java JavaFX 中的多线程挂起 UI
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Multithreading in JavaFX hangs the UI
提问by Click Upvote
I have a simple JavaFX 2 app, with 2 buttons, saying Start and Stop. When the start button is clicked, I want to create a background thread which will do some processing and update the UI (e.g a progress bar) as it goes along. If the stop button is clicked, I want the thread to terminate.
我有一个简单的 JavaFX 2 应用程序，有 2 个按钮，分别是启动和停止。单击开始按钮时，我想创建一个后台线程，该线程将执行一些处理并在执行过程中更新 UI（例如进度条）。如果单击停止按钮，我希望线程终止。
I've tried to do this using the javafx.concurrent.Taskclass which I gathered from the documentation would work fine for this. But whenever I click Start, the UI freezes/hangs rather than staying normal.
我尝试使用javafx.concurrent.Task我从文档中收集的类来做到这一点，对此我可以很好地工作。但是每当我单击“开始”时，UI 都会冻结/挂起而不是保持正常。
Her's the code from the main Myprogram extends Applicationclass for showing the buttons:
她是来自主Myprogram extends Application类的用于显示按钮的代码：
public void start(Stage primaryStage)
{
final Button btn = new Button();
btn.setText("Begin");
//This is the thread, extending javafx.concurrent.Task :
final MyProcessor handler = new MyProcessor();
btn.setOnAction(new EventHandler<ActionEvent>()
{
public void handle(ActionEvent event)
{
handler.run();
}
});
Button stop = new Button();
stop.setText("Stop");
stop.setOnAction(new EventHandler<ActionEvent>()
{
public void handle(ActionEvent event)
{
handler.cancel();
}
}
);
// Code for adding the UI controls to the stage here.
}
Here's the code of MyProcessorclass:
这是MyProcessor类的代码：
import javafx.concurrent.Task;
public class MyProcessor extends Task
{
@Override
protected Integer call()
{
int i = 0;
for (String symbol : feed.getSymbols() )
{
if ( isCancelled() )
{
Logger.log("Stopping!");
return i;
}
i++;
Logger.log("Doing # " + i);
//Processing code here which takes 2-3 seconds per iteration to execute
Logger.log("# " + i + ", DONE! ");
}
return i;
}
}
Pretty simple, but the UI hangs whenever I click the Start button, though the console messages continue to get displayed (Logger.logsimply does System.out.println)
非常简单，但是每当我单击“开始”按钮时 UI 都会挂起，尽管控制台消息会继续显示（Logger.log只是这样做System.out.println）
What am I doing wrong?
我究竟做错了什么？
回答by assylias
Taskimplements Runnable, so when you call handler.run();you actually run the callmethod in the UI Thread. That will hang the UI.
Task实现Runnable，因此当您调用时，handler.run();您实际上是call在 UI 线程中运行该方法。这将挂起 UI。
You should start the task in a background thread, either via an executor or simply by calling new Thread(handler).start();.
您应该在后台线程中启动任务，通过执行程序或简单地调用new Thread(handler).start();.
This is explained (maybe not very clearly) in the javadocor in the JavaFX concurrency tutorial.
这在javadoc或JavaFX concurrency tutorial 中有解释（可能不是很清楚）。
