fix(album): prevent black screen when switching preview variants

suixinkan/UI/TravelAlbum/TravelAlbumPhotoPreviewViewController.swift

@@ -639,11 +639,6 @@ private final class TravelAlbumPreviewImageCell: UICollectionViewCell, UIScrollV
         resetZoom()
     }
 
-    override func layoutSubviews() {
-        super.layoutSubviews()
-        imageView.frame = scrollView.bounds
-    }
-
     func apply(asset newAsset: TravelAlbumPreviewAsset?) {
         asset = newAsset
         resetZoom()
@@ -687,6 +682,7 @@ private final class TravelAlbumPreviewImageCell: UICollectionViewCell, UIScrollV
         imageView.contentMode = .scaleAspectFit
         imageView.backgroundColor = .black
         imageView.kf.indicatorType = .activity
+        imageView.accessibilityIdentifier = "travelAlbum.previewImageView"
 
         retryButton.setTitle("图片加载失败，点击重试", for: .normal)
         retryButton.setTitleColor(UIColor.white.withAlphaComponent(0.82), for: .normal)
@@ -699,6 +695,11 @@ private final class TravelAlbumPreviewImageCell: UICollectionViewCell, UIScrollV
         scrollView.addSubview(imageView)
         contentView.addSubview(retryButton)
         scrollView.snp.makeConstraints { $0.edges.equalToSuperview() }
+        imageView.snp.makeConstraints { make in
+            make.edges.equalTo(scrollView.contentLayoutGuide)
+            make.width.equalTo(scrollView.frameLayoutGuide)
+            make.height.equalTo(scrollView.frameLayoutGuide)
+        }
         retryButton.snp.makeConstraints { $0.center.equalToSuperview() }
 
         let singleTap = UITapGestureRecognizer(target: self, action: #selector(singleTapped))

suixinkanTests/TravelAlbumDetailViewControllerTests.swift

@@ -110,6 +110,60 @@ final class TravelAlbumDetailViewControllerTests: XCTestCase {
         window.isHidden = true
     }
 
+    func testPreviewImageViewKeepsViewportConstraintsWhenSwitchingVariant() throws {
+        UIView.setAnimationsEnabled(false)
+        defer { UIView.setAnimationsEnabled(true) }
+        let project = TravelAlbumPreviewProject(
+            originalMaterialId: 1,
+            assets: [
+                TravelAlbumPreviewAsset(
+                    id: "original-1",
+                    kind: .original,
+                    fileURL: "",
+                    coverURL: "",
+                    fileName: "原图.jpg",
+                    fileSize: 0
+                ),
+                TravelAlbumPreviewAsset(
+                    id: "retouched-1",
+                    kind: .retouched,
+                    fileURL: "",
+                    coverURL: "",
+                    fileName: "精修后.jpg",
+                    fileSize: 0
+                ),
+            ]
+        )
+        let controller = TravelAlbumPhotoPreviewViewController(
+            projects: [project],
+            totalCount: 1,
+            startProjectIndex: 0
+        )
+        controller.loadViewIfNeeded()
+        controller.view.frame = CGRect(x: 0, y: 0, width: 390, height: 844)
+        controller.view.layoutIfNeeded()
+
+        let retouchedButton = try XCTUnwrap(
+            controller.view.findSubview {
+                ($0 as? UIButton)?.accessibilityLabel == "精修后"
+            } as? UIButton
+        )
+        retouchedButton.sendActions(for: .touchUpInside)
+        controller.view.layoutIfNeeded()
+
+        let imageView = try XCTUnwrap(
+            controller.view.findSubview {
+                $0.accessibilityIdentifier == "travelAlbum.previewImageView"
+            } as? UIImageView
+        )
+        let scrollView = try XCTUnwrap(imageView.superview as? UIScrollView)
+        scrollView.layoutIfNeeded()
+
+        XCTAssertEqual(imageView.bounds.size, scrollView.bounds.size)
+        XCTAssertFalse(imageView.constraintsAffectingLayout(for: .horizontal).isEmpty)
+        XCTAssertFalse(imageView.constraintsAffectingLayout(for: .vertical).isEmpty)
+    }
+
     func testSelectionModeShowsAIRetouchOnLeftAndDeleteOnRight() async throws {
         let controller = TravelAlbumDetailViewController(albumId: 0)
         controller.loadViewIfNeeded()