如何禁止App在后台运行以及如何保存和恢复App的状态

新年逐渐走远，又要开始新的一年了，逐渐开始自己博客的更新吧，欢迎小伙伴们继续互相学习。在了解生命周期的基础上，下面转载一片文章 一起看看关于App后台运行的问题吧

如果禁止App在后台运行

iOS上的App类似于Windows上的进程,有几种不同的生存周期:



而App中的任何View也有类似的生存周期:



如果App处在非活动的状态下,那么接着它将进入挂起状态.

某些情况下我们可能不希望这样,我们想要当App进入后台时就将其结束掉.可以通过修改项目的info.plist文件来实现:



如上图,将Application does not run in background设置为YES就可以做到这一点.这时当你在运行App时按Home键后,你的App不会进入后台而是直接被结果掉了,下一次运行你的App将会重新运行.

如何保存和恢复App的状态

第二个问题是如果App不从后台恢复的话如何自动保存其之前的状态呢?

举一个UI的例子,在主界面上有一个Text控件:

<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-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><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;">weak</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;">IBOutlet</span> UITextField *inputText;</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-width: 1px; border-right-style: solid; border-right-color: 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></ul>

我们希望在输入一些字符,当App关掉再次运行的时候之前输入的那些字符会自动显示在Text中.

首先在Main.stroyboard中将ViewController的Restoration ID设置为viewController:



然后在AppDelegate.m中添加如下回调方法:

<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-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">-(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)application:(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">UIApplication</span>*)application shouldSaveApplicationState:
(nonnull NSCoder *)coder{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span>;
}

-(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)application:(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">UIApplication</span> *)application shouldRestoreApplicationState:(NSCoder *)coder{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</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-width: 1px; border-right-style: solid; border-right-color: 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></ul>

如果你想要保存App级别的数据可以使用以下2个回调方法:

<code class="hljs erlang has-num
bcd6
bering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-pp" style="box-sizing: border-box;">-<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(void)</span>application:<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(<span class="hljs-variable" style="box-sizing: border-box;">UIApplication</span> *)</span>application didDecodeRestorableStateWithCoder:<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(<span class="hljs-variable" style="box-sizing: border-box;">NSCoder</span> *)</span>coder{
float val = [coder decodeFloatForKey:kAppValue];
NSLog<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"value is %f"</span>,val)</span>;
}

-<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(void)</span>application:<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(<span class="hljs-variable" style="box-sizing: border-box;">UIApplication</span> *)</span>application willEncodeRestorableStateWithCoder:<span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">(nonnull <span class="hljs-variable" style="box-sizing: border-box;">NSCoder</span> *)</span>coder{
[coder encodeFloat:99</span>.<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">99</span> for<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">Key</span>:k<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">AppValue</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-width: 1px; border-right-style: solid; border-right-color: 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></ul>

如果你想要保存某个View界面中的数据,就像一开始说的那样,你可以在ViewController.m里添加如下2个方法:

<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-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background: transparent;">-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)decodeRestorableStateWithCoder:(NSCoder *)coder{
[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> decodeRestorableStateWithCoder:coder];
<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;">.inputText</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.text</span> = [coder decodeObjectForKey:kSaveKey];
}

-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)encodeRestorableStateWithCoder:(NSCoder *)coder{
[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> encodeRestorableStateWithCoder:coder];
[coder encodeObject:<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;">.inputText</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.text</span> forKey:kSaveKey];
}</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-width: 1px; border-right-style: solid; border-right-color: 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></ul>

现在你运行App,输入一些字符然后关闭App.当你再次运行该App时你会发现View界面中的文本框会显示之前输入的字符串:



转自http://blog.csdn.net/mydo/article/details/50646490