我曾经在Swing工作，但现在看到它已经过时了，JX8是Java应用程序的未来，所以我从ScreenBuilder的FXML GUI开始。并将我的RDT 3.0 TCP服务器 - 客户端代码集成到FXML GUI中。
但我有很多错误;我尝试解决了大部分问题但每次都得到nullPointerException并且我知道这是因为没有分配内存。我怎样才能摆脱它们，以及如何让我的应用程序运行？
以下是代码：
ClientFXMLController.java：
package rdt_app;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.Initializable;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.PrintStream;
import static java.lang.Thread.sleep;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.*;
/**
* FXML Controller class
*
* @author Dell
*/
public class ClientFXMLController implements Initializable {
ToggleGroup group = new ToggleGroup();
@FXML
RadioButton case1;
@FXML
RadioButton case2;
@FXML
RadioButton case3;
@FXML
RadioButton case4;
@FXML
RadioButton case5;
boolean buttonPressed=false;
String str=null;
@FXML
TextArea msg_rcv;
@FXML
Button send_button;
Socket s;
DataInputStream in;
// DataInputStream inn;
PrintStream ps;
String pre = "";
@FXML
private void handleButtonAction(ActionEvent event) {
// buttonPressed=true;
if(s!=null){
if(case1.isSelected())
str= "1";
else if(case2.isSelected())
str= "2";
else if(case3.isSelected())
str= "3";
else if(case4.isSelected())
str= "4";
else if(case5.isSelected())
str= "5";
}
else{
// Alert alert = new Alert(Alert.AlertType.ERROR); //AlertType.WARNING
// alert.setTitle("Error!");
// alert.setHeaderText("Message Cannot be send at this moment!");
// alert.setContentText("Please wait for response from Client or timeout and then proceed");
//
// alert.showAndWait();
}
}
/**
* Initializes the controller class.
*/
@Override
public void initialize(URL url, ResourceBundle rb) {
try {
sleep(200);
} catch (InterruptedException ex) {
Logger.getLogger(ClientFXMLController.class.getName()).log(Level.SEVERE, null, ex);
}
try {
// TODO
case1.setToggleGroup(group);
case1.setSelected(true);
case2.setToggleGroup(group);
case3.setToggleGroup(group);
case4.setToggleGroup(group);
case5.setToggleGroup(group);
msg_rcv.appendText("Key:\n1:Operation with no Loss\n2:Lost Packet\n3:Lost ACK\n4:Premature Timeout\nNull:No Response\n");
s = new Socket("localHost",8100);
in = new DataInputStream(s.getInputStream());
// inn = new DataInputStream(System.in);
ps = new PrintStream(s.getOutputStream());
pre = "";
while (true)
{
str = in.readLine();
if (!str.equalsIgnoreCase("fin") && str!=null)
{
msg_rcv.appendText("Sender just sended a Message: "+str+"\n");
if (pre.equalsIgnoreCase("3") || pre.equalsIgnoreCase("null"))
{
msg_rcv.appendText("Duplicate Detected!\n");
}
msg_rcv.appendText("Enter a Response: \n");
if(str.equalsIgnoreCase("1") || str.equalsIgnoreCase("2") || str.equalsIgnoreCase("3") || str.equalsIgnoreCase("4") ||
str.equalsIgnoreCase("5")){
pre=str;
ps.println(str);
// buttonPressed=false;
}
// str = inn.readLine();
}
else if(str==null){
// do nothing carry on with loop
}
else
{
s.close();
break;
}
}
} catch (IOException ex) {
Logger.getLogger(ClientFXMLController.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
FXMLDocumentController（服务器）：
package rdt_app;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.*;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.PrintStream;
import static java.lang.Thread.sleep;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;
/**
*
* @author Dell
*/
public class FXMLDocumentController implements Initializable {
@FXML
private Label info_label;
@FXML
private Label waitingLabel;
@FXML
private Button send_button;
@FXML
private TextField msg_send;
@FXML
private TextArea msg_rcv;
@FXML
private ProgressBar pbar;
String str =null;
ServerSocket ss;
int correct = 0;
Socket s;
DataInputStream in;
DataInputStream inn;
PrintStream ps;
@FXML
private AnchorPane rootPane;
@FXML
private void handleButtonAction(ActionEvent event) {
if(ss!=null && msg_send.getText()!=null){
if(correct==0)
str= msg_send.getText();
else{
Alert alert = new Alert(AlertType.ERROR); //AlertType.WARNING
alert.setTitle("Error!");
alert.setHeaderText("Message Cannot be send at this moment!");
alert.setContentText("Please wait for response from Client or timeout and then proceed");
alert.showAndWait();
}
}
}
@Override
public void initialize(URL url, ResourceBundle rb) {
try {
// TODO
// AnchorPane pane = FXMLLoader.load(getClass().getResource("clientFXML.fxml"));
// rootPane.getChildren().setAll(pane);
pbar.setProgress(0.0);
send_button.setVisible(false);
info_label.setVisible(false);
msg_send.setVisible(false);
msg_rcv.setVisible(false);
for(int i=0;i<100;i++){
pbar.setProgress(i/100.0);
sleep(20);
}
pbar.setProgress(0.0);
send_button.setVisible(true);
info_label.setVisible(true);
msg_send.setVisible(true);
msg_rcv.setVisible(true);
pbar.setVisible(false);
waitingLabel.setVisible(false);
ss=new ServerSocket(8100);
s=ss.accept();
int ack = 0;
in = new DataInputStream(System.in);
inn = new DataInputStream(s.getInputStream());
ps = new PrintStream(s.getOutputStream());
while (true)
{
// if (correct==0)
// {
// System.out.println("Enter a Message: ");
// str = in.readLine();
// }
if (str.equalsIgnoreCase("fin"))
{
ss.close();
break;
}
if(correct ==0 && str!=null){
ack = ack % 2;
ps.println(str);
str=null;
}
String str2 = inn.readLine();
int reply=0;
if (str2.equalsIgnoreCase("1") || str2.equalsIgnoreCase("2") || str2.equalsIgnoreCase("3") || str2.equalsIgnoreCase("4"))
{
reply = Integer.parseInt(str2);
}
if (!str2.equalsIgnoreCase("fin"))
{
if (reply==1) //operation with no loss
{
// System.out.println("Sender received a valid ACK for "+ack+" , send next message!");
msg_rcv.appendText("Sender received a valid ACK for "+ack+" , send next message!\n");
ack++;
correct=0;
}
if (reply==2) //Lost Packet
{
// System.out.println("Sender didn't recieve a ACK!");
msg_rcv.appendText("Sender didn't recieve a ACK!\n");
for (int i=0;i<5;i++)
{
msg_rcv.appendText("Waiting\n");
}
msg_rcv.appendText("Timeout! Sending Message Again\n");
correct++;
}
if (reply==3) //Lost ACK
{
msg_rcv.appendText("Sender received a corrupted ack (ACK is lost), keep waiting!\n");
for (int i=0;i<5;i++)
{
msg_rcv.appendText("Waiting\n");
}
msg_rcv.appendText("Timeout! Sending Message Again\n");
correct++;
}
if (reply==0 || reply==4) //Premature Timeout
{
if (reply==0)
{
msg_rcv.appendText("Sender didn't recieve a ACK because of Timeout!\n");
for (int i=0;i<5;i++)
{
msg_rcv.appendText("Waiting\n");
}
msg_rcv.appendText("Timeout! Sending Message Again\n");
correct++;
}
else if (reply==4)
{
msg_rcv.appendText("Sender received a valid ACK for "+ack+" , send next message!\n");
msg_rcv.appendText("Sender recieved a Duplicate ACK for "+ack+" , ACK ignored\n");
correct=0;
ack++;
}
}
}
else
{
ss.close();
break;
}
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
现在运行它们我使用这段代码：
Rdt_App.java：
package rdt_app;
import static java.lang.Thread.sleep;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
/**
*
* @author Dell
*/
public class Rdt_App extends Application {
@Override
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));
Scene scene = new Scene(root);
stage.setScene(scene);
stage.show();
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
}
我得到的错误：
Apr 14, 2018 3:59:54 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 9.0.1 by JavaFX runtime of version 8.0.101
java.lang.NullPointerException
at rdt_app.FXMLDocumentController.initialize(FXMLDocumentController.java:114)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at rdt_app.Rdt_App.start(Rdt_App.java:24)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$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)
答案 0 :(得分：0)
您是否在FXML文档中设置了控制器？如果没有为FXML设置控制器类，FXML组件永远不会被初始化，因此你得到NullPointerException。此外，您不需要实现Initializable接口。 @Override功能将@FXML更改为intialize ()。