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影付きビューの表示を高速化する

More than 5 years have passed since last update.

シャドウの効いたビューをiPhone上でスクロールしたりすると、
アニメーションが非常にもっさりしてしまうことがあります。

ただ影を付けたければこんな感じで説定できますが

self.layer.shadowOffset = CGSizeMake(0,1);
self.layer.shadowColor = [UIColor grayColor].CGColor;
self.layer.shadowRadius = 1.0;
self.layer.shadowOpacity = 1.0;

高速化するためには以下の記述が必要になります。

self.layer.shouldRasterize = YES;
self.layer.rasterizationScale = [UIScreen mainScreen].scale;

加えて、ビューのサイズが確定した後に次の行を実行するようにすることで、さらに滑らかになります。

self.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;

一昔前のデバイスで試すと、効果が一目瞭然です。

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