[英]How do i move a screenshot from an extension to a content script?
所以這個想法是這樣的...我想要做的就是在加載特定內容腳本后立即調用擴展背景頁面。 (在這種情況下加載頁面時)我的內容腳本中有類似的內容。
var port = chrome.extension.connect({name: "screenshot"});
port.postMessage({request: "screenshot"});
port.onMessage.addListener(function(msg) {
var img = document.createElement('img');
img.src = msg.response;
document.body.appendChild(img);
});
在我的background.js頁面中有類似的東西
function takeScreenshot(){
chrome.tabs.captureVisibleTab(null, function(img) {
return img;
});
}
chrome.extension.onConnect.addListener(function(port) {
console.assert(port.name == "screenshot");
port.onMessage.addListener(function(msg) {
if (msg.request == "screenshot"){
port.postMessage({response: takeScreenshot() });
}
});
});
但我沒有運氣......我得到的圖像顯示在身體上但是當從takeScreenshot返回img時它實際上沒有傳遞圖像
問題是您正在嘗試在后台頁面中實現同步和異步事件之間的同步
a) chrome.tabs.captureVisibleTab()是異步的
b) port.postMessage()是同步的
當port.postMessage({response: takeScreenshot() });
被稱為不等待takeScreenshot() 回調 ie; return img;
所以一個空的JSON對象被發送到內容腳本
chrome.extension.onConnect.addListener(function(port) {
console.assert(port.name == "screenshot");
port.onMessage.addListener(function(msg) {
if (msg.request == "screenshot"){
chrome.tabs.captureVisibleTab(null,{format:"jpeg",quality:100},function(img) {
//post message only after call back return with Data URL
port.postMessage(img);
});
}
});
});
工作版演示
的manifest.json
{
"name":"Screen Shot Demo",
"description":"This demonstrates Screen Shot API",
"manifest_version":2,
"version":"1",
"permissions":["tabs","<all_urls>"],
"background":{
"scripts":["background.js"]
},
"content_scripts": [
{
"matches": ["<all_urls>"],
"js": ["myscript.js"]
}
]
}
background.js
chrome.extension.onConnect.addListener(function(port) {
console.assert(port.name == "screenshot");
port.onMessage.addListener(function(msg) {
if (msg.request == "screenshot"){
chrome.tabs.captureVisibleTab(null,{format:"jpeg",quality:100},function(img) {
//post message only after call back return with Data URL
port.postMessage(img);
});
}
});
});
myscript.js (內容腳本 )
var port = chrome.extension.connect({
name: "screenshot"
});
port.postMessage({
request: "screenshot"
});
port.onMessage.addListener(function (msg) {
var img = document.createElement('img');
img.src = msg;
document.body.appendChild(img);
});
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