Swift 委托(delegate)和 SocketScan scanApi.setDelegate()

Question

适用于 iOS 的 SocketScan API 是用 Objective-C 编写的，旨在将 CHS 模式下的 SocketMobile 扫描器集成到 native 应用程序中。

启动 ScanApi 时，需要将 ViewController 设置为 ScanApiHelperDelegate，这需要在 viewDidLoad 上进行一些设置以及一些用于从扫描器接收操作的函数。

设置变量:

var scanApi = ScanApiHelper()
var scanApiConsumer = NSTimer()

然后在viewDidLoad中，实现了如下代码:

scanApi.setDelegate(self)
scanApi.open()
scanApiConsumer = NSTimer.scheduledTimerWithTimeInterval(0.2, target: self, selector:Selector("onTimer"), userInfo: nil, repeats: true)

然后，scanApiConsumer 调用以下函数来监听来自扫描器的通知:

func onTimer () -> Void{
    scanApi.doScanApiReceive()
    scanApi.getDevicesList()
}

扫描条形码时，它会执行以下操作:

func onDecodedData(device: DeviceInfo, decodedData: ISktScanDecodedData) {
    //code to execute here
}

如果需要，用户会被引导到另一个 View ，在该 View 中扫描条形码会执行不同的代码。 scanApi.setDelegate 设置如下:

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "manifestToRepackContainer" {
        let vc = (segue.destinationViewController as RepackContainer)
        scanApi.setDelegate(vc)
        vc.containerBarcode = GlobalVars.barcodeData
    }
}

这也很好用。一旦您到达那里，扫描仪就会正确执行指定的功能。而且，在原始查看器的 viewDidAppear 上，我有这个设置，它也可以按预期工作:

override func viewDidAppear(animated: Bool) {
    scanApi.setDelegate(self)
}

当用户需要在 Storyboard的一个完全不同的区域(“远程” View )中扫描功能时，就会出现问题，其中 prepareForSegue 方法不可能触发 scanApi.setDelegate()

我最初的想法是通过在“远程” View 的 viewDidAppear 中执行 scanApi.setDelegate(self) 来简单地在“远程” View 中定义 scanApi 委托(delegate)。当然，此 View 也被指定为 scanApiHelperDelegate 并包含所有需要的功能。但是，它不起作用。原来的 viewController 仍然是 delegate，扫描条码继续触发原 viewController 中列出的功能，而不是当前的。编译器不会返回任何错误。

我怀疑是 a) Swift 与 Objective-C API 交互的方式或 b) 我使用“self”错误地声明了新的 scanApi 委托(delegate)应该是什么。

那么，在这种情况下声明新的 scanApi 委托(delegate)的正确方法是什么，或者这是 API 的问题？

Answer 1

当前版本的 ScanApiHelper 不支持多个委托(delegate) View ，但 future 的版本会支持。如果您想将它添加到项目中的 ScanApiHelper，这是我们所做的修改。

注意:更改是向后兼容的，因此您可以安全地应用这些更改或在发布时升级到最新版本的 ScanApiHelper，即使您不需要支持多个委托(delegate) View 也是如此

ScanApiHelper.h

Index: ScanApiHelper.h
===================================================================
--- ScanApiHelper.h (revision 12778)
+++ ScanApiHelper.h (revision 12779)
@@ -65,6 +65,7 @@
 @end

 @protocol ScanApiHelperDelegate <NSObject>
+@optional
 /**
  * called each time a device connects to the host
  * @param result contains the result of the connection
@@ -103,7 +104,6 @@
  */
 -(void) onErrorRetrievingScanObject:(SKTRESULT) result;

-@optional
 /**
  * called each time ScanAPI receives decoded data from scanner
  * @param result is ESKT_NOERROR when decodedData contains actual
@@ -179,9 +179,15 @@
     id<ISktScanApi>_scanApi;
     id<ISktScanObject>_scanObjectReceived;
     NSObject* _commandContextsLock;
+    BOOL _shared;// to indicate when ScanApiHelper is shared across multiple views
+    NSMutableArray* _delegateStack;
 }

++(ScanApiHelper*)sharedScanApiHelper;

+-(void)pushDelegate:(id<ScanApiHelperDelegate>)delegate;
+-(void)popDelegate:(id<ScanApiHelperDelegate>)delegate;
+
 /**
  * register for notifications in order to receive notifications such as
  * "Device Arrival", "Device Removal", "Decoded Data"...etc...

ScanApiHelper.mm

Index: ScanApiHelper.mm
===================================================================
--- ScanApiHelper.mm    (revision 12778)
+++ ScanApiHelper.mm    (revision 12779)
@@ -105,12 +105,16 @@
 @implementation ScanApiHelper

 -(id)init{
+    static ScanApiHelper* sharedScanApiHelper=nil;
     self=[super init];
     if(self!=nil){
+        sharedScanApiHelper=self;
         _commandContextsLock=[[NSObject alloc]init];
         _deviceInfoList=[[NSMutableDictionary alloc]init];
         _scanApiOpen=FALSE;
         _scanApiTerminated=TRUE;// by default ScanApi is not started
+        _shared=NO;
+        _delegateStack=[[NSMutableArray alloc]init];
     }
     return self;
 }
@@ -130,6 +134,7 @@
     _commandContextsLock=nil;

     _deviceInfoList=nil;
+    _delegateStack=nil;
 }
 #else
 -(void)dealloc{
@@ -151,10 +156,54 @@

     [_deviceInfoList release];
     _deviceInfoList=nil;
+    
+    [_delegateStack release];
+    _delegateStack=nil;
+    
     [super dealloc];
 }
 #endif

++(ScanApiHelper*)sharedScanApiHelper{
+    static ScanApiHelper* scanApiHelper=nil;
+    if(scanApiHelper==nil){
+        scanApiHelper=[[ScanApiHelper alloc]init];
+        scanApiHelper->_shared=YES;
+    }
+    return scanApiHelper;
+}
+
+-(void)pushDelegate:(id<ScanApiHelperDelegate>)delegate{
+    if(_delegate != delegate){
+        if(_delegate!=nil){
+            [_delegateStack addObject:_delegate];
+        }
+        _delegate=delegate;
+        [self generateDeviceArrivals];
+    }
+}
+
+-(void)popDelegate:(id<ScanApiHelperDelegate>)delegate{
+    if(_delegate ==delegate){
+        if(_delegateStack.count>0){
+            id<ScanApiHelperDelegate> newDelegate=[_delegateStack objectAtIndex:_delegateStack.count-1];
+            [_delegateStack removeLastObject];
+            _delegate = newDelegate;
+            // generate a device Arrival for each scanner we've already receive
+            // so that the new view can be aware of the connected scanners
+            if(_delegate!=nil){
+                for (NSString* key in _deviceInfoList) {
+                    DeviceInfo* device=[_deviceInfoList objectForKey:key];
+                    [_delegate onDeviceArrival:ESKT_NOERROR device:device];
+                }
+            }
+        }
+        else{
+            _delegate=nil;
+        }
+    }
+}
+
 /**
  * register for notifications in order to receive notifications such as
  * "Device Arrival", "Device Removal", "Decoded Data"...etc...
@@ -1519,14 +1568,15 @@
 #endif    
     // release the previous ScanAPI object instance if
     // it exists
-    if(_scanApi!=nil){
-        [_scanApi close];
-        [SktClassFactory releaseScanApiInstance:_scanApi];
-    }
     _scanApi=[SktClassFactory createScanApiInstance];
     SKTRESULT result=[_scanApi open:nil];
-    if(_delegate!=nil)
-        [_delegate onScanApiInitializeComplete:result];
+    if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onScanApiInitializeComplete:)])){
+        [_delegate onScanApiInitializeComplete:result];
+    }
     _scanApiTerminated=FALSE;

 #if __has_feature(objc_arc)
@@ -1576,8 +1626,9 @@
             }
         }
         else{
-            if(_delegate!=nil)
+            if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onErrorRetrievingScanObject:)])){
                 [_delegate onErrorRetrievingScanObject:result];
+            }
         }
     }
     return result;
@@ -1600,8 +1651,9 @@
             result=[self handleDeviceRemoval:scanObj];
             break;
         case kSktScanMsgIdTerminate:
-            if(_delegate!=nil)
+            if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onScanApiTerminated)])){
                 [_delegate onScanApiTerminated];
+            }
             closeScanApi=TRUE;
             break;
         case kSktScanMsgSetComplete:
@@ -1619,8 +1671,9 @@

     // if there is an error then report it to the ScanAPIHelper user
     if(!SKTSUCCESS(result)){
-        if(_delegate!=nil)
+        if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onError:)])){
             [_delegate onError:result];
+        }
     }
     return closeScanApi;
 }
@@ -1657,8 +1710,9 @@
     }

     // notify the ScanApiHelper user a scanner has connected to this host
-    if(_delegate!=nil)
+    if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onDeviceArrival:device:)])){
         [_delegate onDeviceArrival:result device:deviceInfo];
+    }

 #if __has_feature(objc_arc)
 #else 
@@ -1702,8 +1756,9 @@
     [SktClassFactory releaseDeviceInstance:scanDevice];

     // notify the ScanApiHelper user a scanner has connected to this host
-    if(_delegate!=nil)
+    if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onDeviceRemoval:)])){
         [_delegate onDeviceRemoval:deviceInfo];
+    }

     return result;
 }
@@ -1766,7 +1821,7 @@
             result=[self handleDecodedData:scanObj];
             break;
         case kSktScanEventError:
-            if(_delegate!=nil)
+            if((_delegate!=nil)&&([_delegate respondsToSelector:@selector(onError:)]))
                 [_delegate onError:[[scanObj Msg]Result]];
             break;

@@ -1809,6 +1864,7 @@
     return result;
 }

 /**
  * sendNextCommand
  *
@@ -1855,4 +1911,25 @@
     return result;
 }

+/**
+ *  generateDeviceArrivals
+ *
+ *  internal function to generate device
+ *  arrival notifications when the delegate
+ *  change to a new delegate.
+ *  This is used in a multi views application
+ *  that has more than one view to receive the
+ *  decoded data
+ */
+-(void)generateDeviceArrivals{
+    // generate a device Arrival for each scanner we've already receive
+    // so that the new view can be aware of the connected scanners
+    if(_delegate!=nil){
+        for (NSString* key in _deviceInfoList) {
+            DeviceInfo* device=[_deviceInfoList objectForKey:key];
+            [_delegate onDeviceArrival:ESKT_NOERROR device:device];
+        }
+    }
+}
+
 @end