Javascript 如何将blob从Chrome扩展传递到Chrome应用程序
一点背景 我已经在一个Chrome扩展上工作了几天,该扩展每天多次拍摄给定网页的屏幕截图。我用它作为向导,一切按预期进行 不过,有一个小的需求扩展无法满足。用户必须有权访问保存图像(屏幕截图)的文件夹,但不能访问。另一方面,Chrome应用程序确实如此。因此,在仔细研究之后,我得出结论,我必须创建一个Chrome扩展和一个Chrome应用程序。其想法是,该扩展将创建一个屏幕截图的blob,然后将该blob发送到应用程序,然后应用程序将其作为图像保存到用户指定的位置。这正是我正在做的——我在扩展端创建一个屏幕快照,然后将其发送到应用程序,要求用户选择保存图像的位置 问题 在保存部分,一切都按预期进行。blob在扩展上创建,发送到应用程序,由应用程序接收,询问用户保存位置,并保存图像。。。。这就是事情崩溃的地方生成的图像无法使用。当我试图打开它时,会收到一条消息,上面写着“无法确定类型”。下面是我正在使用的代码:Javascript 如何将blob从Chrome扩展传递到Chrome应用程序,javascript,google-chrome,google-chrome-extension,google-chrome-app,Javascript,Google Chrome,Google Chrome Extension,Google Chrome App,一点背景 我已经在一个Chrome扩展上工作了几天,该扩展每天多次拍摄给定网页的屏幕截图。我用它作为向导,一切按预期进行 不过,有一个小的需求扩展无法满足。用户必须有权访问保存图像(屏幕截图)的文件夹,但不能访问。另一方面,Chrome应用程序确实如此。因此,在仔细研究之后,我得出结论,我必须创建一个Chrome扩展和一个Chrome应用程序。其想法是,该扩展将创建一个屏幕截图的blob,然后将该blob发送到应用程序,然后应用程序将其作为图像保存到用户指定的位置。这正是我正在做的——我在扩展端
chrome.runtime.sendMessage(
APP_ID, /* I got this from the app */
{myMessage: blob}, /* Blob created previously; it's correct */
function(response) {
appendLog("response: "+JSON.stringify(response));
}
);
// listen for external messages
chrome.runtime.onMessageExternal.addListener(
function(request, sender, sendResponse) {
if (sender.id in blacklistedIds) {
sendResponse({"result":"sorry, could not process your message"});
return; // don't allow this extension access
} else if (request.incomingBlob) {
appendLog("from "+sender.id+": " + request.incomingBlob);
// attempt to save blob to choosen location
if (_folderEntry == null) {
// get a directory to save in if not yet chosen
openDirectory();
}
saveBlobToFile(request.incomingBlob, "screenshot.png");
/*
// inspect object to try to see what's wrong
var keys = Object.keys(request.incomingBlob);
var keyString = "";
for (var key in keys) {
keyString += " " + key;
}
appendLog("Blob object keys:" + keyString);
*/
sendResponse({"result":"Ok, got your message"});
} else {
sendResponse({"result":"Ops, I don't understand this message"});
}
}
);
chrome.runtime.sendMessage(
APP_ID, /* I got this from the app */
{myMessage: blob}, /* Blob created previously; it's correct */
function(response) {
appendLog("response: "+JSON.stringify(response));
}
);
// listen for external messages
chrome.runtime.onMessageExternal.addListener(
function(request, sender, sendResponse) {
if (sender.id in blacklistedIds) {
sendResponse({"result":"sorry, could not process your message"});
return; // don't allow this extension access
} else if (request.incomingBlob) {
appendLog("from "+sender.id+": " + request.incomingBlob);
// attempt to save blob to choosen location
if (_folderEntry == null) {
// get a directory to save in if not yet chosen
openDirectory();
}
saveBlobToFile(request.incomingBlob, "screenshot.png");
/*
// inspect object to try to see what's wrong
var keys = Object.keys(request.incomingBlob);
var keyString = "";
for (var key in keys) {
keyString += " " + key;
}
appendLog("Blob object keys:" + keyString);
*/
sendResponse({"result":"Ok, got your message"});
} else {
sendResponse({"result":"Ops, I don't understand this message"});
}
}
);
以下是应用程序上执行实际保存的功能:
function saveBlobToFile(blob, fileName) {
appendLog('entering saveBlobToFile function...');
chrome.fileSystem.getWritableEntry(_folderEntry, function(entry) {
entry.getFile(fileName, {create: true}, function(entry) {
entry.createWriter(function(writer) {
//writer.onwrite = function() {
// writer.onwrite = null;
// writer.truncate(writer.position);
//};
appendLog('calling writer.write...');
writer.write(blob);
// Also tried writer.write(new Blob([blob], {type: 'image/png'}));
});
});
});
}
var worker = new SharedWorker(chrome.runtime.getURL('shared-worker.js'));
worker.port.start();
worker.postMessage('hello from extension'); // Can send blob here too
worker.port.addEventListener("message", function(event) {
$('h1Title').innerHTML = event.data;
});
proxy.js
var worker = new SharedWorker(chrome.runtime.getURL('shared-worker.js'));
worker.port.start();
worker.port.addEventListener("message",
function(event) {
parent.postMessage(event.data, 'chrome-extension://[extension id]');
}
);
var ports = [];
var count = 0;
onconnect = function(event) {
count++;
var port = event.ports[0];
ports.push(port);
port.start();
/*
On both the extension and the app, I get count = 1 and ports.length = 1
I'm running them side by side. This is so maddening!!!
What am I missing?
*/
var msg = 'Hi, you are connection #' + count + ". ";
msg += " There are " + ports.length + " ports open so far."
port.postMessage(msg);
port.addEventListener("message",
function(event) {
for (var i = 0; i < ports.length; ++i) {
//if (ports[i] != port) {
ports[i].postMessage(event.data);
//}
}
});
};
proxy.html
<script src='proxy.js'></script>
这就是执行流程。。。在扩展上,我创建了一个共享worker并向其发送消息。共享工作者应该能够接收blob,但出于测试目的,我只发送一个简单的字符串
接下来,共享工作者接收消息并将其转发给所有已连接的人。应用程序中框架内的proxy.html/js此时确实已连接,并且应该接收共享工作程序转发的任何内容
接下来,proxy.js[should]接收来自共享工作者的消息,并使用parent.postMessage(…)将其发送到应用程序。应用程序正在通过一个窗口进行侦听。addEventListener(“消息”,…)
为了测试这个流程,我首先打开应用程序,然后单击扩展按钮。我在应用程序上没有收到任何消息。我也没有错误
扩展可以与共享工作进程进行来回通信。该应用程序可以很好地与共享工作者通信。但是,我从扩展->代理->应用发送的消息没有到达应用。我错过了什么
很抱歉,那些长贴的家伙,但我希望有人能透露一些信息,因为这让我发疯
谢谢
我的应用程序是否无法访问blob,因为它是在上创建的
分机?谁能帮我解释一下吗
没错!您可能希望传递一个dataUrl
,而不是blob
。下面这样的方法可能会奏效:
/* Chrome Extension */
var blobToDataURL = function(blob, cb) {
var reader = new FileReader();
reader.onload = function() {
var dataUrl = reader.result;
var base64 = dataUrl.split(',')[1];
cb(base64);
};
reader.readAsDataURL(blob);
};
blobToDataUrl(blob, function(dataUrl) {
chrome.runtime.sendMessage(APP_ID, {databUrl: dataUrl}, function() {});
});
/* Chrome App */
function dataURLtoBlob(dataURL) {
var byteString = atob(dataURL.split(',')[1]),
mimeString = dataURL.split(',')[0].split(':')[1].split(';')[0];
var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(ab);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
var blob = new Blob([ia], {type: mimeString});
return blob;
}
chrome.runtime.onMessageExternal.addListener(
function(request) {
var blob = dataURLtoBlob(request.dataUrl);
saveBlobToFile(blob, "screenshot.png");
});
/*Chrome扩展*/
var BLOBTODATURL=函数(blob,cb){
var reader=new FileReader();
reader.onload=函数(){
var dataUrl=reader.result;
var base64=dataUrl.split(',')[1];
cb(base64);
};
reader.readAsDataURL(blob);
};
blobToDataUrl(blob,函数(dataUrl){
sendMessage(APP_ID,{dataUrl:dataUrl},function(){});
});
/*Chrome应用程序*/
函数dataURLtoBlob(dataURL){
var byteString=atob(dataURL.split(',')[1]),
mimeString=dataURL.split(',')[0]。split(':')[1]。split(';')[0];
var ab=新阵列缓冲区(byteString.length);
var ia=新的UINT8阵列(ab);
for(var i=0;i
这真是个有趣的问题。在我看来,可以使用以下技术来完成:
我对这个问题非常感兴趣,因为我正试图完成类似的事情 这些是我发现的问题
var bytes = new Uint8Array(blobAsBinString.length);
for (var i=0; i<bytes.length; i++) {
bytes[i] = blobAsBinString.charCodeAt(i);
}
blob = new Blob([bytes], {type: mimeString});
function sendBlobToApp() {
// read the blob in chunks/chunks and send it to the app
// Note: I crashed the app using 1 KB chunks. 1 MB chunks work just fine.
// I decided to use 256 KB as that seems neither too big nor too small
var CHUNK_SIZE = 256 * 1024;
var start = 0;
var stop = CHUNK_SIZE;
var remainder = blob.size % CHUNK_SIZE;
var chunks = Math.floor(blob.size / CHUNK_SIZE);
var chunkIndex = 0;
if (remainder != 0) chunks = chunks + 1;
var fr = new FileReader();
fr.onload = function() {
var message = {
blobAsText: fr.result,
mimeString: mimeString,
chunks: chunks
};
// APP_ID was obtained elsewhere
chrome.runtime.sendMessage(APP_ID, message, function(result) {
if (chrome.runtime.lastError) {
// Handle error, e.g. app not installed
// appendLog is defined elsewhere
appendLog("could not send message to app");
}
});
// read the next chunk of bytes
processChunk();
};
fr.onerror = function() { appendLog("An error ocurred while reading file"); };
processChunk();
function processChunk() {
chunkIndex++;
// exit if there are no more chunks
if (chunkIndex > chunks) {
return;
}
if (chunkIndex == chunks && remainder != 0) {
stop = start + remainder;
}
var blobChunk = blob.slice(start, stop);
// prepare for next chunk
start = stop;
stop = stop + CHUNK_SIZE;
// convert chunk as binary string
fr.readAsBinaryString(blobChunk);
}
}
chrome.runtime.onMessageExternal.addListener(
function(request, sender, sendResponse) {
if (sender.id in blacklistedIds) {
return; // don't allow this extension access
} else if (request.blobAsText) {
//new chunk received
_chunkIndex++;
var bytes = new Uint8Array(request.blobAsText.length);
for (var i=0; i<bytes.length; i++) {
bytes[i] = request.blobAsText.charCodeAt(i);
}
// store blob
_blobs[_chunkIndex-1] = new Blob([bytes], {type: request.mimeString});
if (_chunkIndex == request.chunks) {
// merge all blob chunks
for (j=0; j<_blobs.length; j++) {
var mergedBlob;
if (j>0) {
// append blob
mergedBlob = new Blob([mergedBlob, _blobs[j]], {type: request.mimeString});
}
else {
mergedBlob = new Blob([_blobs[j]], {type: request.mimeString});
}
}
saveBlobToFile(mergedBlob, "myImage.png", request.mimeString);
}
}
}
);