Android 通过API获取数据库中的图片文件方式

public static class WebApiConfig
{
  public static void Register(HttpConfiguration config)
  {
    // Web API 配置和服务

    // Web API 路由
    config.MapHttpAttributeRoutes();

    config.Routes.MapHttpRoute(
      name: "DefaultApi",
      routeTemplate: "api/{controller}/{id}",
      defaults: new { id = RouteParameter.Optional }
    );

    GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();
  }
}

// GET: api/Pictures
public object GetPictures()
{
  var showData = db.Pictures.ToList();
  List<Tuple<int,string>> list = new List<Tuple<int, string>>();
  foreach (var item in showData)
  {
    list.Add(new Tuple<int, string>(item.Id,Convert.ToBase64String(item.Img)));
  }
  return list;
}

/**
 * ClassName- @MainActivity-@初始换主页面底部的图片
 **/
private void initPictureData() {
  new Thread(new Runnable() {
    @Override
    public void run() {
      //通过http网络访问，获取到我们的网络数据。将Http的GET方法进行了封装
      String httpData = Global.httpGet("Pictures", "");
      //将JSON进行解析并且添加到List中
      List<pictureEntity> list = pictureData_JsonHelper.getJsonData(httpData);
      Log.d("main_pictureData", String.valueOf(list.size()));
      final List<Bitmap> bitmapsList = new ArrayList<>();
      for (int i = 0; i < list.size(); i++) {
        //在循环将String转换为图片。这里将我们的转换方法进行了封装
        bitmapsList.add(Global.stringToBitmap(list.get(i).getPicString()));
      }
      Log.d("BitmapsData", String.valueOf(bitmapsList.size()));
      
      //下面是ViewPager 控件的操作。
      final List<View> viewsList = new ArrayList<>();
      for (int i = 0; i < bitmapsList.size(); i++) {
        View view = View.inflate(MainActivity.this, R.layout.viewpage_item, null);
        ImageView imageView = view.findViewById(R.id.itemImageView);
        imageView.setImageBitmap(bitmapsList.get(i));
        viewsList.add(view);
      }
      runOnUiThread(new Runnable() {
        @Override
        public void run() {
          ViewPager viewPager = findViewById(R.id.viewPager);
          viewPager.setAdapter(new viewPager_Adapter(viewsList));
        }
      });
    }
  }).start();
}

public static Bitmap stringToBitmap(String pictureString) {
  //使用Base64将String 转换为 Bitmap 类型
  byte[] bytes = Base64.decode(pictureString, Base64.NO_WRAP);
  //使用BitmapFactory将字节数组转换为Bitmap
  //这边我们需要对数据库返回的base64的数稍稍的做一下处理。否则可能无法正常显示图像。
  for (int i = 0; i < bytes.length; ++i) {
    if (bytes[i] < 0) {
      bytes[i] += 256;
    }
  }
  //生成图片并且返回。
  return BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
}

String getNetData(String connectURL){
  String result = ""; //用来取得返回的String；
  //发送post请求
  HttpPost httpRequest = new HttpPost(connectURL);
  //Post运作传送变数必须用NameValuePair[]阵列储存
  try {
    //发出HTTP请求
    Log.d("请求连接", "在发送请求");
    List params = new ArrayList();
    params.add(new BasicNameValuePair("start", "123321"));//post请求（必须有，数据自定义）
    //params.add(new BasicNameValuePair("end", end+""));//可添加多个Post请求码，php中按键值对获取
    httpRequest.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
    //取得HTTP response
    HttpResponse httpResponse = new DefaultHttpClient().execute(httpRequest);
    //若状态码为200则请求成功，取到返回数据
    Log.d("连接值", String.valueOf(httpResponse.getStatusLine().getStatusCode()));
    if (httpResponse.getStatusLine().getStatusCode() == 200) {
      //取出字符串
      Log.d("请求连接", "连接成功");
      result = new String(EntityUtils.toString(httpResponse.getEntity(),"utf8"));
    }
  } catch (Exception e) {
    mHandler.post(new Runnable() {
      @Override
      public void run() {
        Toast.makeText(getContext(), "网络出错",Toast.LENGTH_SHORT).show();
      }
    });
    e.printStackTrace();
  }
  return result;
}
//接下来就是解析获取到的json数据了，json数据的解析就需要根据需求自定义了