【发布时间】：2015-04-22 13:55:53
【问题描述】：
我一直在开发一个使用远程 mysql 数据库检索数据的 java 应用程序。我在应用程序和数据库之间有一个网络服务，它以 JSON 格式输出数据。
我正在尝试解析 JSON 文件，没有收到任何错误，但 APP 上的屏幕是空白的。
我已经搜索了几个小时来寻找不同的方法来做到这一点，我已经整理出了我遇到的所有错误，但我不知道如何从这里开始。
MenuActivity.java
import android.content.Intent;
import android.os.AsyncTask;
import android.os.StrictMode;
import android.support.v4.app.NavUtils;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.webkit.WebView;
import android.widget.TextView;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
public class MenuActivity extends ActionBarActivity {
// The JSON REST Service
static String URL = "http://alirajrestaurant.com/app/get.php";
// Will hold the values I pull from the JSON
static String itmName = "";
static String itmDesc = "";
static String itemPrice = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_menu);
//Add Toolbar
Toolbar toolbar=(Toolbar) findViewById(R.id.app_bar);
setSupportActionBar(toolbar);
//Setup Home Navigation Button
getSupportActionBar().setHomeButtonEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true); //display UP Icon
new MyAsyncTask().execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
//Navigate Right Button on Toolbar to get to next Activity
if(id==R.id.navigate_right)
{
startActivity(new Intent(this,ResActivity.class));
}
//What to do if Home Button is clicked
if(id==android.R.id.home)
{
NavUtils.shouldUpRecreateTask(this, new Intent(this,MainActivity.class));
}
return super.onOptionsItemSelected(item);
}
private class MyAsyncTask extends AsyncTask<String, String, String> {
protected String doInBackground(String... arg0) {
// HTTP Client that supports streaming uploads and downloads
DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
// Define that I want to use the POST method to grab data from
// the provided URL
HttpPost httppost = new HttpPost(URL);
// Web service used is defined
httppost.setHeader("Content-type", "application/json");
// Used to read data from the URL
InputStream inputStream = null;
// Will hold the whole all the data gathered from the URL
String result = null;
try {
// Get a response if any from the web service
HttpResponse response = httpclient.execute(httppost);
// The content from the requested URL along with headers, etc.
HttpEntity entity = response.getEntity();
// Get the main content from the URL
inputStream = entity.getContent();
// JSON is UTF-8 by default
// BufferedReader reads data from the InputStream until the Buffer is full
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
// Will store the data
StringBuilder theStringBuilder = new StringBuilder();
String line = null;
// Read in the data from the Buffer untilnothing is left
while ((line = reader.readLine()) != null)
{
// Add data from the buffer to the StringBuilder
theStringBuilder.append(line + "\n");
}
// Store the complete data in result
result = theStringBuilder.toString();
} catch (Exception e) {
e.printStackTrace();
}
finally {
// Close the InputStream when you're done with it
try{if(inputStream != null)inputStream.close();}
catch(Exception e){}
}
// Holds Key Value pairs from a JSON source
JSONObject jsonObject;
try {
JSONObject jObject = new JSONObject(result.substring(3));
// GET ARRAY DATA
JSONArray jArray = new JSONArray();
JSONObject oneObject = jArray.getJSONObject(' ');
// Pulling items from the array
itmName = oneObject.getString("name");
itmDesc =oneObject.getString("desc");
itemPrice = oneObject.getString("price");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
protected void onPostExecute(String result){
// Gain access so I can change the TextViews
TextView line1 = (TextView)findViewById(R.id.name_result);
TextView line2 = (TextView)findViewById(R.id.desc_result);
TextView line3 = (TextView)findViewById(R.id.price_result);
// Change the values for all the TextViews
line1.setText( itmName);
line2.setText(itmDesc);
line3.setText("£: " + itemPrice);
}
}
}
JSONParse.java
public class JSONParse {
public JSONArray GetAllItems()
{
// URL for getting all customers
String url = "http://alirajrestaurant.com/app/get.php";
// Get HttpResponse Object from url.
// Get HttpEntity from Http Response Object
HttpEntity httpEntity = null;
try
{
DefaultHttpClient httpClient = new DefaultHttpClient(); // Default HttpClient
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
httpEntity = httpResponse.getEntity();
} catch (ClientProtocolException e) {
// Signals error in http protocol
e.printStackTrace();
//Log Errors Here
} catch (IOException e) {
e.printStackTrace();
}
// Convert HttpEntity into JSON Array
JSONArray jsonArray = null;
if (httpEntity != null) {
try {
String entityResponse = EntityUtils.toString(httpEntity);
Log.e("Entity Response : ", entityResponse);
jsonArray = new JSONArray(entityResponse);
} catch (JSONException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
return jsonArray;
}
}
PHP 脚本
<?php
$db_host = 'localhost';
$db_name = 'abx';
$db_user= 'abx';
$user_pw = 'abx';
//PDO is a extension which defines a lightweight, consistent interface for accessing databases in PHP.
$dbn='mysql:host='.$db_host.'; dbname='.$db_name;
try {
$db=new PDO('mysql:host='.$db_host.'; dbname='.$db_name,$db_user,$user_pw );
}
catch (PDOException $e) {
$error_message = $e->getMessage();
echo "this is displayed because an error was found";
exit();
}
//here prepare the query for analyzing, prepared statements use less resources and thus run faster
$row=$db->prepare('select itemName, itemDescription, itemPrice from tblMenu');
$row->execute();//execute the query
$json_data=array();//create the array
foreach($row as $rec)//foreach loop
{
$json_array['name']=$rec['itemName'];
$json_array['desc']=$rec['itemDescription'];
$json_array['price']=$rec['itemPrice'];
//here pushing the values in to an array
array_push($json_data,$json_array);
}
//built in PHP function to encode the data in to JSON format
echo json_encode($json_data);
?>
如果有人可以帮助我，我会很感激，现在这开始让我发疯了......
【问题讨论】：