XAMARIN, INC.
XAMARIN COMPONENT STORE TERMS OF SERVICE 1.0
Introduction
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Xamarin Component Store
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Open Source Products
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Products available on the Xamarin Component Store may be subject to export controls or restrictions by the United States or other countries or territories. User agrees to comply with all applicable United States and international export laws and regulations. These laws include restrictions on destinations, end users, and end use.
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Term and Termination
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8.4 When the TOS terminate, Sections 3.6, 3.7, 3.8, 4, 5, 6, 7, 8.4, 9, 10 and 11 will survive.
DISCLAIMER OF WARRANTIES
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LIMITATION OF LIABILITY
SUBSCRIBER UNDERSTANDS AND AGREES THAT XAMARIN AND ITS AFFILIATES SHALL NOT BE LIABLE TO YOU UNDER ANY THEORY OF LIABILITY (WHETHER CONTRACT, TORT INCLUDING NEGLIGENCE OR OTHERWISE) FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL CONSEQUENTIAL OR EXEMPLARY DAMAGES THAT MAY BE INCURRED BY YOU THROUGH USE OF THE XAMARIN COMPONENT STORE OR ANY PRODUCTS OBTAINED FROM THE XAMARIN COMPONENT STORE, INCLUDING ANY LOSS OF DATA, WHETHER OR NOT XAMARIN OR ITS REPRESENTATIVES HAVE BEEN ADVISED OF OR SHOULD HAVE BEEN AWARE OF THE POSSIBILITY OF ANY SUCH LOSSES ARISING.
General Terms
11.1 The TOS constitute the whole legal agreement between User and Xamarin and govern User’s use of the Xamarin Component Store and Products, and completely replace any prior agreements between User and Xamarin in relation to the Xamarin Component Store, Products, and Professional Services.
11.2 If Xamarin does not exercise or enforce any legal right or remedy which is contained in the TOS (or which Xamarin has the benefit of under any applicable law), this will not be taken to be a formal waiver of Xamarin’s rights and that those rights or remedies will still be available to Xamarin.
11.3 If any court of law, having the jurisdiction to decide on this matter, rules that any provision of the TOS is invalid, then that provision will be removed from the TOS without affecting the rest of the TOS. The remaining provisions of the TOS will continue to be valid and enforceable.
11.4 No person or company will be third party beneficiaries to the TOS.
11.5 The rights granted in the TOS may not be assigned or transferred by User, whether by operation of law or otherwise, without the prior written approval of Xamarin.
11.6 The TOS will be governed by the laws of the State of California without regard to its conflict of laws provisions. User and Xamarin agree to bring any and all actions under the TOS in exclusively in a court of competent jurisdiction located within the county of Santa Clara, California to resolve any legal matter arising from the TOS and each party agrees to submit to the exclusive jurisdiction of such court and waives all objections to such venue.
I Disagree
Copyright (c) 2009 Olivier Poitrey
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the &Software&), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is furnished
to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED &AS IS&, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
I Disagree
Thanks for downloading SDWebImage for Xamarin.iOS!
If you haven't already, check out the Getting Started documentation for SDWebImage for Xamarin.iOS .
Compatible with
SDWebImage for Xamarin.iOS 3.7.5
Xamarin Inc
Extensions for UIImageView allowing you to asynchronously load web images.
Adds methods to UIImageView supporting asynchronous web image loading:
using SDWebI
const string CellIdentifier = &Cell&;
public override UITableViewCell GetCell (UITableView tableView, NSIndexPath indexPath)
UITableViewCell cell = tableView.DequeueReusableCell (CellIdentifier) ??
new UITableViewCell (UITableViewCellStyle.Default, CellIdentifier);
// Use the SetImage extension method to load the web image:
cell.ImageView.SetImage (
url: new NSUrl (&http://db.tt/ayAqtbFy&),
placeholder: UIImage.FromBundle (&placeholder.png&)
It provides:
UIImageView and UIButton extension methods adding web image loading and cache management.
An asynchronous image downloader
An asynchronous memory + disk image caching with automatic cache expiration handling
Animated GIF support
WebP format support
A background image decompression
A guarantee that the same URL won't be downloaded several times
A guarantee that bogus URLs won't be retried again and again
A guarantee that main thread will never be blocked
Performances!
Use GCD and ARC
Arm64 support
Release Notes
What's New
New: bumped WebP version to 0.4.4
Fix: numerous bug fixes
Included Releases
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/ Version: 3.7.5
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/ Version: 3.7.3.1
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/ Version: 3.7.3.1
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/ Version: 3.7.3.0
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/ Version: 3.7.1.4
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/ Version: 3.7.1.4
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/ Version: 3.3.1
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/ Version: 3.4
Xamarin Inc.知识点（1）
初代 iPhone
2007 年，初代 iPhone 发布，屏幕的宽高是 320 x 480 像素。下文也是按照宽度，高度的顺序排列。这个分辨率一直到 iPhone 3GS 也保持不变。
那时编写 iOS 的 App(应用程序)，只支持绝对定位。比如一个按钮(x, y, width, height) = (20, 30, 40, 50)，就表示它的宽度是 40 像素，高度是 50 像素，放在(20, 20)像素的位置。
2010 年，iPhone 4 发布，率先采用 Retina 显示屏，在屏幕的物理尺寸不变的情况下，像素成倍增加，达到 640 x 960 像素。
这样就出现一个问题，怎么让原有的 App 运行在新的手机上面？iPhone 手机一个优势，就是有众多优秀的 App，假如不兼容原有的 App，就相当于放弃这个得来不易的优势，是很不明智的。
每当 iPhone 的屏幕有所变化，比如 iPhone 3GS 过渡到 iPhone 4, iPhone 4 过渡到 iPhone 5, iPhone 5 过渡到 iPhone 6，苹果公司都需要想办法来解决上述的兼容问题。
为了运行之前的 App，引入一个新的概念 point(点)。点这个概念在 iOS 开发中十分重要，而实际用户很少关注。iPhone 4 屏幕尺寸继续保持 320 x 480，不过单位并非是像素，而是点。
在 iPhone 3GS 中，1 个点等于 1 个像素。也就是说，点跟像素可以直接互换。
在 iPhone 4 中，1 个点等于 2 个像素。
这篇文章中，我将点和像素当成一维的长度单位，而非二维的面积单位，这样对于我来说更自然些，因此 1 个点等于 2 个像素。别的文章中可能会说 1 个点等于 4 个像素，其实是指 1 个点占据了 4 个像素的面积，这样也没有说错，注意上下文语境。
iPhone 4 和 iPhone 3GS 的屏幕尺寸实际上是一样的，都是 3.5 英寸。同样一个点，实际尺寸看起来是一样的。只是 iPhone 4 在单位英寸上像素更多，看起来更细腻。
开发 iOS 的时候，使用点作为基本单位会更加方便，列表对比：
这里的屏幕模式可以初步理解成，一个点等于多少个像素。2x，就是 1 个点等于 2 个像素。
总结一下单位
手机屏幕的物理长度，使用英寸作为单位。比如 iPhone 4 屏幕是 3.5 英寸，iPhone 5 是 4 英寸，iphone 6 是 4.7 英寸，这里的数字是指手机屏幕对角线的物理长度。
屏幕像素，比如 iPhone 3GS 屏幕是 320 x 480 像素，iPhone 4 是 640 x 960 像素，这里的像素可以想象成屏幕上真正用来显示颜色的发光小点。
点，开发 App 时候使用的单位，是一个虚拟的单位，并非实际存在的，因此点有时也叫虚拟点。点这个单位，用于屏蔽各个屏幕设备的不同，兼容以前的程序。
每英寸有多少个像素，称为 ppi(pixel per inch)。iPhone 4 的屏幕是 640 x 960 像素，3.5 英寸，我们没有宽高的实际尺寸，就按照对角线来粗略计算它的 ppi。将像素当做长度单位，根据勾股定理，对角线就是 1154 像素。屏幕对角线的实际长度为 3.5 英寸，也就是 1154 像素除以 3.5 英寸，得出 330ppi。而官方给出的数字是 326ppi。当像素太密，超过 300ppi 的时候，人眼也就不能区分出每个像素。因此 iPhone 4 的屏幕叫作 Retina 显示屏。Retina
在英文中，是视网膜的意思。
iPhone 4 之后(x, y, width, height) = (20, 30, 40, 50)，就表示高度为 40 个点，宽度为 50 个点，放在(20, 20)个点的位置。这种处理方法，将之前以像素作为单位自动转换成以点作为单位，使得 iPhone 3GS 的应用程序，不用修改也可运行在 iPhone 4 上面。
文字，颜色等是矢量数据，放大不会失真。原有的 iPhone 3GS 程序，在 iPhone 4 上面运行，文字显示也十分清晰。
而图片并非矢量数据，处理方式有所不同。假设图片 example.png，大小为 30 x 40 像素（这里的单位是像素，数字图片的单位通常都为像素）。当这张 example.png 在 iPhone 3GS 和 iPhone 4 中使用时候，都占据屏幕上 30 x 40 个点。而因为 iPhone 4 中 1 个点等于 2 个像素，也就是 30 x 40 像素的图片，占据了 60 x 80 像素的屏幕，因此这图片在 iPhone 4 中看起来就会模糊。
开发的时候，为使得图片清晰，需要进行图片适配。这时需要准备两张内容相同的图片，放在同一目录下。
example.png & & &// 30 x 40 像素
example@2x.png & // 60 x 80 像素
当程序中使用 example.png 的时候，会根据屏幕模式自动选择对应的图片。屏幕 1x 模式，就会选择 example.png, 2x 模式就会优先选择 example@2x.png，假如 example@2x.png 不存在，就选择 example.png。
图片跟屏幕一样，也有 1x 模式，2x 模式。在 iPhone 6 Plus 中，还出现 3x 模式，原理是一样的。
当 iPhone 4 选中 example@2x.png 的图片，就会生成一张大小为 30 x 40 个点，2x 模式的图片。这个时候，图片看起来就会很清晰了。而没有适配的旧程序，example@2x.png 不存在，就选中 example.png，生成大小为 30 x 40 个点，1x 模式的图片，看起来比较模糊。但它们占据的屏幕点数是一样的。
2012 年，苹果发布 iPhone 5。我们将所有机型对比，依然采用点作为单位。
跟 iPhone 4 做比较, iPhone 5 的宽度保持不变。高度增加 568 - 480 = 88 个点。
在 iOS 开发中，44 这个数字比较特殊。iOS 界面指南写着，人类的手指有一定大小，点击区域低于 44 个点的时候，就难以点中。44 的两倍就是 88。
当原有程序没有适配 iPhone 5 的时候，也可以正常运行，但多出来的 88 个点将会将会被自动均分为上下两部分，使得上下出现黑边。我找不到好看的图片。
那么怎样才能告诉 iOS 系统，应用程序已经适配了 iPhone 5 呢？在这里，我们先扯开一下，谈一下启动图片。
点击主屏幕的图标，进入 App 的时候，会立即显示一张图片，这张图片就是启动图片(Launch Image)。App 在正式启动的时需要做一些初始化处理，这通常比较费时。先出现启动图片，可以使用户觉得系统立即有响应，减少等待的焦虑感。
每个机型，比如同时支持 iPhone 和 iPad 的程序，需要分别为 iPhone 跟 iPad 指定启动图片。当旧的 iPhone 4 的程序，运行在 iPhone 5 上面，没有 iPhone 5 的启动图片，就采用兼容模式，上下留黑边。当为 iPhone 5 指定了新的启动图片，系统就认为这个应用程序是已经适配了 iPhone 5 的，上下就不会留黑边了。下面是微信启动图片，应该都很熟悉了。
微信启动图片中出现的那个地球，叫蓝色弹珠（The Blue Marble），是在 1972 年 12 月 7 日由阿波罗 17 号太空船的船员所拍摄的。这张照片当年很震撼，是普通人第一次可以通过照片直接看到地球的全貌。见问题？
微信的启动图，为适配 iPhone 5，相比与 iPhone 4, 很明显狭长了。
典型 iPhone 应用程序（游戏除外），很多是上面一个导航栏，下面一个工具栏或者标签栏, 中间一大块用于显示的内容区。iPhone 5 拉长了，对于程序的适配，也不算麻烦，内容区的内容基本是动态生成的。适配时候可以简单上下不变，中间的内容区拉长就行了。注意，导航栏和工具栏的高度也是 44 个点。下面是同一程序，在 iPhone 4 跟 iPhone 5 的对比。
AutoLayout
到了这个时候，传统绝对定位的弱点就显露出来了。这时 iPhone 按照点作为单位，已经出现了两种不同尺寸的屏幕，算上 iPad, 就有 3 种尺寸（有些 App 可以同时兼容 iPhone 和 iPad，称为 Universal）。
从iOS 6系统发布后，iOS开发中可以采用一种 AutoLayout 的技术。AutoLayout 就像网页一样，指定 View，Button，Text 之间的相对位置，比如靠左多少，靠右多少，居中多少等等。举个例子，像下面的简单布局。
假设左上角的区域为 view1, 右上角的区域为 view2, 下面的区域为 view3。AutoLayout 会说:
view1.left&=&20&&&&&&&&&&&&&&&
view1.top&=&20&&&&&&&&&&&&&&&&
view2.right&=&20&&&&&&&&&&&&&&
view2.top&=&20&&&&&&&&&&&&&&&&
view2.left&=&view1.right&+&20&
view2.width&=&view1.width&&&&&
view2.height&=&view1.height&&&
view3.left&=&view1.left&&&&&&&
view3.right&=&view2.right&&&&&
view3.top&=&view1.bottom&+&20&
view3.bottom&=&20&&&&&&&&&&&&&
view3.height&=&view1.height&&&
指定上面的约束条件后，AutoLayout 就会自动算出对应的布局。上面我写得比较繁琐，事实上很多操作都是可以使用鼠标拖拉来指定的，并不一定需要使用代码。但就算用代码，也有简写的方法。下面是在 xib 中，拖拉鼠标指定约束时的界面。
而绝对定位，会直接说
view1.frame&=&(x1,&y1,&width1,&height1)
view2.frame&=&(x2,&y2,&width2,&height2)
view3.frame&=&(x3,&y3,&width3,&height3)
绝对定位并非指定约束条件，而是开发者自己来精确指定 View，Button, Text 等的实际坐标大小。
对于一个屏幕，绝对定位可能跟 AutoLayout 的区别不算大，甚至绝对定位会更方便些。但当需要同时适配多个屏幕，AutoLayout 根本不需要更改。而绝对定位就需要根据屏幕大小，一个个算出来。比如横屏，在 AutoLayout 下面，就自动变成：
这里不过是 3 个控件的布局，当出现的控件数越多，屏幕尺寸越多，AutoLayout 的优势就显露出来了。另外 AutoLayout 有个好处是容易支持多语言，不同语言下，同一个意思文字的长度是不同的，使用 AutoLayout 也可以自动适配。
在 iOS 6 的时候，AutoLayout 还比较少人使用，当时屏幕尺寸还比较少。iOS 7 的时候，就开始很多人使用了。而到现在 iOS 8 了, 更加上 iPhone 6, iPhone 6 Plus 需要适配，AutoLayout 大势所趋，不用不行了。
iPhone 6和iPhone 6 Plus
2014 年，iPhone 6和iPhone 6 Plus 发布后，情况又有新的变化。再次比较所有 iPhone 机型。
屏幕尺寸再度分裂。但是我们比较 iPhone 5 跟 iPhone 6 的宽高比例。
可以看出，iPhone 6 跟 iPhone 5 虽然屏幕尺寸改变了，但是它们的比例是不变的。都是 9 ÷ 16 = 0.5625 的屏幕。
当旧的 iPhone 5 程序运行在 iPhone 6 上面，假如没有经过适配，旧程序自动等比放大，铺满新手机，旧程序也可以正常运行。这种方案可算是自动适配。但因为旧程序拉伸了，整体看起来有点虚，也不能更好利用大屏空间。
当需要开发者手动适配的时候，跟 iPhone 4 过渡到 iPhone 5 一样，在新程序中，指定一张新的启动图片。当指定了启动图，屏幕分辨率就已经变成应有的大小，这时候利用 AutoLayout 进行布局，同一份代码，就可以支持多个机型。新手机的屏幕更大，有更多的虚拟点，可以显示更多的内容。
值得注意一点是，iPhone 6 Plus。它的宽高是 414 × 736 个点，3x 模式，理想上来说，应该有 1242 × 2208 像素。但 iPhone 6 Plus 的实际像素是 1080 × 1920，是比理想值要少一点的。iPhone 6 Plus 的处理方式是将程序整体稍微缩小一点。分辨率很高，这点区别，实际上也看不出来。
那为什么需要这样做呢？上面表格中 iPhone 6, iPhone 6 Plus 屏幕宽高的逻辑点的数字是怎么来的？下面我猜测一下原因，但不能证实。
先看 iPhone 6，这个比较简单。iPhone 6 的屏幕宽高比例跟 iPhone 5 一样，使用对角线来计算，就是放大了 4.7 ÷ 4 = 1.175 倍。用这个数字，乘以 iPhone 5 的 320 x 568 个点，忽略误差，差不多就是 iPhone 6 屏幕的 375 x 667 个点。这里需要注意，屏幕宽高比例一样，才能使用对角线来计算。
按照上面的方式来计算 iPhone 6 Plus, 应该是得到 440 x 781 个点，实际上却是 414 × 736 个点。这里我猜测是因为，iPhone 6 Plus 屏幕明显更大，相同尺寸的点放在大的屏幕上面，会使得人感觉尺寸变小，所以就将每个点的实际尺寸放大一些，从而得到更少的点数目。人眼看东西会有种错觉，并非是孤立的看的，而是跟周围的环境作比较。
确定了点数目之后，再确定了像素 1080 × 1920(很多高清电视就是这个尺寸)，应该是 .6x，但 2.6x 这个数字开发就太麻烦了，就按照 3x 来处理。其实假如像素达到 1242 × 2208，3x 下也可以精确到 1:1, 这样会更好。但现今的技术在考虑电池，处理器，屏幕尺寸等综合因素下，很可能达不到这样的细腻程度。
上述只是猜测，我相信那些手机参数是经过反复考虑再确定的。iPhone 6 Plus 这个处于手机跟平板中间地带的产物经过不少特殊处理。
由分析可以看到，慢慢的为了适配多个机型，程序的启动图片也逐渐增多，为解决这个问题。iOS 8 之后，可以使用 xib 来搭建启动界面，这样就可以同一个启动界面，适配多个机型，减少启动图片占用的空间。
以后的应用程序，都使用 AutoLayout, 不要再用绝对定位。
使用类似网页的方式来设计界面。
设计师好，程序员也好，尽量使用点这个单位进行思考，而不要使用像素。比如，你需要做 44 x 66 个点的按钮，2x 模式，就乘以 2, 3x 模式就乘以 3。这样的思考方式可以大致估计到真实的物理长度。44 个点，就是手机上导航栏，工具栏的高度。假如用像素思考，容易使得做出的图片过大或者过小。
非矢量素材，就可以做尺寸最大的，之后再进行缩小。比如你需要兼容 3x 的屏幕，就直接做最高那种图片。
而当使用 Flash 之类的矢量工具来做素材的时候，应该直接做点那个尺寸。比如 44 x 66 个点的按钮。就建立一个 44 x 66 的场景。之后再导出成 2 倍图，3 倍图，因为矢量放大不失真。不要建立一个 3x 的场景，导出成大图片，再进行缩小，这样就容易失真。更理想的是直接使用矢量图。
假如是那种导航栏，工具栏之类的背景图，需要横跨整个屏幕。可以只切一小块，让程序拉伸，拉伸方式是保持两边的像素不动，只拉伸最中间的一列像素。需要拉伸的话，横方向就不要出现一些渐变色。
按钮的点击区域，不应该少于 44 像素，就算按钮的图片看起来比较小，也应该使得点按钮周围的透明区也有反应。
可以按照你当前最方便测试机子的型号来做一些主要预览图，效果图。比如你手头有 iPhone 5，可以按照 iPhone 5 的尺寸，320 x 568 个点，需要兼容 iPhone 6 Plus，就使用 3x 的模式。这样方便将图片放进手机里面看实际的效果。有多个测试机，就选较大的，之后再进行一些细调。假如支持 iPhone 6 Plus 的横屏模式，需要另外处理。
上面说的是应用的处理方式，游戏会有些特殊。现在很多游戏，按照 1136 x 768 的像素尺寸来设计场景，这样可以同时兼容 iPad 和 iPhone，并只使用一份图。iPad 1x 模式下尺寸是 1024 x 768 像素，iPhone 5 在 2x 模式下，是 1136 * 640 像素。这种尺寸，可以将场景居中显示，各自将场景拉伸到最大。
原帖：/ios/76.html
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