From 37e376df1128a554acc71d277a3053ba9b360b8e Mon Sep 17 00:00:00 2001
From: ddcat1115 <ddcat1115@gmail.com>
Date: Thu, 26 May 2016 16:06:15 +0800
Subject: [PATCH] fix #1777

---
 components/affix/demo/on-change.md | 21 +++++++++++++++++++++
 components/affix/index.jsx         | 11 +++++++----
 components/affix/index.md          |  1 +
 3 files changed, 29 insertions(+), 4 deletions(-)
 create mode 100644 components/affix/demo/on-change.md

diff --git a/components/affix/demo/on-change.md b/components/affix/demo/on-change.md
new file mode 100644
index 0000000000..7d8762f5df
--- /dev/null
+++ b/components/affix/demo/on-change.md
@@ -0,0 +1,21 @@
+---
+order: 3
+title: 固定状态改变的回调
+---
+
+可以获得是否固定的状态。
+
+````jsx
+import { Affix, Button } from 'antd';
+
+
+const onChange = function (affixed) {
+  console.log(affixed); // true or false
+};
+
+ReactDOM.render(
+  <Affix offsetTop={120} onChange={onChange}>
+    <Button>固定在距离顶部 120px 的位置</Button>
+  </Affix>
+, mountNode);
+````
diff --git a/components/affix/index.jsx b/components/affix/index.jsx
index 39f575c04c..c0b693ee4b 100644
--- a/components/affix/index.jsx
+++ b/components/affix/index.jsx
@@ -39,6 +39,10 @@ export default class Affix extends React.Component {
     offsetBottom: React.PropTypes.number,
   }
 
+  static defaultProps = {
+    onChange() {},
+  }
+
   constructor(props) {
     super(props);
     this.state = {
@@ -51,7 +55,6 @@ export default class Affix extends React.Component {
 
     // Backwards support
     offsetTop = offsetTop || offset;
-
     const scrollTop = getScroll(window, true);
     const elemOffset = getOffset(ReactDOM.findDOMNode(this));
     const elemSize = {
@@ -78,7 +81,7 @@ export default class Affix extends React.Component {
             left: elemOffset.left,
             width: ReactDOM.findDOMNode(this).offsetWidth,
           },
-        });
+        }, () => this.props.onChange(!!this.state.affixStyle));
       }
     } else if (scrollTop < elemOffset.top + elemSize.height + offsetBottom - window.innerHeight &&
                offsetMode.bottom) {
@@ -91,12 +94,12 @@ export default class Affix extends React.Component {
             left: elemOffset.left,
             width: ReactDOM.findDOMNode(this).offsetWidth,
           },
-        });
+        }, () => this.props.onChange(!!this.state.affixStyle));
       }
     } else if (this.state.affixStyle) {
       this.setState({
         affixStyle: null,
-      });
+      }, () => this.props.onChange(!!this.state.affixStyle));
     }
   }
 
diff --git a/components/affix/index.md b/components/affix/index.md
index c602f3dc68..c8293cbab9 100644
--- a/components/affix/index.md
+++ b/components/affix/index.md
@@ -20,3 +20,4 @@ english: Affix
 |-------------|----------------|--------------------|--------------|
 | offsetTop    | 距离窗口顶部达到指定偏移量后触发   | Number |         |
 | offsetBottom | 距离窗口底部达到指定偏移量后触发   | Number |         |
+| onChange | 固定状态改变时触发的回调函数   | Function | 无        |