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 插件设置屏幕方向时遇到问题IOS？

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);
});

我在控制台上遇到异常：

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$launchApplication6(LauncherImpl.java)
    at com.sun.javafx.application.LauncherImpl$$Lambda.run(Unknown Source)
    at java.lang.Thread.run(Thread.java)
Caused by: java.lang.NullPointerException
    at com.gluonhq.charm.down.plugins.ios.IOSOrientationService.getOrientation(IOSOrientationService.java)
    at my.app.Preloader.lambda$start(Preloader.java)
    at my.app.Preloader$$Lambda.accept(Unknown Source)
    at java.util.Optional.ifPresent(Optional.java)
    at my.app.Preloader.start(Preloader.java)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication11(LauncherImpl.java)
    at com.sun.javafx.application.LauncherImpl$$Lambda.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait6(PlatformImpl.java)
    at com.sun.javafx.application.PlatformImpl$$Lambda.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null4(PlatformImpl.java)
    at com.sun.javafx.application.PlatformImpl$$Lambda.run(Unknown Source)
    at java.security.AccessController.doPrivileged(AccessController.java)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater5(PlatformImpl.java)
    at com.sun.javafx.application.PlatformImpl$$Lambda.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？）

提前致谢和问候，

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，并且只在非 IOS 左右的平台上运行）

Answer 1

我可以重现你的NPE。

错误发生在您 'eagerly' 调用 service.getOrientation() 时。

如果你看一下code，orientationText没有初始化，只有当服务初始化和观察者启动时，才会从[=32中检索值=] 原生图层并设置 Platform::runLater.

这意味着 orientationText.

需要一段时间才能获得初始值

避免 NPE 的快速解决方案是使用常规 ChangeListener<Observation> 而不是您的 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。

从 Gluon Charm Down 读取屏幕方向的空指针

Null Pointer on reading the screen orientation from Gluon Charm Down

java

ios

javafx

javafxports

gluon-mobile