我希望能够使用我的 android 设备连接到 mySQL 数据库，发送将在 SQL 语句中使用的参数，并且我希望返回结果并能够呈现它。这听起来很简单，但我能找到的所有教程和示例都受到以下问题的影响：
- 极度过度构建（至少 10 个类才能制作出完美的按钮）
- 令人难以置信的混乱（没有评论、解释和迟钝的变量名称）
- 依赖于不存在的类
如果我去掉一些不必要的东西，一切都会崩溃，所以我无法提取真正重要的东西以使其远程可读/可理解。
因此，以最简单的方式：我的 android 应用程序需要什么来连接到我的数据库？如何向 php-script 发送参数？如何从中生成 android 应用程序可以读取的结果？
更新，剥离必需品 1 因此，正如我在对 SoftCoder 的回答的评论之一中提到的，我将尝试使用他的完整应用程序并去掉花哨的东西，以获得连接到 mySQL 所需的东西。
首先，我已<uses-permission android:name="android.permission.INTERNET" />在清单中添加。.php 看起来像这样（主机、用户、密码等实际上是另一回事）：
<?php
$con = mysql_connect("HOST","USER","PASSWORD");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("database_name", $con);
$result = mysql_query("SELECT * FROM Table;");
while($row = mysql_fetch_array($result))
{
echo $row['col1'];
echo $row['col2'];
}
mysql_close($con);
?>
此脚本打印出表中的所有条目。
现在到完整的活动！
package com.example.project;
import java.io.*;
import org.apache.http.HttpResponse;
import org.apache.http.client.*;
import org.apache.http.client.methods.*;
import org.apache.http.impl.client.*;
import org.json.*;
import android.app.*;
import android.os.*;
import android.util.*;
import android.view.*;
import android.widget.*;
public class MainActivity extends Activity
{
private String jsonResult;
private String url = "url_to_php";
InputStream is=null;
String result=null;
String line=null;
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//supposedly the app wont crash with "NetworkOnMainThreadException". It crashes anyway
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
//create our Async class, because we can't work magic in the mainthread
JsonReadTask task = new JsonReadTask();
task.execute(new String[] { url });
}
private class JsonReadTask extends AsyncTask<String, Void, String>
{
// doInBackground Method will not interact with UI
protected String doInBackground(String... params)
{
// the below code will be done in background
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(params[0]);
try
{
//not sure what this does but it sounds important
HttpResponse response = httpclient.execute(httppost);
//took the "stringbuilder" apart and shoved it here instead
String rLine = "";
StringBuilder answer = new StringBuilder();
BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
while ((rLine = rd.readLine()) != null)
answer.append(rLine);
//put the string into a json, don't know why really
jsonResult = answer.toString();
}
catch (ClientProtocolException e)
{
e.printStackTrace();
Log.e("Fail 12", e.toString());
}
catch (IOException e)
{
Log.e("Fail 22", e.toString());
e.printStackTrace();
}
return null;
}
}
// after the doInBackground Method is done the onPostExecute method will be called
protected void onPostExecute(String result) throws JSONException
{
// I skipped the method "drwer"-something and put it here instead, since all this method did was to call that method
// getting data from server
JSONObject jsonResponse = new JSONObject(jsonResult);
if(jsonResponse != null)
{
//I think the argument here is what table we'll look at... which is weird since we use php for that
JSONArray jsonMainNode = jsonResponse.optJSONArray("Tablename");
// get total number of data in table
for (int i = 0; i < jsonMainNode.length(); i++)
{
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
String name = jsonChildNode.optString("col1"); // here name is the table field
String number = jsonChildNode.optString("col2"); // here id is the table field
String outPut = name + number ; // add two string to show in listview
//output to log instead of some weird UI on the device, just to see if it connects
Log.d("Log", outPut.toString());
}
}
}
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
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();
if (id == R.id.action_settings)
return true;
return super.onOptionsItemSelected(item);
}
}
所以这就是我迄今为止想出的“尽可能简单”，没有花哨的 UI 或在方法之间跳转（使用良好的代码约定在这里并不重要）。由于就像其他人已经说过的那样，一切都会因“NetworkOnMainThreadException”而崩溃，因此无法对其进行测试。即使我同时使用 AsyncTask 并调用 Strict-thingy，为什么它会因此异常而崩溃？