Activity log not getting continuously updated in JavaFX - concurrency

Question

I am executing some commands on linux using JSCH and taking output of that command and printing same on the activity log in my JAVAFX application.
Here is a problem: the activity log area is getting stuck after printing some line. But, if I switch from the window and back application continues to print lines on log area. I have debugged several times but wasn't able to catch the problem.
Below is the code
channel.connect();
PrintStream commander = new PrintStream(channel.getOutputStream(), true);
commander.println(command_cd);
commander.println(" exit;");
commander.close();
InputStream outputstream_from_the_channel = channel.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(outputstream_from_the_channel));
String jarOutput;
BufferedWriter bw = new BufferedWriter(new FileWriter(resultLogFile.getAbsolutePath(), true));
while ((jarOutput = reader.readLine()) != null) {
this.logger.info("Status Update = " + jarOutput);
System.out.print("Status Update on screen ="+jarOutput + "\n");
bw.write(jarOutput);
bw.newLine();
outputFromUnix.append(jarOutput).append("\n");
// Display in activity log area in realtime.
if (DeploymentTaskController.actLogTArea != null) {
System.out.println("outputFromUnix.toString()---->>>>> " + outputFromUnix.toString());
//actlogArea is TextArea
DeploymentTaskController.actLogTArea.setText(outputFromUnix.toString());
DeploymentTaskController.actLogTArea.end();
}
}
bw.close();
reader.close();

Answer 1

JavaFX has a special thread named "JavaFX Application Thread" to update all UI. This thread shouldn't be used for any non-UI operations, and all UI operations must be run on that thread.
Make sure you run your code in a separate Thread and wrap all UI code into Platform#runLater() to have executed
// Using separate thread to run data loading code
new Thread(new Runnable() {
public void run() {
channel.connect();
// [...] all your channel reading code
// Updating UI from JavaFX Application Thread
if (DeploymentTaskController.actLogTArea != null) {
System.out.println("outputFromUnix.toString()---->>>>> " + outputFromUnix.toString());
final String outputStr = outputFromUnix.toString();
Platform.runLater(new Runnable() {
#Override
public void run() {
DeploymentTaskController.actLogTArea.setText(outputStr);
DeploymentTaskController.actLogTArea.end();
}
});
}
bw.close();
reader.close();
}
}).start();
There is also a special concurrency API in JavaFX for such tasks, see here: http://docs.oracle.com/javafx/2/threads/jfxpub-threads.htm