保存數據：本地使用Google App Engine的PNG圖像的網址

我使用的是Google App Engine（python），並且在服務器上有可用的PNG圖像的數據：url。 PNG圖像從來不在文件中，因爲它是使用toDataUrl（）從一些畫布代碼生成的，並且被添加到服務器。我想讓用戶點擊一個按鈕，並能夠選擇一個文件名並保存在本地PNG圖像。另存爲對話框將提供默認的文件名。目標瀏覽器是FireFox。我提供的示例代碼不起作用。在stackoverflow上有幾個問題有點像這個，但每個都有點不同。保存數據：本地使用Google App Engine的PNG圖像的網址

我使用建議的文件名將content-disposition設置爲附件。我將頭文件content-type設置爲application/octet-stream。但是我沒有得到SaveAs對話框。我錯過了什麼？

的app.yaml文件是標準

application: saveas 
version: 1 
runtime: python 
api_version: 1 

handlers: 
- url: /.* 
    script: main.py

中的index.html如下：

<!DOCTYPE html> 
<html lang="en"> 

<head> 
<meta charset="utf-8"/> 

<script> 

function saveAsPng() 
{ 
var alldata; 
var httpRequest; 
var response; 
var myheaders; 

httprequest = new XMLHttpRequest(); 

if (!httprequest) 
    { 
    alert("In saveAsPng, XMLHttpRequest failed."); 
    return; 
    } 

/* Make this a json string */ 
alldata = JSON.stringify("no data"); 

try 
    { 
    httprequest.open('POST', '/handlebitmap', true); 
    httprequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); 
    httprequest.setRequestHeader("Content-length", alldata.length); 
    httprequest.setRequestHeader("Connection", "close"); 
    httprequest.onreadystatechange = function() 
     { 
     if (httprequest.readyState == 4) 
     { 
     if (httprequest.status == 200) 
      { 
      /* a status of 200 is good. */ 
      response = null; 
      try 
       { 
       response = JSON.parse(httprequest.responseText); 
       } 
      catch (e) 
       { 
       response = httprequest.responseText; 
       } 

      if (response == "error") 
       { 
       alert("In saveAsPng callback, response == error"); 
       return false; 
       } 
      else 
       { 
       /* This is the successful exit. */ 

       //alert("response = " +response); 

       window.location.href = response; 

       return true; 
       } 
      } 
     else 
      { 
      /* httprequest.status was not 200, so must be an error. */ 
      alert("saveAsPNG callback, status = " +httprequest.status); 
      return false; 
      } 

     } /* End of if where readyState was 4. */ 

     } /* End of the callback function */ 

    /* Make the actual request */ 
    httprequest.send(alldata); 
    } 
catch(e) 
    { 
    alert("In saveAsPng, Can't connect to the server"); 
    } 

} /* End of the saveAsPng function */

的Python代碼如下：

# !/usr/bin/env python 

import os 
import base64 

from google.appengine.ext import webapp 
from google.appengine.ext.webapp import template 
from google.appengine.ext.webapp import util 

class MainPage(webapp.RequestHandler): 
    """ Renders the main template.""" 
    def get(self): 
     template_values = { 'title':'Test Save As PNG', } 
     path = os.path.join(os.path.dirname(__file__), "index.html") 
     self.response.out.write(template.render(path, template_values)) 

class BitmapHandler(webapp.RequestHandler): 
    """ Shows the Save As with a default filename. """ 
    def post(self): 
     origdata = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==" 
     urldata = "iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==" 
     decodeddata = base64.b64decode(urldata) 
     self.response.headers['Content-Type'] = 'application/octet-stream' 
     self.response.headers['Content-Disposition'] = 'attachment; filename="untitled.png"' 
     self.response.out.write(decodeddata) 

def main(): 
    app = webapp.WSGIApplication([ 
     ('/', MainPage), 
     ('/handlebitmap',BitmapHandler), 
     ], debug=True) 
    util.run_wsgi_app(app) 

if __name__ == '__main__': 
    main()

來源

2012-04-23 RFF

也許你想改變「DEF後」到「DEF得到」？我剛剛嘗試過你的示例，它似乎正如預期的那樣改變後（只試過/ handlebitmap）

來源

2012-04-24 06:29:25 Bemmu

我嘗試GET而不是POST，但最終結果總是：localhost：8080 /％ED％BF％BDPNG HTTP /1.0 404未找到。我沒有發送任何數據到服務器，只是得到一個data：url返回。我一定在做一些根本錯誤的事情。 – RFF 2012-04-24 14:53:09

保存數據：本地使用Google App Engine的PNG圖像的網址

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