Fix orientation when activity handles rotations (#1117)

Author: natario1

cameraview/src/main/java/com/otaliastudios/cameraview/CameraView.java

@@ -2370,12 +2370,10 @@ public void run() {
         }
 
         @Override
-        public void onDisplayOffsetChanged(int displayOffset, boolean willRecreate) {
-            LOG.i("onDisplayOffsetChanged", displayOffset, "recreate:", willRecreate);
-            if (isOpened() && !willRecreate) {
-                // Display offset changes when the device rotation lock is off and the activity
-                // is free to rotate. However, some changes will NOT recreate the activity, namely
-                // 180 degrees flips. In this case, we must restart the camera manually.
+        public void onDisplayOffsetChanged() {
+            if (isOpened()) {
+                // We can't handle display offset (View angle) changes without restarting.
+                // See comments in OrientationHelper for more information.
                 LOG.w("onDisplayOffsetChanged", "restarting the camera.");
                 close();
                 open();

cameraview/src/main/java/com/otaliastudios/cameraview/internal/OrientationHelper.java

@@ -1,6 +1,8 @@
 package com.otaliastudios.cameraview.internal;
 
+import android.app.Activity;
 import android.content.Context;
+import android.content.res.Configuration;
 import android.hardware.SensorManager;
 import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
@@ -9,6 +11,7 @@
 import android.os.Build;
 import android.os.Handler;
 import android.os.Looper;
+import android.view.View;
 import android.view.Display;
 import android.view.OrientationEventListener;
 import android.view.Surface;
@@ -18,6 +21,36 @@
  * Helps with keeping track of both device orientation (which changes when device is rotated)
  * and the display offset (which depends on the activity orientation wrt the device default
  * orientation).
+ *
+ * Note: any change in the display offset should restart the camera engine, because it reads
+ * from the angles container at startup and computes size based on that. This is tricky because
+ * activity behavior can differ:
+ *
+ * - if activity is locked to some orientation, {@link #mDisplayOffset} won't change, and
+ *   {@link View#onConfigurationChanged(Configuration)} won't be called.
+ *   The library will work fine.
+ *
+ * - if the activity is unlocked and does NOT handle orientation changes with android:configChanges,
+ *   the actual behavior differs depending on the rotation.
+ *   - the configuration callback is never called, of course.
+ *   - for 90°/-90° rotations, the activity is recreated. Sometime you get {@link #mDisplayOffset}
+ *     callback before destruction, sometimes you don't - in any case it's going to recreate.
+ *   - for 180°/-180°, the activity is NOT recreated! But we can rely on {@link #mDisplayOffset}
+ *     changing with a 180 delta and restart the engine.
+ *
+ * - lastly, if the activity is unlocked and DOES handle orientation changes with android:configChanges,
+ *   as it will often be the case in a modern Compose app,
+ *   - you always get the {@link #mDisplayOffset} callback
+ *   - for 90°/-90° rotations, the view also gets the configuration changed callback.
+ *   - for 180°/-180°, the view won't get it because configuration only cares about portrait vs. landscape.
+ *
+ * In practice, since we don't control the activity and we can't easily inspect the configChanges
+ * flags at runtime, a good solution is to always restart when the display offset changes. We might
+ * do useless restarts in one rare scenario (unlocked, no android:configChanges, 90° rotation,
+ * display offset callback received before destruction) but that's acceptable.
+ *
+ * Tried to avoid that by looking at {@link Activity#isChangingConfigurations()}, but it's always
+ * false by the time the display offset callback is invoked.
  */
 public class OrientationHelper {
 
@@ -26,7 +59,7 @@ public class OrientationHelper {
      */
     public interface Callback {
         void onDeviceOrientationChanged(int deviceOrientation);
-        void onDisplayOffsetChanged(int displayOffset, boolean willRecreate);
+        void onDisplayOffsetChanged();
     }
 
     private final Handler mHandler = new Handler(Looper.getMainLooper());
@@ -87,9 +120,7 @@ public void onDisplayChanged(int displayId) {
                     int newDisplayOffset = findDisplayOffset();
                     if (newDisplayOffset != oldDisplayOffset) {
                         mDisplayOffset = newDisplayOffset;
-                        // With 180 degrees flips, the activity is not recreated.
-                        boolean willRecreate = Math.abs(newDisplayOffset - oldDisplayOffset) != 180;
-                        mCallback.onDisplayOffsetChanged(newDisplayOffset, willRecreate);
+                        mCallback.onDisplayOffsetChanged();
                     }
                 }
             };

cameraview/src/main/java/com/otaliastudios/cameraview/preview/SurfaceCameraPreview.java

@@ -46,6 +46,7 @@ protected SurfaceView onCreateView(@NonNull Context context, @NonNull ViewGroup
             public void surfaceCreated(SurfaceHolder holder) {
                 // This is too early to call anything.
                 // surfaceChanged is guaranteed to be called after, with exact dimensions.
+                LOG.i("callback: surfaceCreated.");
             }
 
             @Override
@@ -64,7 +65,7 @@ public void surfaceChanged(SurfaceHolder holder, int format, int width, int heig
 
             @Override
             public void surfaceDestroyed(SurfaceHolder holder) {
-                LOG.i("callback:", "surfaceDestroyed");
+                LOG.i("callback: surfaceDestroyed");
                 dispatchOnSurfaceDestroyed();
                 mDispatched = false;
             }