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View 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（即在视图A和用户的手指之间显示一条线）。在下降（释放拖动手势）时，我想触发另一个'dragAndDropEnd'事件，这次是在视图B上。

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

使用手势处理程序的React原生文档有点神秘，我没有看到任何证明其用途的示例。

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View Rectangle到其他视图Rectangle如果你的一个视图矩形在某个点相互交叉它将返回true然后你得到通知A视图被拖到B视图这里是我的示例代码可能它会帮助你。

＆＃13;

＆＃13;

-(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 ");
            

        }
      
        
     
       
    }
}
  

＆＃13;

＆＃13;

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