Ios 文本编辑类详解 Attributes和ParagraphStyle介绍
NSMutableParagraphStyle的部分属性：
typedef NS_ENUM(NSInteger, NSLineBreakMode) {/* What to do with long lines */
NSLineBreakByWordWrapping = 0, /* Wrap at word boundaries, default */
NSLineBreakByCharWrapping,/* Wrap at character boundaries */
NSLineBreakByClipping,/* Simply clip */剪掉后面显示不了的部分
NSLineBreakByTruncatingHead,/* Truncate at head of line: "...wxyz" */头部分的内容以……方式省略
NSLineBreakByTruncatingTail,/* Truncate at tail of line: "abcd..." */结尾部分的内容以……方式省略
NSLineBreakByTruncatingMiddle/* Truncate middle of line: "ab...yz" */中间部分的内容以……方式省略
} NS_ENUM_AVAILABLE_IOS(6_0);
typedef NS_ENUM(NSInteger, NSWritingDirection) {
NSWritingDirectionNatural = -1, // Determines direction using the Unicode Bidi Algorithm rules P2 and P3
NSWritingDirectionLeftToRight = 0, // Left to right writing direction 左到右的书写方向
NSWritingDirectionRightToLeft = 1 // Right to left writing direction 右到左的书写方向
} NS_ENUM_AVAILABLE_IOS(6_0);
NSParagraphStyleAttributeName 段落的风格（设置首行，行间距，对齐方式什么的）看自己需要什么属性，写什么
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
paragraphStyle.lineSpacing = 10;// 字体的行间距
paragraphStyle.firstLineHeadIndent = 20.0f;//首行缩进
paragraphStyle.alignment = NSTextAlignmentJustified;//（两端对齐的）文本对齐方式：（左，中，右，两端对齐，自然）
paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;//结尾部分的内容以……方式省略 ( "...wxyz" ,"abcd..." ,"ab...yz")
paragraphStyle.headIndent = 20;//整体缩进(首行除外)
paragraphStyle.tailIndent = 20;//
paragraphStyle.minimumLineHeight = 10;//最低行高
paragraphStyle.maximumLineHeight = 20;//最大行高
paragraphStyle.paragraphSpacing = 15;//段与段之间的间距
paragraphStyle.paragraphSpacingBefore = 22.0f;//段首行空白空间/* Distance between the bottom of the previous paragraph (or the end of its paragraphSpacing, if any) and the top of this paragraph. */
paragraphStyle.baseWritingDirection = NSWritingDirectionLeftToRight;//从左到右的书写方向（一共??三种）
paragraphStyle.lineHeightMultiple = 15;/* Natural line height is multiplied by this factor (if positive) before being constrained by minimum and maximum line height. */
paragraphStyle.hyphenationFactor = 1;//连字属性 在iOS，唯一支持的值分别为0和1
NSFontAttributeName 字体大小
NSParagraphStyleAttributeName 段落的风格（设置首行，行间距，对齐方式什么的）
NSKernAttributeName 字间距
NSDictionary *attributes = @{
NSFontAttributeName:[UIFont systemFontOfSize:15],
NSParagraphStyleAttributeName:paragraphStyle,
NSKernAttributeName:@(10),
};
textView.attributedText = [[NSAttributedString alloc] initWithString:textView.text attributes:attributes];
1.NSKernAttributeName: @10 调整字句 kerning 字句调整
2.NSFontAttributeName : [UIFont systemFontOfSize:_fontSize] 设置字体
3.NSForegroundColorAttributeName :[UIColor redColor] 设置文字颜色
4.NSParagraphStyleAttributeName : paragraph 设置段落样式
5.NSMutableParagraphStyle *paragraph = [[NSMutableParagraphStyle alloc] init];
paragraph.alignment = NSTextAlignmentCenter;
6.NSBackgroundColorAttributeName: [UIColor blackColor] 设置背景颜色
7.NSStrokeColorAttributeName设置文字描边颜色，需要和NSStrokeWidthAttributeName设置描边宽度，这样就能使文字空心.
NSStrokeWidthAttributeName这个属性所对应的值是一个 NSNumber 对象(小数)。该值改变描边宽度（相对于字体size 的百分比）。默认为 0，即不改变。正数只改变描边宽度。负数同时改变文字的描边和填充宽度。例如，对于常见的空心字，这个值通常为3.0。
同时设置了空心的两个属性，并且NSStrokeWidthAttributeName属性设置为整数，文字前景色就无效果了
