Camera previews are not displayed on SurfaceView

The preview is not displayed on the surface , the surface itself is created but remains empty.

 public class MainActivity extends AppCompatActivity { Camera camera; SurfaceView preview; SurfaceHolder surfaceHolder; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE); setContentView(R.layout.activity_main); preview = (SurfaceView) findViewById(R.id.surfaceView); surfaceHolder = preview.getHolder(); try { camera.setPreviewDisplay(surfaceHolder); } catch (IOException e) { e.printStackTrace(); } camera.startPreview(); } }