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                  <h1>OC 多线程之 GCD知识从基础到进阶 （1）</h1>
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                        	<h2 id="toc_0">概念认知</h2>

<p>基本概念：</p>

<ul>
<li><p>GCD 全称 (Grand Center Dispatch),翻译成通俗中文“牛B的中心调度机制”</p></li>
<li><p>线程：执行任务调度的最小单位</p></li>
<li><p>任务：就是一段代码，GCD中就是block中的内容。执行任务有两种方式：同步执行（sync）和异步执行（async）。两者的主要区别是：是否等待队列的任务执行结束，以及是否具备开启新线程的能力</p></li>
<li><p>队列：用来存放任务的线性结构，采用 FIFO（先进先出）的原则。</p></li>
</ul>


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                   <a href="15261167596297.html">Read more</a>&nbsp;&nbsp;
                    <span class="date">2018/5/12</span>
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                  <h1>OC中的各种遍历</h1>
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                        	<blockquote>
<p>iOS开发中我们经常遇到各种的数据处理，所以就会经常遇到数组遍历 和 字典遍历。但是不同的遍历方式，效率不同，并且还有不同的限制。</p>
</blockquote>

<p>首先把数据源准备好：</p>

<pre><code class="language-text">_dataSource = [NSMutableArray array];
_dataDic = [NSMutableDictionary dictionary];
for (int i=0; i&lt;5; i++) {
    [_dataSource addObject:@(i)];
    [_dataDic setObject:@(i) forKey:[NSString stringWithFormat:@&quot;我是第%d个Item&quot;,i]];
}
</code></pre>


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                    <span class="date">2018/5/8</span>
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                  <h1>多线程 之 NSThread</h1>
                  <div class="a-content">

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                        	<h2 id="toc_0">基本使用</h2>

<h2 id="toc_1">基本知识点学习笔记</h2>

<ul>
<li>新创建的线程放到了内存的<code>可调度线程池内</code></li>
<li>线程关系：
<img src="https://ws1.sinaimg.cn/large/006tKfTcly1fqyaf1gkuvj31gm0nmx2b.jpg" alt=""/></li>
<li></li>
</ul>


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                    <span class="date">2018/5/3</span>
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                  <h1>音视频学习笔记 1</h1>
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                      <div class="a-content-text">

                        	<h2 id="toc_0">音视频概念</h2>

<h3 id="toc_1">声音的物理性质</h3>

<ul>
<li>声波三要素：频率、振幅、波形</li>
<li>人耳听到的频率范围 20Hz-20KHz</li>
<li><p>声音在空气中的传播速度 340m/s、蒸馏水中1497m/s、铁棒5200m/s</p></li>
<li><p>一般声音的采样频率为 44.1KHz---&gt; 一秒钟采样44100次，这样 20KHz的频率也能被数字化</p></li>
<li><p>音频的裸数据格式 脉冲编码调制  PCM （Pluse Code Modulation）</p></li>
<li><p>PCM 相关概念：量化格式、采样频率、声道数</p></li>
</ul>

<h3 id="toc_2">音频编码</h3>

<p>音频压缩编码算法有：PCM、WAV、AAC、MP3、Ogg。</p>

<ul>
<li>WAV：音频质量好，大多数软件都支持，但是占用空间大；适合当做多媒体开发的中间文件，保存音乐、音效素材</li>
<li>MP3：不错的压缩比，LAME编码中高码率文件。音质在128Kbit/s 以上表现不错，压缩比高，大多数软件都支持。适合高比特率下对兼容性有要求的音乐欣赏。</li>
<li>AAC：包括LC-AAC、HE-AAC、HE-AAC v2,小于128Kbit/s表现优异。</li>
</ul>

<table>
<thead>
<tr>
<th style="text-align: center">LC-AAC</th>
<th style="text-align: center">HE-AAC</th>
<th style="text-align: center">HE-AAC v2</th>
</tr>
</thead>

<tbody>
<tr>
<td style="text-align: center">中高码率&gt;80Kbit/s</td>
<td style="text-align: center">中低码率&lt;=80Kbit/s</td>
<td style="text-align: center">低码率&lt;48Kbit/s</td>
</tr>
</tbody>
</table>


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                    <span class="date">2018/4/12</span>
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                  <h1>疯狂iOS讲义笔记 1</h1>
                  <div class="a-content">

                      <div class="a-content-text">

                        	<h2 id="toc_0">多点触摸与 手势检测</h2>

<h3 id="toc_1">响应者链</h3>

<ul>
<li>响应者链：第一响应者 ---&gt; 第一响应者的视图控制器 ---&gt; 父控制器（如果有的话）---&gt; UIWindow ---&gt; UIApplication ---&gt; 应用程序委托对象</li>
<li>手势交互触发事件的过程，iOS系统遍历视图的时候 是 深度遍历 还是 广度遍历？</li>
</ul>

<p>事件的传递：是广度遍历<br/>
事件的响应：深度遍历</p>


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                    <span class="date">2018/4/10</span>
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                  <h1>iOS GCD&&多线程</h1>
                  <div class="a-content">

                      <div class="a-content-text">

                        	<h2 id="toc_0">基础篇</h2>

<h3 id="toc_1">GCD用途</h3>

<blockquote>
<p>GCD 是 Grand Central Dispatch 的缩写。</p>
</blockquote>

<ul>
<li>GCD 可用于多核的并行运算</li>
<li>GCD 会自动利用更多的 CPU 内核（比如双核、四核）</li>
<li>GCD 会自动管理线程的生命周期（创建线程、调度任务、销毁线程）</li>
<li>程序员只需要告诉 GCD 想要执行什么任务，不需要编写任何线程管理代码</li>
</ul>


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                    <span class="date">2018/3/28</span>
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                  <h1>iOS Block 知识点拾遗</h1>
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                      <div class="a-content-text">

                        	<ol>
<li><p>Block为什么要用copy</p>
<ul>
<li>block在创建的时候默认分配的内存是在栈上，而不是在堆上。这样的话其本身的作用域是属于创建时候的作用域，一旦在创建的作用域之外调用就会导致程序的崩溃。所以使用了copy将其拷贝到堆内存上。</li>
<li>block创建在栈上，而block的代码中可能会用到本地的一些变量，在栈上可能随时会被系统释放掉，只有将其拷贝到堆上，才能一直保持Block的存在，并用这些外部变量</li>
</ul></li>
<li><p>Block为什么不用retain</p>
<ul>
<li>retain只是增加了一次引用计数，block的内存还是在栈上，并没有存在堆上，存在栈上的block可能随时被系统回收</li>
</ul></li>
<li><p>为什么进入block中的对象引用计数需要自动加1？</p>
<ul>
<li>Block执行的是回调，因此block并不知道其中的对象obj创建后会在什么时候被释放，为了不在block使用obj之前，对象已经被释放，block就retain了obj一次</li>
</ul></li>
<li><p>block和函数的关系</p>
<ul>
<li>Block的使用很<strong>像函数指针</strong>，不过与函数最大的不同是Block可以访问函数以外、词法作用域以内的外部变量的值。换句话说，Block不仅 实现函数的功能，还能<strong>携带函数的执行环境</strong>。</li>
<li>函数指针 <code>void(*fun)(int)</code></li>
<li>block <code>void(^fun)(int)</code></li>
</ul></li>
<li><p>block本质（对于block的理解）<a href="https://www.cnblogs.com/yoon/p/4953618.html">请查阅Block实现原理</a></p>
<ul>
<li>block实际上是: 指向结构体的指针</li>
<li>编译器会将block的内部代码生成对应的函数</li>
</ul></li>
<li><p>对于基本数据类型，进入到block中会被当做常量处理。对象 retain 会一次</p>


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                    <span class="date">2018/3/3</span>
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                  <h1>iOS 离屏渲染</h1>
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                        	<h2 id="toc_0">触发方式</h2>

<p>设置以下方式会触发离屏渲染：</p>

<ul>
<li>shouldRasterize（光栅化）</li>
<li>masks（遮罩）</li>
<li>shadows（阴影）</li>
<li>edge antialiasing（抗锯齿）</li>
<li>group opacity（不透明）</li>
<li>复杂形状设置圆角等</li>
<li>渐变 </li>
</ul>


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                    <span class="date">2018/3/3</span>
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                  <h1>iOS 面试题总结</h1>
                  <div class="a-content">

                      <div class="a-content-text">

                        	<h2 id="toc_0">基础篇</h2>

<h3 id="toc_1">内存管理 ：assign copy strong weak...</h3>

<ul>
<li>简述OC中内存管理机制,与retain配对使用的方法是dealloc还是release，为什么？</li>
</ul>

<blockquote>
<p>管理机制：<br/>
  使用了一种叫做 <strong>引用计数</strong> 的机制来管理内存中的对象。OC中每个对象都对应着他们自己的引用计数，引用计数可以理解为一个整数计数器，当使用alloc方法创建对象的时候，持有计数会自动设置为1。当你向一个对象发送retain消息 时，持有计数数值会增加1。相反，当你像一个对象发送release消息时，持有计数数值会减小1。当对象的持有计数变为0的时候，对象会释放自己所占用的内存</p>
</blockquote>

<ul>
<li><p>修饰词的作用</p>
<ul>
<li>retain(引用计数加1)-&gt;release（引用计数减1）</li>
<li>alloc（申请内存空间）-&gt;dealloc(释放内存空间)</li>
<li>readwrite: 表示既有getter，也有setter   (默认)</li>
<li>readonly: 表示只有getter，没有setter</li>
<li>nonatomic:不考虑线程安全</li>
<li>atomic:线程操作安全   （默认）</li>
<li>retain: release旧的对象，将旧对象的值赋予输入对象，再提高输入对象的索引计数为1</li>
<li>assign: 简单赋值，不更改索引计数    （默认）</li>
<li>copy: 其实是建立了一个相同的对象,地址不同（retain：指针拷贝  copy：内容拷贝）</li>
<li>strong:（ARC下的）和（MRC）retain一样    （默认）</li>
<li>weak:（ARC下的）和（MRC）assign一样， weak当指向的内存释放掉后自动nil化，防止野指针</li>
<li>unsafe_unretained 声明一个弱引用，但是不会自动nil化，也就是说，如果所指向的内存区域被释放了，这个指针就是一个野指针了。 autoreleasing 用来修饰一个函数的参数，这个参数会在函数返回的时候被自动释放。<br/>
### .类变量的@protected ,@private,@public,@package，声明各有什么含义？</li>
</ul></li>
</ul>


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                    <span class="date">2018/2/28</span>
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                  <h1>iOS 项目组件化</h1>
                  <div class="a-content">

                      <div class="a-content-text">

                        	<h2 id="toc_0">组件化需要解决的问题</h2>

<ul>
<li>APP 如何跳到任意指定界面（APP外部跳转，APP内部跳转）</li>
<li>自家APP之间如何相互跳转 </li>
<li>如何降低APP组件和APP界面之间的耦合度</li>
<li>如何动态下发配置文件；iOS 安卓共用配置文件</li>
<li>AOP统计界面跳转</li>
<li>组件之间通信，组件和界面之间通信</li>
</ul>

<h2 id="toc_1">组件化步骤</h2>

<ul>
<li>拆分UI组件</li>
<li>拆分业务组件</li>
<li>组件管理</li>
<li>组件通信</li>
</ul>

<h2 id="toc_2">组件化架构 &amp;&amp; 思路</h2>


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                    <span class="date">2018/2/23</span>
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