在OS X Java应用程序中处理自定义URL方案

Question

在Info.plist我们的基于Java的应用程序中包含以下项目:

<?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>

它应该处理像这样的URL myapp://foobar/bazz.打开应用程序工作正常,但应用程序应如何获取单击的URL？

Answer 1

对于Objective C,可以在这里找到答案:当通过注册的URL方案启动OS X应用程序时,如何访问完整的URL？

Java的解决方案是将ObjC代码重写为普通的C,然后在一组类的帮助下将其转换为Java org.eclipse.swt.internal.cocoa.*.

作为ObjC-to-C转换的参考,我们需要Apple的Objective-C运行时参考.

普通C版

首先,让我们翻译

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

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"),并且查找类objc_getClass().类型id和SEL等价于指针(如void*)或全尺寸int(即与void*相同的大小).

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,我们在这里有两个子程序调用:第一个调用类的sharedAppleEventManager消息,从NSAppleEventManager该类中检索单个对象.第二个调用是将setEventHandler ...消息发送到该对象,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,原来是:

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

在普通C中看起来像这样:

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

这意味着当调用函数时,它不仅会发送其对象引用(id),还会发送其方法占用(选择器).

ObjC中的回调代码如下所示,以获取URL:

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

而在平原C:

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

其中一部分仍然缺失:

targetObject需要在调用上面的代码之前初始化,并且handleAppleEvent:withReplyEvent:需要在该目标对象中创建匹配足迹的方法,然后链接到我们的普通C事件处理程序(handleAppleEvent()).

这意味着我们必须创建一个Objective C类,向其中添加一个方法,然后创建一个它的对象实例:

// 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)

这是普通的C版本.

(注意:上面的代码是在没有测试的情况下编写的,因此它可能包含错误.但是,下面的Java代码已经过测试.)

Java版本

从Plain C到Java的翻译现在相当简单.

前面提到的ObjC运行时函数都可以从org.eclipse.swt.internal.cocoa.OS获得.

首先,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);

剩下要做的是从此代码构建应用程序包,然后将CFBundleURLTypes条目添加到其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

Answer 2

使用 Java 9，这变得非常容易，并且不再需要 Apple 的 EAWT 类或任何 ObjC hackery。

    Desktop.getDesktop().setOpenURIHandler((event) -> {
        System.out.println("Open URI: " + event.getURI());
        // do something with the URI
    });

需要捆绑应用程序，并且必须设置 CFBundleURLTypes 键。

<!-- Open URIs with scheme example:// -->
<key>CFBundleURLTypes</key>
<array>
  <dict>
    <key>CFBundleURLSchemes</key>
    <array>
        <string>example</string>
    </array>
    <key>CFBundleURLName</key>
    <string></string>
  </dict>
</array>

不幸的是，这仅在应用程序已运行时捕获 URI。如果应用程序是通过打开 URI 启动的，则不会传递该事件（请参阅 ed22 答案的评论）。