如何使用 JavaFX 从另一个类调用方法 [重复]

Question

我们有两个窗口：

第一个代表一个包含一些数据库数据的 tableview 和 3 个按钮（添加、删除、刷新）

第二个窗口在点击添加按钮时被调用：这里我们有一些文本字段来将数据保存到数据库中。

现在的问题是，我想在第二个窗口中单击提交按钮后刷新表格视图（在第一个窗口中），以便我可以在表格中看到这些更改，我试图从第一堂课，然后调用刷新方法，但它给了我 java.lang.NullPointerException。

这是第一个包含 tableview 的控制器

public class DeptControl implements Initializable {

 @Override
public void initialize(URL url, ResourceBundle rb) {
    deptid.setCellValueFactory(new PropertyValueFactory<>("DeptNo"));
    deptid.setEditable(false);
    deptname.setCellValueFactory(new PropertyValueFactory<>("DeptName"));
    deptname.setCellFactory(TextFieldTableCell.forTableColumn());
    deptlocation.setCellValueFactory(new PropertyValueFactory<>("Location"));
    deptlocation.setCellFactory(TextFieldTableCell.forTableColumn());
    table.setTableMenuButtonVisible(true);

    filltable(); // THIS IS THE REFRESH METHODE
}

int id;
String DEPTNAME;
String DEPTLOCATION;

public void set(){
     id  =table.getSelectionModel().getSelectedItem().getDeptNo();
     DEPTNAME = table.getSelectionModel().getSelectedItem().getDeptName();
     DEPTLOCATION = table.getSelectionModel().getSelectedItem().getLocation();
}  
public  void filltable(){
    Department dep = new Department();
    dep.GetAllRows(table);
}

现在是第二个控制器 java（添加窗口）

public class DeptAddControl  implements Initializable{

@Override
public void initialize(URL location, ResourceBundle resources) {
    clear();
}

private void clear(){
    txtDeptID.setText(new Department().AutoNumber());
    txtDeptName.clear();
    txtLocation.clear();
    txtDeptName.requestFocus();
}


@FXML
private void submit(ActionEvent event) {
        int num = (Integer.parseInt(txtDeptID.getText()));
        String name = (txtDeptName.getText());
        String location = (txtLocation.getText());
        Department e = new Department(num,name,location);
        btnback.fire();
        e.add();
        /// Now the data is added and I want to call filltable() from the other class 
        DeptControl dp = new DeptControl();
        dp.filltable();  //I tried this but gives Exception
    }

@FXML
private void back(ActionEvent event) {
    Stage stage = (Stage)btnback.getScene().getWindow();
    stage.close();
    }

}

例外

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8413)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:416)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    ... 52 more
Caused by: java.lang.NullPointerException
    at Entity.Department.GetAllRows(Department.java:125)
    at controllers.DeptControl.filltable(DeptControl.java:119)
    at controllers.DeptAddControl.submit(DeptAddControl.java:68)
    ... 62 more

引发异常的 GetAllRows()

@Override
    public void GetAllRows(TableView table) {
        ObservableList<Department> list = FXCollections.observableArrayList();
        ResultSet rs = go.FillTable("department_data");
        try{
        while (rs.next()){
                list.add(new Department( rs.getInt(1) , rs.getString(2), rs.getString(3)));
            }
            con.close();
            table.setItems(list);

        }catch(SQLException e){
            tools.Notification_Error("Error", e.getMessage(), Pos.CENTER);
        }
    }

这里是 Filltable()

public static ResultSet FillTable(String TableNameOrStatement) {
        try {
            connect();
            Statement s = con.createStatement();
            String Query;          
            if("select ".equals(TableNameOrStatement.substring(0, 7).toLowerCase())){
                Query = TableNameOrStatement;
            }             
            else {
                Query = "select * from " + TableNameOrStatement;
            }
            ResultSet rs = s.executeQuery(Query);
            return rs;
        } catch (SQLException ex) {
            tools.Notification_Error("Error", ex.getMessage(), Pos.CENTER);  
            return null;
        }
    }

Answer 1

DeptControl.filltable();

不过可能是其他问题。