JavaFX程序何时调用start方法？

Question

我正在学习JavaFX.我只能在main方法中看到启动(args)方法.当我调试进入发布时.我看不到任何语句调用start().那么JavaFX程序何时调用start方法？这是launch(args)源代码.

    public static void launch(String... args) {
    // Figure out the right class to call
    StackTraceElement[] cause = Thread.currentThread().getStackTrace();

    boolean foundThisMethod = false;
    String callingClassName = null;
    for (StackTraceElement se : cause) {
        // Skip entries until we get to the entry for this class
        String className = se.getClassName();
        String methodName = se.getMethodName();
        if (foundThisMethod) {
            callingClassName = className;
            break;
        } else if (Application.class.getName().equals(className)
                && "launch".equals(methodName)) {

            foundThisMethod = true;
        }
    }

    if (callingClassName == null) {
        throw new RuntimeException("Error: unable to determine Application class");
    }

    try {
        Class theClass = Class.forName(callingClassName, true,
                           Thread.currentThread().getContextClassLoader());
        if (Application.class.isAssignableFrom(theClass)) {
            Class<? extends Application> appClass = theClass;
            LauncherImpl.launchApplication(appClass, args);
        } else {
            throw new RuntimeException("Error: " + theClass
                    + " is not a subclass of javafx.application.Application");
        }
    } catch (RuntimeException ex) {
        throw ex;
    } catch (Exception ex) {
        throw new RuntimeException(ex);
    }
}

Answer 1

LauncherImpl调用Application#start,但是通过将actuall调用放到JavaFX事件队列中来实现PlatformImpl.runAndWait.这是在Preloader启动后完成的

Application#launch调用LauncherImpl.launchApplication,创建一个Thread和调用launchApplication1,launchApplication然后Thread通过a 等待终止CountDownLatch.

这Thread然后调用LauncherImpl.launchApplication1,它启动Preloader,如果指定,那么,根据有关的状态的数量决定Preloader的呼叫Application#start,包裹在一个runAndWait电话,以确保start在JavaFX的的GUI /事件队列线程的上下文中调用...

这基于Java 8

更新...

theApp.start,被称为LauncherImpl.launcherApplication1你的实例Application.

Application通过步行StackTrace...来查找你的课程名称......

StackTraceElement[] cause = Thread.currentThread().getStackTrace();

boolean foundThisMethod = false;
String callingClassName = null;
for (StackTraceElement se : cause) {
    // Skip entries until we get to the entry for this class
    String className = se.getClassName();
    String methodName = se.getMethodName();
    if (foundThisMethod) {
        callingClassName = className;
        break;
    } else if (Application.class.getName().equals(className)
            && "launch".equals(methodName)) {

        foundThisMethod = true;
    }
}

这将获取您的类的名称,然后Class使用它创建一个实例Class.forName并将其传递给LauncherImpl...

launcherApplication1然后构造此类的新实例并将其分配给引用theApp,该引用是您的实例Application

PlatformImpl.runAndWait(new Runnable() {
        @Override public void run() {
            try {
                Constructor<? extends Application> c = appClass.getConstructor();
                app.set(c.newInstance());
                // Set startup parameters
                ParametersImpl.registerParameters(app.get(), new ParametersImpl(args));
                PlatformImpl.setApplicationName(appClass);
            } catch (Throwable t) {
                System.err.println("Exception in Application constructor");
                constructorError = t;
                error = true;
            }
        }
    });
}
final Application theApp = app.get();

然后它继续调用theApp.start,这是调用你Application的start方法....我知道很奇怪,但确实如此