19 Android 简单示例

由于在某些嵌入式系统中使用的是Android系统，这里给出一个简单的Android App的示例，具体代码可以从clone自https://github.com/phodal/iot-android

代码说明，经过测试的版本有

• Android 2.3
• Android 4.0.4

机型有

• HTC G1 (android 2.3)
• Motor xt300 (android 2.3)
• Sony ST25I (android 4.0.4)
• MI2

应该可以在大部分的手机上工作。

19.1 调用Web Services GET

这里我们参考一篇文章来调用Web Services——Calling Web Services in Android using HttpClient

19.1.1 创建RESTClient

在这里我们首先会定义四个REST方法GET、POST、PUT、DELETE

public void Execute(RequestMethod method) throws Exception {
  switch (method) {
  case GET: {
    // add parameters
    String combinedParams = "";
    if (!params.isEmpty()) {
      combinedParams += "?";
      for (NameValuePair p : params) {
        String paramString = p.getName() + "="
            + URLEncoder.encode(p.getValue(), HTTP.UTF_8);
        if (combinedParams.length() > 1) {
          combinedParams += "&" + paramString;
        } else {
          combinedParams += paramString;
        }
      }
    }

    HttpGet request = new HttpGet(url + combinedParams);
    request.addHeader("Accept-Encoding", "gzip");

    // add headers
    for (NameValuePair h : headers) {
      request.addHeader(h.getName(), h.getValue());
    }

    executeRequest(request, url);
    break;
  }
  case POST: {
    HttpPost request = new HttpPost(url);
    request.addHeader("Accept-Encoding", "gzip");

    // add headers
    for (NameValuePair h : headers) {
      request.addHeader(h.getName(), h.getValue());
    }
    if (!data.equals("")) {
      request.setEntity(new StringEntity(data, HTTP.UTF_8));
    }

    if (!params.isEmpty()) {
      request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
    }

    executeRequest(request, url);
    break;
  }
  case PUT: {
    HttpPut request = new HttpPut(url);
    request.addHeader("Accept-Encoding", "gzip");

    // add headers
    for (NameValuePair h : headers) {
      request.addHeader(h.getName(), h.getValue());
    }
    if (!data.equals("")) {
      request.setEntity(new StringEntity(data, HTTP.UTF_8));
    }

    if (!params.isEmpty()) {
      request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
    }

    executeRequest(request, url);
    break;
  }
  case DELETE: {
    HttpDelete request = new HttpDelete(url);
    request.addHeader("Accept-Encoding", "gzip");

    // add headers
    for (NameValuePair h : headers) {
      request.addHeader(h.getName(), h.getValue());
    }

    executeRequest(request, url);
    break;
  }
  }
}

这四个方法最后都执行executeRequest来获取响应结果。

protected void executeRequest(HttpUriRequest request, String url) {

    HttpParams httpParameters = new BasicHttpParams();
    HttpConnectionParams.setConnectionTimeout(httpParameters,
        timeoutConnection);
    HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
    
    HttpProtocolParams.setUseExpectContinue(httpParameters, false);
    request.setParams(httpParameters);
    
    setOauth(request);
    
    DefaultHttpClient client = new DefaultHttpClient();

    HttpResponse httpResponse;

    try {
      httpResponse = client.execute(request);
      responseCode = httpResponse.getStatusLine().getStatusCode();
      message = httpResponse.getStatusLine().getReasonPhrase();

      HttpEntity entity = httpResponse.getEntity();

      if (entity != null) {
        InputStream instream = httpResponse.getEntity().getContent();
        Header contentEncoding = httpResponse
            .getFirstHeader("Content-Encoding");

        if (contentEncoding != null
            && contentEncoding.getValue().equalsIgnoreCase("gzip")) {
          instream = new GZIPInputStream(instream);
        }

        // instream = entity.getContent();
        response = convertStreamToString(instream);

        // Closing the input stream will trigger connection release
        instream.close();
      }

    } catch (ClientProtocolException e) {
      client.getConnectionManager().shutdown();
      e.printStackTrace();
    } catch (IOException e) {
      client.getConnectionManager().shutdown();
      e.printStackTrace();
    }
  }

接着，我们便可以执行getResponse()函数来获取结果。

19.2 使用REST Client获取结果

使用RESTClient时，便可以用下面的示例

RestClient client = new RestClient(tUrl);
try {
  client.Execute(RequestMethod.GET);
  if (client.getResponseCode() != 200) {
    //do something
  }
  //JSONArray jArray = new JSONArray(client.getResponse());
} catch (Exception e) {
  //do something
}

而这时，我们只需要对相应的数据进行处理就可以了，如

JSONArray jArray = new JSONArray(client.getResponse());
JSONObject jObj=jArray.getJSONObject(0);
vshow.setText(jObj.toString());

outputJSON(jObj);

将他转换为String，接着在Android端上显示最后的结果。