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Weex Android SDK原始碼分析

阿新 • • 發佈：2019-02-18

前言

最近開始試水Weex開發，使用這麼長一段時間，感覺寫Weex還是非常方便的。作為一個Android開發，免不了要追查一下weex的sdk原始碼。今天，就以Weex SDK for Android為例，分析SDK的

認識Weex SDK

整體分析下拉，按照js檔案的渲染過程，繪製出了下面架構圖：

sdk_framework

WEEX檔案渲染過程

為了更加詳細的說明整個渲染過程，我對原始碼進行了分析。並結合示例，進行了日誌分析；比如，我們要開發如下一個簡單的元件(紅色方框內)：
demo

那麼，我們的wxc-title.we原始碼為：

<!-- wxc-title.we created by mochuan.zhb-->
 

<template>
    <div class="container">
        <image class="image" src="{{item.pic}}"></image>
        <text class="text">{{item.name}}</text>
    </div>
</template>

<style>
    .container {
        position: relative;
        flex-direction: row;
        width
 
: 750px;
        height: 60px;
        align-items: center;
    }
    .image {
        margin-left: 100px;
        width: 45px;
        height: 45px;
    }
    .text {
        margin-left: 10px;
        font-size: 28px;
        color: #444444;
    }
</style>

<script>
    module.exports = {
        data: {
            item: {
                pic: '//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png'
 
,
                name: '當地玩樂'
            }
        },
        methods: {

        }
    }
</script>

上述.we檔案經過weex編譯之後，生成的js檔案，經過格式化如下：

...
([function (module, exports) {
    module.exports = {
        "type": "div",
        "classList": [
            "container"
        ],
        "children": [
            {
                "type": "image",
                "classList": [
                    "image"
                ],
                "attr": {
                    "src": function () {
                        return this.item.pic
                    }
                }
            },
            {
                "type": "text",
                "classList": [
                    "text"
                ],
                "attr": {
                    "value": function () {
                        return this.item.name
                    }
                }
            }
        ]
    }
}, function (module, exports) {

    module.exports = {
        "container": {
            "position": "relative",
            "flexDirection": "row",
            "width": 750,
            "height": 60,
            "alignItems": "center"
        },
        "image": {
            "marginLeft": 100,
            "width": 45,
            "height": 45
        },
        "text": {
            "marginLeft": 10,
            "fontSize": 28,
            "color": "#444444"
        }
    }
}, function (module, exports) {
        module.exports = function (module, exports, __weex_require__) {
            'use strict';
            module.exports = {
                data: function () {
                    return {
                        item: {
                            pic: '//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png',
                            name: '當地玩樂'
                        }
                    }
                },
                methods: {}
            };
        }
    }
]);

上述分別使用了三個function，對template、style和script進行了封裝；那麼，這個檔案是怎麼被weex sdk執行並解析，最終生成結構化的View的呢？

渲染過程

時序圖1：

從掃碼開始，首先經歷如下過程；依次經過readerPage，createInstance，一直到WXBridge的exeJs方法；也就是說，最終，Java通過呼叫native的exeJs方法，來執行js檔案的。

https://img.alicdn.com/tps/TB1CKC.OFXXXXXkXpXXXXXXXXXX-2530-840.png

時序圖2：

緊接著時序圖1：執行到JNI層的Java_com_taobao_weex_bridge_WXBridge_execJS方法;

https://img.alicdn.com/tps/TB1K2uBOFXXXXbnaXXXXXXXXXXX-2374-1352.png

然後js通過native呼叫WXBridge的callNative方法，達到js呼叫Java程式碼的目的；
JNI層的部分程式碼如下：

jint Java_com_taobao_weex_bridge_WXBridge_execJS(JNIEnv *env, jobject this1, jstring jinstanceid,
                                                 jstring jnamespace, jstring jfunction,
                                                 jobjectArray jargs) {

    v8::HandleScope handleScope;
    v8::Isolate::Scope isolate_scope(globalIsolate);
    v8::Context::Scope ctx_scope(V8context);
    v8::TryCatch try_catch;
    int length = env->GetArrayLength(jargs);
    v8::Handle<v8::Value> obj[length];

    jclass jsObjectClazz = (env)->FindClass("com/taobao/weex/bridge/WXJSObject");
    for (int i = 0; i < length; i++) {
        jobject jArg = (env)->GetObjectArrayElement(jargs, i);

        jfieldID jTypeId = (env)->GetFieldID(jsObjectClazz, "type", "I");
        jint jTypeInt = env->GetIntField(jArg, jTypeId);

        jfieldID jDataId = (env)->GetFieldID(jsObjectClazz, "data", "Ljava/lang/Object;");
        jobject jDataObj = env->GetObjectField(jArg, jDataId);
        if (jTypeInt == 1) {
            jclass jDoubleClazz = (env)->FindClass("java/lang/Double");
            jmethodID jDoubleValueId = (env)->GetMethodID(jDoubleClazz, "doubleValue", "()D");
            jdouble jDoubleObj = (env)->CallDoubleMethod(jDataObj, jDoubleValueId);
            obj[i] = v8::Number::New((double) jDoubleObj);
            env->DeleteLocalRef(jDoubleClazz);
        } else if (jTypeInt == 2) {
            jstring jDataStr = (jstring) jDataObj;
            obj[i] = jString2V8String(env, jDataStr);
        } else if (jTypeInt == 3) {
            v8::Handle<v8::Value> jsonObj[1];
            v8::Handle<v8::Object> global = V8context->Global();
            json = v8::Handle<v8::Object>::Cast(global->Get(v8::String::New("JSON")));
            json_parse = v8::Handle<v8::Function>::Cast(json->Get(v8::String::New("parse")));
            jsonObj[0] = jString2V8String(env, (jstring) jDataObj);
            v8::Handle<v8::Value> ret = json_parse->Call(json, 1, jsonObj);
            obj[i] = ret;
        }
        env->DeleteLocalRef(jDataObj);
        env->DeleteLocalRef(jArg);
    }
    env->DeleteLocalRef(jsObjectClazz);

    const char *func = (env)->GetStringUTFChars(jfunction, 0);
    v8::Handle<v8::Object> global = V8context->Global();
    v8::Handle<v8::Function> function;
    v8::Handle<v8::Value> result;
    if (jnamespace == NULL) {
        function = v8::Handle<v8::Function>::Cast(global->Get(v8::String::New(func)));
        result = function->Call(global, length, obj);
    }
    else {
        v8::Handle<v8::Object> master = v8::Handle<v8::Object>::Cast(
                global->Get(jString2V8String(env,jnamespace)));
        function = v8::Handle<v8::Function>::Cast(
                master->Get(jString2V8String(env,jfunction)));
        result = function->Call(master, length, obj);
    }
    if (result.IsEmpty()) {
        assert(try_catch.HasCaught());
        ReportException(globalIsolate, &try_catch, jinstanceid, func);
        env->ReleaseStringUTFChars(jfunction, func);
        env->DeleteLocalRef(jfunction);
        return false;
    }
    env->ReleaseStringUTFChars(jfunction, func);
    env->DeleteLocalRef(jfunction);
    return true;
}
}

時序圖3：createBody&generateComponentTree

接著上面的時序圖，開始做頁面的建立；關鍵的程式碼在WXRenderStatement中的createBodyOnDomThread，該方法通過建立跟佈局的mGodComponent,通過遞迴generateComponentTree生成Component的邏輯樹結構;然後，在WXRenderStatement的createBody方法中，生成View，繫結屬性和資料；具體如下圖所示：

https://img.alicdn.com/tps/TB1OTG7OFXXXXbYXpXXXXXXXXXX-2528-1184.png

時序圖4：addElement


https://img.alicdn.com/tps/TB1xVe5OFXXXXc3XpXXXXXXXXXX-2508-1002.png

時序圖5：callNative呼叫Module


https://img.alicdn.com/tps/TB1MSi4OFXXXXb9XpXXXXXXXXXX-1438-860.png

呼叫過程日誌記錄

以上面的weex頁面為例：使用PlayGround掃碼之後的呼叫過程中的日誌為：

12-04 15:51:04.705: D/weex(30188): ###render in WXSDKInstance. pageName = WXPageActivity,template = /******/ (function(modules) { // webpackBootstrap
12-04 15:51:04.705: D/weex(30188): ###createInstance in WXSDKManager code = /******/ (function(modules) { // webpackBootstrap
12-04 15:51:04.710: D/weex(30188): ###createInstance in WXBrideManager instanceId = 3,template = /******/ (function(modules) { // webpackBootstrap
12-04 15:51:04.710: D/weex(30188): ###invokeCreateInstance in WXBrideManager instanceId = 3,template = /******/ (function(modules) { // webpackBootstrap
12-04 15:51:04.725: D/weex(30188): ###execJS instanceId = 3,namespace = null,function = createInstance,args = [{"data":"3","type":2},{"data":"/******/ (function(modules) { // webpackBootstrap\n .......
12-04 15:51:04.740: D/weex(30188): ###callNative in WXBridge instanceId = 3,tasks = [{"module":"dom","method":"createBody","args":[{"ref":"_root","type":"div","attr":{},"style":{"position":"relative","flexDirection":"row","width":750,"height":60,"alignItems":"center"}}]}],callback = -1
12-04 15:51:04.740: D/weex(30188): ###callDomMethod to create component...task = {"args":[{"attr":{},"ref":"_root","style":{"alignItems":"center","flexDirection":"row","height":60,"position":"relative","width":750},"type":"div"}],"method":"createBody","module":"dom"}
12-04 15:51:04.745: D/weex(30188): ###callDomMethod task = {"args":[{"attr":{},"ref":"_root","style":{"alignItems":"center","flexDirection":"row","height":60,"position":"relative","width":750},"type":"div"}],"method":"createBody","module":"dom"}
12-04 15:51:04.745: D/weex(30188): ###createBody element = {"attr":{},"ref":"_root","style":{"alignItems":"center","flexDirection":"row","height":60,"position":"relative","width":750},"type":"div"}
12-04 15:51:04.745: D/weex(30188): ###handleMessage in WXDomHandler...what = 0,obj = {"args":[{"attr":{},"ref":"_root","style":{"alignItems":"center","flexDirection":"row","height":60,"position":"relative","width":750},"type":"div"}],"instanceId":"3"}
12-04 15:51:04.750: D/weex(30188): ###createBodyOnDomThread in WXRenderStatement dom = layout: {left: 0.0, top: 0.0, width: 0.0, height: 0.0, direction: LTR}direction =INHERIT
12-04 15:51:04.750: D/weex(30188): ###createView in WXComponent className = WXDiv
12-04 15:51:04.755: D/weex(30188): ###generateComponentTree in WXRenderStatement component = WXDiv
12-04 15:51:04.755: D/weex(30188): ###callAddElement in WXBridge instanceId = 3,ref = _root,dom = {"ref":"153","type":"image","attr":{"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"},"style":{"marginLeft":100,"width":45,"height":45}},index=-1,callback = -1
12-04 15:51:04.755: D/weex(30188): ###callAddElement in WXBridgeManager instanceId = 3,ref = _root,dom = {"ref":"153","type":"image","attr":{"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"},"style":{"marginLeft":100,"width":45,"height":45}},index = -1,callback = -1
12-04 15:51:04.760: D/weex(30188): ###addElement parentRef = _root,element = {"attr":{"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"},"ref":"153","style":{"height":45,"marginLeft":100,"width":45},"type":"image"},index = -1
12-04 15:51:04.760: D/weex(30188): ###handleMessage in WXDomHandler...what = 3,obj = {"args":["_root",{"attr":{"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"},"ref":"153","style":{"height":45,"marginLeft":100,"width":45},"type":"image"},-1],"instanceId":"3"}
12-04 15:51:04.760: D/weex(30188): ###callAddElement in WXBridge instanceId = 3,ref = _root,dom = {"ref":"154","type":"text","attr":{"value":"當地玩樂"},"style":{"marginLeft":10,"fontSize":28,"color":"#444444"}},index=-1,callback = -1
12-04 15:51:04.765: D/weex(30188): ###callAddElement in WXBridgeManager instanceId = 3,ref = _root,dom = {"ref":"154","type":"text","attr":{"value":"當地玩樂"},"style":{"marginLeft":10,"fontSize":28,"color":"#444444"}},index = -1,callback = -1
12-04 15:51:04.765: D/weex(30188): ###addElement parentRef = _root,element = {"attr":{"value":"當地玩樂"},"ref":"154","style":{"color":"#444444","fontSize":28,"marginLeft":10},"type":"text"},index = -1
12-04 15:51:04.765: D/weex(30188): ###addDom in WXDomManager instanceId = 3,parentRef = _root,element = {"attr":{"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"},"ref":"153","style":{"height":45,"marginLeft":100,"width":45},"type":"image"},index = -1
12-04 15:51:04.765: D/weex(30188): ###callNative in WXBridge instanceId = 3,tasks = [{"module":"dom","method":"createFinish","args":[]}],callback = -1
12-04 15:51:04.770: D/weex(30188): ###addDom in WXDomStatement dom = {"attr":{"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"},"ref":"153","style":{"height":45,"marginLeft":100,"width":45},"type":"image"},parentRef = _root,index = -1
12-04 15:51:04.770: D/weex(30188): ###createComponentOnDomThread in WXRenderManager dom = layout: {left: 0.0, top: 0.0, width: 0.0, height: 0.0, direction: LTR}direction =INHERIT
12-04 15:51:04.770: D/weex(30188): ###createComponentOnDomThread in WXRenderStatement dom = layout: {left: 0.0, top: 0.0, width: 0.0, height: 0.0, direction: LTR}direction =INHERIT
12-04 15:51:04.770: D/weex(30188): ###generateComponentTree in WXRenderStatement component = WXImage
12-04 15:51:04.775: D/weex(30188): ###callDomMethod to create component...task = {"args":[],"method":"createFinish","module":"dom"}
12-04 15:51:04.775: D/weex(30188): ###handleMessage in WXDomHandler...what = 255,obj = null
12-04 15:51:04.775: D/weex(30188): ###callDomMethod task = {"args":[],"method":"createFinish","module":"dom"}
12-04 15:51:04.775: D/weex(30188): ###createFinish
12-04 15:51:04.775: D/weex(30188): ###handleMessage in WXDomHandler...what = 3,obj = {"args":["_root",{"attr":{"value":"當地玩樂"},"ref":"154","style":{"color":"#444444","fontSize":28,"marginLeft":10},"type":"text"},-1],"instanceId":"3"}
12-04 15:51:04.775: D/weex(30188): ###addDom in WXDomManager instanceId = 3,parentRef = _root,element = {"attr":{"value":"當地玩樂"},"ref":"154","style":{"color":"#444444","fontSize":28,"marginLeft":10},"type":"text"},index = -1
12-04 15:51:04.780: D/weex(30188): ###addDom in WXDomStatement dom = {"attr":{"value":"當地玩樂"},"ref":"154","style":{"color":"#444444","fontSize":28,"marginLeft":10},"type":"text"},parentRef = _root,index = -1
12-04 15:51:04.780: D/weex(30188): ###createComponentOnDomThread in WXRenderManager dom = layout: {left: 0.0, top: 0.0, width: 0.0, height: 0.0, direction: LTR}direction =INHERIT
12-04 15:51:04.780: D/weex(30188): ###createComponentOnDomThread in WXRenderStatement dom = layout: {left: 0.0, top: 0.0, width: 0.0, height: 0.0, direction: LTR}direction =INHERIT
12-04 15:51:04.785: D/weex(30188): ###generateComponentTree in WXRenderStatement component = WXText
12-04 15:51:04.785: D/weex(30188): ###handleMessage in WXDomHandler...what = 9,obj = {"instanceId":"3"}
12-04 15:51:04.790: D/weex(30188): ###handleMessage in WXDomHandler...what = 255,obj = null
12-04 15:51:04.820: D/weex(30188): ###createBody in WXRenderStatement component = WXDiv
12-04 15:51:04.820: D/weex(30188): ###createView in WXComponent className = WXDiv
12-04 15:51:04.820: D/weex(30188): ###applyLayoutAndEvent in WXComponent className = WXDiv
12-04 15:51:04.825: D/weex(30188): ###bindData in WXContainer 
12-04 15:51:04.825: D/weex(30188): ###bindData in WXComponent = WXDiv
12-04 15:51:04.825: D/weex(30188): ###updateProperties in props = {"alignItems":"center","backgroundColor":"#ffffff","flexDirection":"row","height":60,"position":"relative","width":750}
12-04 15:51:04.825: D/weex(30188): ###setProperty in WXComponent = WXDiv
12-04 15:51:04.825: D/weex(30188): ###setProperty in WXComponent = WXDiv
12-04 15:51:04.825: D/weex(30188): ###setProperty in WXComponent = WXDiv
12-04 15:51:04.825: D/weex(30188): ###setProperty in WXComponent = WXDiv
12-04 15:51:04.825: D/weex(30188): ###setProperty in WXComponent = WXDiv
12-04 15:51:04.830: D/weex(30188): ###setProperty in WXComponent = WXDiv
12-04 15:51:04.830: D/weex(30188): ###updateProperties in props = {}
12-04 15:51:04.830: D/weex(30188): ###addComponent in WXRenderManager instanceId = 3,component = WXImage,parentRef = _root,index = -1
12-04 15:51:04.830: D/weex(30188): ###addComponent in WXRenderStatement to start render the component to view...
12-04 15:51:04.835: D/weex(30188): ###createView in WXComponent className = WXImage
12-04 15:51:04.835: D/weex(30188): ###applyLayoutAndEvent in WXComponent className = WXImage
12-04 15:51:04.835: D/weex(30188): ###bindData in WXComponent = WXImage
12-04 15:51:04.835: D/weex(30188): ###updateProperties in props = {"height":45,"marginLeft":100,"width":45}
12-04 15:51:04.835: D/weex(30188): ###setProperty in WXComponent = WXImage
12-04 15:51:04.835: D/weex(30188): ###setProperty in WXComponent = WXImage
12-04 15:51:04.835: D/weex(30188): ###setProperty in WXComponent = WXImage
12-04 15:51:04.840: D/weex(30188): ###updateProperties in props = {"src":"//img.alicdn.com/tfs/TB1AEcQNXXXXXX8XXXXXXXXXXXX-50-50.png"}
12-04 15:51:04.840: D/weex(30188): ###addComponent in WXRenderManager instanceId = 3,component = WXText,parentRef = _root,index = -1
12-04 15:51:04.840: D/weex(30188): ###addComponent in WXRenderStatement to start render the component to view...
12-04 15:51:04.840: D/weex(30188): ###createView in WXComponent className = WXText
12-04 15:51:04.840: D/weex(30188): ###applyLayoutAndEvent in WXComponent className = WXText
12-04 15:51:04.840: D/weex(30188): ###bindData in WXComponent = WXText
12-04 15:51:04.840: D/weex(30188): ###updateProperties in props = {"color":"#444444","fontSize":28,"marginLeft":10}
12-04 15:51:04.845: D/weex(30188): ###setProperty in WXComponent = WXText
12-04 15:51:04.845: D/weex(30188): ###updateProperties in props = {"value":"當地玩樂"}
12-04 15:51:04.850: D/weex(30188): ###execJS instanceId = 3,namespace = null,function = callJS,args = [{"data":"3","type":2},{"data":"[{\"args\":[\"_root\",\"viewappear\",null,null],\"method\":\"fireEvent\"}]","type":3}]
12-04 15:51:04.850: D/weex(30188): ###callNative in WXBridge instanceId = 3,tasks = [{"module":"dom","method":"updateFinish","args":[]}],callback = -1
12-04 15:51:04.855: D/weex(30188): ###callDomMethod to create component...task = {"args":[],"method":"updateFinish","module":"dom"}
12-04 15:51:04.855: D/weex(30188): ###callDomMethod task = {"args":[],"method":"updateFinish","module":"dom"}
12-04 15:51:04.855: D/weex(30188): ###updateFinish
12-04 15:51:04.860: D/weex(30188): ###handleMessage in WXDomHandler...what = 11,obj = {"instanceId":"3"}
12-04 15:51:04.875: D/weex(30188): ###handleMessage in WXDomHandler...what = 255,obj = null

View繪製過程對比

首先，我們看一下Android原聲的View繪製過程：
android_view

主要是measure測量大小，layout確定位置。

其次，我們對比一下Weex的WXComponent的測量和佈局過程；


主要是通過CSSLayout進行測量，使用view的setLayoutParams來確定View在父ViewGroup中的位置。

核心程式碼如下：


        Spacing parentPadding = mParent.getDomObject().getPadding();
        Spacing parentBorder = mParent.getDomObject().getBorder();
        Spacing margin = mDomObj.getMargin();
        int realWidth = (int) mDomObj.getLayoutWidth();
        int realHeight = (int) mDomObj.getLayoutHeight();
        int realLeft = (int) (mDomObj.getLayoutX() - parentPadding.get(Spacing.LEFT) -
                parentBorder.get(Spacing.LEFT));
        int realTop = (int) (mDomObj.getLayoutY() - parentPadding.get(Spacing.TOP) -
                parentBorder.get(Spacing.TOP));
        int realRight = (int) margin.get(Spacing.RIGHT);
        int realBottom = (int) margin.get(Spacing.BOTTOM);

        if (mPreRealWidth == realWidth && mPreRealHeight == realHeight && mPreRealLeft == realLeft && mPreRealTop == realTop) {
            return;
        }

        if (mParent != null) {
            mAbsoluteY = (int) (mParent.mAbsoluteY + mDomObj.getLayoutY());
            mAbsoluteX = (int) (mParent.mAbsoluteX + mDomObj.getLayoutX());
        }

        //calculate first screen time

        if (!mInstance.mEnd && !(mHost instanceof ViewGroup) && mAbsoluteY + realHeight > mInstance.getWeexHeight() + 1) {
            mInstance.firstScreenRenderFinished();
        }

        if (mHost == null) {
            return;
        }

        MeasureOutput measureOutput = measure(realWidth, realHeight);
        realWidth = measureOutput.width;
        realHeight = measureOutput.height;

        if (mHost instanceof WXCircleIndicator) {
            FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(realWidth, realHeight);
            params.setMargins(realLeft, realTop, realRight, realBottom);
            mHost.setLayoutParams(params);
            return;
        }

        //fixed style
        if (mDomObj.isFixed() && mInstance.getRootView() != null) {
            if (mHost.getParent() instanceof ViewGroup) {
                ViewGroup viewGroup = (ViewGroup) mHost.getParent();
                viewGroup.removeView(mHost);
            }
            FrameLayout.LayoutParams params

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