必需（
Android MediaRouter 的默认行为）：
A 当发送方应用未连接到 Cast 接收器时，点按“投屏”按钮会显示“投屏”对话框
B 系统会显示“投屏到”的“投屏”对话框标题
C “投屏”对话框会显示可用的 Web 接收器列表
D 当前正在投屏的每个接收器都应显示“正在投屏 app name”
对于 iOS 设备，首次投放时，用户必须同意允许 Cast 设备使用本地网络访问权限 (LNA)。系统会向用户显示一个插页式信息界面，说明需要此权限的原因，然后显示标准的 Apple LNA 权限对话框。
首次投放后，如果用户在 Wi-Fi 连接状态下点按“投放”按钮时找不到任何设备，系统会显示一个帮助屏幕，说明 Web 接收器可能不可用的原因（例如，本地网络访问已停用，或 Wi-Fi 网络存在问题）。
必需：
首次投放：首次点按“投放”按钮后，必须显示一个插页式广告，向用户说明为何应允许应用访问本地网络设备。插页式广告应包含有关需要本地网络访问权限的原因的信息，以提高用户接受本地权限访问的可能性。
B 接收器不可用：点按“投放”按钮后，系统会显示一个帮助屏幕，其中说明用户无法发现 Web 接收器的可能原因，以及用于修正 LNA 权限问题的“设置”链接。
[null,null,["最后更新时间 (UTC)：2025-08-31。"],[[["\u003cp\u003eThe Cast dialog enables users to connect to, manage, and disconnect from Web Receivers and should be implemented consistently across platforms.\u003c/p\u003e\n"],["\u003cp\u003eOn iOS, users must grant local network access permission for initial casting and may encounter a help screen if no devices are found.\u003c/p\u003e\n"],["\u003cp\u003eWhen connected, the Cast dialog displays the receiver name and a "STOP CASTING" button, offering controls for the casting session.\u003c/p\u003e\n"],["\u003cp\u003eFor optimal user experience, it's recommended to include persistent controls alongside those within the Cast dialog, enhancing user interaction.\u003c/p\u003e\n"],["\u003cp\u003eAndroid apps can leverage the MediaRouter component for built-in Cast dialog UX, simplifying implementation.\u003c/p\u003e\n"]]],[],null,["# Cast Dialog\n\nThe Cast dialog is shown whenever the Cast button is pressed. The Cast dialog lets users\nconnect, control, and disconnect from Web Receivers.\n| **Note:** For Android apps, use the `MediaRouter` component from the MediaRouter Support Library to implement the Cast dialog. It has all of the UX requirements built right in.\n| **Note:** For iOS senders, a special Local Network Access interstitial dialog must be displayed the first time a user attempts to cast.\n\nIf you're developing a custom implementation or building an app for iOS or Chrome, you must\nimplement this dialog in a consistent way, so that users recognize and trust it to function\nconsistently across devices, apps and platforms. Refer to the\n[Reference apps](/cast/docs/sample_apps#reference_apps) for examples.\n\n### [Cast dialog, not connected (receivers available)](#sender-cast-menu-available)\n\n\n**Required** (default behavior of [Android MediaRouter](https://developer.android.com/reference/androidx/mediarouter/media/MediaRouter)):\n\n\nA When the sender app is not connected to a Cast receiver,\ntapping the Cast button shows the Cast dialog\n\n\nB The Cast dialog title, \"Cast to\" appears\n\n\nC The Cast dialog shows a list of available Web Receivers\n\n\nD Each receiver currently casting should display, \"Casting\n*app name*\"\n\n**Note the multi-user scenarios:**\n\n- When another user connects to a receiver currently casting from the same app and account, the sender app provides the controls for the cast content.\n- When another user connects to a receiver currently casting from an app that is not casting, the previous sender app disconnects and the new sender app connects.\n\n### Android\n\nCast dialog, not connected \nCast home screen \n\n### iOS\n\nCast dialog, not connected \nCast home screen \n\n### Chrome\n\nCast dialog, not connected \nCast home screen \n\n### [Cast dialog, not connected (iOS only)](#sender-cast-menu-available)\n\n\nFor iOS, when casting for the first time, users must consent to allow local network access (LNA) to\nCast devices. An interstitial information screen is presented\nto users explaining why this permission is needed, followed by the standard Apple LNA\npermissions dialog.\n\n\nAfter casting for the first time, if no devices are found when the Cast button is tapped while the\nuser is on Wi-Fi, a help screen is presented\nexplaining why Web Receivers might not be available (for example,\nlocal network access is disabled, or there is a problem with the Wi-Fi network).\n\n\n**Required** :\n\n\nA First-time casting: After tapping on the Cast button\nfor the first time,\nan Interstitial must be shown to explain to the user why they should allow\nthe app to access local network devices. The interstitial should include information on\nwhy local network access is needed, to increase the likelihood of the user accepting\nlocal permission access.\n\n\nB Receivers unavailable: Tapping the Cast button\ndisplays a help screen explaining possible reasons the user\nis unable to discover Web Receivers, along with links to Settings to fix LNA permissions issues. \n\n### First-time casting (iOS)\n\nFirst-time casting: interstitial and local network access permissions \n\n### Receivers unavailable\n\nReceivers unavailable \n\n### [Cast dialog, connected but not casting](#sender-cast-menu-connected)\n\n\n**Required**\n\n\nA When the sender app is connected to a Web Receiver,\ntapping the Cast button shows the Cast dialog\n\n\nB The Cast dialog title \"Receiver-Name\" appears\n\n\nC The Cast dialog shows a button to stop casting\nwith button label \"STOP CASTING\" (for more information about disconnecting, see\n[Sender stops cast](/cast/docs/design_checklist/sender#sender-control-end)) \n\n### Android\n\nCast dialog, connected but not casting \nReceiver app loaded / idle \n\n### iOS\n\nCast dialog, connected but not casting \nReceiver app loaded / idle \n\n### [Cast dialog, while casting](#sender-cast-menu-casting)\n\n\n**Required**\n\n\nA The Cast dialog title \"Receiver-Name\" appears\n\n\nB The receiver or content currently casting is shown below\nthe title\n\n\nC The Cast dialog shows a \"STOP CASTING\" button that stops\ncasting (for more information see\n[Sender stops cast](/cast/docs/design_checklist/sender#sender-control-end))\n\n**Best practice**\n\n- For the best user experience, provide [persistent controls](/cast/docs/design_checklist/sender#sender-mini-controller) in addition to the controls in the Cast dialog.\n\n### Android\n\nCast dialog, while casting \nReceiver playing content \n\n### iOS\n\nCast dialog, while casting \nReceiver playing content \n\n### Chrome\n\nCast dialog, while casting \nReceiver playing content \n\n**Images used in this design guide**\nare courtesy of the Blender Foundation, shared under copyright or Creative Commons license.\n\n- Elephant's Dream: (c) copyright 2006, Blender Foundation / Netherlands Media Art Institute / www.elephantsdream.org\n- Sintel: (c) copyright Blender Foundation \\| www.sintel.org\n- Tears of Steel: (CC) Blender Foundation \\| mango.blender.org\n- Big Buck Bunny: (c) copyright 2008, Blender Foundation / www.bigbuckbunny.org"]]
