Can someone more experienced explain how the Pan Responder differs from the Gesture Responder and when it is better to use them.
Document:
Pan Responder:
https://reactnative.dev/docs/panresponder
Gesture Responder:
https://reactnative.dev/docs/gesture-responder-system
The Gesture Responder System is the basic system of how gestures are managed in React Native.
PanResponder is built on top of it and gives you a little more comfort when working with it. It also holds an InteractionManager to prevent interruption of active gestures.
While the Gesture Reponder System only provides you the native touch events, Pan Responder also provides you a gestureState object, which contains the state of the whole gesture (from starting the touch until releasing the finger). This can make your life a lot easier, since you don't have to calculate everything on your own.
If you don't need this gestureState or the properties provided by the gestureState objects are not sufficient for your use case, you could work directly with the Gesture Responder System. Otherwise I would recommend using PanResponder.
Related
I am using a panresponder for each item of the flat-list. I want the pan responder to respond oly when the user swipes from left to right. But pan responder is getting active also when i am scrolling . I want that there will be no interuption while scrolling
Yes i have found a solution for this problem. It basically happens because the scrollView/Flatlist itself uses one responder to sense the gesture and i am also using one pan Responder . So two pan responders cannot work at same time. So the fix for this is when my pan responder becomes active at that time i disables my flatList scrolling and when the pan responder is released or the panresponderEnd method is called i enables the flatlist scrolling . So this way i solved my problem.
I also tell about a problem that faced when i was using panresponder that sometimes panresponder release method is not called , so the card get stucks in the middle. So i used panresponderEnd method which will be called every time when you release it .
I need to create an animation in React Native which is best described as follows:
A user grabs some UI item and drags it from its original position.
While the user moves it, there is also some rotation, the UI item rotates around the Z-axis according to its motion on the XY plane.
When the user releases the item, both its position and its rotation are animated back to their original values (a "fire-and-forget" animation).
This is similar to a "pull down to refresh" UI widget. While the user is pulling down, we have both the Y translation and the rotation of the loading wheel coupled to the touch movement, and when the user lets go, there is a fire-and-forget animation without control by the user.
How would I implement this in a performant way?
I'm thinking of something like this:
We store the user's motion in the state of the component. With every move of the touch, the UI is re-rendered (not sure if that is performant).
When the user releases the touch, we use Animated.timing to generate the fire-and-forget animation.
Because of 2., the value in the state needs to be an Animated.Value instance. I'm not sure if 1. can be implemented in a performant way, using an Animated.Value as a state.
The answer is (of course): use react-native-reanimated. With this library, you have complete, declarative control over native animations and their interactions with gestures.
This is an example app which has what I was looking for:
Here is the source code.
I would like to create a carousel that scrolls automatically until the user scrolls / touches the ScrollView itself.
The auto-scrolling itself works fine with using scrollView.scrollTo but how could I detect if the user is interacting with the ScrollView? I took a look at the onScroll event but this does not seem to distinct between a user generated event and an event that was generated by calling scrollTo.
Also I'd like to know if it is possible to get the current scroll position from the ScrollView directly instead of reading it everytime from the onScroll event.
I'm very thankful for any tips and suggestions.
By digging into ScrollView's source code you can notice a few undocumented callbacks that will help you achieve what you're after, namely onTouchStart and onTouchEnd. These two callbacks are triggered only when user interacts with the ScrollView and not when you scroll programmatically.
You will probably want to clear your auto-scroll interval on onTouchStart and restart it after a delay on onTouchEnd.
Regarding your next question, the answer is no. As far as I know, no getter is currently exposed to retrieve the current scroll position. Therefore, you need to rely on the event passed to onScroll, retrieve event.nativeEvent.contentOffset['x' or 'y'], and store it in your component's state.
Note that if you're doing some heavy animations that need to follow scroll position closely (e.g. animated header or parallax image), it would be a good idea to use the native driver for Animated.event. You can learn more about it on React Native's blog.
I try to use two PanResponder to handle multi-touch event. One PanResponder in charge of upper half screen, and one lower. The two PanResponders work fine as long as there only one finger touch the screen. But when I put two finger on the screen, only one PanResponder works. So I only know coordinate( movement) of one finger and have no idea what status of the other finger is.
I can confirm I have this behavior and was unable to get an array of 2 touches with PanResponder.
It seems other people reported the problem in the past: https://react-native.canny.io/feature-requests/p/panresponderonpanrespondermove-not-responding-for-pinch
Here's my user's iPad requirement. Two users are sitting down at a table with an iPad between them. Each user needs the ability to "take control" of the app by doing a gesture to rotate the screen towards him. This would be equivalent to picking up the iPad and changing its rotation to face the user. A few questions about this:
1) Is there any default behavior within iOS to to be able to do this?
2) Do you know of any apps where this is done so I can see it in action?
3) Lastly, how do I go about enabling this functionality for my app? This functionality should be available for all UIViewControllers within my app.
I'm no expert on the topic, but here are my thoughts:
If you want to also have the app respond to device rotations, the proposal is a bit more complicated. However, if you want to eliminate physical device rotation reactions in favor of rotating the app yourself, there are only a few steps necessary:
Stop the views from auto-rotating. In iOS 6, this is as simple as implementing the shouldAutorotate: method and returning NO and the supportedInterfaceOrientations method to only return the one orientation you want to allow in the view controller at the root of your controller hierarchy. In iOS 5 and earlier, you want to implement the shouldAutorotateToInterfaceOrientation: to only return YES for one orientation in the view controller that is at the top of the view controller hierarchy.
Add code that reacts to the gesture you want to use to rotate the screen (maybe a gesture recognizer).
When the gesture is performed by the user, rotate whichever view is at the bottom of the view hierarchy in your app. Likely, you will rotate the view managed by the rootViewController. Remember that you will need to deal with the new size of this view, not just the orientation. To affect the rotation, I think the best route is to apply an affine transform to the view's layer. This is pretty helpful if you are not familiar with affine transforms.