层

层

如果您尝试调试合成问题，则可以使用debugDumpLayerTree()。对于上面的例子，它会输出：

I/flutter : TransformLayer
I/flutter :  │ creator: [root]
I/flutter :  │ offset: Offset(0.0, 0.0)
I/flutter :  │ transform:
I/flutter :  │   [0] 3.5,0.0,0.0,0.0
I/flutter :  │   [1] 0.0,3.5,0.0,0.0
I/flutter :  │   [2] 0.0,0.0,1.0,0.0
I/flutter :  │   [3] 0.0,0.0,0.0,1.0
I/flutter :  │
I/flutter :  ├─child 1: OffsetLayer
I/flutter :  │ │ creator: RepaintBoundary ← _FocusScope ← Semantics ← Focus-[GlobalObjectKey MaterialPageRoute(560156430)] ← _ModalScope-[GlobalKey 328026813] ← _OverlayEntry-[GlobalKey 388965355] ← Stack ← Overlay-[GlobalKey 625702218] ← Navigator-[GlobalObjectKey _MaterialAppState(859106034)] ← Title ← ⋯
I/flutter :  │ │ offset: Offset(0.0, 0.0)
I/flutter :  │ │
I/flutter :  │ └─child 1: PictureLayer
I/flutter :  │
I/flutter :  └─child 2: PictureLayer

这是根Layer的toStringDeep输出的。

根部的变换是应用设备像素比的变换; 在这种情况下，每个逻辑像素代表3.5个设备像素。

RepaintBoundary widget在渲染树的层中创建了一个RenderRepaintBoundary。这用于减少需要重绘的需求量。