ios - 如何使案例优先

Question

我有很多情况会为每种情况生成不同的图像。问题是，图像似乎在生成后便会堆叠起来。如何设置每种情况以覆盖上一张图像？

- (void)setTileValue:(NSInteger)tileValue {
  _tileValue = tileValue;
  self.numberLabel.text = [@(tileValue) stringValue];
    UIImageView *backgroundView = [self backgroundView:[@(tileValue) intValue]];
    [self.numberLabel addSubview:backgroundView];
  self.value = tileValue;
}


- (UIImageView *)backgroundView:(NSUInteger)value {
    switch (value) {
        case 1:
            return [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background"]]; // light gray
        case 2:
            return [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background1"]]; // gray
        case 4:
            return [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background2"]]; // gark gray
        case 8:
            return [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background3"]]; // red
        case 16:
            return [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background4"]]; // orange
        default:
            return [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background"]];
    }
}

更新代码:因此，程序每次使用initWithImage创建一个新图像。我将return设置为仅现在返回UIImage。为什么此代码也不能解决问题？

- (void)setTileValue:(NSInteger)tileValue {
  _tileValue = tileValue;
  self.numberLabel.text = [@(tileValue) stringValue];
//    UIImageView *backgroundView = [self backgroundView:[@(tileValue) intValue]];
    UIImageView *backgroundView = [[UIImageView alloc] initWithImage:[self tileBG:[@(tileValue) intValue]]];    [self.numberLabel addSubview:backgroundView];
    self.numberLabel.backgroundColor = [self tileColorForValue:[@(tileValue) intValue]];
    self.backgroundColor = [self tileColorForValue:[@(tileValue) intValue]];
    self.numberLabel.textColor = [self numberColorForValue:[@(tileValue) intValue]];
  self.value = tileValue;
}

- (UIColor *)defaultBackgroundColor {
  return [UIColor lightGrayColor];
}

- (UIColor *)defaultNumberColor {
  return [UIColor colorWithWhite:0.0 alpha:0.0];
}

- (UIImage *)tileBG:(NSUInteger)value {
    switch (value) {
        case 1:
            return [UIImage imageNamed:@"background"]; // light gray
        case 2:
            return [UIImage imageNamed:@"background1"]; // gray
        case 4:
            return [UIImage imageNamed:@"background2"]; // gark gray
        case 8:
            return [UIImage imageNamed:@"background3"]; // red
        case 16:
            return [UIImage imageNamed:@"background4"]; // red
        case 32:
            return [UIImage imageNamed:@"background5"]; // red

        default:
            return [UIImage imageNamed:@"background"]; // red
    }
}

Answer 1

请阅读我上面的评论。然后修改您的setTitleCode如下所示。

- (void)setTileValue:(NSInteger)tileValue
{
  _tileValue = tileValue;
  self.numberLabel.text = [@(tileValue) stringValue];
  UIImageView *backgroundView = (UIImageView *)[self.numberLabel viewWithTag:1000]; // edited code to avoid warning
  if (!backgroundView)
  {
    backgroundView  = [[UIImageView alloc] initWithImage:[self tileBG:[@(tileValue) intValue]]];
    backgroundView.tag = 1000;
    [self.numberLabel addSubview:backgroundView];
  }

  backgroundView.image = [self tileBG:[@(tileValue) intValue]];
  self.numberLabel.backgroundColor = [self tileColorForValue:[@(tileValue) intValue]];
  self.backgroundColor = [self tileColorForValue:[@(tileValue) intValue]];
  self.numberLabel.textColor = [self numberColorForValue:[@(tileValue) intValue]];
  self.value = tileValue;
}