Xamarin Forms开发亚马逊Fire TV Stick应用：HDMI CEC实现电视开关机功能求助

Hey there! I totally get your frustration trying to find a straightforward way to control your TV via HDMI CEC in a Xamarin Forms app for Fire TV Stick—let’s break down a working solution that doesn’t require any Java code.

Key Background #

Fire TV Stick runs on Android, so we can leverage Android’s built-in HDMI CEC API directly through Xamarin Android bindings (no Java needed). You won’t even need a third-party NuGet package for this—Xamarin already includes the necessary classes in the Android SDK bindings.

Step 1: Set Up Permissions #

First, add the required permissions to your Android project’s AndroidManifest.xml:

<uses-permission android:name="android.permission.HDMI_CEC" />
<uses-feature android:name="android.hardware.hdmi.cec" android:required="true" />

This tells the system your app needs access to HDMI CEC functionality.

Step 2: Create a Cross-Platform Service #

Since Xamarin Forms is cross-platform, we’ll use a dependency service to access Android-specific HDMI CEC code from the shared project.

1. Define an Interface in the Shared Project

public interface IHdmiCecController
{
    void PowerOnTv();
    void PowerOffTv();
}

2. Implement the Interface in the Android Project

Create a class in your Android project that implements the interface (this is where we’ll call the Android HDMI CEC APIs):

[assembly: Dependency(typeof(AndroidHdmiCecController))]
namespace YourAppName.Droid.Services
{
    using Android.Content;
    using Android.Hardware.Hdmi;
    using Xamarin.Forms;

    public class AndroidHdmiCecController : IHdmiCecController
    {
        private readonly HdmiManager _hdmiManager;
        private readonly HdmiControlManager _controlManager;

        public AndroidHdmiCecController()
        {
            // Get the system HDMI service
            _hdmiManager = (HdmiManager)Android.App.Application.Context.GetSystemService(Context.HdmiService);
            _controlManager = _hdmiManager?.GetHdmiControlManager();
        }

        public void PowerOnTv()
        {
            if (_controlManager == null) return;

            // Send CEC command to turn the TV on (ImageViewOn opcode)
            var powerOnCommand = HdmiControlManager.SendCommand(
                HdmiDeviceInfo.DeviceTypeTv, 
                HdmiCecOpcode.ImageViewOn);
            
            _controlManager.SendCecCommand(powerOnCommand);
        }

        public void PowerOffTv()
        {
            if (_controlManager == null) return;

            // Send CEC command to put the TV in standby (Standby opcode)
            var powerOffCommand = HdmiControlManager.SendCommand(
                HdmiDeviceInfo.DeviceTypeTv, 
                HdmiCecOpcode.Standby);
            
            _controlManager.SendCecCommand(powerOffCommand);
        }
    }
}

Step 3: Use the Service in Xamarin Forms #

From your shared Xamarin Forms code, you can now call the HDMI CEC functions like this:

var cecController = DependencyService.Get<IHdmiCecController>();

// Turn TV on
cecController.PowerOnTv();

// Turn TV off
cecController.PowerOffTv();

Important Notes #

• Device Support: Make sure your Fire TV Stick and connected TV both support HDMI CEC (most modern models do, but double-check).
• System Settings: Some Fire TV devices require users to enable HDMI CEC in the system settings (look for "CEC Control" or "HDMI-CEC" in the Fire TV settings menu).
• Testing: Always test on a physical Fire TV Stick—emulators won’t have HDMI CEC hardware support.

备注：内容来源于stack exchange，提问作者Marc