解析JSON Android？

Question

我正在尝试使用 Android Java 创建 JSON 解析器。 我是开发android JAVA的新人。 我需要解析用户名和密码以获取一些操作，例如登录活动。 在我想使用的嵌套参数下面，如果 url 和验证成功，我将得到下面提到的响应。 下面提到解析参数的网址。请帮帮我！

http://sample.com/login/username/ <username> /password <password>?  



   {
        "response":{
                    "School":"SBOA",
                    "Name":"Anitha",
                    "Class":"Tenth",
                  },
                    "Result":"Good",
    }

下面的代码我正在尝试：

import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;
import com.loopj.android.http.RequestParams;

/**
 *
 * Login Activity Class
 *
 */
public class LoginActivity extends Activity {
    // Progress Dialog Object
    ProgressDialog prgDialog;
    // Error Msg TextView Object
    TextView errorMsg;
    // Email Edit View Object
    EditText emailET;
    // Passwprd Edit View Object
    EditText pwdET;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        // Find Error Msg Text View control by ID
        //errorMsg = (TextView)findViewById(R.id.login_error);
        // Find Email Edit View control by ID
        emailET = (EditText)findViewById(R.id.email);
        // Find Password Edit View control by ID
        pwdET = (EditText)findViewById(R.id.password);
        // Instantiate Progress Dialog object
        prgDialog = new ProgressDialog(this);
        // Set Progress Dialog Text
        prgDialog.setMessage("Please wait...");
        // Set Cancelable as False
        prgDialog.setCancelable(false);
    }

    /**
     * Method gets triggered when Login button is clicked
     *
     * @param view
     */
    public void loginUser(View view){

        navigatetoHomeActivity();

        // Get Email Edit View Value
        String email = emailET.getText().toString();
        // Get Password Edit View Value
        String password = pwdET.getText().toString();
        // Instantiate Http Request Param Object
        RequestParams usernames = new RequestParams();
        RequestParams passwords = new RequestParams();

        // When Email Edit View and Password Edit View have values other than Null
        if(Utility.isNotNull(email) && Utility.isNotNull(password)){
            // When Email entered is Valid
            if(Utility.validate(email)){
                // Put Http parameter username with value of Email Edit View control
                usernames.put("username", email);
                // Put Http parameter password with value of Password Edit Value control
                passwords.put("password", password);
                // Invoke RESTful Web Service with Http parameters
                invokeWS(usernames);
                invokeWS(passwords);

            }
            // When Email is invalid
            else{
                Toast.makeText(getApplicationContext(), "Please enter valid email", Toast.LENGTH_LONG).show();
            }
        } else{
            Toast.makeText(getApplicationContext(), "Please fill the form, don't leave any field blank", Toast.LENGTH_LONG).show();
        }

    }

    /**
     * Method that performs RESTful webservice invocations
     *
     * @param usernames
     */
    public void invokeWS(final RequestParams usernames){
        // Show Progress Dialog
        prgDialog.show();
        // Make RESTful webservice call using AsyncHttpClient object
        AsyncHttpClient client = new AsyncHttpClient();
        client.get("URL" ,params,new AsyncHttpResponseHandler() {


            // When the response returned by REST has Http response code '200'
            @Override
            public void onSuccess(String response) {
                // Hide Progress Dialog
                prgDialog.hide();
                try {
                    // JSON Object
                    JSONObject obj = new JSONObject(response);
                    // When the JSON response has status boolean value assigned with true
                    if(obj.getBoolean("response")){
                        Toast.makeText(getApplicationContext(), "You are successfully logged in!", Toast.LENGTH_LONG).show();
                        // Navigate to Home screen
                        navigatetoHomeActivity();
                    }
                    // Else display error message
                    else{
                        errorMsg.setText(obj.getString("error_msg"));
                        Toast.makeText(getApplicationContext(), obj.getString("error_msg"), Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    Toast.makeText(getApplicationContext(), "Error Occured [Server's JSON response might be invalid]!", Toast.LENGTH_LONG).show();
                    e.printStackTrace();

                }
            }
            // When the response returned by REST has Http response code other than '200'
            @Override
            public void onFailure(int statusCode, Throwable error,
                                  String content) {
                // Hide Progress Dialog
                prgDialog.hide();
                // When Http response code is '404'
                if(statusCode == 404){
                    Toast.makeText(getApplicationContext(), "Requested resource not found", Toast.LENGTH_LONG).show();
                }
                // When Http response code is '500'
                else if(statusCode == 500){
                    Toast.makeText(getApplicationContext(), "Something went wrong at server end", Toast.LENGTH_LONG).show();
                }
                // When Http response code other than 404, 500
                else{
                    Toast.makeText(getApplicationContext(), "Unexpected Error occcured! [Most common Error: Device might not be connected to Internet or remote server is not up and running]", Toast.LENGTH_LONG).show();
                }
            }
        });
    }

    /**
     * Method which navigates from Login Activity to Home Activity
     */
    public void navigatetoHomeActivity(){
        Intent homeIntent = new Intent(getApplicationContext(),WatchListActivity.class);
        homeIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(homeIntent);
    } 

Answer 1

使用此代码从 url 获取 json。

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
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() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            //name value pairs for posting username and password
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("username","john"));
    params.add(new BasicNameValuePair("password","123"));
    httpPost .setEntity(new UrlEncodedFormEntity(params));    

            HttpResponse httpResponse = httpClient.execute(httpPost);
            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;

    }
}

在您的活动中，在 AsyncTask 中使用您的 url 调用此 json 解析器。

后获得JSON数据借鉴JSON的一些基本W3Schools的查看完整的代码在这里

Answer 2

我建议您阅读Gson制作 json 字符串的教程，并使用Volley 库进行请求和响应。