是static
,所以您创建的FXMLLoader
实例的控制器属性未通过调用此load
方法进行初始化。所以controller
在Main
将是null
。
相反,设置的位置,并使用实例方法load()
:
@Override
public void start(Stage primaryStage) throws Exception{
FXMLLoader fxmlLoader = new FXMLLoader();
fxmlLoader.setLocation(getClass().getResource("sample.fxml"));
Parent root = fxmlLoader.load();
controller = fxmlLoader.getController();
primaryStage.setTitle("uPick Smart Service");
primaryStage.setScene(new Scene(root, 1600, 600));
primaryStage.show();
}
这并不能完全解决你的问题,但。当您启动应用程序时,JavaFX将在该实例上创建一个Main
的实例并调用start()
。通过以上更改,的controller
字段将被正确初始化。
然而,在TakeOrder.run()
您创建的Main
另一个实例:
Main main = new Main();
该实例的controller
场不会被初始化(即使你做初始化它,它是不一样的情况下,你想)。因此,您确实需要安排TakeOrder
访问在启动方法中创建的控制器实例。
这是最简单的修复程序代码,以使这项工作:
public class ConnectionHandling implements Runnable{
private final Controller controller ;
public ConnectionHandling(Controller controller) {
this.controller = controller ;
}
// ...
public void run(){
// existing code ...
TakeOrder ORDER = new TakeOrder(SOCK, connection);
// ...
}
}
和
public class TakeOrder implements Runnable {
Socket SOCK;
Controller controller;
//OrderIndexes: "Order","Waiter","Payment"
private int NonConnectedDatas = 2;
public TakeOrder(Socket X, Controller controller){
this.SOCK = X;
this.controller = controller ;
}
// ...
public void run() {
// ...
Platform.runLater(controller::createBill);
// ...
}
}
最后
public class Main extends Application {
@Override
public void start(Stage primaryStage) throws Exception{
FXMLLoader fxmlLoader = new FXMLLoader();
Parent root = fxmlLoader.load(getClass().getResource("sample.fxml"));
Controller controller = fxmlLoader.getController();
primaryStage.setTitle("uPick Smart Service");
primaryStage.setScene(new Scene(root, 1600, 600));
primaryStage.show();
ConnectionHandling connectionHandling = new ConnectionHandling(controller);
Thread X = new Thread (connectionHandling);
X.start();
}
public static void main(String args[]){
launch(args);
}
public Controller getController(){
return controller;
}
}
一般的应用,如此,你可能想要考虑使用MVC或MVP方法(即你需要一个模型班级,这将举行服务,如您的ConnectionHandler
)。
您可能也有兴趣在this article集成JavaFX服务。
好的,非常感谢。对我来说,更多的Google搜索似乎是:D – user6535530
@ user6535530如果你在你的问题中解释你创建'TakeOrder'实例的位置,这可能很容易回答。 –
如果您手动实例化Application
(在本例中为Main
类),则不会调用start()
函数。试着用
Application.launch
,而不是
Main main = new Main()
此外,launch
方法启动您的应用程序不返回,直到退出应用程序。因此,您可能需要对您的调用重新排序getController()
还有另一种管理控制器实例的方法,即使用FXMLLoader中的setController(Object controller)
。
文档:
这说明什么回报? 'controller = fxmlLoader.getController();'它是否不将控制器设置为null? – ppeterka
是的,它返回null – user6535530
你在哪里实例化TakeOrder并执行它的run()方法(或将它传递给Thread)? –