BufferedReader freezes the UI in Javafx - javafx

Question

Im working on Javafx. I have created an echo ServerClient system i.e Sending data to server and back to all clients(broadcast). It works fine when Client sends data to Server. But the frame freezes when Server sends the data back to Client. Here is the code:
Client:
/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package com.rajeshpatkar;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
/**
*
* #author Dimpi
*/
public class Client extends Application{
int flag = 999;
public void start(Stage primaryStage) throws Exception {
Connect cnn = new Connect(primaryStage);
cnn.sconnect();
}
public static TextArea Frame(Stage primaryStage, PrintWriter nos, BufferedReader nis) throws IOException {
TextField tf = new TextField();
TextArea ta = new TextArea();
Button btn = new Button();
btn.setText("Click");
btn.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
String get = tf.getText();
nos.println(get);
try {
Connect.chat(nis,ta);
} catch (IOException ex) {
Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
BorderPane root = new BorderPane();
root.setCenter(ta);
BorderPane panel = new BorderPane();
root.setBottom(panel);
panel.setCenter(tf);
panel.setRight(btn);
Scene scene = new Scene(root, 300, 250);
primaryStage.setTitle("Hello World!");
primaryStage.setScene(scene);
primaryStage.show();
return ta;
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
}
class Connect {
Stage primaryStage;
Connect(Stage primaryStage) {
this.primaryStage = primaryStage;
}
public void sconnect() throws IOException {
System.out.println("Client Signing IN");
Socket soc = new Socket("localhost", 9081);
PrintWriter nos = new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(soc.getOutputStream()
)
), true);
BufferedReader nis = new BufferedReader(
new InputStreamReader(soc.getInputStream()
)
);
TextArea ta=Client.Frame(primaryStage, nos, nis);
}
public static void chat(BufferedReader nis,TextArea ta) throws IOException{
String set = nis.readLine();
while (!set.equals("End")) {
ta.appendText(set+"\n");
set = nis.readLine();
}
}
}
Server: /*
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*/
package com.rajeshpatkar;
import static com.rajeshpatkar.Server.a1;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
/**
*
* #author Dimpi
*/
public class Server extends Application {
public static ArrayList<PrintWriter> a1=new ArrayList<PrintWriter>();
#Override
public void start(Stage primaryStage) throws IOException {
System.out.println("Server signing IN");
ServerSocket ss = new ServerSocket(9081);
for (int i = 0; i < 5; i++) {
Socket soc = ss.accept();
Conversation c = new Conversation(soc);
c.start();
}
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
}
class Conversation extends Thread {
Socket soc;
Conversation(Socket soc) {
this.soc = soc;
}
public void run() {
try {
PrintWriter nos = new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(soc.getOutputStream()
)
), true);
BufferedReader nis = new BufferedReader(
new InputStreamReader(soc.getInputStream()
)
);
Server.a1.add(nos);
String get=nis.readLine();
while(true){
for(PrintWriter p:a1){
System.out.println(get);
p.println(get);
}
get=nis.readLine();
}
} catch (Exception e) {
}
}
}

Answer 1

the issue of freezing the client-ui is caused your method: chat(). which is called by your button. it contains the method readLine() of BufferedReader which will wait for an input to happen. this wait will cause your freeze since it happens on the Application Thread.
so what you can do is: on your button-eventhandler: only write output:
String get = tf.getText();
nos.println(get);
but add a Thread which will update your TextArea if your InputStream receives an input, e.g. like this:
static void handleInput(BufferedReader nis, TextArea ta) throws IOException {
final Task<Void> task = new Task<Void>() {
#Override
protected Void call() throws Exception {
String output;
while ((output = nis.readLine()) != null) {
final String value = output;
Platform.runLater(new Runnable() {
#Override
public void run() {
ta.appendText(value + System.getProperty("line.separator"));
}
});
}
return null;
}
};
new Thread(task).start();
}
and call that method once:
handleInput(nis, ta);