在 Objective C 中使用动画实现 UISlider

Question

我是 Objective C 的新手，我在如何使用动画实现 UISlider 时遇到了一些麻烦。我想使用滑块来改变动画的速度（这是一个在单击动画按钮后改变其大小的图像），但我不知道如何将滑块与动画的持续时间联系起来。因此，我想就如何使其发挥作用提出建议。 （我预先设置了滑块的最小值为 1，最大值为 5，默认为 3）。任何建议将不胜感激。这是我的 ViewController.m 代码

//
//  ViewController.m
//  Project5-TMN
//
//  Created by Lab on 4/6/17.
//  Copyright © 2017 Toan Nguyen. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIImageView *image;
@property (weak, nonatomic) IBOutlet UILabel *speedValue;
- (IBAction)animate:(id)sender;

- (IBAction)stop:(id)sender;

- (IBAction)speed:(UISlider *)sender;


@end

@implementation ViewController
// Declare two variables to hold the width and height of the image
float w, h;
// Declare a global variable to set the animation status
BOOL animating = YES;

- (void)viewDidLoad {
    [super viewDidLoad];
    // set w to the size of the image width
    w = _image.bounds.size.width;

    // set h to the size of the image height
    h = _image.bounds.size.height;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)animate:(id)sender {
    // set animation status to YES again to let it animating continously after stop
    animating = YES;

    [UIView animateWithDuration:5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^ {
        // Create a CGRect rect, and set the core graphic Rect to the image bound
        CGRect rect = _image.bounds;

        // Set the width of rect to the difference of the bounds of rect and the image width
        rect.size.width = w - rect.size.width;

        // Set the height of rect to the difference of the bounds of rect and the image height
        rect.size.height = h - rect.size.height;

        // Assign rect to the image bounds
        _image.bounds = rect;
    }
    completion:^(BOOL finished) {
        if (finished) {
            if (animating) {
                [self animate:sender];
            }
        }

    }];

}

- (IBAction)stop:(id)sender {
    // set animating to NO
    animating = NO;

}

- (IBAction)speed:(UISlider *)sender {
    UISlider *slider = (UISlider *)sender;
    _speedValue.text = [NSString stringWithFormat:@"%.0f", slider.value];

}

@end

Answer 1

要更改动画的速度，您可以更改持续时间的值。在您的示例中，您的在线持续时间为 5 秒：

[UIView animateWithDuration:5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^ {

您可以从滑块重定向值，而不是常量 5。在您的示例中，您只在标签处显示滑块值，但不将其用于动画参数。你可以像这样使用这个标签的值：

[UIView animateWithDuration:[_speedValue.text intValue] delay:0 options:UIViewAnimationOptionCurveLinear animations:^ {

或者您可以为滑块创建出口并直接使用它的值：

@property (weak, nonatomic) IBOutlet UISlider *speedSlider; //this line at interface should be created by control drag from slider to code

[UIView animateWithDuration:_speedSlider.value delay:0 options:UIViewAnimationOptionCurveLinear animations:^ {

或者你可以使用某种缓冲区变量：

@property (assign, nonatomic) float currentSpeed; // declare at interface

[UIView animateWithDuration:_currentSpeed delay:0 options:UIViewAnimationOptionCurveLinear animations:^ { // at - (IBAction)animate:(id)sender

self.currentSpeed = slider.value; // at - (IBAction)speed:(UISlider *)sender