UITableViewCell Background Selection State Flipping Issue

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Introduction

In this article, we will explore a common issue when working with UITableViewCell in iOS development. The problem is that the table cell’s background selection state can flip back unexpectedly, even after a long press gesture has ended. We’ll delve into the details of the issue and discuss possible solutions to keep the background selected indefinitely.

Background Selection State and Gesture Recognizers

When you add a UILongPressGestureRecognizer to a UITableViewCell, it allows the user to perform a long press gesture on the cell. The state of the gesture recognizer can change from UIGestureRecognizerStateBegan (when the gesture starts) to UIGestureRecognizerStateEnded (when the gesture ends).

However, when you select a table row using the tableView:didSelectRowAtIndexPath: method, it also triggers a change in the cell’s background selection state. If the cell has a blue background, it will turn opaque; if it has an opaque background, it will become blue.

The issue arises when you use both gestures and cell selection simultaneously. In some cases, the table view may trigger a cell selection event before the long press gesture ends, causing the background selection state to flip back unexpectedly.

Solution: Using the `stateChanged` Property

One possible solution to this issue is to use the stateChanged property of the UILongPressGestureRecognizer. This property allows you to specify a block that will be executed when the gesture recognizer’s state changes, regardless of whether it starts or ends.

To fix the issue, we need to change the test condition from UIGestureRecognizerStateEnded to UIGestureRecognizerStateBegan and use the stateChanged property to execute a block when the long press gesture begins. Here is an example:

UILongPressGestureRecognizer *_recognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(cellLongPressRecognized:)];
_recognizer.allowableMovement = 20;
_recognizer.minimumPressDuration = 1.0f;
_recognizer.stateChanged = ^(UIGestureRecognizerState state) {
    if (state == UIGestureRecognizerStateBegan)
        ALog(@"[MyViewController] -cellLongPressRecognized: gesture began...");
};
[[cell contentView] addGestureRecognizer:_recognizer];

By using the stateChanged property, we ensure that the block is executed when the long press gesture begins, not just when it ends. This allows us to keep the background selected indefinitely, as long as the user holds their finger on the device.

Additional Tips

Here are some additional tips for working with UITableViewCell and UILongPressGestureRecognizer:

When using UILongPressGestureRecognizer, make sure to set the allowableMovement property to a non-zero value. This will prevent the gesture recognizer from triggering when the user moves their finger by more than the specified movement distance.
Use the minimumPressDuration property to control how long the long press gesture must be held before it ends. A lower value may cause the cell’s background selection state to flip back unexpectedly.
Consider using a custom UITableViewCell subclass that overrides the cellForRowAtIndexPath: method to modify the cell’s appearance when selected.

Conclusion

The issue of table cell background selection state flipping is more common than you think, and it can be tricky to solve. By understanding how UILongPressGestureRecognizer works and using the stateChanged property, we can keep the background selected indefinitely. Remember to set the allowableMovement and minimumPressDuration properties carefully to achieve the desired behavior.

With these tips and techniques, you should be able to resolve the issue of table cell background selection state flipping and create a more seamless user experience for your iOS app.

Additional Resources

Note: The code snippets in this article are just examples and should be adapted to your specific use case.

Last modified on 2023-09-08