java - 如何在 Java 中用 JSON 生成 "raw"字符串

Question

我正在为学校 atm 编写一个 android 应用程序。我有股票，想请你帮我。到目前为止，我了解如何使用 PHP 从 MySQL 数据库中打印数据，准备好用 Java 进行解析。然后是我的代码(取自此处:http://www.helloandroid.com/tutorials/connecting-mysql-database)takes 数据并将其转换为我认为的字符串。

所以我的问题是:我如何为 eksample make 和 if 语句检查用户数据是否正确？我只是不明白!

这是我使用的 Activity (登录表单)的所有代码:

package com.example.fungi;


import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;




public class MainActivity extends Activity {
//Intent i = new Intent(getBaseContext(), MainPageActivity.class);                      
//startActivity(i);
Button login;
EditText username;
EditText password;
TextView lol;
JSONArray jArray;
String result = null;
InputStream is = null;
StringBuilder sb=null;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //ActionBar actionBar = getActionBar();
    //actionBar.hide();
    lol = (TextView) findViewById(R.id.textView1);
    login = (Button) findViewById(R.id.loginbutton);
    username = (EditText) findViewById(R.id.usernametext);
    password = (EditText) findViewById(R.id.passwordtext);
    login.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String usernameget = username.getText().toString();
            String passwordget = password.getText().toString();

            if(usernameget.contentEquals("")){
                username.setText("usernam required");
            }else {
                if(passwordget.contentEquals("")){
                    username.setText("password required");
                }else {
                    String userid = username.getText().toString();
                    Intent intent = new Intent(getBaseContext(), Side.class);
                    intent.putExtra("sessionid", userid);
                    startActivity(intent);

                    }

            }

        }

    });
    String result = "";
    //the year data to send
    ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
    nameValuePairs.add(new BasicNameValuePair(result, result));

    //http post
    try{
          HttpClient httpclient = new DefaultHttpClient();
          HttpPost httppost = new HttpPost("http://http://fungi.webatu.com/Index.php");
          httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
          HttpResponse response = httpclient.execute(httppost);
          HttpEntity entity = response.getEntity();
          InputStream is = entity.getContent();
      }catch(Exception e11){
      Log.e("log_tag", "Fejl i HTTP connection "+e11.toString());
      }

    //convert response to string
    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();

          result=sb.toString();
    }catch(Exception e){
          Log.e("log_tag", "Fejl i resultat konvertering "+e.toString());
    }

    //parse json data
    try{
          JSONArray jArray = new JSONArray(result);
          for(int i=0;i<jArray.length();i++){
                  JSONObject json_data = jArray.getJSONObject(i);
                  Log.i("log_tag","id: "+json_data.getInt("id")+
                          ", username: "+json_data.getString("username")+
                         ", password: "+json_data.getString("password")+
                          ", alder: "+json_data.getInt("alder"));


                //maybe if statement here?


                  ;
          }

    } 
    catch(JSONException e1){
          Log.e("log_tag", "Error parsing data "+e1.toString());
    }


}



}

提前致谢!!

Answer 1

我不确定你的问题，但我认为你想从网络服务中获取一些 JSON 数据。

开发到Android，不能在主线程使用网络资源。所以你需要开始一个新线程。为此，您可以使用 AsyncTask 或使用 Thread 类。

    public static JSONArray getJSONArrayFromURL(String url) {

    // initialize
    InputStream is = null;
    String result = "";
    JSONArray jArray = null;

    Log.d("URL_SEARCH", url);

    // http post
    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();
    } catch (Exception e) {
        Log.e("log_tag", "Error in http connection " + e.toString());
    }

    // convert response to string
    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "utf-8"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        result = sb.toString();
    } catch (Exception e) {
        Log.e("log_tag", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jArray = new JSONArray(result);

        Log.d("URL_SEARCH", "JSON: " + jArray.length());

    } catch (JSONException e) {
        Log.e("log_tag", "Error parsing data " + e.toString());
    }

    return jArray;
}