Native回撥JS

流程圖

解析

• Native
  Native方法執行完，通過sendPluginResult開始，回撥結果給js

  • sendPluginResult:

    - (void)sendPluginResult:(CDVPluginResult*)result callbackId:(NSString*)callbackId
    {
        int status = [result.status intValue];
        BOOL keepCallback = [result.keepCallback boolValue];
        NSString* argumentsAsJSON = [result argumentsAsJSON];
        BOOL
     
     debug = NO;
    
        NSString* js = [NSString stringWithFormat:@"cordova.require('cordova/exec').nativeCallback('%@',%d,%@,%d, %d)", callbackId, status, argumentsAsJSON, keepCallback, debug];
    
        [self evalJsHelper:js];
    }

  • evalJsHelper:
    執行JS，這裡的流程跟JS調Native執行JS一模一樣的程式碼，利用UIWebView-stringByEvaluatingJavaScriptFromString:

    方法執行JS

    - (void)evalJsHelper2:(NSString*)js
    {
        [_viewController.webViewEngine evaluateJavaScript:js completionHandler:^(id obj, NSError* error) {
            // TODO: obj can be something other than string
            if ([obj isKindOfClass:[NSString class]]) {
                NSString* commandsJSON = (NSString
     
    *)obj;
                if ([commandsJSON length] > 0) {
                    CDV_EXEC_LOG(@"Exec: Retrieved new exec messages by chaining.");
                }
    
                [_commandQueue enqueueCommandBatch:commandsJSON];
                [_commandQueue executePending];
            }
        }];
    }

    • 其執行回撥裡仍然有處理命令佇列的程式碼

• JS

  • nativeCallback
    這一步，並不是直接就回調結束了，還會通過nativeEvalAndFetch-nativeFetchMessages返回當前的commandQueue裡的內容，會到前一步evaluateJavaScript執行結束的回撥中，直到全部執行結束。觸發cordova.callbackFromNative

    iOSExec.nativeCallback = function(callbackId, status, message, keepCallback, debug) {
        return iOSExec.nativeEvalAndFetch(function() {
            var success = status === 0 || status === 1;
            var args = convertMessageToArgsNativeToJs(message);
            function nc2() {
                cordova.callbackFromNative(callbackId, success, status, args, keepCallback);
            }
            setTimeout(nc2, 0);
        });
    };

  • callbackFromNative
    這裡的原始碼註釋也非常清楚了，根據Native返回的結果進行回撥處理

    /**
    * Called by native code when returning the result from an action.
    */
    callbackFromNative: function(callbackId, isSuccess, status, args, keepCallback) {
        try {
            var callback = cordova.callbacks[callbackId];
            if (callback) {
                if (isSuccess && status == cordova.callbackStatus.OK) {
                    callback.success && callback.success.apply(null, args);
                } else if (!isSuccess) {
                    callback.fail && callback.fail.apply(null, args);
                }
                /*
                else
                    Note, this case is intentionally not caught.
                    this can happen if isSuccess is true, but callbackStatus is NO_RESULT
                    which is used to remove a callback from the list without calling the callbacks
                    typically keepCallback is false in this case
                */
                // Clear callback if not expecting any more results
                if (!keepCallback) {
                    delete cordova.callbacks[callbackId];
                }
            }
        }
        catch (err) {
            // ...
        }
    }

其他補充

• CDVViewController

  • 看構成，就知道CDVViewController是作為一個功能整合的類，這裡麵包含的命令佇列、協議代理，在上面都已經有涉及
  • 內部主要初始化外掛、配置、設定代理、處理生命週期
    

    @interface CDVViewController : UIViewController <CDVScreenOrientationDelegate>{
        @protected
        id <CDVWebViewEngineProtocol> _webViewEngine;
        @protected
        id <CDVCommandDelegate> _commandDelegate;
        @protected
        CDVCommandQueue* _commandQueue;
        NSString* _userAgent;
    }

• CDVUIWebViewEngine:CDVPlugin 以外掛的形式實現

  • 成員變數engineWebView，建立webview，賦值engineWebView
  • pluginInitialize，初始化外掛，設定代理。CDVUIWebViewNavigationDelegate代理在此處設定