first commit

moehu/moehu_fontend/lib/widget/ContentPositioningLayout.dart

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+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:peach/config/Colors.dart';
+import 'package:peach/config/Index.dart';
+import 'package:peach/utils/_.dart';
+
+/*
+ * 接受头部和内容，当页面向上滑动时内容部分到达顶部会定位
+ * 并且当到达顶部是会触发回调函数
+ */
+class ContentPositioningLayout extends StatelessWidget {
+  final Widget title;
+  final Widget child;
+  final double titleHeight;
+  final double scrollHeight;
+
+  const ContentPositioningLayout(
+      {this.title, this.child, this.titleHeight = 45, this.scrollHeight = 0});
+
+  static Color color = Colors.transparent;
+
+  @override
+  Widget build(BuildContext context) {
+    ScrollController mController = new ScrollController();
+    mController.addListener(() {
+      if (scrollHeight == 0) {
+        return;
+      }
+      if ((scrollHeight.truncate() - mController.offset.truncate()) <= 3) {
+        color = ColorConfig.WhiteBackColor;
+      } else {
+        color = Colors.transparent;
+      }
+    });
+    return Stack(
+      children: <Widget>[
+        Positioned(
+          height: Screen.height(context),
+          child: SingleChildScrollView(
+            physics: BouncingScrollPhysics(),
+            controller: mController,
+            child: this.child,
+          ),
+        ),
+        Positioned(
+          height: Screen.setHeight(this.titleHeight) + Config.top,
+          child: Container(
+            padding: EdgeInsets.only(top: Config.top),
+            decoration: BoxDecoration(color: color),
+            child: this.title,
+          ),
+        ),
+      ],
+    );
+  }
+}