1、無JsBridge.
- js如果要調用java(native、也說原生)方法:則java必須實現js接口供掛載在window對象上供js來執行。
這裏簡單的可以只調用,調用後java端什麼也不做。複雜的調用可以是js調用了java端,然後java用loadUrl("javascript:")繼續調用js,這裏的調用可以是上一個js調用java的回調,也可以是一個純js,也可以是下一個js調用java。
- java調用js就簡單多了,都是用的loadUrl("javascript:XXX")。這裏也可以在js串加入調用java作爲回調。
2、基於JsBridge
- java(native)調用js,方法還是loadUrl,但是jsbridge在這個基礎上封裝了下,封裝成了callHandler(String handlerName, String data, CallBackFunction callBack)
- js調用java就不用接口了,而是使用一個隱藏的iframe。通過變更src路徑,java端webview上攔截這個變更來實現js調用java.
example:
webView.callHandler("functionInJs", "data from Java",
new CallBackFunction() {
@Override
public void onCallBack(String data) {
// TODO Auto-generated method stub
Log.i(TAG, "reponse data from js " + data);
}
});
這裏三個參數,第三個是作爲回調的,成功後會調用這個對象裏的onCallBack方法。
public void callHandler(String handlerName, String data, CallBackFunction callBack) {
doSend(handlerName, data, callBack);
}
直接跳到doSend方法
private void doSend(String handlerName, String data, CallBackFunction responseCallback) {
Message m = new Message();
if (!TextUtils.isEmpty(data)) {
m.setData(data);
}
if (responseCallback != null) {
String callbackStr = String.format(BridgeUtil.CALLBACK_ID_FORMAT, ++uniqueId + (BridgeUtil.UNDERLINE_STR + SystemClock.currentThreadTimeMillis()));
responseCallbacks.put(callbackStr, responseCallback); //responseCallbacks數組存回調對象
m.setCallbackId(callbackStr); //數據塞在message對象中
}
if (!TextUtils.isEmpty(handlerName)) { //handler不爲空就把他設置給message對象
m.setHandlerName(handlerName);
}
queueMessage(m);
}
創建message對象並queueMessage處理, 回調對象入responseCallbacks(Map) private void queueMessage(Message m) {
if (startupMessage != null) { //startupMessage不爲空的時候
startupMessage.add(m);//message對象加入列表
} else {
dispatchMessage(m); //這裏派遣(發出)信息--向js
}
}
這裏startupMessage是否爲空呢?看這裏:@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
if (toLoadJs != null) {
BridgeUtil.webViewLoadLocalJs(view, toLoadJs);
}
//
if (startupMessage != null) {
for (Message m : startupMessage) {
dispatchMessage(m);
}
startupMessage = null;
}
}
這個方法是在webview加載完後執行,必然會把startupMessage置爲null,那麼到了
dispatchMessage這個方法... 英文意思是派遣消息,是?
private void dispatchMessage(Message m) {
String messageJson = m.toJson();
//escape special characters for json string
messageJson = messageJson.replaceAll("(\\\\)([^utrn])", "\\\\\\\\$1$2");
messageJson = messageJson.replaceAll("(?<=[^\\\\])(\")", "\\\\\"");
// JS_HANDLE_MESSAGE_FROM_JAVA=="javascript:WebViewJavascriptBridge._handleMessageFromNative('%s');"
//javascriptCommand==javascript:WebViewJavascriptBridge._handleMessageFromNative('{\"data\":\"data from Java\",\"handlerName\":\"functionInJs\",\"callbackId\":\"JAVA_CB_3_2640\"}');
String javascriptCommand = String.format(BridgeUtil.JS_HANDLE_MESSAGE_FROM_JAVA, messageJson);
if (Thread.currentThread() == Looper.getMainLooper().getThread()) {
this.loadUrl(javascriptCommand); //java這裏主線程執行js
}
}
把message對象轉爲json處理,BridgeUtil裏面聲明瞭final static String JS_HANDLE_MESSAGE_FROM_JAVA = "javascript:WebViewJavascriptBridge._handleMessageFromNative('%s');"; 最終處理後需要loadUrl的字符串如上,我們可以知道最終會調用_handleMessageFromNative方法處理,並帶上json串:{\"data\":\"data
from Java\",\"handlerName\":\"functionInJs\",\"callbackId\":\"JAVA_CB_3_2640\"},現在來看這個js方法:
// 提供給native調用,receiveMessageQueue 在會在頁面加載完後賦值爲null,所以
function _handleMessageFromNative(messageJSON) {
if (receiveMessageQueue) {
receiveMessageQueue.push(messageJSON);
} else {
_dispatchMessageFromNative(messageJSON);
}
}
作者提供的代碼說了,這個跟startMessage一樣,receiveMessageQueue會在頁面加載完後置爲null.繼續_dispatchMessageFromNative
// 提供給native使用,
function _dispatchMessageFromNative(messageJSON) { //native -doSend..後loadUrl(js這個方法)-獲取json數據
setTimeout(function() {
var message = JSON.parse(messageJSON);
var responseCallback;
// java call finished, now need to call js callback function
if (message.responseId) { //沒有responseId to else
responseCallback = responseCallbacks[message.responseId];
if (!responseCallback) {
return;
}
responseCallback(message.responseData);
delete responseCallbacks[message.responseId];
} else {
// 直接發送
if (message.callbackId) {
var callbackResponseId = message.callbackId;
responseCallback = function(responseData) {
_doSend({
responseId : callbackResponseId, //響應javaId:JAVA_CB_3_2640
responseData : responseData
});
};
}
var handler = WebViewJavascriptBridge._messageHandler;
if (message.handlerName) {
handler = messageHandlers[message.handlerName];//handler名是functionJs
}
// 查找指定handler
try {
handler(message.data, responseCallback);
} catch (exception) {
if (typeof console != 'undefined') {
console
.log(
"WebViewJavascriptBridge: WARNING: javascript handler threw.",
message, exception);
}
}
}
});
}
上面的加了註釋不難理解,有2句解釋下:
handler = messageHandlers[message.handlerName];//handler名是functionJs
這裏jsbridge在啓動的時候有這段:
bridge.registerHandler("functionInJs", function (data, responseCallback) {
document.getElementById("show").innerHTML = ("data from Java: = " + data);
var responseData = "Javascript Says Right back aka!";
responseCallback(responseData);
});
這裏會註冊這個functioinJs方法:所以上面獲得的是這裏定義的方法.所以後面的
handler(message.data, responseCallback);
data就是前面java裏面封裝的data,responseCallBack是上面的responseCallback = function(responseData) {
_doSend({
responseId : callbackResponseId, //響應javaId:JAVA_CB_3_2640
responseData : responseData
});
};
他是作爲數據在id爲show的div上顯示數據後要回調的方法。現在數據顯示出來了,我們知道了,這裏的responseId,responseData是上面的一個 var responseData = "Javascript Says Right back aka!";
轉到_doSend方法:
// sendMessage add message, 觸發native處理 sendMessage
function _doSend(message, responseCallback) {
if (responseCallback) {
var callbackId = 'cb_' + (uniqueId++) + '_' + new Date().getTime();
responseCallbacks[callbackId] = responseCallback;//這裏在js端存儲JAVA_CB_3_2640作爲js callbackId的屬性
message.callbackId = callbackId;//待發送的信息裏面存儲了一個剛纔生成的js callbackId
}
sendMessageQueue.push(message); //把這個message放入sendMessageQueue數組中.
messagingIframe.src = CUSTOM_PROTOCOL_SCHEME + '://'
+ QUEUE_HAS_MESSAGE; //這裏變更iframe的src屬性,這樣會觸發Java端WebViewClient的shouldOverrideUrlLoading方法執行
}
下面轉到shouldOverrideUrlLoading方法.
public boolean shouldOverrideUrlLoading(WebView view, String url) {
try {
url = URLDecoder.decode(url, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
if (url.startsWith(BridgeUtil.YY_RETURN_DATA)) { // 如果是返回數據 _fetchQueue
handlerReturnData(url);
return true;
} else if (url.startsWith(BridgeUtil.YY_OVERRIDE_SCHEMA)) { //第一次 _doSend/////
flushMessageQueue();
return true;
} else {
return super.shouldOverrideUrlLoading(view, url);
}
}
.........................