在上一篇文章中，我在连接了网络摄像头的模拟器中启动摄像头应用程序时收到此错误：
CameraService::connect X (pid 702) rejected (invalid cameraId 0).
更新开发工具后，我得到了另一个错误（然后，在制作新的模拟器后，我又得到了第一个错误）：
03-15 03:44:04.272: E/EmulatedCamera_QemuClient(40): queryStart: Query failed: Cannot start the camera
03-15 03:44:04.272: E/EmulatedCamera_QemuDevice(40): startDevice: Unable to start device 'AndroidEmulatorVC0' for NV21[640x480] frames
[...]
03-15 03:31:15.922: E/AndroidRuntime(785): FATAL EXCEPTION: Thread-76
03-15 03:31:15.922: E/AndroidRuntime(785): java.lang.RuntimeException: startPreview failed
03-15 03:31:15.922: E/AndroidRuntime(785): at com.android.camera.Camera.startPreview(Camera.java:1867)
03-15 03:31:15.922: E/AndroidRuntime(785): at com.android.camera.Camera.access$3100(Camera.java:87)
03-15 03:31:15.922: E/AndroidRuntime(785): at com.android.camera.Camera$5.run(Camera.java:1112)
03-15 03:31:15.922: E/AndroidRuntime(785): at java.lang.Thread.run(Thread.java:856)
03-15 03:31:15.922: E/AndroidRuntime(785): Caused by: java.lang.RuntimeException: startPreview failed
03-15 03:31:15.922: E/AndroidRuntime(785): at android.hardware.Camera.startPreview(Native Method)
03-15 03:31:15.922: E/AndroidRuntime(785): at com.android.camera.Camera.startPreview(Camera.java:1864)
03-15 03:31:15.922: E/AndroidRuntime(785): ... 3 more
是什么导致了这个错误？我怎样才能最好地解决这个问题？