iOS开发基础144-逐字打印效果
在AIGC类的APP中，实现那种一个字一个字、一行一行地打印出文字的效果，可以通过多种方法来实现。下面是一些实现方法，使用Swift和OC来举例说明。
OC版
1. 基于定时器的逐字打印效果
可以使用
NSTimer
来逐字逐行地显示文字。
#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) UITextView *textView;
@property (nonatomic, strong) NSString *content;
@property (nonatomic, assign) NSInteger currentIndex;
@property (nonatomic, strong) NSTimer *timer;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.textView = [[UITextView alloc] initWithFrame:self.view.bounds];
self.textView.font = [UIFont systemFontOfSize:18];
self.textView.editable = NO;
self.textView.scrollEnabled = YES;
[self.view addSubview:self.textView];
self.content = @"这是需要逐字逐行打印的文字内容。\n让我们来实现它。";
self.currentIndex = 0;
[self startPrinting];
}
- (void)startPrinting {
self.timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(printNextCharacter) userInfo:nil repeats:YES];
}
- (void)printNextCharacter {
if (self.currentIndex >= self.content.length) {
[self.timer invalidate];
self.timer = nil;
return;
}
NSRange range = NSMakeRange(self.currentIndex, 1);
NSString *nextCharacter = [self.content substringWithRange:range];
self.textView.text = [self.textView.text stringByAppendingString:nextCharacter];
self.currentIndex += 1;
}
@end
2. 使用CADisplayLink来实现高精度逐字打印
CADisplayLink
可以在屏幕刷新时调用指定的方法，相较于
NSTimer
，其精度和性能更高。
#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) UITextView *textView;
@property (nonatomic, strong) NSString *content;
@property (nonatomic, assign) NSInteger currentIndex;
@property (nonatomic, strong) CADisplayLink *displayLink;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.textView = [[UITextView alloc] initWithFrame:self.view.bounds];
self.textView.font = [UIFont systemFontOfSize:18];
self.textView.editable = NO;
self.textView.scrollEnabled = YES;
[self.view addSubview:self.textView];
self.content = @"这是需要逐字逐行打印的文字内容。\n让我们来实现它。";
self.currentIndex = 0;
[self startPrinting];
}
- (void)startPrinting {
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(printNextCharacter)];
self.displayLink.preferredFramesPerSecond = 10; // 控制打印速度
[self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}
- (void)printNextCharacter {
if (self.currentIndex >= self.content.length) {
[self.displayLink invalidate];
self.displayLink = nil;
return;
}
NSRange range = NSMakeRange(self.currentIndex, 1);
NSString *nextCharacter = [self.content substringWithRange:range];
self.textView.text = [self.textView.text stringByAppendingString:nextCharacter];
self.currentIndex += 1;
}
@end
3. CATextLayer + Animation
还可以使用
CATextLayer
和动画来实现更为复杂和流畅的逐字逐行打印效果。
#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
@interface ViewController ()
@property (nonatomic, strong) CATextLayer *textLayer;
@property (nonatomic, strong) NSString *content;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.textLayer = [CATextLayer layer];
self.textLayer.frame = self.view.bounds;
self.textLayer.fontSize = 18;
self.textLayer.alignmentMode = kCAAlignmentLeft;
self.textLayer.contentsScale = [UIScreen mainScreen].scale;
self.textLayer.wrapped = YES;
[self.view.layer addSublayer:self.textLayer];
self.content = @"这是需要逐字逐行打印的文字内容。\n让我们来实现它。";
[self startPrinting];
}
- (void)startPrinting {
self.textLayer.string = @"";
for (NSInteger index = 0; index < self.content.length; index++) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(index * 0.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
NSString *nextCharacter = [self.content substringWithRange:NSMakeRange(index, 1)];
self.textLayer.string = [self.textLayer.string stringByAppendingString:nextCharacter];
});
}
}
@end
Swift版
1. 基于定时器的逐字打印效果
可以使用
Timer
来逐字逐行地显示文字。
import UIKit
class ViewController: UIViewController {
private let textView = UITextView()
private let content = "这是需要逐字逐行打印的文字内容。\n让我们来实现它。"
private var currentIndex = 0
private var timer: Timer?
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(textView)
textView.frame = view.bounds
textView.font = UIFont.systemFont(ofSize: 18)
textView.isEditable = false
textView.isScrollEnabled = true
startPrinting()
}
private func startPrinting() {
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(printNextCharacter), userInfo: nil, repeats: true)
}
@objc private func printNextCharacter() {
guard currentIndex < content.count else {
timer?.invalidate()
timer = nil
return
}
let nextIndex = content.index(content.startIndex, offsetBy: currentIndex)
textView.text.append(content[nextIndex])
currentIndex += 1
}
}
2. 使用CADisplayLink来实现高精度逐字打印
CADisplayLink
可以在屏幕刷新时调用指定的方法，相较于
Timer
，其精度和性能更高。
import UIKit
class ViewController: UIViewController {
private let textView = UITextView()
private let content = "这是需要逐字逐行打印的文字内容。\n让我们来实现它。"
private var currentIndex = 0
private var displayLink: CADisplayLink?
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(textView)
textView.frame = view.bounds
textView.font = UIFont.systemFont(ofSize: 18)
textView.isEditable = false
textView.isScrollEnabled = true
startPrinting()
}
private func startPrinting() {
displayLink = CADisplayLink(target: self, selector: #selector(printNextCharacter))
displayLink?.preferredFramesPerSecond = 10 // 控制打印速度
displayLink?.add(to: .main, forMode: .default)
}
@objc private func printNextCharacter() {
guard currentIndex < content.count else {
displayLink?.invalidate()
displayLink = nil
return
}
let nextIndex = content.index(content.startIndex, offsetBy: currentIndex)
textView.text.append(content[nextIndex])
currentIndex += 1
}
}
3. CATextLayer + Animation
还可以使用
CATextLayer
和动画来实现更为复杂和流畅的逐字逐行打印效果。
import UIKit
class ViewController: UIViewController {
private let textLayer = CATextLayer()
private let content = "这是需要逐字逐行打印的文字内容。\n让我们来实现它。"
override func viewDidLoad() {
super.viewDidLoad()
textLayer.frame = view.bounds
textLayer.fontSize = 18
textLayer.alignmentMode = .left
textLayer.contentsScale = UIScreen.main.scale
textLayer.isWrapped = true
view.layer.addSublayer(textLayer)
startPrinting()
}
private func startPrinting() {
textLayer.string = ""
for (index, character) in content.enumerated() {
DispatchQueue.main.asyncAfter(deadline: .now() + Double(index) * 0.1) {
self.textLayer.string = "\(self.textLayer.string ?? "")\(character)"
}
}
}
}