Question

public class BindingActivity extends Activity {
    LocalService mService;
    boolean mBound = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    @Override
    protected void onStart() {
        super.onStart();
        // Bind to LocalService
        Intent intent = new Intent(this, LocalService.class);
        bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onStop() {
        super.onStop();
        // Unbind from the service
        if (mBound) {
            unbindService(mConnection);
            mBound = false;
        }
    }

    /** Called when a button is clicked (the button in the layout file attaches to
      * this method with the android:onClick attribute) */
    public void onButtonClick(View v) {
        if (mBound) {
            // Call a method from the LocalService.
            // However, if this call were something that might hang, then this request should
            // occur in a separate thread to avoid slowing down the activity performance.
            int num = mService.getRandomNumber();
            Toast.makeText(this, "number: " + num, Toast.LENGTH_SHORT).show();
        }
    }

    /** Defines callbacks for service binding, passed to bindService() */
    private ServiceConnection mConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName className,
                IBinder service) {
            // We've bound to LocalService, cast the IBinder and get LocalService instance
            LocalBinder binder = (LocalBinder) service;
            mService = binder.getService();
            mBound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            mBound = false;
        }
    };
}

这是http://developer.android.com/guide/components/bound-services.html中的一个例子。我想直接使用mService，不需要先点击按钮，我该怎么办。我尝试了很多方法，但它们都行不通。

Answer 1

我怀疑你遇到的问题是绑定到服务是异步的。因此，您需要等到恢复服务后才可以打电话给它。如果调用bindService（intent，mConnection，Context.BIND_AUTO_CREATE）;从onCreate开始，你可能在活动启动生命周期中的任何时候都没有服务...... mService仍然是null。如果您不想让用户这样做等待您（通过花几秒钟点击按钮），您只需从onServiceConnected方法调用mService即可，它应该可以正常工作。无论哪种方式，关键是等待对mService进行任何调用，直到运行onServiceConnected并且mService不再为null。（这可能会发生在甚至onResume之后）。这有意义吗？

绑定后使用服务而不单击按钮

1 个答案: