react-native-gesture-handler#TapGestureHandlerGestureEvent TypeScript Examples

AlphabetScroller: React.FC<Props> = ({ onSelect }) => {
    const [ height, setHeight ] = useState(0);
    const [ index, setIndex ] = useState<number>();

    // Handler for setting the correct height for a single alphabet item
    const handleLayout = useCallback((event: LayoutChangeEvent) => {
        setHeight(event.nativeEvent.layout.height);
    }, []);

    // Handler for passing on a new index when it is tapped or swiped
    const handleGestureEvent = useCallback((event: PanGestureHandlerGestureEvent | TapGestureHandlerGestureEvent) => {
        const newIndex = Math.floor(event.nativeEvent.y / height);

        if (newIndex !== index) {
            setIndex(newIndex);
            onSelect(newIndex);
        }
    }, [height, index, onSelect]);

    return (
        <Container>
            <TapGestureHandler onHandlerStateChange={handleGestureEvent}>
                <PanGestureHandler onGestureEvent={handleGestureEvent}>
                    <View>
                        {ALPHABET_LETTERS.split('').map((l, i) => (
                            <View
                                key={l}
                                onLayout={i === 0 ? handleLayout : undefined}
                            >
                                <Letter>{l}</Letter>
                            </View>
                        ))}
                    </View>
                </PanGestureHandler>              
            </TapGestureHandler>
        </Container>
    );
}

ImageTransformer = React.memo<ImageTransformerProps>(
  ({
    outerGestureHandlerRefs = [],
    source,
    width,
    height,
    onStateChange = workletNoop,
    renderImage,
    windowDimensions = Dimensions.get('window'),
    isActive,
    outerGestureHandlerActive,
    style,
    onTap = workletNoop,
    onDoubleTap = workletNoop,
    onInteraction = workletNoop,
    DOUBLE_TAP_SCALE = 3,
    MAX_SCALE = 3,
    MIN_SCALE = 0.7,
    OVER_SCALE = 0.5,
    timingConfig = defaultTimingConfig,
    springConfig = defaultSpringConfig,
    enabled = true,
    ImageComponent = Image,
  }) => {
    // fixGestureHandler();

    assertWorklet(onStateChange);
    assertWorklet(onTap);
    assertWorklet(onDoubleTap);
    assertWorklet(onInteraction);

    if (typeof source === 'undefined') {
      throw new Error(
        'ImageTransformer: either source or uri should be passed to display an image',
      );
    }

    const imageSource = useMemo(
      () =>
        typeof source === 'string'
          ? {
              uri: source,
            }
          : source,
      [source],
    );

    const interactionsEnabled = useSharedValue(false);
    const setInteractionsEnabled = useCallback((value: boolean) => {
      interactionsEnabled.value = value;
    }, []);
    const onLoadImageSuccess = useCallback(() => {
      setInteractionsEnabled(true);
    }, []);

    // HACK ALERT
    // we disable pinch handler in order to trigger onFinish
    // in case user releases one finger
    const [pinchEnabled, setPinchEnabledState] = useState(true);
    useEffect(() => {
      if (!pinchEnabled) {
        setPinchEnabledState(true);
      }
    }, [pinchEnabled]);
    const disablePinch = useCallback(() => {
      setPinchEnabledState(false);
    }, []);
    // HACK ALERT END

    const pinchRef = useRef(null);
    const panRef = useRef(null);
    const tapRef = useRef(null);
    const doubleTapRef = useRef(null);

    const panState = useSharedValue<State>(State.UNDETERMINED);
    const pinchState = useSharedValue<State>(State.UNDETERMINED);

    const scale = useSharedValue(1);
    const scaleOffset = useSharedValue(1);
    const translation = vectors.useSharedVector(0, 0);
    const panVelocity = vectors.useSharedVector(0, 0);
    const scaleTranslation = vectors.useSharedVector(0, 0);
    const offset = vectors.useSharedVector(0, 0);

    const canvas = useMemo(
      () =>
        vectors.create(
          windowDimensions.width,
          windowDimensions.height,
        ),
      [windowDimensions.width, windowDimensions.height],
    );
    const targetWidth = windowDimensions.width;
    const scaleFactor = width / targetWidth;
    const targetHeight = height / scaleFactor;
    const image = useMemo(
      () => vectors.create(targetWidth, targetHeight),
      [targetHeight, targetWidth],
    );

    const canPanVertically = useDerivedValue(() => {
      return windowDimensions.height < targetHeight * scale.value;
    }, []);

    const resetSharedState = useWorkletCallback(
      (animated?: boolean) => {
        'worklet';

        if (animated) {
          scale.value = withTiming(1, timingConfig);
          scaleOffset.value = 1;

          vectors.set(offset, () => withTiming(0, timingConfig));
        } else {
          scale.value = 1;
          scaleOffset.value = 1;
          vectors.set(translation, 0);
          vectors.set(scaleTranslation, 0);
          vectors.set(offset, 0);
        }
      },
      [timingConfig],
    );

    const maybeRunOnEnd = useWorkletCallback(() => {
      'worklet';

      const target = vectors.create(0, 0);

      const fixedScale = clamp(MIN_SCALE, scale.value, MAX_SCALE);
      const scaledImage = image.y * fixedScale;
      const rightBoundary = (canvas.x / 2) * (fixedScale - 1);

      let topBoundary = 0;

      if (canvas.y < scaledImage) {
        topBoundary = Math.abs(scaledImage - canvas.y) / 2;
      }

      const maxVector = vectors.create(rightBoundary, topBoundary);
      const minVector = vectors.invert(maxVector);

      if (!canPanVertically.value) {
        offset.y.value = withSpring(target.y, springConfig);
      }

      // we should handle this only if pan or pinch handlers has been used already
      if (
        (checkIsNotUsed(panState) || checkIsNotUsed(pinchState)) &&
        pinchState.value !== State.CANCELLED
      ) {
        return;
      }

      if (
        vectors.eq(offset, 0) &&
        vectors.eq(translation, 0) &&
        vectors.eq(scaleTranslation, 0) &&
        scale.value === 1
      ) {
        // we don't need to run any animations
        return;
      }

      if (scale.value <= 1) {
        // just center it
        vectors.set(offset, () => withTiming(0, timingConfig));
        return;
      }

      vectors.set(
        target,
        vectors.clamp(offset, minVector, maxVector),
      );

      const deceleration = 0.9915;

      const isInBoundaryX = target.x === offset.x.value;
      const isInBoundaryY = target.y === offset.y.value;

      if (isInBoundaryX) {
        if (
          Math.abs(panVelocity.x.value) > 0 &&
          scale.value <= MAX_SCALE
        ) {
          offset.x.value = withDecay({
            velocity: panVelocity.x.value,
            clamp: [minVector.x, maxVector.x],
            deceleration,
          });
        }
      } else {
        offset.x.value = withSpring(target.x, springConfig);
      }

      if (isInBoundaryY) {
        if (
          Math.abs(panVelocity.y.value) > 0 &&
          scale.value <= MAX_SCALE &&
          offset.y.value !== minVector.y &&
          offset.y.value !== maxVector.y
        ) {
          offset.y.value = withDecay({
            velocity: panVelocity.y.value,
            clamp: [minVector.y, maxVector.y],
            deceleration,
          });
        }
      } else {
        offset.y.value = withSpring(target.y, springConfig);
      }
    }, [
      MIN_SCALE,
      MAX_SCALE,
      image,
      canvas,
      springConfig,
      timingConfig,
    ]);

    const onPanEvent = useAnimatedGestureHandler<
      PanGestureHandlerGestureEvent,
      {
        panOffset: vectors.Vector<number>;
        pan: vectors.Vector<number>;
      }
    >({
      onInit: (_, ctx) => {
        ctx.panOffset = vectors.create(0, 0);
      },

      shouldHandleEvent: () => {
        return (
          scale.value > 1 &&
          (typeof outerGestureHandlerActive !== 'undefined'
            ? !outerGestureHandlerActive.value
            : true) &&
          interactionsEnabled.value
        );
      },

      beforeEach: (evt, ctx) => {
        ctx.pan = vectors.create(evt.translationX, evt.translationY);
        const velocity = vectors.create(evt.velocityX, evt.velocityY);

        vectors.set(panVelocity, velocity);
      },

      onStart: (_, ctx) => {
        cancelAnimation(offset.x);
        cancelAnimation(offset.y);
        ctx.panOffset = vectors.create(0, 0);
        onInteraction('pan');
      },

      onActive: (evt, ctx) => {
        panState.value = evt.state;

        if (scale.value > 1) {
          if (evt.numberOfPointers > 1) {
            // store pan offset during the pan with two fingers (during the pinch)
            vectors.set(ctx.panOffset, ctx.pan);
          } else {
            // subtract the offset and assign fixed pan
            const nextTranslate = vectors.add(
              ctx.pan,
              vectors.invert(ctx.panOffset),
            );
            translation.x.value = nextTranslate.x;

            if (canPanVertically.value) {
              translation.y.value = nextTranslate.y;
            }
          }
        }
      },

      onEnd: (evt, ctx) => {
        panState.value = evt.state;

        vectors.set(ctx.panOffset, 0);
        vectors.set(offset, vectors.add(offset, translation));
        vectors.set(translation, 0);

        maybeRunOnEnd();

        vectors.set(panVelocity, 0);
      },
    });

    useAnimatedReaction(
      () => {
        if (typeof isActive === 'undefined') {
          return true;
        }

        return isActive.value;
      },
      (currentActive) => {
        if (!currentActive) {
          resetSharedState();
        }
      },
    );

    const onScaleEvent = useAnimatedGestureHandler<
      PinchGestureHandlerGestureEvent,
      {
        origin: vectors.Vector<number>;
        adjustFocal: vectors.Vector<number>;
        gestureScale: number;
        nextScale: number;
      }
    >({
      onInit: (_, ctx) => {
        ctx.origin = vectors.create(0, 0);
        ctx.gestureScale = 1;
        ctx.adjustFocal = vectors.create(0, 0);
      },

      shouldHandleEvent: (evt) => {
        return (
          evt.numberOfPointers === 2 &&
          (typeof outerGestureHandlerActive !== 'undefined'
            ? !outerGestureHandlerActive.value
            : true) &&
          interactionsEnabled.value
        );
      },

      beforeEach: (evt, ctx) => {
        // calculate the overall scale value
        // also limits this.event.scale
        ctx.nextScale = clamp(
          evt.scale * scaleOffset.value,
          MIN_SCALE,
          MAX_SCALE + OVER_SCALE,
        );

        if (
          ctx.nextScale > MIN_SCALE &&
          ctx.nextScale < MAX_SCALE + OVER_SCALE
        ) {
          ctx.gestureScale = evt.scale;
        }

        // this is just to be able to use with vectors
        const focal = vectors.create(evt.focalX, evt.focalY);
        const CENTER = vectors.divide(canvas, 2);

        // since it works even when you release one finger
        if (evt.numberOfPointers === 2) {
          // focal with translate offset
          // it alow us to scale into different point even then we pan the image
          ctx.adjustFocal = vectors.sub(
            focal,
            vectors.add(CENTER, offset),
          );
        } else if (
          evt.state === State.ACTIVE &&
          evt.numberOfPointers !== 2
        ) {
          runOnJS(disablePinch)();
        }
      },

      afterEach: (evt, ctx) => {
        if (
          evt.state === State.END ||
          evt.state === State.CANCELLED
        ) {
          return;
        }

        scale.value = ctx.nextScale;
      },

      onStart: (_, ctx) => {
        onInteraction('scale');
        cancelAnimation(offset.x);
        cancelAnimation(offset.y);
        vectors.set(ctx.origin, ctx.adjustFocal);
      },

      onActive: (evt, ctx) => {
        pinchState.value = evt.state;

        const pinch = vectors.sub(ctx.adjustFocal, ctx.origin);

        const nextTranslation = vectors.add(
          pinch,
          ctx.origin,
          vectors.multiply(-1, ctx.gestureScale, ctx.origin),
        );

        vectors.set(scaleTranslation, nextTranslation);
      },

      onFinish: (evt, ctx) => {
        // reset gestureScale value
        ctx.gestureScale = 1;
        pinchState.value = evt.state;
        // store scale value
        scaleOffset.value = scale.value;

        vectors.set(offset, vectors.add(offset, scaleTranslation));
        vectors.set(scaleTranslation, 0);

        if (scaleOffset.value < 1) {
          // make sure we don't add stuff below the 1
          scaleOffset.value = 1;

          // this runs the timing animation
          scale.value = withTiming(1, timingConfig);
        } else if (scaleOffset.value > MAX_SCALE) {
          scaleOffset.value = MAX_SCALE;
          scale.value = withTiming(MAX_SCALE, timingConfig);
        }

        maybeRunOnEnd();
      },
    });

    const onTapEvent = useAnimatedGestureHandler({
      shouldHandleEvent: (evt) => {
        return (
          evt.numberOfPointers === 1 &&
          (typeof outerGestureHandlerActive !== 'undefined'
            ? !outerGestureHandlerActive.value
            : true) &&
          interactionsEnabled.value
        );
      },

      onStart: () => {
        cancelAnimation(offset.x);
        cancelAnimation(offset.y);
      },

      onActive: () => {
        onTap(scale.value > 1);
      },

      onEnd: () => {
        maybeRunOnEnd();
      },
    });

    const handleScaleTo = useWorkletCallback(
      (x: number, y: number) => {
        'worklet';

        scale.value = withTiming(DOUBLE_TAP_SCALE, timingConfig);
        scaleOffset.value = DOUBLE_TAP_SCALE;

        const targetImageSize = vectors.multiply(
          image,
          DOUBLE_TAP_SCALE,
        );

        const CENTER = vectors.divide(canvas, 2);
        const imageCenter = vectors.divide(image, 2);

        const focal = vectors.create(x, y);

        const origin = vectors.multiply(
          -1,
          vectors.sub(vectors.divide(targetImageSize, 2), CENTER),
        );

        const koef = vectors.sub(
          vectors.multiply(vectors.divide(1, imageCenter), focal),
          1,
        );

        const target = vectors.multiply(origin, koef);

        if (targetImageSize.y < canvas.y) {
          target.y = 0;
        }

        offset.x.value = withTiming(target.x, timingConfig);
        offset.y.value = withTiming(target.y, timingConfig);
      },
      [DOUBLE_TAP_SCALE, timingConfig, image, canvas],
    );

    const onDoubleTapEvent = useAnimatedGestureHandler<
      TapGestureHandlerGestureEvent,
      {}
    >({
      shouldHandleEvent: (evt) => {
        return (
          evt.numberOfPointers === 1 &&
          (typeof outerGestureHandlerActive !== 'undefined'
            ? !outerGestureHandlerActive.value
            : true) &&
          interactionsEnabled.value
        );
      },

      onActive: ({ x, y }) => {
        onDoubleTap(scale.value > 1);

        if (scale.value > 1) {
          resetSharedState(true);
        } else {
          handleScaleTo(x, y);
        }
      },
    });

    const animatedStyles = useAnimatedStyle<ViewStyle>(() => {
      const noOffset = offset.x.value === 0 && offset.y.value === 0;
      const noTranslation =
        translation.x.value === 0 && translation.y.value === 0;
      const noScaleTranslation =
        scaleTranslation.x.value === 0 &&
        scaleTranslation.y.value === 0;

      const isInactive =
        scale.value === 1 &&
        noOffset &&
        noTranslation &&
        noScaleTranslation;

      onStateChange(isInactive);

      return {
        transform: [
          {
            translateX:
              scaleTranslation.x.value +
              translation.x.value +
              offset.x.value,
          },
          {
            translateY:
              scaleTranslation.y.value +
              translation.y.value +
              offset.y.value,
          },
          { scale: scale.value },
        ],
      };
    }, []);

    return (
      <Animated.View
        style={[styles.container, { width: targetWidth }, style]}
      >
        <PinchGestureHandler
          enabled={enabled && pinchEnabled}
          ref={pinchRef}
          onGestureEvent={onScaleEvent}
          simultaneousHandlers={[
            panRef,
            tapRef,
            ...outerGestureHandlerRefs,
          ]}
        >
          <Animated.View style={styles.fill}>
            <PanGestureHandler
              enabled={enabled}
              ref={panRef}
              minDist={4}
              avgTouches
              simultaneousHandlers={[
                pinchRef,
                tapRef,
                ...outerGestureHandlerRefs,
              ]}
              onGestureEvent={onPanEvent}
            >
              <Animated.View style={styles.fill}>
                <TapGestureHandler
                  enabled={enabled}
                  ref={tapRef}
                  numberOfTaps={1}
                  maxDeltaX={8}
                  maxDeltaY={8}
                  simultaneousHandlers={[
                    pinchRef,
                    panRef,
                    ...outerGestureHandlerRefs,
                  ]}
                  waitFor={doubleTapRef}
                  onGestureEvent={onTapEvent}
                >
                  <Animated.View style={[styles.fill]}>
                    <Animated.View style={styles.fill}>
                      <Animated.View style={styles.wrapper}>
                        <TapGestureHandler
                          enabled={enabled}
                          ref={doubleTapRef}
                          numberOfTaps={2}
                          maxDelayMs={140}
                          maxDeltaX={16}
                          maxDeltaY={16}
                          simultaneousHandlers={[
                            pinchRef,
                            panRef,
                            ...outerGestureHandlerRefs,
                          ]}
                          onGestureEvent={onDoubleTapEvent}
                        >
                          <Animated.View style={animatedStyles}>
                            {typeof renderImage === 'function' ? (
                              renderImage({
                                source: imageSource,
                                width: targetWidth,
                                height: targetHeight,
                                onLoad: onLoadImageSuccess,
                              })
                            ) : (
                              <ImageComponent
                                onLoad={onLoadImageSuccess}
                                source={imageSource}
                                style={{
                                  width: targetWidth,
                                  height: targetHeight,
                                }}
                              />
                            )}
                          </Animated.View>
                        </TapGestureHandler>
                      </Animated.View>
                    </Animated.View>
                  </Animated.View>
                </TapGestureHandler>
              </Animated.View>
            </PanGestureHandler>
          </Animated.View>
        </PinchGestureHandler>
      </Animated.View>
    );
  },
)