我正在为一个应用程序进行原型设计，我使用JSON和HttpPost将本地SQLite数据库的全部内容发送到远程MySQL数据库。
一切都适用于文本数据。 现在我将图像添加到派对中，虽然我可以将图像作为base64字符串添加到我发送的JSON中。我的图像是800 x 600像素，每个大小或多或少500kb。
如果我将我的应用程序生成的JSON手动粘贴到网页上，那很好，我会得到我的图片和其他所有内容。
使用应用程序上传脚本，我尝试上传一个包含4张图片的JSON字符串，但应用程序卡在我的进度对话框中，Logcat一遍又一遍地显示：
11-15 14:32:27.809: I/dalvikvm-heap(15562): Grow heap (frag case) to 21.964MB for 2680048-byte allocation
11-15 14:32:27.840: D/dalvikvm(15562): GC_CONCURRENT freed 1744K, 30% free 20666K/29447K, paused 2ms+3ms
11-15 14:32:27.879: D/dalvikvm(15562): GC_FOR_ALLOC freed 4362K, 39% free 18049K/29447K, paused 16ms
11-15 14:32:27.918: D/dalvikvm(15562): GC_FOR_ALLOC freed 0K, 33% free 19794K/29447K, paused 22ms
11-15 14:32:27.918: I/dalvikvm-heap(15562): Grow heap (frag case) to 21.964MB for 2680276-byte allocation
11-15 14:32:27.958: D/dalvikvm(15562): GC_CONCURRENT freed 1744K, 30% free 20667K/29447K, paused 1ms+4ms
11-15 14:32:27.997: D/dalvikvm(15562): GC_FOR_ALLOC freed 4362K, 39% free 18049K/29447K, paused 17ms
11-15 14:32:28.028: D/dalvikvm(15562): GC_FOR_ALLOC freed 0K, 33% free 19795K/29447K, paused 17ms
它会永远持续下去。我打赌这些图像太大了，无法以这种方式发送，和/或我正在某处泄漏内存。
将大尺寸图像和JSON数据上传到服务器的更好方法是什么？否则，我该如何避免内存泄漏？
代码很标准......
从Cursor到JSON：
private JSONObject get_images_data_JSON(Cursor c) {
JSONObject image_jo = new JSONObject();
//get unit identifier
long unit_identifier = c.getLong(c.getColumnIndex("_id"));
//set unit details
try {
image_jo.put("_id", unit_identifier);
image_jo.put("unit_id", c.getLong(c.getColumnIndex("unit_id")));
//encode blob in Base64 for json parsing
String encodedImage = Base64.encodeToString(c.getBlob(c.getColumnIndex("image")), Base64.DEFAULT);
image_jo.put("image", encodedImage);
image_jo.put("caption", c.getString(c.getColumnIndex("caption")));
} catch (JSONException e) {
e.printStackTrace();
}
return image_jo;
}//end get_images_data_JSON
和POST功能：
public String postData(JSONArray array) {
String responseMessage = "";
//set connection timeout values
HttpParams myParams = new BasicHttpParams();
//set timeout in milliseconds until a connection is established
HttpConnectionParams.setConnectionTimeout(myParams, 10000);
//set timeout for waiting data
HttpConnectionParams.setSoTimeout(myParams, 10000);
HttpClient httpclient = new DefaultHttpClient(myParams);
//Get a string out of the JSONArray
String json = array.toString();
try {
HttpPost httppost = new HttpPost(URL);
httppost.setHeader("Content-type", "application/json");
StringEntity se = new StringEntity(json);
se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
httppost.setEntity(se);
HttpResponse response = httpclient.execute(httppost);
InputStream inputStream = response.getEntity().getContent();
responseMessage = inputStreamToString(inputStream);
//log out response from server
longInfo(responseMessage);
}
//show error if connection not working
catch (SocketTimeoutException e) {
e.printStackTrace();
responseMessage = "unreachable";
}
catch (ConnectTimeoutException e) {
e.printStackTrace();
responseMessage = "unreachable";
}
catch (Exception e) {
e.printStackTrace();
responseMessage = "unreachable";
}
return responseMessage;
}
非常感谢任何帮助
答案 0 :(得分：1)
您的解决方案只会加载要发送到内存的所有数据。这几乎不可扩展。请考虑使用多部分实体。
File image1;
MultipartEntity entity = new MultipartEntity();
entity.addPart("json", new StringBody(serializedJson, Charset.forName("UTF-8"));
entity.addPart("image1", new FileBody(image1, "application/octet-stream");
此示例显示了我即将发送磁盘上可用文件的情况。通过为AbstractContentBody创建自己的实现，您应该能够发送位于数据库中的内容，而不会占用太多内存......
答案 1 :(得分：0)
对于任何来到这里的人，我解决了Vajk建议之后的所有问题，这是我的新POST功能：
public String postData(Cursor images, JSONArray json_array) {
int counter = 0;
String responseMessage = "";
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(URL);
//convert JSON array to String
String json_encoded_string = json_array.toString();
//MultipartEntity entity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
MultipartEntity entity = new MultipartEntity();
//add json data
entity.addPart("json", new StringBody(json_encoded_string));
//get all images plus data and add them to the Multipart Entity
for (images_cursor.moveToFirst(); !images_cursor.isAfterLast(); images_cursor.moveToNext()) {
counter++;
//Get image as byte array
byte[] image_ba = images_cursor.getBlob(images_cursor.getColumnIndex("image"));
long image_unit_id = images_cursor.getLong(images_cursor.getColumnIndex("unit_id"));
String image_caption = images_cursor.getString(images_cursor.getColumnIndex("caption"));
//add image to multipart
entity.addPart("image" + counter, new ByteArrayBody(image_ba, "image" + counter + ".jpg"));
//add unit _id to multipart
entity.addPart("image_unit_id" + counter, new StringBody(String.valueOf(image_unit_id)));
//add caption to multipart
entity.addPart("image_caption" + counter, new StringBody(String.valueOf(image_caption)));
}
httppost.setEntity(entity);
HttpResponse response = httpclient.execute(httppost);
InputStream inputStream = response.getEntity().getContent();
responseMessage = inputStreamToString(inputStream);
//log out response from server
longInfo(responseMessage);
}
//show error if connection not working
catch (SocketTimeoutException e) {
e.printStackTrace();
responseMessage = "unreachable";
}
catch (ConnectTimeoutException e) {
e.printStackTrace();
responseMessage = "unreachable";
}
catch (Exception e) {
e.printStackTrace();
responseMessage = "unreachable";
}
return responseMessage;
}
有人可能觉得这很有用;）