UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];

    self.layout = layout;

    // 设置每格的大小

    layout.itemSize = CGSizeMake(DD_SCREEN_WIDTH * 0.5, 80);

    // 上左下右间距

    layout.sectionInset = UIEdgeInsetsMake(0, 0, 0, 0);

    layout.minimumLineSpacing = 0;

    layout.minimumInteritemSpacing = 0;

    return [self initWithCollectionViewLayout:layout];

注意: minimumInteritemSpacing, sectionInset这两个属性是关联的, 必须设置准确