java - 单独的线程不会运行，阻塞主 UI

Question

我有一个执行一组 PowerShell 命令的程序。现在的问题是，当用户单击某个选项并且执行命令的过程开始时，我需要更新标签的状态并显示图标。如果我只是在 try-catch 语句之前键入命令，它们将在整个 try-catch 语句结束后执行。因此，我尝试在下面提供的代码中的单独线程上运行它们，但在这种情况下，它们甚至没有被执行，只是 try-catch block 。 NORMAL_MODE() 方法由鼠标点击触发。

@FXML
    private void NORMAL_MODE(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                LABEL.setText("123");
                ICON.setVisible(true);
            }
        }).start();
        try (PowerShell powerShell = PowerShell.openSession()) {
            PowerShellResponse response = powerShell.executeCommand("Set-Location “C:\\Windows\\Temp”");
            response = powerShell.executeCommand("Remove-Item * -whatif -recurse -force");
            System.out.println(response.getCommandOutput());
            response = powerShell.executeCommand("Set-Location “C:\\Windows\\Prefetch”");
            response = powerShell.executeCommand("Remove-Item * -whatif -recurse -force");
            System.out.println(response.getCommandOutput());
            response = powerShell.executeCommand("Set-Location “C:\\Documents and Settings”");
            response = powerShell.executeCommand("Remove-Item * -whatif -recurse -force");
            System.out.println(response.getCommandOutput());
            response = powerShell.executeCommand("Set-Location $env:TEMP");
            System.out.println(response.getCommandOutput());
            response = powerShell.executeCommand("Remove-Item -whatif -Recurse -Force");
            System.out.println(response.getCommandOutput());
        } catch(PowerShellNotAvailableException ex) {
        }
    }

Answer 1

所有 JavaFX 事件处理程序都在 JavaFX 应用程序线程上运行，并且这些处理程序需要快速返回，而 PowerShell 不会发生这种情况。对 GUI 的任何修改都需要在 JavaFX 应用程序线程上进行。

看来您刚刚将错误的代码移至后台线程。

Task class可以帮助处理在后台线程上执行的代码的完成/异常。

@FXML
private void NORMAL_MODE(){
    LABEL.setText("123");
    ICON.setVisible(true);

    Task<Void> task = new Task<Void>() {
        @Override
        protected Void call() throws Exception {
             try (PowerShell powerShell = PowerShell.openSession()) {
                PowerShellResponse response = powerShell.executeCommand("Set-Location “C:\\Windows\\Temp”");
                response = powerShell.executeCommand("Remove-Item * -whatif -recurse -force");
                System.out.println(response.getCommandOutput());
                response = powerShell.executeCommand("Set-Location “C:\\Windows\\Prefetch”");
                response = powerShell.executeCommand("Remove-Item * -whatif -recurse -force");
                System.out.println(response.getCommandOutput());
                response = powerShell.executeCommand("Set-Location “C:\\Documents and Settings”");
                response = powerShell.executeCommand("Remove-Item * -whatif -recurse -force");
                System.out.println(response.getCommandOutput());
                response = powerShell.executeCommand("Set-Location $env:TEMP");
                System.out.println(response.getCommandOutput());
                response = powerShell.executeCommand("Remove-Item -whatif -Recurse -Force");
                System.out.println(response.getCommandOutput());
            }
            return null;
        }

    };
    task.setOnSucceeded(event -> {
        // todo: update gui to indicate success
    });
    task.setOnFailed(event -> {
        // todo: update gui to indicate an exception happened
    });

    new Thread(task).start();
}

onSucceeded 和 onFailed 事件处理程序在 JavaFX 应用程序线程上执行，因此您不需要使用 Platform.runLater对这些处理程序中完成的 GUI 的修改。