Question

我开发了一个标签应用程序。

有2个用户，一个用户向其提供数据并将其存储在远程数据库中。其他用户访问平板电脑中的这些数据。但问题是每次第二个用户手动加载JSON值时，意味着它不会自动同步。

我希望它是自动的。意味着，每60秒新的JSON值将被检索并存储在本地存储区域中。它不会干扰以前存储的值。

Answer 1

加载JSON

创建新Calss JSONPASER

        import java.io.BufferedReader;
        import java.io.IOException;
        import java.io.InputStream;
        import java.io.InputStreamReader;
        import java.io.UnsupportedEncodingException;
        import java.util.List;

        import org.apache.http.HttpEntity;
        import org.apache.http.HttpResponse;
        import org.apache.http.NameValuePair;
        import org.apache.http.client.ClientProtocolException;
        import org.apache.http.client.entity.UrlEncodedFormEntity;
        import org.apache.http.client.methods.HttpGet;
        import org.apache.http.client.methods.HttpPost;
        import org.apache.http.client.utils.URLEncodedUtils;
        import org.apache.http.impl.client.DefaultHttpClient;
        import org.json.JSONException;
        import org.json.JSONObject;

        import android.util.Log;

        public class JSONParser {

        static InputStream is = null;
        static JSONObject jObj = null;
        static String json = "";

        // constructor
        public JSONParser() {

        }

        // function get json from url
        // by making HTTP POST or GET method
        public JSONObject makeHttpRequest(String url, String method,
        List<NameValuePair> params) {

    // Making HTTP request
    try {

        // check for request method
        if(method == "POST"){
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        }else if(method == "GET"){
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }           

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}
}

在现有类中创建另一个内部类（异步类）

    class AttemptJson extends AsyncTask<String, String, String> {

     /**
     * Before starting background thread Show Progress Dialog
     * */
    boolean failure = false;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(Login.this);
        pDialog.setMessage("JSON Attempting ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    @Override
    protected String doInBackground(String... args) {
        // TODO Auto-generated method stub
         // Check for success tag
        int success;
        String username = user.getText().toString();
        String password = pass.getText().toString();
        try {
            // Building Parameters
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("Key", value));


            Log.d("request!", "starting");
            // getting product details by making HTTP request
            JSONObject json = jsonParser.makeHttpRequest(
                   LOGIN_URL, "POST", params);

            // check your log for json response
            Log.d("attempt", json.toString());

            // json success tag
            success = json.getInt(TAG_SUCCESS);
            if (success == 1) {
                Log.d("Login Successful!", json.toString());
                Intent i = new Intent(Login.this, ReadComments.class);
                finish();
            startActivity(i);
                return json.getString(TAG_MESSAGE);
            }else{
                Log.d("Login Failure!", json.getString(TAG_MESSAGE));
                return json.getString(TAG_MESSAGE);

            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;

    }
    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once product deleted
        pDialog.dismiss();
        if (file_url != null){
            Toast.makeText(Login.this, file_url, Toast.LENGTH_LONG).show();
        }

    }

}

每60秒刷新一次

 new Handler().postDelayed(new new Runnable() {
    public void run() {
    // call JSON methods here
    new AttemptJson ().execute();
      }
 }, 60000  );

存储在本地存储中

   JSONObject jOb = json; // json is ths object where u have crated in the class

Answer 2

使用

在60秒后调用JSON函数

new Handler().postDelayed(new new Runnable() {
    public void run() {
        // call JSON methods here
    }
}, 60000);

Answer 3

每隔60秒使用线程刷新一次并使用本地数据库中的唯一值来存储

在Android中自动加载每60秒JSON值

3 个答案: