title: Android: Camera with SurfaceView
body: <p>I am trying to use Android's Camera with a SurfaceView, so the the user can preview the camera.  I followed various tutorials on StackOverflow, and finally ended up with Google's own tutorial, but my app crashed.  Here is my code.  I am using Eclipse's Android Virtual Device, emulated camera (which I don't think would affect anything) and 100mb sd card space alloted.</p>
  
  <p>There are two classes, a CameraPreview object and the CameraActivity.</p>
  
  <pre><code>public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback{
  
      private SurfaceHolder mHolder;
      private Camera mCamera;
      private final String TAG = "TAG";
  
      public CameraPreview(Context context, Camera camera) {
          super(context);
          mCamera = camera;
  
          // Install a SurfaceHolder.Callback so we get notified when the
          // underlying surface is created and destroyed.
          mHolder = getHolder();
          mHolder.addCallback(this);
          // deprecated setting, but required on Android versions prior to 3.0
          mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
      }
  
      public void surfaceCreated(SurfaceHolder holder) {
          // The Surface has been created, now tell the camera where to draw the preview.
          try {
              mCamera.setPreviewDisplay(holder);
              mCamera.startPreview();
          } catch (IOException e) {
              Log.d(TAG, "Error setting camera preview: " + e.getMessage());
          }
      }
  
      public void surfaceDestroyed(SurfaceHolder holder) {
          // empty. Take care of releasing the Camera preview in your activity.
      }
  
      public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
          // If your preview can change or rotate, take care of those events here.
          // Make sure to stop the preview before resizing or reformatting it.
  
          if (mHolder.getSurface() == null){
            // preview surface does not exist
            return;
          }
  
          // stop preview before making changes
          try {
              mCamera.stopPreview();
          } catch (Exception e){
            // ignore: tried to stop a non-existent preview
          }
  
          // set preview size and make any resize, rotate or
          // reformatting changes here
  
          // start preview with new settings
          try {
              mCamera.setPreviewDisplay(mHolder);
              mCamera.startPreview();
  
          } catch (Exception e){
              Log.d(TAG, "Error starting camera preview: " + e.getMessage());
          }
      }
  }
  
  
  public class CameraActivity extends Activity{
   private Camera mCamera;
      private CameraPreview mPreview;
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          // Create an instance of Camera
          mCamera = getCameraInstance();
  
          // Create our Preview view and set it as the content of our activity.
          mPreview = new CameraPreview(this, mCamera);
          FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
          preview.addView(mPreview);
      }
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          // Inflate the menu; this adds items to the action bar if it is present.
          getMenuInflater().inflate(R.menu.main, menu);
          return true;
      }
  
      public Camera getCameraInstance(){
          Camera c = null;
          try {
              c = Camera.open(); // attempt to get a Camera instance
          }
          catch (Exception e){
              // Camera is not available (in use or does not exist)
          }
          return c; // returns null if camera is unavailable
      }
  }
  </code></pre>
  
  <p>06-04 14:28:07.726: W/dalvikvm(6115): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
  06-04 14:28:07.956: E/AndroidRuntime(6115): FATAL EXCEPTION: main
  06-04 14:28:07.956: E/AndroidRuntime(6115): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mobilequote/com.example.mobilequote.CameraActivity}: java.lang.NullPointerException
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.os.Handler.dispatchMessage(Handler.java:99)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.os.Looper.loop(Looper.java:137)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.ActivityThread.main(ActivityThread.java:5041)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at java.lang.reflect.Method.invokeNative(Native Method)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at java.lang.reflect.Method.invoke(Method.java:511)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at dalvik.system.NativeStart.main(Native Method)
  06-04 14:28:07.956: E/AndroidRuntime(6115): Caused by: java.lang.NullPointerException
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at com.example.mobilequote.CameraActivity.onCreate(CameraActivity.java:24)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.Activity.performCreate(Activity.java:5104)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
  06-04 14:28:07.956: E/AndroidRuntime(6115):     ... 11 more</p>
  
  <p>The line CameraActivity.java:24 is
      preview.addView(mPreview);</p>