Question

我必须从服务器上的MySQL数据库中获取一些数据。我有以下代码。但是当我运行它时应用程序崩溃了。即使我在Android Manifest中指定了Internet权限，我也会在Logcat中获得 Permission denied（缺少INTERNET权限？）。知道这里可能有什么问题吗？

Java文件

import android.app.Activity;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends Activity {

    TextView text;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

        connect();
    }
    private void connect() {
        String data;
        List<String> r = new ArrayList<String>();
        ArrayAdapter<String>adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,r);
        ListView list=(ListView)findViewById(R.id.listView1);
        try {
            DefaultHttpClient client = new DefaultHttpClient();
            HttpGet request = new HttpGet("http://xxxxx/data.php");
            HttpResponse response = client.execute(request);
            HttpEntity entity=response.getEntity();
            data=EntityUtils.toString(entity);
            Log.e("STRING", data);

            try {

                JSONArray json=new JSONArray(data);
                for(int i=0;i<json.length(); i++)
                {
                    JSONObject obj=json.getJSONObject(i);
                    String name=obj.getString("name");
                    String desc=obj.getString("description");
                   // String lat=obj.getString("lat");
                    Log.e("STRING", name);
                    r.add(name);
                    r.add(desc);
                  //  r.add(lat);
                    list.setAdapter(adapter);

                }

            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        } catch (ClientProtocolException e) {
            Log.d("HTTPCLIENT", e.getLocalizedMessage());
        } catch (IOException e) {
            Log.d("HTTPCLIENT", e.getLocalizedMessage());
        }


    }

}

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.diana.menu" >

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <uses-permission android:name="android.permission.INTERNET"/>
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

data.php

<?php
$conn=mysql_connect('localhost', 'xxxx', 'xxxxx','u199776286_pois');

if(!$conn )
{
  die('Could not connect: ' . mysql_error());
}

$sql = 'SELECT name, description FROM pois';

mysql_select_db('u199776286_pois');
$retval = mysql_query( $sql, $conn );

if(! $retval )
{
  die('Could not get data: ' . mysql_error());
}
while($row = mysql_fetch_array($retval, MYSQL_ASSOC))
{
    echo "NAME : {$row['name']} <br> ".
         "DESCRIPTION : {$row['description']} <br> ".
         "--------------------------------<br>";
} 
echo "Fetched data successfully\n";
mysql_close($conn);


?>

我的logcat enter image description here

Answer 1

这是因为您从主UI线程连接到MySQL服务器。创建一个辅助线程（或异步任务）来连接并获得结果。

Answer 2

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

编写上面的代码并不是摆脱NetworkOnMainThreadException的更好方法。您必须使用任何后台线程在api 11上面的android中进行网络操作，例如Asynch Task，Intent Service等。

How to fix android.os.NetworkOnMainThreadException?

您还可以将执行程序用于网络任务

Executors.newSingleThreadExecutor().submit(new Runnable() { 
    @Override
    public void run() {
        //You can performed your task here.
    }
});

Answer 3

使用Async Task从数据库中获取数据..

Answer 4

在AndroidManifest.xml

中添加互联网权限

<uses-permission android:name="android.permission.INTERNET" />

使用Asynck Task

 List<String> r = new ArrayList<String>();

需要声明connect（）;

Oncreate

 new LongOperation().execute("");

现在创建

 private class LongOperation extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... params) {
             connect();
            return "Executed";
        }

        @Override
        protected void onPostExecute(String result) {
          ArrayAdapter<String>adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,r);
         ListView list=(ListView)findViewById(R.id.listView1);
         list.setAdapter(adapter);
        }

        @Override
        protected void onPreExecute() {}

        @Override
        protected void onProgressUpdate(Void... values) {}
    }

//需要从connect();中移除Ui控件并且需要值在onPostExecute

上绑定它

Answer 5

使用Async。如需更多帮助，请查看this

Android从mySql获取数据

5 个答案: