远程服务不绑定/asInterface 返回“null”

Question

我在本书中的示例之后创建了一个远程服务并尝试绑定它在此活动中：

public class TuCanMobileActivity extends Activity {
/** Called when the activity is first created. */
//private HTTPSbrowser mBrowserService;
private HTTPBrowserRemote mBrowserRemoteService;
private Boolean mbound=false;
private ServiceConnection mBrowserRemoteServiceConnection = 
    new ServiceConnection() {           
        @Override
        public void onServiceDisconnected(ComponentName name) {
            try {
                mBrowserRemoteService.unregister_course_callback(courseCallback);
            } catch (RemoteException e) {}
        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mBrowserRemoteService=HTTPBrowserRemote.Stub.asInterface(service);
            mbound=true;
            try {
                mBrowserRemoteService.register_course_callback(courseCallback);

            }
            catch (RemoteException e) {
                // TODO: handle exception
            }
        }

};

private final IClassesCallback courseCallback =
    new IClassesCallback.Stub() {
        @Override
        public void expressClassesdata(HTTPSResponse ClassesResponse)
                throws RemoteException {
            Toast.makeText(TuCanMobileActivity.this, "Just works??", Toast.LENGTH_SHORT).show();

            final TextView txtLoginName = 
                (TextView) findViewById(R.id.textView1);
            txtLoginName.setText(ClassesResponse.HTMLResponse);
        }
    };

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
}
public void onClickSendLogin (final View sfNormal) {
    final Intent browserIntent = new Intent(TuCanMobileActivity.this,HTTPBrowserRemoteImpl.class);

    this.bindService(browserIntent, mBrowserRemoteServiceConnection, Context.BIND_AUTO_CREATE);
    if(mbound==true){
        Toast.makeText(TuCanMobileActivity.this, "Service Bound", Toast.LENGTH_SHORT).show();
    }
    else {
        Toast.makeText(TuCanMobileActivity.this, "Service NOT Bound", Toast.LENGTH_SHORT).show();
    }
    try {

        mBrowserRemoteService.call_course_overview();


    } catch (RemoteException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


    /*final Intent i = new Intent(this,MainMenu.class);
    startActivity(i);*/
    unbindService(mBrowserRemoteServiceConnection);
}
}

但是 mBrowsserRemoteService 为 null（在 onClickSendLogin 方法中）并返回 NullPointerException，我不知道为什么？服务中的 onBind 方法似乎也从未被调用过。我的问题出在哪里。

提前致谢 泰德

Answer 1

您收到 NullPointerException 的原因是因为您正在执行

mBrowserRemoteService.call_course_overview();

而不考虑 mbound； mbound 此时可能为真或为假。

我怀疑更大的问题是您无法绑定到此服务，很可能是因为您的 AndroidManifest.xml 配置不正确。如果您仍然遇到问题，请发布您的 AndroidManifest 文件。