如何在 React Native 中创建拖放操作？

Question

假设我有两个视图，A 和 B。我希望能够在触摸视图 A 时触发“dragAndDropStart”事件，然后启用从 A 到 B 的拖放...在整个过程中向用户显示反馈（即显示出现在视图 A 和用户手指之间的一条线）。在放置时（释放拖动手势）我想触发另一个“dragAndDropEnd”事件，这次是在视图 B 上。

touchStart 和 touchEnd 处理程序过于有限，因为它们似乎不允许将手势从一个视图切换到另一个视图。它们似乎也没有启用中间“拖动”状态。

关于使用手势处理程序的 React 本机文档有点神秘，我还没有看到任何示例来演示它们的使用。

有什么想法吗？

Answer 1

export default class Viewport extends Component{
    constructor(props){
        super(props);

        this.state = {
            showDraggable   : true,
            dropZoneValues  : null,
            pan             : new Animated.ValueXY()
        };

        this.panResponder = PanResponder.create({
            onStartShouldSetPanResponder    : () => true,
            onPanResponderMove              : Animated.event([null,{
                dx  : this.state.pan.x,
                dy  : this.state.pan.y
            }]),
            onPanResponderRelease           : (e, gesture) => {
                if(this.isDropZone(gesture)){
                    this.setState({
                        showDraggable : false
                    });
                }else{
                    Animated.spring(
                        this.state.pan,
                        {toValue:{x:0,y:0}}
                    ).start();
                }
            }
        });
    }

    isDropZone(gesture){
        var dz = this.state.dropZoneValues;
        return gesture.moveY > dz.y && gesture.moveY < dz.y + dz.height;
    }

    setDropZoneValues(event){
        this.setState({
            dropZoneValues : event.nativeEvent.layout
        });
    }

    render(){
        return (
            <View style={styles.mainContainer}>
                <View 
                    onLayout={this.setDropZoneValues.bind(this)}
                    style={styles.dropZone}>
                    <Text style={styles.text}>Drop me here!</Text>
                </View>

                {this.renderDraggable()}
            </View>
        );
    }

    renderDraggable(){
        if(this.state.showDraggable){
            return (
                <View style={styles.draggableContainer}>
                    <Animated.View 
                        {...this.panResponder.panHandlers}
                        style={[this.state.pan.getLayout(), styles.circle]}>
                        <Text style={styles.text}>Drag me!</Text>
                    </Animated.View>
                </View>
            );
        }
    }
}

来源http://moduscreate.com/animated_drag_and_drop_with_react_native/

https://github.com/crysfel/DragAndDrop

Answer 2

你必须看到当前的视图矩形到另一个视图矩形如果你的一个视图矩形在某个点彼此相交它将返回 true 然后你会收到通知 A 视图被拖到 B 视图这里是我的示例代码可能会不会对你有帮助。

-(void)moveViewWithGestureRecognizer:(UIPanGestureRecognizer *)panGestureRecognizer{

// your current View touch location suppose View A
    CGPoint touchLocation = [panGestureRecognizer locationInView:self.contentView];

    CGRect movingAViewRect = CGRectMake(touchLocation.x, touchLocation.y, self.aView.width, self.aView.height);

 //   NSLog(@"Point not Matched first => %@  and second => %@",NSStringFromCGPoint(touchLocation),NSStringFromCGPoint(self.bView.frame.origins));
    self.aView.center = touchLocation;
      

    if(panGestureRecognizer.state == UIGestureRecognizerStateEnded)
    {
        //All fingers are lifted.
      
    

        if(CGRectIntersectsRect(movingAViewRect,self.bView.frame)){
     
            NSLog(@"Point Matched first => %@  and second => %@",NSStringFromCGRect(movingAViewRect),NSStringFromCGRect (self.bView.frame ));

       // and here you can perform some action for this 
            
            
        }else{
        
            NSLog(@"aView is not drag on bView please drag aView to bView ");
            

        }
      
        
     
       
    }
}