Android无法正确连接到MySQL数据库 [英] Android failing to connect to MySQL database properly
问题描述
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(我的实现与该学习示例无关).到目前为止，这是代码:
I'm trying to get the basics of an Android app that sends and receives data from a MySQL server (my implementation will have nothing to do with this learning example). Here's the code so far:
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:
And here's the code for the XML file 'chartfragment':
<?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>
这是我遇到的LogCat问题:
And here are the LogCat problems I'm encountering:
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
因此很明显，主线程上的网络连接问题意味着我需要将其移至Asynctask中，对吗?但是由于有如此多的错误，我想知道我是否还缺少其他东西，这很明显吗?我最终希望能够将用户/密码注册到数据库上，然后获取查询并发送响应，因此基本上这只是一个热身.如果您转到 http://www.davidjkelley.net/city.php ，您会看到数据库确实可以正确响应我在Android代码内链接的查询PHP文件，所以这不是问题.
So obviously the network connection on main thread problem means I need to move this into an Asynctask, right? But with such a bevy of errors, I wonder if I am missing something else, that's obvious? I eventually want to be able to register user/passwords onto a database, then get queries and send responses, so this is just a warm up basically. If you goto http://www.davidjkelley.net/city.php you can see that the database is indeed properly responding to the query PHP file that I have linked inside the Android code, so that's not the problem.
编辑〜我应该注意，本教程之后，我的活动"先前扩展了活动"列表:
Edit~ I should note that my Activity previously extended list Activity, following this tutorial: http://blog.sptechnolab.com/2011/02/10/android/android-connecting-to-mysql-using-php/ which is why my XML is just a ListView at the moment, because that helped clear up an error that said I needed a ListView component with the id 'list'.
编辑〜我的php代码:
Edit~ My php code:
<?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，星号集是正确的信息，因为当您访问上面发布的链接时，SQL读数正确显示.
Obviously the sets of stars are the correct information, as when you visited the link posted above, the SQL readout appears properly.
推荐答案
您如何运行数据库?发布PHP的连接方式可能更相关.在PHP中，您很可能没有将请求从应用程序连接到实际数据库(具有错误的url或数据库本身的名称).查看此教程.我可以确认它工作正常，并且似乎也可以完成您需要的功能.在该教程中，有关于更改代码位置的说明，以便您可以在托管服务器而不是localhost上运行它.
How are your running your database? Posting how the PHP connects may be more relevant. It's very possible that in the PHP you aren't connecting the request from the app to the actual database (either with an incorrect url or the name of the database itself). Check out this tutorial. I can confirm it works fine and it seems to accomplish the functionality you need as well. In that tutorial there are notes on where to change the code so that you can run it on your hosted server instead of localhost.
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