java - 从 Gluon Charm Down 读取屏幕方向的空指针

Question

我想问一下，是否有人在使用 Gluon Charm Down 插件进行 IOS 屏幕方向时遇到过问题？

JFXMobile 插件:org.javafxports:jfxmobile-plugin:1.3.2

魅力版本:com.gluonhq:charm:4.2.0

downConfig {
        version = '3.1.0'
        plugins 'display', 'lifecycle', 'statusbar', 'storage', 'orientation'
}

当我尝试调用它时，像这样:

Services.get(OrientationService.class).ifPresent(service -> {
    onOrientationChange(service.orientationProperty(), null, service.getOrientation().orElse(Orientation.VERTICAL));
    service.orientationProperty().addListener(this::onOrientationChange);
});

我在控制台上得到一个异常:

Exception in Preloader start method
2017-02-06 10:43:37.104693 MyApp[447:282589] Orientation is Unknown
QuantumRenderer: shutdown
java.lang.RuntimeException: Exception in Preloader start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$156(LauncherImpl.java)
    at com.sun.javafx.application.LauncherImpl$$Lambda$2.run(Unknown Source)
    at java.lang.Thread.run(Thread.java)
Caused by: java.lang.NullPointerException
    at com.gluonhq.charm.down.plugins.ios.IOSOrientationService.getOrientation(IOSOrientationService.java)
    at my.app.Preloader.lambda$start$24(Preloader.java)
    at my.app.Preloader$$Lambda$3.accept(Unknown Source)
    at java.util.Optional.ifPresent(Optional.java)
    at my.app.Preloader.start(Preloader.java)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java)
    at com.sun.javafx.application.LauncherImpl$$Lambda$7.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$176(PlatformImpl.java)
    at com.sun.javafx.application.PlatformImpl$$Lambda$7.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$174(PlatformImpl.java)
    at com.sun.javafx.application.PlatformImpl$$Lambda$19.run(Unknown Source)
    at java.security.AccessController.doPrivileged(AccessController.java)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$175(PlatformImpl.java)
    at com.sun.javafx.application.PlatformImpl$$Lambda$6.run(Unknown Source)
    at org.robovm.apple.uikit.UIApplication.main(UIApplication.java)
    at org.robovm.apple.uikit.UIApplication.main(UIApplication.java)
    at org.javafxports.jfxmobile.ios.BasicLauncher.main(BasicLauncher.java)

查看 code ，我认为这个问题可能只有一个原因:

@Override
public final Optional<Orientation> getOrientation() {
    switch (orientationText) {
        case "Portrait":
        case "PortraitUpsideDown":  
            return Optional.of(Orientation.VERTICAL);
        case "LandscapeLeft":
        case "LandscapeRight":      
            return Optional.of(Orientation.HORIZONTAL);
        case "Unknown":             
        default:                  
            return Optional.empty();
    }
}

我的猜测是，orientationText 是 null，因此它崩溃了。

我猜 2017-02-06 10:43:37.104693 MyApp[447:282589] Orientation is Unknown 行对此有所贡献。

这是一个错误吗？有什么办法可以避免这种情况吗？ (例如，IOS 上是否需要一些设置，例如 Android 上的权限系统？)

在此先致谢并致以问候，

丹尼尔

---

#edit: onOrientationChange 方法不是很复杂:

private void onOrientationChange(ObservableValue<? extends Orientation> obs, Orientation o, Orientation n) {
    if (n == null || splashPane == null)
        return;
    splashPane.pseudoClassStateChanged(vertical, Orientation.VERTICAL == n);
    splashPane.pseudoClassStateChanged(horizontal, Orientation.HORIZONTAL == n);
}

所以我想更新代码就足够了。像这样

Services.get(OrientationService.class).ifPresent(service -> {

service.orientationProperty().addListener(this::onOrientationChange); });

(它在 Android 上运行，所以我可以选择检查平台并只在非 IOS 上运行)

Answer 1

我可以重现你的 NPE。

错误发生在您“急切地”调用 service.getOrientation() 时.

如果您查看 code , orientationText未初始化，只有在服务初始化和观察者启动时，该值才会从 iOS native 层检索并设置为 Platform::runLater .

这意味着需要很短的时间才能获得 orientationText 的初始值.

避免 NPE 的快速解决方案是使用常规 ChangeListener<Observation>而不是你的 onOrientationChange方法:

private final ChangeListener<Orientation> onOrientationChange = 
    (ObservableValue<? extends Orientation> obs, Orientation ov, Orientation nv) -> {
    if (nv == null || splashPane == null)
        return;
    splashPane.pseudoClassStateChanged(vertical, Orientation.VERTICAL == nv);
    splashPane.pseudoClassStateChanged(horizontal, Orientation.HORIZONTAL == nv);
}

Services.get(OrientationService.class).ifPresent(service -> {
    service.orientationProperty().addListener(onOrientationChange);
});

无论如何，我会提交一个问题来为 orientationText 添加一个初始值.