{"id":4573,"date":"2021-12-14T19:57:42","date_gmt":"2021-12-14T11:57:42","guid":{"rendered":"http:\/\/123.57.164.21\/?p=4573"},"modified":"2021-12-14T19:57:42","modified_gmt":"2021-12-14T11:57:42","slug":"swiftui-lab-%e6%8e%a2%e7%a9%b6view%e6%a0%91-preferencekey","status":"publish","type":"post","link":"https:\/\/92it.top\/?p=4573","title":{"rendered":"[SwiftUI-Lab] \u63a2\u7a76View\u6811 PreferenceKey"},"content":{"rendered":"\n<p>\u6587\u7ae0\u6e90\u5730\u5740:<a rel=\"noreferrer noopener\" href=\"https:\/\/links.jianshu.com\/go?to=https%3A%2F%2Fswiftui-lab.com%2Fgeometryreader-to-the-rescue%2F\" target=\"_blank\">https:\/\/swiftui-lab.com\/geometryreader-to-the-rescue\/<\/a><\/p>\n\n\n\n<p>\u5728SwiftUI\u4e2d\u6211\u4eec\u4e00\u822c\u4e0d\u7528\u5173\u5fc3\u5b50\u7ea7\u89c6\u56fe\u5185\u90e8\u53d1\u751f\u4e86\u4ec0\u4e48\u3002\u4e0d\u540c\u7684View\u5404\u81ea\u7ba1\u5404\u81ea\u5185\u90e8\u7684\u4e8b\u60c5\u3002\u4f46\u603b\u662f\u4f1a\u9047\u5230\u4e00\u4e9b\u7279\u6b8a\u7684\u9700\u6c42\u3002\u6bd4\u8f83\u60e8\u7684\u662f<a href=\"https:\/\/links.jianshu.com\/go?to=https%3A%2F%2Fdeveloper.apple.com%2Fdocumentation%2Fswiftui%2Fview%2F3278633-preference\" target=\"_blank\" rel=\"noreferrer noopener\">\u6587\u6863<\/a>\u90fd\u8bb2\u7684\u6bd4\u8f83\u7c97\u7565\u3002 \u63a2\u7a76View\u6811\u7684\u4e09\u7bc7\u6587\u7ae0\u4f1a\u505a\u4e2a\u8865\u5145\u3002\u6211\u4eec\u5c06\u8981\u53bb\u4e86\u89e3 <strong>PreferenceKey<\/strong> \u7684\u534f\u8bae\u548c\u76f8\u5173\u7684\u4fee\u6539\u5668(<code>modifier<\/code>):\u5982<\/p>\n\n\n\n<ul><li><strong>.preference(),<\/strong><\/li><li><strong>.transformPreference(),<\/strong><\/li><li><strong>.anchorPreference(),<\/strong><\/li><li><strong>.transformAnchorPreference(),<\/strong><\/li><li><strong>.onPreferenceChange(),<\/strong><\/li><li><strong>.backgroundPreferenceValue()<\/strong><\/li><li><strong>.overlayPreferenceValue().<\/strong><\/li><li>\u6709\u5f88\u591a\uff0c\u90a3\u6211\u4eec\u5f00\u59cb\u5427~<\/li><\/ul>\n\n\n\n<p>SwiftUI\u6709\u4e00\u4e2a\u8ba9\u6211\u4eec\u53bb\u7ed9View\u6dfb\u52a0\u5f88\u591a\u5c5e\u6027\u7684\u673a\u5236\u3002\u8fd9\u4e9b\u5c5e\u6027\u6211\u4eec\u53eb\u505a <strong>\u504f\u597d<\/strong>(Preferences) \u3002 \u5b83\u4eec\u53ef\u4ee5\u8f7b\u677e\u7684\u6cbf\u89c6\u56fe\u4f9d\u6b21\u8c03\u7528\u4e0b\u53bb\uff0c\u751a\u81f3\u65e0\u8bba\u600e\u4e48\u4fee\u6539\u504f\u597d\uff0c\u6dfb\u52a0\u7684\u56de\u8c03\u90fd\u4f1a\u4e0d\u53d7\u5f71\u54cd\u7684\u6267\u884c\u3002<\/p>\n\n\n\n<p>\u6709\u6ca1\u6709\u60f3\u8fc7navigationView\u662f\u5982\u4f55\u901a\u8fc7 <strong>.navigationBarTitle()<\/strong> \u6765\u83b7\u53d6title\u3002\u8bf7\u6ce8\u610f .navigationBarTitle() \u5e76\u6ca1\u6709\u76f4\u63a5\u4fee\u6539NavigationView\u3002\u800c\u662f\u5728\u6cbf\u7740View\u7684\u5c42\u7ea7\u53bb\u8c03\u7528\u3002\u90a3\u4e48\u5b83\u662f\u600e\u4e48\u505a\u5230\u7684\u5462\uff1f \u53ef\u80fd\u4f60\u5df2\u7ecf\u731c\u5230\u4e86\u3002\u5176\u5b9e\u662f\u7528\u4e86\u504f\u597d\u3002\u57282019WWDC\u7684SwiftUI\u4e13\u680f\u91cc\u6709\u4e00\u4e2a\u5f88\u7b80\u77ed\u7684\u4ecb\u7ecd\u3002\u5927\u6982\u53ea\u670920\u79d2\u3002\u611f\u5174\u8da3\u7684\u8bdd\u53ef\u4ee5\u67e5\u770b<a href=\"https:\/\/links.jianshu.com\/go?to=https%3A%2F%2Fdeveloper.apple.com%2Fvideos%2Fplay%2Fwwdc2019%2F216%2F\" target=\"_blank\" rel=\"noreferrer noopener\">Session 216 (SwiftUI Essentials)<\/a>\u76f4\u63a5\u8df3\u523052:35\u3002<\/p>\n\n\n\n<p>\u6211\u4eec\u5df2\u7ecf\u627e\u5230\u6709\u4e00\u4e9b\u7279\u6b8a\u7684\u504f\u597d \u53eb&#8221;anchored preferences(\u951a\u5b9a\u504f\u597d)&#8221;\uff0c \u53ef\u4ee5\u5229\u7528\u5b83\u4eec\u6765\u65b9\u4fbf\u7684\u68c0\u7d22\u5b50\u7ea7View\u7684\u6240\u6709\u51e0\u4f55\u5b66\u6570\u636e\u3002\u5728\u4e0b\u4e2d\u4f1a\u8be6\u7ec6\u4ecb\u7ecd\u951a\u5b9a\u504f\u597d(anchored preferences)<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u72ec\u7acb\u7684Views<\/h4>\n\n\n\n<p>\u6211\u4eec\u5c06\u4f1a\u7528\u5f88\u77ed\u7684\u65f6\u95f4\u53bb\u4e86\u89e3 <strong>PreferenceKey<\/strong> \uff0c\u4e3a\u4e86\u66f4\u597d\u7684\u4e86\u89e3\u4eca\u5929\u7684\u8bdd\u9898\uff0c\u6211\u4eec\u5148\u7528\u4e00\u4e2a\u6ca1\u6709\u4f7f\u7528\u504f\u597d\u7684\u4f8b\u5b50\u5f00\u59cb\u3002\u5728\u4f8b\u5b50\u4e2d\uff0c\u5148\u521b\u5efa\u4e00\u4e2a\u663e\u793a\u6708\u4efd\u540d\u7684View\u3002\u5f53\u6708\u4efd\u6807\u7b7e\u88ab\u70b9\u51fb\u7684\u65f6\u5019\uff0c\u4f1a\u5728\u6708\u4efd\u6807\u7b7e\u4e0a\u9762\u6162\u6162\u7684\u663e\u793a\u4e00\u4e2a\u8fb9\u6846(\u4ece\u4e4b\u524d\u9009\u4e2d\u7684\u6708\u4efd\u6807\u7b7e\u79fb\u9664)\u3002<br><\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/123.57.164.21\/wp-content\/uploads\/2021\/12\/image-202-1024x510.png\" alt=\"\" class=\"wp-image-4574\" width=\"558\" height=\"278\" srcset=\"https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-1024x510.png 1024w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-300x149.png 300w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-768x383.png 768w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-830x414.png 830w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-230x115.png 230w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-350x174.png 350w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202-480x239.png 480w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-202.png 1196w\" sizes=\"(max-width: 558px) 100vw, 558px\" \/><\/figure><\/div>\n\n\n\n<p>\u4f8b1<\/p>\n\n\n\n<p>\u4ee3\u7801\u5f88\u7b80\u5355\uff0c\u5148\u521b\u5efa\u6211\u4eec\u7684ContentView:<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">import SwiftUI\n\nstruct EasyExample : View {\n    @State private var activeIdx: Int = 0\n    \n    var body: some View {\n        VStack {\n            Spacer()\n            \n            HStack {\n                MonthView(activeMonth: $activeIdx, label: \"January\", idx: 0)\n                MonthView(activeMonth: $activeIdx, label: \"February\", idx: 1)\n                MonthView(activeMonth: $activeIdx, label: \"March\", idx: 2)\n                MonthView(activeMonth: $activeIdx, label: \"April\", idx: 3)\n            }\n            \n            Spacer()\n            \n            HStack {\n                MonthView(activeMonth: $activeIdx, label: \"May\", idx: 4)\n                MonthView(activeMonth: $activeIdx, label: \"June\", idx: 5)\n                MonthView(activeMonth: $activeIdx, label: \"July\", idx: 6)\n                MonthView(activeMonth: $activeIdx, label: \"August\", idx: 7)\n            }\n            \n            Spacer()\n            \n            HStack {\n                MonthView(activeMonth: $activeIdx, label: \"September\", idx: 8)\n                MonthView(activeMonth: $activeIdx, label: \"October\", idx: 9)\n                MonthView(activeMonth: $activeIdx, label: \"November\", idx: 10)\n                MonthView(activeMonth: $activeIdx, label: \"December\", idx: 11)\n            }\n            \n            Spacer()\n        }\n    }\n}<\/pre>\n\n\n\n<p>\u548c\u81ea\u5b9a\u4e49views:<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">struct MonthView: View {\n    @Binding var activeMonth: Int\n    let label: String\n    let idx: Int\n    \n    var body: some View {\n        Text(label)\n            .padding(10)\n            .onTapGesture { self.activeMonth = self.idx }\n            .background(MonthBorder(show: activeMonth == idx))\n    }\n}\n\nstruct MonthBorder: View {\n    let show: Bool\n    \n    var body: some View {\n        RoundedRectangle(cornerRadius: 15)\n            .stroke(lineWidth: 3.0).foregroundColor(show ? Color.red : Color.clear)\n            .animation(.easeInOut(duration: 0.6))\n    }\n}\n<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\n<\/pre>\n\n\n\n<p>\u4ee3\u7801\u903b\u8f91\u4e5f\u5f88\u7b80\u5355\uff0c\u5f53\u6708\u4efd\u6807\u7b7e\u88ab\u70b9\u51fb\uff0c\u6539\u53d8 <code>@State<\/code> \u4e3a\u6700\u65b0\u70b9\u51fb\u7684\u6708\u4efd\u6807\u7b7e\u7684\u5e8f\u53f7\u3002 \u800c\u4e14\u6bcf\u4e2a\u6708\u4efd\u8fb9\u6846\u7684\u989c\u8272\u90fd\u7531\u81ea\u5df1\u7684\u53d8\u91cf\u6765\u63a7\u5236\u3002 \u5982\u679c\u6708\u4efd\u6807\u7b7e\u88ab\u9009\u4e2d\uff0c\u8fb9\u6846\u4f1a\u88ab\u8bbe\u7f6e\u6210\u7ea2\u8272\uff0c\u5426\u5219\u8fb9\u6846\u5c31\u4f1a\u53d8\u900f\u660e\u3002\u8fd9\u4e2a\u4f8b\u5b50\u5f88\u7b80\u7b54\uff0c\u6bcf\u4e2aView\u7ed8\u5236\u81ea\u5df1\u7684\u8fb9\u6846\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u76f8\u4e92\u534f\u4f5c\u7684Views<\/h4>\n\n\n\n<p>\u4e0b\u9762\u96be\u5ea6\u518d\u5347\u7ea7\u4e00\u4e9b\uff0c\u6211\u4eec\u60f3\u8ba9\u8fb9\u6846\u4ece\u4e00\u4e2a\u6708\u4efd\u79fb\u52a8\u5230\u53e6\u5916\u4e00\u4e2a\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/123.57.164.21\/wp-content\/uploads\/2021\/12\/image-203-1024x534.png\" alt=\"\" class=\"wp-image-4575\" width=\"576\" height=\"300\" srcset=\"https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-1024x534.png 1024w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-300x157.png 300w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-768x401.png 768w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-830x433.png 830w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-230x120.png 230w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-350x183.png 350w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203-480x250.png 480w, https:\/\/92it.top\/wp-content\/uploads\/2021\/12\/image-203.png 1196w\" sizes=\"(max-width: 576px) 100vw, 576px\" \/><\/figure><\/div>\n\n\n\n<p>\u4f8b\u5b502<\/p>\n\n\n\n<p>\u4f60\u53ef\u4ee5\u5148\u60f3\u60f3\u5982\u4f55\u53bb\u5b9e\u73b0\uff0c\u4e0d\u50cf\u4e4b\u524d\u670912\u4e2a\u8fb9\u6846\uff0c\u73b0\u5728\u53ea\u6709\u4e00\u4e2a\u8fb9\u6846\uff0c\u4f60\u9700\u8981\u52a8\u753b\u6539\u53d8\u8fb9\u6846\u7684\u4f4d\u7f6e\u548c\u5927\u5c0f\u3002<\/p>\n\n\n\n<p>\u4f8b\u5b502\u4e2d\uff0c\u8fb9\u6846\u5e76\u4e0d\u662f\u6708\u4efd\u7684\u4e00\u90e8\u5206\uff0c\u4f60\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5355\u72ec\u7684\u8fb9\u6846View\uff0c\u5e76\u76f8\u5e94\u7684\u6539\u53d8\u4f4d\u7f6e\u548c\u5927\u5c0f\uff0c\u8fd9\u610f\u5473\u7740\u5fc5\u987b\u6709\u4e00\u79cd\u65b9\u5f0f\u53bb\u8ddf\u8e2a\u6bcf\u4e2a\u6708\u4efd\u7684\u5927\u5c0f\u548c\u4f4d\u7f6e\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u4f60\u770b\u8fc7\u6211\u4e0a\u4e00\u6279\u6587\u7ae0(<a href=\"https:\/\/links.jianshu.com\/go?to=https%3A%2F%2Fswiftui-lab.com%2Fgeometryreader-to-the-rescue%2F\" target=\"_blank\" rel=\"noreferrer noopener\">GeometryReader to the Rescue<\/a>),<br>\u4f60\u5c31\u5df2\u7ecf\u6709\u4e00\u79cd\u65b9\u5f0f\u53bb\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u4e86\uff0c\u5982\u679c\u4f60\u4e0d\u77e5\u9053GeometryReader\u662f\u600e\u4e48\u5de5\u4f5c\u7684\uff0c\u53ef\u4ee5\u5148\u770b\u770b\u8fd9\u7bc7\u6587\u7ae0\u3002<\/p>\n\n\n\n<p>\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u7684\u4e00\u79cd\u65b9\u5f0f\u5c31\u662f\uff1a \u6bcf\u4e00\u4e2a\u6708\u4efd\u6807\u7b7e\u90fd\u901a\u8fc7GeometryReader\u53bb\u83b7\u5f97\u81ea\u8eab\u7684\u5927\u5c0f\u548c\u4f4d\u7f6e\u3002\u6bcf\u4e2a\u6708\u4efd\u6807\u7b7e\u4f9d\u6b21\u66f4\u65b0\u7236\u7ea7\u89c6\u56fe\u4e2d\u7684\u5b58\u653e\u4f4d\u7f6e\u7684\u6570\u7ec4(\u901a\u8fc7 <strong>@Binding<\/strong> )\u3002 \u4e00\u65e6\u7236\u7ea7\u89c6\u56fe\u627e\u5230\u4e86\u6bcf\u4e00\u4e2a\u5b50\u89c6\u56fe\u7684\u4f4d\u7f6e\u548c\u5927\u5c0f\uff0c\u8fb9\u6846\u5c31\u53ef\u4ee5\u5f88\u5bb9\u6613\u7684\u66ff\u6362\u4e86\u3002\u8fd9\u4e2a\u65b9\u6848\u8fd8\u4e0d\u9519\uff0c\u4f46\u5b50\u7ea7\u89c6\u56fe\u4fee\u6539\u6570\u7ec4\u7684\u65f6\u5019\u53ef\u80fd\u4f1a\u4ea7\u751f\u95ee\u9898\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8e\u67d0\u4e9b\u5e03\u5c40\uff0c\u5982\u679c\u5728\u6784\u5efa\u89c6\u56fe\u7684\u65f6\u5019\uff0c\u4fee\u6539\u5176\u67d0\u4e2a\u53d8\u91cf\uff0c\u5176\u7236\u7ea7\u89c6\u56fe\u4e5f\u4f1a\u53d7\u5230\u5f71\u54cd\uff0c\u53cd\u8fc7\u6765\u5b50\u7ea7\u89c6\u56fe\u4e5f\u4f1a\u53d7\u5230\u5f71\u54cd\u3002\u8fd9\u4f7f\u6211\u4eec\u6b63\u5728\u6784\u5efa\u7684\u89c6\u56fe\u5931\u6548\uff0c\u6709\u65f6\u53ef\u80fd\u9700\u8981\u518d\u91cd\u65b0\u5f00\u59cb\u6784\u5efa\u89c6\u56fe\u3002 \u8fd8\u6709\u65f6\u5019\u4f1a\u53d8\u6210\u4e00\u4e2a\u5faa\u73af\u3002\u597d\u7684\u662fSwiftUI\u89c6\u4e4e\u53ef\u4ee5\u68c0\u6d4b\u5230\u8fd9\u79cd\u60c5\u51b5\uff0c\u4e5f\u4e0d\u4f1a\u4ea7\u751f\u5d29\u6e83\u3002\u5b83\u4f1a\u7ed9\u4f60\u4e00\u4e2a\u8fd0\u884c\u65f6\u7684\u8b66\u544a: <strong>Modifying state during view update(\u5f53\u89c6\u56fe\u66f4\u65b0\u7684\u65f6\u5019\u4fee\u6539\u89c6\u56fe)<\/strong>. \u5feb\u901f\u4fee\u590d\u8fd9\u4e2a\u95ee\u9898\u7684\u65b9\u6cd5\u662f\u5ef6\u8fdf\u53d8\u91cf\u7684\u6539\u53d8\uff0c\u76f4\u5230\u89c6\u56fe\u7684\u66f4\u65b0\u5b8c\u6210\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">DispatchQueue.main.async {\n  self.rects[k] = rect\n}<\/pre>\n\n\n\n<p>\u4e0d\u8fc7\u8fd9\u597d\u50cf\u6709\u70b9\u53d6\u5de7(hack), \u867d\u7136\u8fd9\u8d77\u4f5c\u7528\u4e86\uff0c\u4f46\u53ea\u662f\u4e00\u4e2a\u6682\u65f6\u7684\u89e3\u51b3\u65b9\u6848\u3002\u4e0d\u786e\u5b9a\u4ee5\u540e\u4f1a\u4e0d\u4f1a\u8d77\u4f5c\u7528\u3002 \u6709\u70b9\u5bf9\u6846\u67b6\u5e95\u5c42\u7684\u539f\u7406\u4e0b\u8d4c\u6ce8\u7684\u610f\u601d\u4e86\u3002\u5e78\u8fd0\u7684\u662f PreferenceKey \u53ef\u4ee5\u89e3\u51b3\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">PreferenceKey\u7684\u4ecb\u7ecd<\/h4>\n\n\n\n<p>SwiftUI \u63d0\u4f9b\u7ed9\u6211\u4eec\u4e00\u4e2a\u4fee\u6539\u5668\u8ba9\u6211\u4eec\u6dfb\u52a0\u4e00\u4e9b\u6570\u636e\u5230\u67d0\u4e2a\u5177\u4f53\u7684\u89c6\u56fe\u3002\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u9876\u7ea7\u89c6\u56fe(ancestor view)\u67e5\u8be2\u8fd9\u4e9b\u6570\u636e\u3002\u5e76\u4e14\u6709\u591a\u79cd\u65b9\u5f0f\u53bb\u8bfb\u53d6PreferenceKey\u3002\u8fd9\u53d6\u51b3\u4e8e\u4f60\u7684\u76ee\u7684\u662f\u600e\u6837\u7684\u3002\u65e0\u8bba\u600e\u6837\uff0c\u504f\u597d\u4f3c\u4e4e\u5c31\u662f\u6211\u4eec\u60f3\u8981\u7684\uff0c\u90a3\u6211\u4eec\u5148\u8bd5\u8bd5\u6765\u89e3\u51b3\u6211\u4eec\u7684\u95ee\u9898\u3002<\/p>\n\n\n\n<p>\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u4f8b\u5b50\u6765\u77e5\u9053\u901a\u8fc7preferences\u6765\u66b4\u9732\u54ea\u4e9b\u4fe1\u606f\u3002<\/p>\n\n\n\n<p>1.\u53bb\u6807\u8bb0\u4e00\u4e9bview\uff0c\u8fd9\u91cc\u6211\u4eec\u901a\u8fc7Int\u503c0..11\u53bb\u6807\u8bb0\uff0c\u5176\u5b9e\u4f60\u53ef\u4ee5\u7528\u4efb\u4f55\u503c\u90fd\u53ef\u4ee5\u6807\u8bb0\u7684\u3002<\/p>\n\n\n\n<p>2.\u83b7\u53d6\u6587\u672c\u6846\u7684CGRect.<\/p>\n\n\n\n<p>\u6211\u4eec\u5148\u547d\u540d\u4e00\u4e2a\u9075\u5b88 <strong>Equatable<\/strong> \u534f\u8bae\u7684MyTextPreferenceData\u7684\u7ed3\u6784\u4f53\u3002<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">struct MyTextPreferenceData: Equatable {\n    let viewIdx: Int\n    let rect: CGRect\n}\n<\/pre>\n\n\n\n<p>\u7136\u540e\u6211\u4eec\u5b9a\u4e49\u4e00\u4e2a\u9075\u5faa\u00a0<strong>PreferenceKey<\/strong>\u00a0\u7684\u7ed3\u6784\u4f53MyTextPreferenceKey\u3002<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">struct MyTextPreferenceKey: PreferenceKey {\n    typealias Value = [MyTextPreferenceData]\n\n    static var defaultValue: [MyTextPreferenceData] = []\n    \n    static func reduce(value: inout [MyTextPreferenceData], nextValue: () -> [MyTextPreferenceData]) {\n        value.append(contentsOf: nextValue())\n    }\n}\n<\/pre>\n\n\n\n<p>\u6211\u5f3a\u70c8\u5efa\u8bae\u4f60\u9605\u8bfb\u4e00\u4e9bPreferenceKey\u7684\u6587\u6863\uff0c\u9075\u5b88\u534f\u8bae\u540e\u4f60\u5fc5\u987b\u8981\u5b9e\u73b0\u5982\u4e0b:<\/p>\n\n\n\n<ul><li><strong>value<\/strong> \u6211\u4eec\u60f3\u8981\u901a\u8fc7PreferenceKey\u83b7\u5f97\u4ec0\u4e48\u7c7b\u578b\u7684\u4e00\u4e2a\u522b\u540d\uff0c\u4f8b\u5b50\u4e2d\u6211\u4eec\u7528\u7684\u662f[MyTextPreferenceData]\u6570\u7ec4\u3002<\/li><li><strong>defaultValue<\/strong> \u6ca1\u6709\u663e\u5f0f\u8bbe\u7f6e\u9996\u9009\u9879\u65f6\uff0cSwiftUI\u4f1a\u7528\u8fd9\u4e2a\u9ed8\u8ba4\u503c\u3002<\/li><li><strong>reduce<\/strong> \u7528\u6765\u8986\u76d6\u5728\u89c6\u56fe\u6811\u4e2d\u627e\u5230\u7684\u6240\u6709\u952e\u503c\u5bf9\uff0c\u662f\u4e00\u4e2a\u9759\u6001\u51fd\u6570\u3002\u901a\u5e38\u4f60\u53ef\u4ee5\u7528\u6765\u7d2f\u52a0\u63a5\u6536\u5230\u7684\u6240\u6709\u503c\u3002\u5728\u6211\u4eec\u7684\u4f8b\u5b50\u4e2d\uff0c\u5f53SwiftUI\u904d\u5386\u89c6\u56fe\u6811\u65f6\uff0c\u4f1a\u628a\u6240\u6709preference\u952e\u503c\u5bf9\u5b58\u50a8\u5728\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u4e0b\u9762\u6211\u4eec\u4f1a\u8bb2\u3002\u4f60\u5e94\u8be5\u6e05\u695a <strong>\u503c\u662f\u6309\u7167\u89c6\u56fe\u6811\u7684\u987a\u5e8f\u7ed9reduce\u51fd\u6570\u7684<\/strong> \u6211\u4eec\u4f1a\u5728\u53e6\u5916\u4e00\u4e2a\u4f8b\u5b50\u4e2d\u8ba8\u8bba\u3002<\/li><\/ul>\n\n\n\n<p>\u6211\u4eec\u73b0\u5728\u6709\u4e86 PreferenceKey \u4e86\uff0c\u5f00\u59cb\u5bf9\u4e4b\u524d\u7684\u4ee3\u7801\u5c31\u884c\u4fee\u6539\u3002<\/p>\n\n\n\n<p>\u5148\u4fee\u6539MonthView\uff0c \u901a\u8fc7GeometryReader\u6765\u83b7\u53d6\u6587\u5b57\u7684\u5927\u5c0f\u548c\u4f4d\u7f6e\uff0c\u8fd9\u4e9b\u503c\u9700\u8981\u8f6c\u6362\u4e00\u4e0b\u5750\u6807\u7cfb\uff0c\u624d\u80fd\u7ed8\u5236\u51fa\u6b63\u786e\u7684\u8fb9\u6846\u3002\u89c6\u56fe\u53ef\u4ee5\u901a\u8fc7\u4fee\u6539\u5668\u6765\u547d\u540d\u5b83\u4eec\u7684\u7a7a\u95f4\u5750\u6807\u7cfb <code>.coordinateSpace(name: \"name\")<\/code>\u3002 \u4e00\u65e6\u6211\u4eec\u8f6c\u6362\u4e86rect\uff0c\u6211\u4eec\u4e5f\u8981\u76f8\u5e94\u7684\u8bbe\u7f6epreference<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">struct MonthView: View {\n    @Binding var activeMonth: Int\n    let label: String\n    let idx: Int\n    \n    var body: some View {\n        Text(label)\n            .padding(10)\n            .background(MyPreferenceViewSetter(idx: idx)).onTapGesture { self.activeMonth = self.idx }\n    }\n}\n\nstruct MyPreferenceViewSetter: View {\n    let idx: Int\n    \n    var body: some View {\n        GeometryReader { geometry in\n            Rectangle()\n                .fill(Color.clear)\n                .preference(key: MyTextPreferenceKey.self,\n                            value: [MyTextPreferenceData(viewIdx: self.idx, rect: geometry.frame(in: .named(\"myZstack\")))])\n        }\n    }\n}<\/pre>\n\n\n\n<p>\u7136\u540e\uff0c\u6211\u4eec\u521b\u5efa\u4e00\u4e2a\u5355\u72ec\u7684\u8fb9\u6846\u89c6\u56fe\uff0c\u8be5\u89c6\u56fe\u5c06\u66f4\u6539\u5176\u504f\u79fb\u91cf\u548cframe\u4ee5\u5339\u914d\u4e0e\u6700\u540e\u70b9\u51fb\u7684\u89c6\u56fe\u76f8\u5bf9\u5e94\u7684\u77e9\u5f62\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">RoundedRectangle(cornerRadius: 15).stroke(lineWidth: 3.0).foregroundColor(Color.green)\n    .frame(width: rects[activeIdx].size.width, height: rects[activeIdx].size.height)\n    .offset(x: rects[activeIdx].minX, y: rects[activeIdx].minY)\n    .animation(.easeInOut(duration: 1.0))\n<\/pre>\n\n\n\n<p>\u6700\u540e\uff0c\u6211\u4eec\u53ea\u8981\u4fdd\u8bc1\u5f53preferences\u6539\u53d8\u7684\u65f6\u5019\uff0c\u6211\u4eec\u76f8\u5e94\u7684\u5173\u7cfbrect\u6570\u7ec4\u3002 \u4f8b\u5982\u5f53\u8bbe\u5907\u65cb\u8f6c\uff0c\u6216\u8005window\u7684\u5927\u5c0f\u6539\u53d8\uff0c \u4e0b\u9762\u7684\u4ee3\u7801\u90fd\u4f1a\u88ab\u8c03\u7528\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">.onPreferenceChange(MyTextPreferenceKey.self) { preferences in\n    for p in preferences {\n        self.rects[p.viewIdx] = p.rect\n    }\n}<\/pre>\n\n\n\n<p>\u4e0b\u9762\u662f\u5b8c\u6574\u7684\u4ee3\u7801\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">import SwiftUI\n\nstruct MyTextPreferenceKey: PreferenceKey {\n    typealias Value = [MyTextPreferenceData]\n\n    static var defaultValue: [MyTextPreferenceData] = []\n    \n    static func reduce(value: inout [MyTextPreferenceData], nextValue: () -> [MyTextPreferenceData]) {\n        value.append(contentsOf: nextValue())\n    }\n}\n\nstruct MyTextPreferenceData: Equatable {\n    let viewIdx: Int\n    let rect: CGRect\n}\n\nstruct ContentView : View {\n    \n    @State private var activeIdx: Int = 0\n    @State private var rects: [CGRect] = Array&lt;CGRect>(repeating: CGRect(), count: 12)\n    \n    var body: some View {\n        ZStack(alignment: .topLeading) {\n            RoundedRectangle(cornerRadius: 15).stroke(lineWidth: 3.0).foregroundColor(Color.green)\n                .frame(width: rects[activeIdx].size.width, height: rects[activeIdx].size.height)\n                .offset(x: rects[activeIdx].minX, y: rects[activeIdx].minY)\n                .animation(.easeInOut(duration: 1.0))\n            \n            VStack {\n                Spacer()\n                \n                HStack {\n                    MonthView(activeMonth: $activeIdx, label: \"January\", idx: 0)\n                    MonthView(activeMonth: $activeIdx, label: \"February\", idx: 1)\n                    MonthView(activeMonth: $activeIdx, label: \"March\", idx: 2)\n                    MonthView(activeMonth: $activeIdx, label: \"April\", idx: 3)\n                }\n                \n                Spacer()\n                \n                HStack {\n                    MonthView(activeMonth: $activeIdx, label: \"May\", idx: 4)\n                    MonthView(activeMonth: $activeIdx, label: \"June\", idx: 5)\n                    MonthView(activeMonth: $activeIdx, label: \"July\", idx: 6)\n                    MonthView(activeMonth: $activeIdx, label: \"August\", idx: 7)\n                }\n                \n                Spacer()\n                \n                HStack {\n                    MonthView(activeMonth: $activeIdx, label: \"September\", idx: 8)\n                    MonthView(activeMonth: $activeIdx, label: \"October\", idx: 9)\n                    MonthView(activeMonth: $activeIdx, label: \"November\", idx: 10)\n                    MonthView(activeMonth: $activeIdx, label: \"December\", idx: 11)\n                }\n                \n                Spacer()\n                }.onPreferenceChange(MyTextPreferenceKey.self) { preferences in\n                    for p in preferences {\n                        self.rects[p.viewIdx] = p.rect\n                    }\n            }\n        }.coordinateSpace(name: \"myZstack\")\n    }\n}\n\nstruct MonthView: View {\n    @Binding var activeMonth: Int\n    let label: String\n    let idx: Int\n    \n    var body: some View {\n        Text(label)\n            .padding(10)\n            .background(MyPreferenceViewSetter(idx: idx)).onTapGesture { self.activeMonth = self.idx }\n    }\n}\n\nstruct MyPreferenceViewSetter: View {\n    let idx: Int\n    \n    var body: some View {\n        GeometryReader { geometry in\n            Rectangle()\n                .fill(Color.clear)\n                .preference(key: MyTextPreferenceKey.self,\n                            value: [MyTextPreferenceData(viewIdx: self.idx, rect: geometry.frame(in: .named(\"myZstack\")))])\n        }\n    }\n}<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\">\u660e\u667a\u5730\u4f7f\u7528Preferences(\u9996\u9009\u9879)<\/h4>\n\n\n\n<p>\u5f53\u6211\u4eec\u4f7f\u7528preferences\uff0c\u53ef\u80fd\u4f1a\u4f7f\u7528\u5b50\u7ea7\u89c6\u56fe\u7684\u51e0\u4f55\u4fe1\u606f\u6765\u5e03\u5c40\u5b83\u4eec\u7684\u4e00\u4e2a\u9876\u5c42\u89c6\u56fe(ancestors)\uff0c\u5982\u679c\u662f\u8fd9\u6837\u7684\u8bdd\uff0c\u4f60\u5e94\u8be5\u6ce8\u610f\u3002 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