Android中使用HttpURLConnection实现GET POST JSON数据与下载图片

Android6.0中把Apache HTTP Client所有的包与类都标记为deprecated不再建议使用所有跟HTTP相关的数据请求与提交操作都通过HttpURLConnection类实现，现实是很多Android开发者一直都Apache HTTP Client来做andoird客户端与后台HTTP接口数据交互，小编刚刚用HttpURLConnection做了一个android的APP，不小心踩到了几个坑，总结下最常用的就通过HttpURLConnection来POST提交JSON数据与GET请求JSON数据。此外就是下载图片，下载图片分为显示进度与不显示进度两种。其中提交数据的时候涉及中文一定要先把中文转码成utf-8之后在POST提交，否则就会一直遇到HTTP 400的错误。

一、GET请求JSON数据的例子

public UserDto execute(String... params) {
 InputStream inputStream = null;
 HttpURLConnection urlConnection = null; 

 try {
  // read responseURLEncoder.encode(para, "GBK");
  String urlWithParams = DOMAIN_ADDRESS + MEMBER_REQUEST_TOKEN_URL + "?userName=" + java.net.URLEncoder.encode(params[0],"utf-8") + "&password=" + params[1];
  URL url = new URL(urlWithParams);
  urlConnection = (HttpURLConnection) url.openConnection(); 

  /* optional request header */
  urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8"); 

  /* optional request header */
  urlConnection.setRequestProperty("Accept", "application/json"); 

  /* for Get request */
  urlConnection.setRequestMethod("GET");
  int statusCode = urlConnection.getResponseCode(); 

  /* 200 represents HTTP OK */
  if (statusCode == 200) {
   inputStream = new BufferedInputStream(urlConnection.getInputStream());
   String response = HttpUtil.convertInputStreamToString(inputStream);
   Gson gson = new Gson();
   UserDto dto = gson.fromJson(response, UserDto.class);
   if (dto != null && dto.getToken() != null) {
    Log.i("token", "find the token = " + dto.getToken());
   }
   return dto;
  } 

 } catch (Exception e) {
  e.printStackTrace();
 } finally {
  if (inputStream != null) {
   try {
    inputStream.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
  if (urlConnection != null) {
   urlConnection.disconnect();
  }
 }
 return null;
}

二、POST提交JSON数据

public Map<String, String> execute(NotificationDto dto) {
 InputStream inputStream = null;
 HttpURLConnection urlConnection = null;
 try {
  URL url = new URL(getUrl);
  urlConnection = (HttpURLConnection) url.openConnection(); 

  /* optional request header */
  urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8"); 

  /* optional request header */
  urlConnection.setRequestProperty("Accept", "application/json");
  dto.setCreator(java.net.URLEncoder.encode(dto.getCreator(), "utf-8")); 

  // read response
  /* for Get request */
  urlConnection.setRequestMethod("POST");
  urlConnection.setDoOutput(true);
  DataOutputStream wr = new DataOutputStream(urlConnection.getOutputStream());
  Gson gson = new Gson();
  String jsonString = gson.toJson(dto);
  wr.writeBytes(jsonString);
  wr.flush();
  wr.close();
  // try to get response
  int statusCode = urlConnection.getResponseCode();
  if (statusCode == 200) {
   inputStream = new BufferedInputStream(urlConnection.getInputStream());
   String response = HttpUtil.convertInputStreamToString(inputStream);
   Map<String, String> resultMap = gson.fromJson(response, Map.class);
   if (resultMap != null && resultMap.size() > 0) {
    Log.i("applyDesigner", "please check the map with key");
   }
   return resultMap;
  }
 }
 catch(Exception e)
 {
  e.printStackTrace();
 }
 finally
 {
  if (inputStream != null) {
   try {
    inputStream.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
  if (urlConnection != null) {
   urlConnection.disconnect();
  }
 }
 return null;
}

三、下载图片显示下载进度

package com.example.demo; 

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL; 

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.util.Log; 

public class ImageLoadTask extends AsyncTask<String, Void, Bitmap> {
 private Handler handler; 

 public ImageLoadTask(Handler handler) {
  this.handler = handler;
 } 

 protected void onPostExecute(Bitmap result) {
  Message msg = new Message();
  msg.obj = result;
  handler.sendMessage(msg);
 } 

 protected Bitmap doInBackground(String... getUrls) {
  InputStream inputStream = null;
  HttpURLConnection urlConnection = null; 

  try {
   // open connection
   URL url = new URL(getUrls[0]);
   urlConnection = (HttpURLConnection) url.openConnection();
   /* for Get request */
   urlConnection.setRequestMethod("GET");
   int fileLength = urlConnection.getContentLength();
   int statusCode = urlConnection.getResponseCode();
   if (statusCode == 200) {
    inputStream = urlConnection.getInputStream();
    byte data[] = new byte[4096];
    long total = 0;
    int count;
    ByteArrayOutputStream output = new ByteArrayOutputStream();
    while ((count = inputStream.read(data)) != -1) {
     total += count;
     // publishing the progress....
     if (fileLength > 0 && handler != null) {
      handler.sendEmptyMessage(((int) (total * 100 / fileLength)) - 1);
     }
     output.write(data, 0, count);
    }
    ByteArrayInputStream bufferInput = new ByteArrayInputStream(output.toByteArray());
    Bitmap bitmap = BitmapFactory.decodeStream(bufferInput);
    inputStream.close();
    bufferInput.close();
    output.close();
    Log.i("image", "already get the image by uuid : " + getUrls[0]);
    handler.sendEmptyMessage(100);
    return bitmap;
   }
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   if (inputStream != null) {
    try {
     inputStream.close();
    } catch (IOException e) {
     e.printStackTrace();
    }
   }
   if (urlConnection != null) {
    urlConnection.disconnect();
   }
  }
  return null;
 } 

}

总结：使用HttpURLConnection提交JSON数据的时候编码方式为UTF-8所有中文字符请一定要预先转码为UTF-8，然后在后台服务器对应的API中解码为UTF-8，不然就会报错HTTP 400。

以上就是本文的全部内容，希望对大家的学习Android软件编程有所帮助。