問題

最近在做一個(gè)有錄音功能的App，要求當(dāng)用戶接到來電時(shí)，要停止錄音。該如何實(shí)現(xiàn)這個(gè)功能呢？

解決方案

我首先想到了AppDelegate里的applicationWillResignActive:方法，在該方法的注釋中就寫到到收到來電或短信時(shí)，系統(tǒng)會(huì)自動(dòng)調(diào)用該方法，如下：

// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.?
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.

但是有個(gè)問題，當(dāng)程序進(jìn)入后臺(tái)時(shí)，也會(huì)調(diào)用這個(gè)方法，而我的App要求，即使進(jìn)入后臺(tái)，也可以繼續(xù)錄音，而在applicationWillResignActive:方法里無(wú)法判斷是什么原因引起的該方法的調(diào)用（可能有方法，但我沒搜到，哪位朋友知道的話分享一下），因此這個(gè)解決方案行不通。

繼續(xù)查找資料，最終找到CoreTelephony框架，這個(gè)框架包含了電話相關(guān)的API，可以實(shí)現(xiàn)監(jiān)測(cè)來電，查看運(yùn)營(yíng)商信息等功能。見上一篇CoreTelephony框架的博文，下面就是具體的實(shí)現(xiàn)監(jiān)測(cè)來電的代碼

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#import <span class="hljs-title" style="box-sizing: border-box;">"ViewController.h"</span></span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//引入框架</span> @import CoreTelephony;<span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@interface</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ViewController</span> ()</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@property</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">nonatomic</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">strong</span>) CTCallCenter * center; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@end</span><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@implementation</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ViewController</span></span>- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)viewDidLoad {[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> viewDidLoad];<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.center</span> = [[CTCallCenter alloc] init];<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.center</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.callEventHandler</span> = ^(CTCall * call){<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//TODO:檢測(cè)到來電后的處理</span>};} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@end</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>

這里注意一定要把center寫成一個(gè)單獨(dú)的屬性，并且是強(qiáng)引用(strong)，否則如果在viewDidLoad方法里創(chuàng)建center，viewDidLoad方法調(diào)用完后center就銷毀了，就無(wú)法檢測(cè)到來電了，千萬(wàn)不要犯這種低級(jí)錯(cuò)誤。

還有一種方案。使用通知的方式監(jiān)聽AVAudioSessionInterruptionNotification。來電后語(yǔ)音播放會(huì)被停止觸發(fā)中斷。通過通知做后續(xù)操作。比較簡(jiǎn)單就不多說了。

創(chuàng)作挑戰(zhàn)賽新人創(chuàng)作獎(jiǎng)勵(lì)來咯，堅(jiān)持創(chuàng)作打卡瓜分現(xiàn)金大獎(jiǎng)

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