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

2020-04-11 10:59:12

字体：大中小

来源：转载

供稿：网友

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。

上一篇：Android实现带附件的邮件发送功能

下一篇：Android学习之Fragment