aac播放器应用程序崩溃，如果没有网络连接android

Question

嗨，我有我的aacplayer应用程序，但是当我断开所有连接我的意思是WiFi +移动数据，并尝试打开应用程序它崩溃无法打开，我想要做的是在主要活动中向用户显示一条消息：Theres no connectivity please try again。

我的应用程序是这样的：

我有一个列表视图，然后从XML我加载许多电台的数据，那么，当我在一个点击打开AAC播放器正常播放。我也用于流式传输服务。

如何避免应用程序崩溃？

继承人我的主要活动：

public class Principal extends Activity { 

    protected TextView title; 
    protected ImageView icon; 
    static final String URL = "http://www.streaming507.com/estaciones.xml"; 
    static final String KEY_ESTACION = "estacion"; 
    static final String KEY_ID = "id"; 
    static final String KEY_NOMBRE = "nombre"; 
    static final String KEY_WEB = "web"; 
    static final String KEY_SHOUTCAST = "shoutcast"; 
    static final String KEY_MINIATURA = "miniatura"; 
    static final String KEY_LOGO = "logo"; 
    private static final int DIALOG_ALERT = 10; 
    public static Activity handleToClose; 
    ListView list; 
    LazyAdapter adapter; 
    private Button botonactualizar; 

    public void actualizar() { 
     title = (TextView) findViewById(R.id.title); 
     icon = (ImageView) findViewById(R.id.icon); 
     ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>(); 
     XMLParser parser = new XMLParser(); 
     String xml = parser.getXmlFromUrl(URL); 
     Document doc = parser.getDomElement(xml); 
     NodeList nl = doc.getElementsByTagName(KEY_ESTACION); 

     for (int i = 0; i < nl.getLength(); i++) { 
      HashMap<String, String> map = new HashMap<String, String>(); 
      Element e = (Element) nl.item(i); 
      map.put(KEY_ID, parser.getValue(e, KEY_ID)); 
      map.put(KEY_NOMBRE, parser.getValue(e, KEY_NOMBRE)); 
      map.put(KEY_WEB, parser.getValue(e, KEY_WEB)); 
      map.put(KEY_SHOUTCAST, parser.getValue(e, KEY_SHOUTCAST)); 
      map.put(KEY_MINIATURA, parser.getValue(e, KEY_MINIATURA)); 
      map.put(KEY_LOGO, parser.getValue(e, KEY_LOGO)); 
      songsList.add(map); 
     } 

     list = (ListView) findViewById(R.id.list); 
     adapter = new LazyAdapter(this, songsList); 
     list.setAdapter(adapter); 
     list.setOnItemClickListener(new OnItemClickListener() { 

      @Override 
      public void onItemClick(AdapterView<?> parent, View view, 
        int position, long id) { 

       String url = ((TextView) view.findViewById(R.id.shoutcast)) 
         .getText().toString(); 
       String logo = ((TextView) view.findViewById(R.id.logo)) 
         .getText().toString(); 

       try { 
        stopService(new Intent(view.getContext(), MyService.class)); 
       } catch (Exception ex) { 
       } 

       Intent myIntent = new Intent(view.getContext(), 
         AACPlayerActivity.class); 
       myIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP 
         | Intent.FLAG_ACTIVITY_SINGLE_TOP); 
       myIntent.putExtra("URL", url); 
       myIntent.putExtra("LOGO", logo); 
       startActivity(myIntent); 
      } 
     }); 
    } 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     requestWindowFeature(Window.FEATURE_CUSTOM_TITLE); 
     setContentView(R.layout.main); 
     getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, 
       R.layout.window_title); 
     handleToClose = this; 
     actualizar(); 
     botonactualizar = (Button)findViewById(R.id.botonactualizar); 

     botonactualizar.setOnClickListener(new OnClickListener() { 

     @Override 
     public void onClick(View vw) { 
      actualizar(); 
       Toast.makeText(Principal.this, "Lista de estaciones actualizada", 
         Toast.LENGTH_SHORT).show(); 
     } 
     }); 


    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     MenuInflater menuInflater = getMenuInflater(); 
     menuInflater.inflate(R.layout.menu_opciones1, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 

     switch (item.getItemId()) { 
     case R.id.menu_actualizar: 
      actualizar(); 
      Toast.makeText(Principal.this, "Lista de estaciones actualizada", 
        Toast.LENGTH_SHORT).show(); 
      return true; 

     case R.id.menu_salir: 
      showDialog(DIALOG_ALERT); 
      return true; 

     default: 
      return super.onOptionsItemSelected(item); 
     } 
    } 

    @Override 
    protected Dialog onCreateDialog(int id) { 
     switch (id) { 
     case DIALOG_ALERT: 
      Builder builder = new AlertDialog.Builder(this); 
      builder.setMessage("Desea salir de la aplicacion?"); 
      builder.setCancelable(true); 
      builder.setPositiveButton("Si", new OkOnClickListener()); 
      builder.setNegativeButton("No", new CancelOnClickListener()); 
      AlertDialog dialog = builder.create(); 
      dialog.show(); 
     } 
     return super.onCreateDialog(id); 
    } 

    private final class CancelOnClickListener implements 
      DialogInterface.OnClickListener { 
     public void onClick(DialogInterface dialog, int which) { 
     } 
    } 

    private final class OkOnClickListener implements 
      DialogInterface.OnClickListener { 
     public void onClick(DialogInterface dialog, int which) { 
      finish(); 
      stopService(new Intent(Principal.this, MyService.class)); 
      String ns = Context.NOTIFICATION_SERVICE; 
      NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns); 
      mNotificationManager.cancel(1); 
     } 
    } 
} 

我知道有个东西叫connectivitymanager，但我不知道我必须建立在我的主要活动中或在流服务，所以当我打开应用程序没有互联网我可以看到一条消息：请再试一次。然后刷新按钮，所以如果互联网打开，那么我可以从网页XML加载列表。

谢谢。

编辑：

即时得到这个错误，当我打开应用程序没有互联网conectivity

ava.net.UnknownHostException: Unable to resolve host "www.mydomain.com": No address associated with hostname 

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.spoledge.aacplayer/com.spoledge.aacplayer.Principal}: java.lang.NullPointerException 

Answer 1

把这样的方法在你的Activity ...

private boolean isConnected() { 
    boolean haveConnectedWifi = false; 
    boolean haveConnectedMobile = false; 

    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 
    NetworkInfo[] netInfo = cm.getAllNetworkInfo(); 
    for (NetworkInfo ni : netInfo) { 
     if (ni.getTypeName().equalsIgnoreCase("WIFI")) 
      if (ni.isConnected()) 
       haveConnectedWifi = true; 
     if (ni.getTypeName().equalsIgnoreCase("MOBILE")) 
      if (ni.isConnected()) 
       haveConnectedMobile = true; 
    } 
    return haveConnectedWifi || haveConnectedMobile; 
} 

从说它在onResume()内Activity或您希望开始流式传输之前的任何时间。

Answer 2

解决这个将此代码添加到我的主要活动：

public boolean isOnline() { 
     ConnectivityManager connectionManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 
     try { 
      if (connectionManager.getActiveNetworkInfo().isConnected()) { 
       Log.d("ConStatus", "Data Connection On"); 
       return true; 
      } else { 
       Log.d("ConStatus", "Data Connection off"); 
       return false;   
      } 
     } catch (NullPointerException e) { 
      // No Active Connection 
      Log.i("ConStatus", "No Active Connection"); 
      return false; 
     } 
    } 

然后在OnCreate：

} else { 
       Log.d("Connection Status", "Connection Not Available"); 

       AlertDialog alertDialog = new AlertDialog.Builder(this).create(); 
       alertDialog.setTitle("No hay conexion a internet disponible"); 
       alertDialog.setMessage("La conexion a Internet es necesaria para el uso de esta aplicacion."); 
       alertDialog.setButton("OK", new DialogInterface.OnClickListener() { 
        public void onClick(DialogInterface dialog, int which) { 
         // here you can add functions 

         finish(); 
        } 
       }); 
       alertDialog.show(); 
      } 
     } catch(NullPointerException e){ 
        Log.d("Connection Status", "Connection Not Available"); 

        AlertDialog alertDialog = new AlertDialog.Builder(this).create(); 
        alertDialog.setTitle("No hay conexion a internet disponible"); 
        alertDialog.setMessage("La conexion a Internet es necesaria para el uso de esta aplicacion."); 
        alertDialog.setButton("OK", new DialogInterface.OnClickListener() { 
         public void onClick(DialogInterface dialog, int which) { 
          // here you can add functions 

         finish(); 
         } 
        }); 
        alertDialog.show(); 
       } 
    } 

现在的作品，活动开始前，检查连接并显示一个对话框，如果用户不连接到互联网，然后关闭活动。

谢谢