包含onStart方法会导致空指针异常

Question

我试图在我的主要活动绑定一个服务，我得到一个空指针异常。为了绑定服务，我在活动中添加了onStart()和onStop()方法，这些方法本身似乎会导致空指针异常。这是我通过仔细注释代码行得出的结论。

只是为了清楚，我也想提供更多的细节:

不会导致空指针异常:

   public class MainActivity extends Activity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {
    public VivaClientService VivaClient;    
    private static final String TAG = "Viva_MainActivity";
    private Intent ClientIntent;
    private ServiceConnection ClientConnect = new ServiceConnection(){
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                Log.d(TAG, "service connected");
                LocalBinder binder = (LocalBinder)service;
                VivaClient = binder.getService();
            }
            @Override
            public void onServiceDisconnected(ComponentName name) {
                Log.d(TAG, "service disconnected");
            }
     };
    //Fragment managing the behaviors, interactions and presentation of the navigation drawer.
    private NavigationDrawerFragment mNavigationDrawerFragment;
    //Used to store the last screen title. For use in {@link #restoreActionBar()}.
    private CharSequence mTitle;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();
        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
        ClientIntent = new Intent(this, VivaClientService.class);
    }
    /*
    @Override
    protected void onStart(){
        //this.bindService(ClientIntent, ClientConnect, Context.BIND_AUTO_CREATE);
        //this.startService(ClientIntent);
        //JSONObject about = VivaClient.getAbout();
        //System.out.println(about.toString());
    }

    @Override
    protected void onStop(){
    //  this.stopService(ClientIntent);
    //  this.unbindService(ClientConnect);
    }
    */

导致空指针异常:

public class MainActivity extends Activity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {
    public VivaClientService VivaClient;    
    private static final String TAG = "Viva_MainActivity";
    private Intent ClientIntent;
    private ServiceConnection ClientConnect = new ServiceConnection(){
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                Log.d(TAG, "service connected");
                LocalBinder binder = (LocalBinder)service;
                VivaClient = binder.getService();
            }
            @Override
            public void onServiceDisconnected(ComponentName name) {
                Log.d(TAG, "service disconnected");
            }
     };
    //Fragment managing the behaviors, interactions and presentation of the navigation drawer.
    private NavigationDrawerFragment mNavigationDrawerFragment;
    //Used to store the last screen title. For use in {@link #restoreActionBar()}.
    private CharSequence mTitle;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();
        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
        ClientIntent = new Intent(this, VivaClientService.class);
    }

    @Override
    protected void onStart(){
        //this.bindService(ClientIntent, ClientConnect, Context.BIND_AUTO_CREATE);
        //this.startService(ClientIntent);
        //JSONObject about = VivaClient.getAbout();
        //System.out.println(about.toString());
    }

    @Override
    protected void onStop(){
    //  this.stopService(ClientIntent);
    //  this.unbindService(ClientConnect);
    }

从字面上看，两者之间的唯一区别是包含onStart和onStop方法，当包含时，它们是空白的。我不明白为什么会产生错误。请帮忙;_;谢谢!

Answer 1

您没有从覆盖中调用super.onStart()或super.onStop()，这将导致活动抛出异常。