ReactNative PanResponder 限制 X 位置 [英] ReactNative PanResponder limit X position

问题描述

我正在构建一个音乐播放器，我专注于进度条.我能够对滑动手势做出反应，但我无法限制该手势的作用范围.

I'm building a Music Player and I'm focusing on the progress bar. I was able to react to swipe gestures, but I cant limit how far that gesture goes.

这是我迄今为止所做的.我已将所有内容降至最低:

This is what I've done so far. I've reduced everything to the minumal:

constructor(props) {
    super(props);

    this.state = {
      pan: new Animated.ValueXY()
    };
}

componentWillMount() {
    this._panResponder = PanResponder.create({
        onMoveShouldSetResponderCapture: () => true,
        onMoveShouldSetPanResponderCapture: () => true,
        onPanResponderGrant: (e, gestureState) => {


            // Set the initial value to the current state
            let x = (this.state.pan.x._value < 0) ? 0 : this.state.pan.x._value;


            this.state.pan.setOffset({ x, y: 0 });
            this.state.pan.setValue({ x: 0, y: 0 });


        },
        onPanResponderMove: Animated.event([
            null, { dx: this.state.pan.x, dy: 0 },
        ]),
        onPanResponderRelease: (e, { vx, vy }) => {
            this.state.pan.flattenOffset();
        }
    });
}

render() {
    let { pan } = this.state;

    // Calculate the x and y transform from the pan value
    let [translateX, translateY] = [pan.x, pan.y];
    // Calculate the transform property and set it as a value for our style which we add below to the Animated.View component
    let imageStyle = { transform: [{ translateX }, { translateY }] };

    return (
        <View style={styles.container}>
            <Animated.View style={{imageStyle}} {...this._panResponder.panHandlers} />
        </View>
    );
}

这里有一张图片显示了问题所在.

Here there is an image showing what the problem is.

所以我们的想法是一旦达到限制(向左和向右)就停止移动.我尝试检查 _value <0，但它不起作用，因为它似乎是一个偏移量，而不是一个位置.

So the idea is to stop keeping moving once the limit (left as well as right) is reached. I tried checking if _value < 0, but it didn't work since It seems to be an offset, not a position.

任何帮助将不胜感激.

推荐答案

与其让你的动画死在你的边界，你可以插入你的Animated.Value 与 y=x，但将其固定到您的宽度.

Instead of letting your animation die at your borders, you could interpolate your Animated.Value with y=x, but with clamping it to your width.

return (
    <View style={styles.container}>
        <Animated.View 
            style={{
                transform: [{
                    translateX: this.state.pan.x.interpolate({
                        inputRange: [0, trackWidth ],
                        outputRange: [0, trackWidth ],
                        extrapolate: 'clamp'
                    })
                }],

            }} 
            {...this._panResponder.panHandlers}
        />
    </View>
);

这里有一个更深入的例子:https://github.com/olapiv/expo-audio-player/blob/master/src/AudioSlider.js

Here's a more in-depth example: https://github.com/olapiv/expo-audio-player/blob/master/src/AudioSlider.js

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