java - 在 OS X Java 应用程序中处理自定义 URL 方案

Question

我们基于 Java 的应用程序的 Info.plist 包含以下条目:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
<plist version="0.9">
    <dict>
        ...
        <key>CFBundleURLTypes</key>
        <array>
            <dict>
                <key>CFBundleURLName</key>
                <string>myApp handler</string>
                <key>CFBundleURLSchemes</key>
                <array>
                    <string>myapp</string>
                </array>
            </dict>
        </array>
        ...
    </dict>
</plist>

它应该处理像 myapp://foobar/bazz 这样的 URL。打开应用没问题，但是应用应该如何获取点击的URL呢？

Answer 1

对于 Objective C，答案可以在这里找到:When an OS X app is launched by a registered URL scheme, how do you access the full URL?

Java 的解决方案是将 ObjC 代码重写为纯 C，然后借助 org.eclipse.swt.internal.cocoa.* 下的一组类将其转换为 Java .

作为 ObjC 到 C 翻译的引用，我们需要 Apple 的 Objective-C Runtime Reference .

纯 C 版本

首先，让我们翻译一下

[[NSAppleEventManager sharedAppleEventManager]
    setEventHandler:targetObject
        andSelector:@selector(handleAppleEvent:withReplyEvent:)
      forEventClass:kInternetEventClass
         andEventID:kAEGetURL];

进入普通 C。要在普通 C 中调用 ObjC 函数，我们使用 objc_msgSend()。此外，@selector(method_footprint) 被替换为 sel_registerName("method_footprint")，并使用 objc_getClass() 查找类。 id 和 SEL 类型等同于指针(例如 void*)或全尺寸 int(即与 void* 大小相同)。

结果:

// id mgr = [NSAppleEventManager sharedAppleEventManager]
SEL sel_ sharedAppleEventManager = sel_registerName("sharedAppleEventManager");
id mgr = objc_msgSend (objc_getClass("NSAppleEventManager"), sharedAppleEventManager);

// and the rest
SEL sel_setEventHandler = sel_registerName("setEventHandler:andSelector:forEventClass:andEventID:");
SEL sel_handleAppleEvent = sel_registerName("handleAppleEvent:withReplyEvent:");
objc_msgSend (mgr, sel_setEventHandler, targetObject, sel_handleAppleEvent, kInternetEventClass, kAEGetURL);

如您所见，我们在这里调用了两个子例程:第一个调用 NSAppleEventManager 类的 sharedAppleEventManager 消息，从该类中检索单例对象。第二个调用是向该对象发送 setEventHandler... 消息，传递 4 个参数(目标对象、目标消息和两个事件说明符)。

回调函数的声明，原为:

- (void)handleAppleEvent:(NSAppleEventDescriptor *)event withReplyEvent:(NSAppleEventDescriptor *)replyEvent

在纯 C 中看起来像这样:

void handleAppleEvent (id self, SEL selector, NSAppleEventDescriptor* event, NSAppleEventDescriptor* replyEvent)

这意味着当函数被调用时，它不仅会发送其对象引用 (id)，还会发送其方法足迹(选择器)。

回调代码在 ObjC 中看起来像这样以获取 URL:

NSString url = [[event paramDescriptorForKeyword:keyDirectObject] stringValue];

在纯 C 中:

id desc_id = objc_msgSend (event_id, sel_registerName("paramDescriptorForKeyword:"), '----');
id url_id = objc_msgSend (desc_id, desc_id, sel_registerName("stringValue"));

还缺一部分:

targetObject 需要在调用上面的代码之前进行初始化，并且需要在该目标对象中创建一个匹配 handleAppleEvent:withReplyEvent: 足迹的方法，然后链接到我们普通的 C 事件处理程序 (handleAppleEvent())。

这意味着我们必须创建一个 Objective C 类，向它添加一个方法，然后创建它的一个对象实例:

// create an NSObject subclass for our target object
char objcClassName[] = "ObjCAppleEventHandler";
id objcClass = objc_allocateClassPair (objc_getClass("NSObject"), objcClassName);

// add the callback method to the class
SEL sel_handleAppleEvent = sel_registerName("handleAppleEvent:withReplyEvent:");
class_addMethod (objcClass, sel_handleAppleEvent, handleAppleEvent, "i@:@@");

// register the class
objc_registerClassPair (objcClass)

// create an object instance
id targetObject = class_createInstance (objcClass, 0);

// ... here follows the above code with the setEventHandler invocation
// (note: `SEL sel_handleAppleEvent` appears twice - the 2nd one can be removed)

纯 C 版本到此结束。

(注:以上代码未经测试而写，可能存在错误，但下面的Java代码已经过测试。)

Java 版本

从纯 C 到 Java 的转换现在相当简单。

前面提到的 ObjC Runtime 函数都可以从 org.eclipse.swt.internal.cocoa.OS 获得。

首先是一些预设:

static final long class_NSAppleEventManager = OS.objc_getClass("NSAppleEventManager");
static final long sel_sharedAppleEventManager = OS.sel_registerName("sharedAppleEventManager");
static final long sel_setEventHandler = OS.sel_registerName("setEventHandler:andSelector:forEventClass:andEventID:");
static final long sel_handleAppleEvent = OS.sel_registerName("handleAppleEvent:withReplyEvent:");
static final long sel_paramDescriptorForKeyword = OS.sel_registerName("paramDescriptorForKeyword:");
static final long sel_stringValue = OS.sel_registerName("stringValue");

static final long kInternetEventClass = 0x4755524C; // 'GURL'
static final long kAEGetURL = 0x4755524C; // 'GURL'
static final long kCoreEventClass = 0x61657674; // 'aevt'
static final long kAEOpenApplication = 0x6F617070; // 'oapp'
static final long kAEReopenApplication = 0x72617070; // 'rapp'
static final long keyDirectObject = 0x2d2d2d2d; // '----'

回调函数:

static long handleAppleEvent (long id, long sel, long event_id, long reply_id) {
    // This is a handler for AppleEvents that are registered with [NSAppleEventManager setEventHandler:...]
    // It matches this selector (footprint):
    //   - (void)handleAppleEvent:(NSAppleEventDescriptor *)event withReplyEvent:(NSAppleEventDescriptor *)reply

    // Invoke [[event paramDescriptorForKeyword:keyDirectObject] stringValue] to get the direct object containing the URL
    long direct_desc_id = OS.objc_msgSend (event_id, sel_paramDescriptorForKeyword, keyDirectObject);
    long direct_str_id = OS.objc_msgSend (direct_desc_id, sel_stringValue);
    NSString nsStr = new NSString (direct_str_id);
    String str = nsStr.getString();
    // now 'str' contains the URL

    System.out.println ("handleAppleEvent invoked -- argument: "+url);
    return 0;
}

以及注册回调函数的代码:

// Get access to a callback function for receiving the sel_handleAppleEvent message
aeCallback = new Callback(Main.class, "handleAppleEvent", 4);
long aeProc = aeCallback.getAddress();

// Create a ObjC class that provides a method with the sel_handleAppleEvent footprint
String objcClassName = "ObjCAppleEventHandler";
long objcClass = OS.objc_allocateClassPair(OS.class_NSObject, objcClassName, 0);
OS.class_addMethod(objcClass, sel_handleAppleEvent, aeProc, "i@:@@");
OS.objc_registerClassPair(objcClass);
long objcHandlerInstance = OS.class_createInstance (objcClass, 0);

// Invoke [[NSAppleEventManager sharedAppleEventManager] setEventHandler:objcHandlerInstance andSelector:sel_handleAppleEvent forEventClass:kInternetEventClass andEventID:kAEGetURL]
long sharedAppleEventMgr = OS.objc_msgSend (class_NSAppleEventManager, sel_sharedAppleEventManager);
OS.objc_msgSend (sharedAppleEventMgr, sel_setEventHandler, objcHandlerInstance, sel_handleAppleEvent, kInternetEventClass, kAEGetURL);

剩下要做的是从这段代码构建一个应用程序包，然后将 CFBundleURLTypes 条目添加到它的 Info.plist 中。

可在此处下载完整的示例源文件:http://files.tempel.org/Various/ObjectiveC-bridging.java.zip