Do not set camera preview display if the surface is null.

MediaRecorder.setPreviewDisplay() is not required if applications
use MediaRecorder.setCamera(). Besides, this causes a problem when
apps use Camera.setPreviewTexture. Camera service thinks the
surface texture from Camera.setPreviewTexture and the surface from
MediaRecorder.setPreviewDisplay are different.

bug:5988937

Change-Id: Ia345705b6679ef349db6e354feaa3cc0fe8bcd8c

Author: Wu-cheng Li

media/java/android/media/MediaRecorder.java

@@ -124,9 +124,15 @@ public MediaRecorder() {
     /**
      * Sets a Surface to show a preview of recorded media (video). Calls this
      * before prepare() to make sure that the desirable preview display is
-     * set.
+     * set. If {@link #setCamera(Camera)} is used and the surface has been
+     * already set to the camera, application do not need to call this. If
+     * this is called with non-null surface, the preview surface of the camera
+     * will be replaced by the new surface. If this method is called with null
+     * surface or not called at all, media recorder will not change the preview
+     * surface of the camera.
      *
      * @param sv the Surface to use for the preview
+     * @see android.hardware.Camera#setPreviewDisplay(android.view.SurfaceHolder)
      */
     public void setPreviewDisplay(Surface sv) {
         mSurface = sv;

media/libstagefright/CameraSource.cpp

@@ -515,9 +515,13 @@ status_t CameraSource::initWithCameraAccess(
         return err;
     }
 
-    // This CHECK is good, since we just passed the lock/unlock
-    // check earlier by calling mCamera->setParameters().
-    CHECK_EQ((status_t)OK, mCamera->setPreviewDisplay(mSurface));
+    // Set the preview display. Skip this if mSurface is null because
+    // applications may already set a surface to the camera.
+    if (mSurface != NULL) {
+        // This CHECK is good, since we just passed the lock/unlock
+        // check earlier by calling mCamera->setParameters().
+        CHECK_EQ((status_t)OK, mCamera->setPreviewDisplay(mSurface));
+    }
 
     // By default, do not store metadata in video buffers
     mIsMetaDataStoredInVideoBuffers = false;