android camera函数getcameraIdlist（）函数不返回任何内容

Question

1. The code produces an IllegalArguementException .
2. The list does not seem to populate even though all permissions are given in the manifest .

3. The application crashes as soon as the Activity is opened.

   public class photo extends Activity { private Handler mhandler; public CameraDevice cam; private CameraDevice.StateCallback mcallback;

    public void setCallback(CameraDevice.StateCallback callback) { this.mcallback = callback; } public void setHandler(Handler handler) { this.mhandler = handler; } int count=0; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main_photo); String[] list=new String[10]; CameraManager camera = (CameraManager) getSystemService(Context.CAMERA_SERVICE); setCallback(mcallback); setHandler(mhandler); ListView cami = (ListView) findViewById(R.id.lv); ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.main_photo, R.id.textView2, list); cami.setAdapter(adapter); try { list = camera.getCameraIdList(); count++; } catch (CameraAccessException e) { e.printStackTrace(); } try { camera.openCamera(list[0], mcallback, mhandler); mcallback.onOpened(cam); } catch (CameraAccessException e) { e.printStackTrace(); Log.d("Photo", "Error in opening camera"); } catch (IllegalArgumentException a) { Log.d("Callback", "Callback Problem"); } } 

Answer 1

Unless I'm missing something, as far as I can tell mhandler and mcallback are both null in your calls to setCallback(mcallback) and setHandler(mhandler) . Try verifying these two variables before you call camera.openCamera(list[0], mcallback, mhandler) .

As a side note, the array String[] list=new String[10] is never used and your variable is reassigned 7 lines later. Maybe instead, use String[] list; Then 7 lines later, use list = camera.getCameraIdList(); Or simply String[] list=camera.getCameraIdList();