Android Httppost奇怪的行为

Question

我有一个Android应用程序示例，我试图将其包含到我的应用程序中。此示例显示如何连接到MySql数据库并读取存储在其中的信息（通过php文件）。如果我使用该示例一切正常，但如果我将Java文件包含到我的应用程序中它不会连接到数据库（我总是得到＆＃34;连接失败＆＃34;）。这是一段代码：

public class DbselectActivity extends Activity {    
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Button button = (Button) findViewById(R.id.button1);
    button.setOnClickListener(new View.OnClickListener() {
      public void onClick(View view) {
        String result = null;
        InputStream is = null;
        try {
          HttpClient httpclient = new DefaultHttpClient();
          HttpPost httppost = new HttpPost("http://www.volantinoweb.it/prova/selectall.php");
          HttpResponse response = httpclient.execute(httppost); 
          HttpEntity entity = response.getEntity();
          is = entity.getContent();
        }
            catch(Exception e) {
          Toast.makeText(getApplicationContext(), "Connection fail", Toast.LENGTH_SHORT).show();
        }
            //convert response to string
            try {
          BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
          StringBuilder sb = new StringBuilder();
          String line = null;
          while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
                //  Toast.makeText(getApplicationContext(), "Input Reading pass", Toast.LENGTH_SHORT).show();
          }
          is.close();
          result=sb.toString();
        }
            catch(Exception e) {
              Toast.makeText(getApplicationContext(), " Input reading fail", Toast.LENGTH_SHORT).show();
            }  

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