From bfbf19cdb197135c12edd9dea47248ab7e8b4836 Mon Sep 17 00:00:00 2001
From: jacklam718 <jacklam718@gmail.com>
Date: Mon, 2 Sep 2019 03:30:58 +0800
Subject: [PATCH] Add DraggableView

---
 src/components/DraggableView.js | 198 ++++++++++++++++++++++++++++++++
 1 file changed, 198 insertions(+)
 create mode 100644 src/components/DraggableView.js

diff --git a/src/components/DraggableView.js b/src/components/DraggableView.js
new file mode 100644
index 0000000..eaad54d
--- /dev/null
+++ b/src/components/DraggableView.js
@@ -0,0 +1,198 @@
+// @flow
+
+import React, { Component } from 'react';
+import { View, Animated, PanResponder, StyleSheet, Dimensions } from 'react-native';
+import type { SwipeDirection } from '../type';
+
+export default class DraggableView extends Component {
+  props: {
+    onMove?: () => void;
+    onRelease?: () => void;
+    onSwipeOut?: () => void;
+    swipeThreshold?: number;
+    swipeDirection?: SwipeDirection | Array<SwipeDirection>;
+    backdrop: React.Element;
+    content: React.Element;
+  };
+
+  static defaultProps = {
+    onMove: () => {},
+    onRelease: () => {},
+    swipeThreshold: 100,
+    swipeDirection: [],
+  };
+
+  constructor(props) {
+    super(props)
+    
+    this.pan = new Animated.ValueXY();
+    this.allowedDirections = [].concat(props.swipeDirection);
+    this.layout = null;
+  }
+
+  componentDidMount() {
+    this.panEventListenerId = this.pan.addListener((axis) => {      
+      this.props.onMove(this.createPanEvent(axis));
+    });
+  }
+
+  componentWillUnmount() {
+    this.pan.removeListener(this.panEventListenerId);
+  }
+
+  panResponder = PanResponder.create({
+    onMoveShouldSetPanResponder: (evt, gestureState) => {
+      return gestureState.dx != 0 && gestureState.dy != 0;
+    },
+    onStartShouldSetPanResponder: (event, gestureState) => true,
+    onPanResponderMove: (event, gestureState) => {
+      // get & set currentSwipeDirection
+      if (!this.currentSwipeDirection) {
+        this.currentSwipeDirection = this.getSwipeDirection(gestureState)
+      }
+
+      if (this.isAllowedDirection(gestureState)) { 
+        let animEvent;
+        if (['up', 'down'].includes(this.currentSwipeDirection)) {
+          animEvent = { dy: this.pan.y };
+        } else if (['left', 'right'].includes(this.currentSwipeDirection)) {
+          animEvent = { dx: this.pan.x };
+        }
+        Animated.event([null, animEvent])(event, gestureState);
+
+        this.props.onSwiping(this.createPanEvent({
+          x: this.pan.x._value,
+          y: this.pan.y._value,
+        }));
+      }
+    },
+    onPanResponderRelease: (_, gestureState) => {
+      const event = this.createPanEvent({
+        x: this.pan.x._value,
+        y: this.pan.y._value,
+      });
+
+      if (
+        this.props.onSwipeOut &&
+        Math.abs(this.pan.y._value) > this.props.swipeThreshold ||
+        Math.abs(this.pan.x._value) > this.props.swipeThreshold
+      ) {
+        let toValue
+        if (this.currentSwipeDirection === 'up') {
+          toValue = {
+            x: 0,
+            y: -((Dimensions.get('window').height / 2) + this.layout.height / 2),
+          };
+        } else if (this.currentSwipeDirection === 'down') {
+          toValue = {
+            x: 0,
+            y: ((Dimensions.get('window').height / 2) + this.layout.height / 2),
+          };
+        } else if (this.currentSwipeDirection === 'left') {
+          toValue = {
+            x: -((Dimensions.get('window').width / 2) + this.layout.width / 2),
+            y: 0,
+          };
+        } else if (this.currentSwipeDirection === 'right') {
+          toValue = {
+            x: ((Dimensions.get('window').width / 2) + this.layout.width / 2),
+            y: 0,
+          };
+        }
+        Animated.spring(this.pan, {
+          toValue,
+          velocity: 0,
+          tension: 65,
+          friction: 11,
+        }).start(() => {
+          this.props.onSwipeOut(event);
+        });
+        return;
+      }
+
+      this.currentSwipeDirection = null;
+      this.props.onRelease(event);
+      Animated.spring(this.pan, {
+        toValue: { x: 0, y: 0 },
+        velocity: 0,
+        tension: 65,
+        friction: 11,
+      }).start();
+    },
+  });
+
+  createPanEvent(axis) {
+    return {
+      axis,
+      layout: this.layout,
+      swipeDirection: this.currentSwipeDirection,
+    }
+  }
+
+  isAllowedDirection({ dy, dx }) {
+    const draggedDown = dy > 0;
+    const draggedUp = dy < 0;
+    const draggedLeft = dx < 0;
+    const draggedRight = dx > 0;
+
+    if (draggedDown && this._isAllowedDirection('down')) {
+      return true
+    } else if (draggedUp && this._isAllowedDirection('up')) {
+      return true
+    } else if (draggedLeft && this._isAllowedDirection('left')) {
+      return true
+    } else if (draggedRight && this._isAllowedDirection('right')) {
+      return true
+    }
+    return false
+  }
+
+  _isAllowedDirection(direction) {
+    return this.currentSwipeDirection === direction && this.allowedDirections.includes(direction);
+  }
+
+  isValidSwipe(velocity, directionalOffset) {
+    const velocityThreshold = 0.3;
+    const directionalOffsetThreshold = 80;
+    return Math.abs(velocity) > velocityThreshold && Math.abs(directionalOffset) < directionalOffsetThreshold;
+  }
+
+  isValidHorizontalSwipe({ vx, dy }) {
+    return this.isValidSwipe(vx, dy);
+  }
+
+  isValidVerticalSwipe({ vy, dx }) {
+    return this.isValidSwipe(vy, dx);
+  }
+
+  getSwipeDirection(gestureState) {
+    if (this.isValidHorizontalSwipe(gestureState)) {
+      return (gestureState.dx > 0) ? 'right' : 'left';
+    } else if (this.isValidVerticalSwipe(gestureState)) {
+      return (gestureState.dy > 0) ? 'down' : 'up';
+    }
+    return null;
+  }
+
+  onLayout = (event) => {
+    this.layout = event.nativeEvent.layout;
+  }
+
+  render() {
+    const { style, backdrop, content } = this.props;
+    return (
+      <Animated.View
+        {...this.panResponder.panHandlers}
+        style={style}
+      >
+        {backdrop}
+        <Animated.View
+          style={this.pan.getLayout()}
+          onLayout={this.onLayout}
+        >
+          {content}
+        </Animated.View>
+      </Animated.View>
+    );
+  }
+}