[Android] Use Post To Call API

開發Android時,如何用Post的方式 Call API來取得值

• 首先 ```csharp
  String UrlLocation = 你的API位置; //API位置

        String PostData = 要傳遞的資料(字串); //EX: ID=Toyo&Name=Steven
  
            HttpURLConnection conn = null;
        StringBuilder sb = new StringBuilder();
        try
        {
            URL Url = new URL(UrlLocation);
            conn = (HttpURLConnection)Url.openConnection();
            conn.setRequestMethod("POST"); //要呼意的方式 Get Or Post
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.connect();
            //開始傳輸資料過去給API
            OutputStream Output = conn.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(Output, "UTF-8"));
            writer.write(PostData);
            writer.flush();
            writer.close();
            Output.close();
            //讀取API回傳的值
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    conn.getInputStream(),"utf-8"));
    
                String line;
            while ((line=br.readLine())!=null)
            {
                sb.append(line);
            }
        }
        catch(Exception ex)
        {
            Log.e("API_Post",ex.getMessage());
        }
        finally
        {
            if (conn != null)
                conn.disconnect();
        }
    
            return sb.toString();
  

*   目前測試的結果是,如果不把呼叫API用執行緒AsyncTask的方式處理,在conn.connect()這邊會跳出Http...InMainThread的Exception,原因是Andorid預設呼叫外部處理5秒沒有回應就會跳Exception,所以預設不管這支API反應速度快不快,他都要你把上面那段做成切執行緒的方式處理,當然網路上還是有舊的方式可以用,但既然這是官方目前推薦的做法就照做吧 ```csharp
//這邊有三個參數
//第一個參數String : 呼叫這個方法時要帶入的參數型態,這邊就是可以帶入String,
//第二個參數Void : 處理時會回報狀態跟進度,這邊寫Void表示不回傳目前處理狀態
//第三個參數String : 處理完成時回傳的值
private class Post extends AsyncTask<String,Void,String>
    {

            //事件處理順序onPreExecute , doInBackground ,onPostExecute
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

            @Override
        protected String doInBackground(String ... params) {
            //改寫這邊,呼叫方法時可以傳進多個String,所以這邊改抓params
            String UrlLocation = params[0]; //API位置
            String PostData = params[1]; //要傳資料

                HttpURLConnection conn = null;
            StringBuilder sb = new StringBuilder();
            try
            {
                URL Url = new URL(UrlLocation);
                conn = (HttpURLConnection)Url.openConnection();
                conn.setRequestMethod("POST"); //要呼意的方式 Get Or Post
                conn.setDoInput(true);
                conn.setDoOutput(true);
                conn.connect();
                //開始傳輸資料過去給API
                OutputStream Output = conn.getOutputStream();
                BufferedWriter writer = new BufferedWriter(
                        new OutputStreamWriter(Output, "UTF-8"));
                writer.write(PostData);
                writer.flush();
                writer.close();
                Output.close();

                    //讀取API回傳的值
                BufferedReader br = new BufferedReader(new InputStreamReader(
                        conn.getInputStream(),"utf-8"));

                    String line;
                while ((line=br.readLine())!=null)
                {
                    sb.append(line);
                }
            }
            catch(Exception ex)
            {
                Log.e("API_Post",ex.getMessage());
            }
            finally
            {
                if (conn != null)
                    conn.disconnect();
            }

                return sb.toString();
        }

           @Override
        protected void onPostExecute(String Result) {
            super.onPostExecute(Result);
        }
    }

• 最後,因為在Debug模式AsyncTask並不會進入,所以要在doInBackground的事件裡面加上這行,但因為非Debug模式下這行會造成Android沒有回應, 所以記得在部署時把這行拿掉！！ ```csharp
  android.os.Debug.waitForDebugger();

*   全部完成後,呼叫方式如下 ```csharp
String Url = "http://www.api.com.tw";
String PostData = "id=toyo&name=steven";
String Response = new Post().execute(Url,PostData).get();