本文实例介绍了iOS实现左右拖动抽屉效果，具体内容如下
利用了触摸事件滑动 touchesMoved: 来触发左右视图的出现和消失 利用loadView方法中添加view 在self.view载入前就把 左右中View都设置好frame 每一个方法都由单独的功能。
#import "DarwViewController.h" @interface DarwViewController () @property (nonatomic, weak) UIView *leftView; @property (nonatomic, weak) UIView *rightView; @property (nonatomic, weak) UIView *mainView; /** * 动画是否进行 */ @property (nonatomic ,assign) BOOL animating; @end @implementation DarwViewController - (void)viewDidLoad { [super viewDidLoad]; } -(void)loadView { self.view = [[UIView alloc]initWithFrame:[UIScreen mainScreen].bounds]; //左边view UIView *leftView = [[UIView alloc]initWithFrame:self.view.frame]; [self.view addSubview:leftView]; leftView.backgroundColor= [UIColor redColor]; self.leftView = leftView; //右边View UIView *rightView = [[UIView alloc]initWithFrame:self.view.frame]; [self.view addSubview:rightView]; rightView.backgroundColor= [UIColor blueColor]; self.rightView = rightView; //主页面 UIView *mainView = [[UIView alloc]initWithFrame:self.view.frame]; [self.view addSubview:mainView]; mainView.backgroundColor= [UIColor yellowColor]; self.mainView = mainView; //KVO监听 [self.mainView addObserver:self forKeyPath:@"frame" options:NSKeyValueObservingOptionNew context:nil]; } /** * KVO回调方法 当mainView Frame值改变时触发 * * @param keyPath <#keyPath description#> * @param object <#object description#> * @param change <#change description#> * @param context <#context description#> */ -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context { if (self.animating) return; //如果mainView正在动画 就不执行 if (self.mainView.frame.origin.x > 0 ) { //X > 0 就隐藏右边View 显示左边View self.rightView.hidden = YES; self.leftView.hidden = NO; } else if (self.mainView.frame.origin.x < 0) { //X < 0 就隐藏左边View 显示右边VIew self.leftView.hidden = YES; self.rightView.hidden = NO; } } #pragma mark -- 触摸事件 -(void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { //获得触摸对象 UITouch *touch = [touches anyObject]; //获得当前触摸点 CGPoint currentPoint = [touch locationInView:self.view]; //获得上一个触摸点 CGPoint previousPoint = [touch previousLocationInView:self.view]; //计算x方向的偏移量 CGFloat offsetX = currentPoint.x - previousPoint.x; // 根据x的偏移量计算y的偏移量 self.mainView.frame = [self rectWithOffsetX:offsetX]; } #define screenW [UIScreen mainScreen].bounds.size.width #define screenH [UIScreen mainScreen].bounds.size.height /** * 计算主视图的frame * * @param offsetX x的偏移量 * * @return 偏移后新的frame */ - (CGRect ) rectWithOffsetX:(CGFloat )offsetX { //Y轴的偏移量 CGFloat offsetY = (screenH *1/5) * (offsetX/screenW); //比例 ：（用于宽高的缩放） CGFloat scale = (screenH - offsetY *2) / screenH; if (self.mainView.frame.origin.x < 0 ) { //如果x是负数 及左边View要显示 //比例就要设为比1小 scale = 2 - scale; } //获取当前mainView的frame CGRect frame = self.mainView.frame; //重新设置mainView的frame值 frame.size.width = frame.size.width *scale >screenW ? screenW : frame.size.width *scale; frame.size.height = frame.size.height *scale >screenH ? screenH :frame.size.height *scale; frame.origin.x += offsetX; frame.origin.y =(screenH - frame.size.height)*0.5; //返回偏移后新的frame return frame; } #define maxRightX (screenW *0.8) #define maxLeftX (-screenW *0.6) -(void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { CGFloat targetX = 0; //如果松手的那一下 当前mainVIew的x大于屏幕的一半 if (self.mainView.frame.origin.x > screenW * 0.5) { //向右边定位 targetX = maxRightX; } //如果松手的那一下 当前mainVIew的最大X值小于屏幕的一半 else if (CGRectGetMaxX(self.mainView.frame) < screenW *0.5) { //向左边定位 targetX = maxLeftX; } //计算偏移量 CGFloat offsetX = targetX -self.mainView.frame.origin.x; self.animating = YES; [UIView animateWithDuration:0.4 animations:^{ if (targetX == 0) { //如果targetX==0 复位 self.mainView.frame = self.view.frame; } else { //如果targetX != 0 那就到指定位置 self.mainView.frame = [self rectWithOffsetX:offsetX]; } } completion:^(BOOL finished) { self.animating = NO; }]; } @end
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