title: How can I make a SurfaceView larger than the screen?
body: <p>I would like to effectively make a simple digital zoom for the camera preview, so I thought I would simply resize my SurfaceView to be larger than the screen.  Other questions (such as <a href="https://stackoverflow.com/questions/3813049/how-to-create-a-view-that-is-bigger-than-the-screen">3813049</a>) seem to indicate that this is easy, so I created the sample code below which I expect to let me see only half of the image horizontally (since the SurfaceView is twice as wide as the screen) and have the image only take up half of the screen horizontally.  However, running it (when targeted to SDK version 4 on my Thunderbolt with Android 2.2.1) results in being able to see the whole image horizontally while filling the screen horizontally.  The SurfaceView appears to behave as intended vertically (when I make it smaller than the screen), but Android won't allow me to make the SurfaceView larger than the screen.</p>
  
  <p>How can I implement a digital zoom?  (No, I cannot use Camera.Parameters.setZoom; not only is this not supported by Android 1.6, but different cameras support and implement this differently)</p>
  
  <pre><code>public class MagnifyTestActivity extends Activity implements SurfaceHolder.Callback {
      private MagnificationView mPreview;
      private SurfaceHolder mHolder;
      private Camera mCamera = null;
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          mPreview = new MagnificationView(this);
          setContentView(mPreview);
          mHolder = mPreview.getHolder();
          mHolder.addCallback(this);
          mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
      }
  
      public class MagnificationView extends SurfaceView {
          public MagnificationView(Context context) {
              super(context);
          }
  
          @Override
          protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
              Display display = getWindowManager().getDefaultDisplay();
              int width = display.getWidth()*2;
              int height = display.getHeight()/2;
              widthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
              heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
              super.onMeasure(widthMeasureSpec, heightMeasureSpec);
          }
      }
  
      public void surfaceCreated(SurfaceHolder holder) {
          mCamera = Camera.open();
          try {
              mCamera.setPreviewDisplay(holder);
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      public void surfaceDestroyed(SurfaceHolder holder) {
          mCamera.stopPreview();
          mCamera.release();
          mCamera = null;
      }
  
      public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
          mHolder.setFixedSize(w, h);
          mCamera.startPreview();
      }
  }
  </code></pre>
  
  <p>UPDATE: Based on @Pulkit Sethi's response, it is possible to stretch/magnify the SurfaceView vertically, just not horizontally.  To magnify the SurfaceView vertically, simply replace display.getHeight()/2 with display.getHeight()*2 above.  Also observe that changing the width doesn't produce any horizontal magnification, either in my code or in Pulkit's.</p>