Cannot resolve symbol 'HdmiControlManager'

如果您在编写代码时遇到了 `Cannot resolve symbol 'HdmiControlManager'` 错误，则可能是因为您的项目中缺少对 Android SDK 版本的支持或缺少必要的依赖项。请按照以下步骤尝试解决此问题：

1. 确认您的 Android SDK 版本是否支持 `HdmiControlManager` 类。`HdmiControlManager` 类是在 Android 5.1（API级别 22）中引入的，因此您需要确保您的项目是基于 Android 5.1 或更高版本构建的。

2. 在您的项目的 build.gradle 文件中，确保已将目标SDK版本设置为 22 或更高版本。

例如：

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.2"

    defaultConfig {
        applicationId "com.example.signaldetectiondemo"
        minSdkVersion 22
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    ...
}

3. 确认您的项目依赖项中是否包括 `android.hardware.hdmi` 库。如果没有，请在您的 build.gradle 文件中添加以下依赖项：

dependencies {
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'com.android.support:appcompat-v7:30.0.2'
    implementation 'com.android.support.constraint:constraint-layout:2.1.0'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'com.android.support:appcompat-v7:30.0.2'
    implementation 'com.android.support.constraint:constraint-layout:2.1.0'
    implementation 'com.android.support:support-v4:30.0.2'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'com.android.support:appcompat-v7:30.0.2'
    implementation 'com.android.support.constraint:constraint-layout:2.1.0'
    implementation 'com.android.support:support-v4:30.0.2'
    implementation 'com.android.support:recyclerview-v7:30.0.2'
    implementation 'com.android.support:cardview-v7:30.0.2'
    implementation 'com.android.support:design:30.0.2'
    implementation 'com.android.support:support-annotations:30.0.2'
    implementation 'com.android.support:support-core-utils:30.0.2'
    implementation 'com.android.support:support-media-compat:30.0.2'
    implementation 'com.android.support:support-v13:30.0.2'
    implementation 'com.android.support:support-vector-drawable:30.0.2'
    implementation 'androidx.appcompat:appcompat:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.core:core-ktx:1.6.0'
    implementation 'androidx.recyclerview:recyclerview:1.2.1'
    implementation 'androidx.cardview:cardview:1.0.0'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.annotation:annotation:1.2.0'
    implementation 'androidx.media:media:1.3.0'
    implementation 'com.android.support:support-compat:30.0.2'
    implementation 'com.android.support:support-core-ui:30.0.2'
    implementation 'com.android.support:support-fragment:30.0.2'
    implementation 'com.android.support:support-vector-drawable:30.0.2'
    implementation 'com.android.support:animated-vector-drawable:30.0.2'
    implementation 'com.android.support.constraint:constraint-layout:2.1.0'
    implementation 'com.google.android.gms:play-services-cast-framework:19.0.0'
    implementation 'com.google.android.gms:play-services-cast:17.1.0'
}

这些步骤应该可以帮助您解决 `Cannot resolve symbol 'HdmiControlManager'` 错误。如果问题仍然存在，请检查您的项目设置和依赖项，或者尝试重新创建项目。