原文 Visual Studio跨平台开发实战(3) - Xamarin iOS多页面应用程式开发
前言
在前一篇教学中, 我们学会如何使用Visual Studio 搭配Xcode 进行iOS基本控制项的操作. 但都是属于单一画面的应用程式. 这次我们要来练习如何透过Navigation Controller来建立多页面的iOS应用程式.
设定专案及画面
1. 开启Xamarin Studio 并建立新专案, 专案类型为iOS=>iPhone=>空白专案, 专案名称为02-Navigation.
2. 在专案中添加3个iPhone View Controller 的档案, 档案名称如下：
- HomeScreen
Level1Screen
Level2Screen
新增后档案结构如下图所示：
3. 双击HomeScreen.xib 以开启Xcode.
4. 点选编辑区的HomeScreen, 并在右边的Attributes Inpsctor将Top Bar变更为”Navigation Bar”
5. 在Object Library中拖拉一个Button至画面中并将文字改为”Go to Level 1 Screen”
6. 为Button建立一个Outlet并命名为”btnToLv1”. 之后请关闭Xcode
7. 在Visual Studio 中开启此专案, 在专案属性中设定应用程式名称及版本等资讯, 并开启” AppDelegate.cs” 档. 在FinishedLaunching事件中加入以下程式码:
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">var rootNavigationController = new UINavigationController();</span> var rootNavigationController = new UINavigationController();</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">HomeScreen home = new HomeScreen();</span> HomeScreen home = new HomeScreen();</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">rootNavigationController.PushViewController(home, false);</span> rootNavigationController.PushViewController(home, false);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.window.RootViewController = rootNavigationController;</span> this.window.RootViewController = rootNavigationController;</span>
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完成后的FinishedLaunching方法如下图所示：
在上面的程式码中, 我们先初始化Window, UINavigationController以及HomeScreen物件. 接着透过PushViewController方法将HomeScreen加入到NavigationController. 然后将rootNavigationController指定到Window.RootViewController属性. 最后则是显示Window.
8. 开启HomeScreen.cs, 在建构子中设定主画面的标题
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">public HomeScreen()</span> public HomeScreen()</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">: base("HomeScreen", null)</span> : base("HomeScreen", null)</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.Title = "我是主畫面";</span> this.Title = "我是主画面";</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>
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9. 执行专案后的结果如下：
载入Level 1 Screen
1. 我们要在点击主页面上的button后载入Level1Screen. 因此我们开启HomeScreen.cs. 在类别下先宣告Level1Screen物件.
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Level1Screen lv1scr;</span> Level1Screen lv1scr;</span>
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在ViewDidLoad事件中, 加入btnToLv1的touchupinside事件处理, 程式码如下:
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.btnToLv1.TouchUpInside += (sender, e) =>{</span> this.btnToLv1.TouchUpInside += (sender, e) =>{</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">if (this.lv1scr == null) { this.lv1scr = new Level1Screen(); }</span> if (this.lv1scr == null) { this.lv1scr = new Level1Screen(); }</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.NavigationController.PushViewController(lv1scr, true);</span> this.NavigationController.PushViewController(lv1scr, true);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">};</span> };</span>
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在上述程式码中, 我们同样透过PushViewController方法将Level1Screen加入到Navigation控制项.
2. 执行专案并在主画面中点击按钮以载入Level 1 Screen. 您会看到空白画面被载入, 且NavigationBar左边的按钮会显示上一个页面的Title
新增NavigationBar右边的按钮载入Level 2 Screen
在前一个练习, 我们载入了Level 1 Screen, NavigationBar左边是回到上一个页面, 在这个练习中, 我们要在NavigationBar中新增右边的按钮, 并透过按钮来载入Level 2 Screen.
1. 开启level1screen.cs, 并在类别下加入Level2Screen的宣告
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">Level2Screen lv2scr;</span> Level2Screen lv2scr;</span>
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2. 在level1screen.cs的ViewDidLoad事件中, 加入以下程式码：
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">if (this.lv2scr == null) { this.lv2scr = new Level2Screen(); }</span> if (this.lv2scr == null) { this.lv2scr = new Level2Screen(); }</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.NavigationController.PushViewController(lv2scr, true);</span> this.NavigationController.PushViewController(lv2scr, true);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}), true);</span> }), true);</span>
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我们透过SetRightBarButtonItem方法, 新增一个UIBarButtonItem, 在这里我们使用系统内建的Edit项目. 您也可以使用自订的图示或文字来建立. 并在第2个参数, 直接透过Lambda Expression 来建立按钮按下去的处理. 我们同样透过PushViewController方法将Level 2 Screen载入.
3. 执行专案的结果如下：
按下Level 1 右边的”Edit”按钮, 便会载入Level 2 Screen. 因为我们没有设定Level 1 Screen的Title, 因此在Level 2 Screen左边的按钮会显示预设的”Back”
客制NavigationBar左边的按钮
在目前的练习中, NavigationBar左边按钮的显示文字为上一个画面的Title, 若没有设定Title则会显示Back. 接下来我们来客制Level 1 Screen左边的按钮文字, 方法如下：
1. 开启level1screen.cs, 在ViewDidLoad事件中, 新增以下程式码：
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">(sender, e) =></span> (sender, e) =></span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">{</span> {</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.NavigationController.PopViewControllerAnimated(true);</span> this.NavigationController.PopViewControllerAnimated(true);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}), true);</span> }), true);</span>
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由上述的程式码可知, 我们同样是呼叫SetLeftBarButtonItem (刚刚是SetRightBarButtonItem)的方式, 新增一个按钮来取代预设的按钮. 然后输入自订的文字”回到主画面”.
2. 执行专案的结果如下：
可以对照一下先前的执行结果, NavigationBar左边按钮的文字已经取代为我们自订的文字了.
隐藏主画面的NavigationBar
如果不想在主画面中也显示NavigationBar, 可以透过在HomeScreen.cs中新增ViewWillAppear及ViewWillDisappear事件处理来将主画面中的NavigationBar隐藏起来, 程式码如下：
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">base.ViewWillAppear(animated);</span> base.ViewWillAppear(animated);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.NavigationController.SetNavigationBarHidden(true, true);</span> this.NavigationController.SetNavigationBarHidden(true, true);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">public override void ViewWillDisappear(bool animated) {</span> public override void ViewWillDisappear(bool animated) {</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">base.ViewWillDisappear(animated);</span> base.ViewWillDisappear(animated);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">this.NavigationController.SetNavigationBarHidden(false, true);</span> this.NavigationController.SetNavigationBarHidden(false, true);</span>
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<span class="notranslate" onmouseover="_tipon(this)" onmouseout="_tipoff()"><span class="google-src-text" style="direction: ltr; text-align: left">}</span> }</span>
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执行结果如下：
结语
本篇文章说明如何透过Navigation controller来建立多页面的iOS 应用程式. 在iOS中还有其他建立多页面应用程式的方法, 例如Tab控制项可以透过画面下方的页签来切换不同画面. Storyboard 可以透过Interface Builder来建立应用程式的多个画面以及画面之间的连结. 有兴趣的朋友可以参考以下文章：
Using XCode, Interface Builder, and Storyboards
http://docs.xamarin.com/guides/ios/user_interface/tables/part_5_-_using_xcode,_interface_builder,_and_storyboards
Creating Tabbed Applications
http://docs.xamarin.com/guides/ios/user_interface/creating_tabbed_applications
范例程式码下载: Lab02-Navigation.zip
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