books

assets/draw/p09/s02.dart

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+import 'dart:ui';
+import 'package:flutter/material.dart';
+
+import '../components/coordinate_pro.dart';
+/// create by 张风捷特烈 on 2020-03-19
+/// contact me by email 1981462002@qq.com
+/// 说明: 纸
+
+class Paper extends StatelessWidget {
+  const Paper({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(child: _buildChild());
+  }
+
+  Widget _buildChild() {
+    final Widget just = CustomPaint(
+      painter: BgPainter(), // 背景
+    );
+
+    final Widget withSize = CustomPaint(
+      size: Size(100,100),
+      painter: BgPainter(), // 背景
+    );
+
+
+    final Widget withLayoutBuilder = LayoutBuilder(
+      builder: _builderByLayout,
+    );
+
+
+    final Widget withChild = CustomPaint(
+      painter: BgPainter(),
+      child: Container(
+        width: 100,
+        height: 100,
+      ), // 背景
+    );
+
+    return withChild;
+  }
+
+  Widget _builderByLayout(BuildContext context, BoxConstraints constraints) {
+    return CustomPaint(
+      size: Size(constraints.maxWidth, constraints.maxHeight),
+      painter: BgPainter(), // 背景
+    );
+  }
+}
+
+class BgPainter extends CustomPainter {
+  @override
+  void paint(Canvas canvas, Size size) {
+    canvas.clipRect(Offset.zero&size);
+
+    canvas.drawRect(
+        Rect.fromPoints(Offset.zero, Offset(size.width, size.height)),
+        Paint()..color = Colors.red);
+  }
+
+  @override
+  bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
+}
+