Android无法正确连接到MySQL数据库

时间：2012-03-26 20:38:17

标签： php android mysql android-networking

我正在尝试获取从MySQL服务器发送和接收数据的Android应用程序的基础知识（我的实现将与此学习示例无关）。这是迄今为止的代码：

package com.davekelley.polling;

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.ParseException;
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.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ActionBar;
import android.app.Activity;
import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

public class Chart extends Activity {

    JSONArray jArray;
    String result = null;
    InputStream is = null;
    StringBuilder sb=null;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.chartfragment);

        ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
        //http post
        try{
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://www.davidjkelley.net/city.php");
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            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,"iso-8859-1"),8);
            sb = new StringBuilder();
            sb.append(reader.readLine() + "\n");

            String line="0";
            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());
        }
        //paring data
        int ct_id;
        String ct_name;
        try{
            jArray = new JSONArray(result);
            JSONObject json_data=null;
            for(int i=0;i<jArray.length();i++){
                json_data = jArray.getJSONObject(i);
                ct_id=json_data.getInt("CITY_ID");
                ct_name=json_data.getString("CITY_NAME");
            }
        }
        catch(JSONException e1){
            Toast.makeText(getBaseContext(), "No City Found" ,Toast.LENGTH_LONG).show();
        } catch (ParseException e1) {
            e1.printStackTrace();
        }
    }
}

这是XML文件'chartfragment'的代码：

<?xml version="1.0" encoding="utf-8"?>
    <ListView xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

<!-- <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/chartTitleTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge" android:gravity="center"/>
-->

    </ListView>

以下是我遇到的LogCat问题：

03-26 20:34:13.782: E/log_tag(1025): Error in http connection android.os.NetworkOnMainThreadException
03-26 20:34:13.802: E/log_tag(1025): Error converting result java.lang.NullPointerException
03-26 20:34:13.802: D/AndroidRuntime(1025): Shutting down VM
03-26 20:34:13.802: W/dalvikvm(1025): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
03-26 20:34:13.832: E/AndroidRuntime(1025): FATAL EXCEPTION: main
03-26 20:34:13.832: E/AndroidRuntime(1025): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.davekelley.polling/com.davekelley.polling.Chart}: java.lang.NullPointerException
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.os.Looper.loop(Looper.java:137)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.ActivityThread.main(ActivityThread.java:4424)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at java.lang.reflect.Method.invokeNative(Native Method)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at java.lang.reflect.Method.invoke(Method.java:511)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at dalvik.system.NativeStart.main(Native Method)
03-26 20:34:13.832: E/AndroidRuntime(1025): Caused by: java.lang.NullPointerException
03-26 20:34:13.832: E/AndroidRuntime(1025):     at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at org.json.JSONTokener.nextValue(JSONTokener.java:94)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at org.json.JSONArray.<init>(JSONArray.java:87)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at org.json.JSONArray.<init>(JSONArray.java:103)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at com.davekelley.polling.Chart.onCreate(Chart.java:68)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.Activity.performCreate(Activity.java:4465)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
03-26 20:34:13.832: E/AndroidRuntime(1025):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
03-26 20:34:13.832: E/AndroidRuntime(1025):     ... 11 more

很明显，主线程问题上的网络连接意味着我需要将其移动到Asynctask中，对吧？但是有了这么多错误，我想知道我是否遗漏了其他东西，这是显而易见的？我最终希望能够将用户/密码注册到数据库，然后获取查询并发送响应，所以这只是一个热身。如果您转到http://www.davidjkelley.net/city.php，您可以看到数据库确实正确响应了我在Android代码中链接的查询PHP文件，所以这不是问题所在。

编辑〜我应该注意我的Activity以前扩展了列表Activity，遵循本教程：http://blog.sptechnolab.com/2011/02/10/android/android-connecting-to-mysql-using-php/这就是为什么我的XML目前只是一个ListView，因为这有助于清除一个错误，说我需要一个ListView组件的id为'list'。

编辑〜我的PHP代码：

<?php
mysql_connect("127.0.0.1","***","***");
mysql_select_db("***");
$sql=mysql_query("select * from CITY where CITY_NAME like 'A%'");
while($row=mysql_fetch_assoc($sql))
$output[]=$row;
print(json_encode($output));
mysql_close();
?>

显然，星组是正确的信息，就像您访问上面发布的链接一样，SQL读数正确显示。

1 个答案:

答案 0 :(得分：2)

您如何运行数据库？发布PHP连接的方式可能更相关。很可能在PHP中，您没有将请求从应用程序连接到实际数据库（使用不正确的URL或数据库本身的名称）。查看this教程。我可以确认它工作正常，它似乎也完成了你需要的功能。在该教程中，有关于更改代码的位置的说明，以便您可以在托管服务器而不是localhost上运行它。

相关问题
最新问题