Xamarin Android 监听音量键(下)

发布时间:2019-08-12 14:00:34发布者:Mr.Zhang阅读(406)

上篇在 MainActivity 中重写了按键事件(OnKeyDown),获取了音量键键值并打印了出来,当然,手机物理按键和虚拟按键(音量键、返回键、菜单键等)均可通过该按键事件被捕获。

 

但是,按键重写在 MainActivity 中,音量键按下时执行的方法在其他页面中。

 

作者冒出了一个不成熟的想法:利用(publish-subscribe)模式,在 MainActivity 中定义发布者(publish),实例化后层层传递到达 我的页面中,,再将实例化后的订阅者(subscribe)连接上。如图从左到右依次为类实例化的顺序:

方案实现:

1、发布者订阅者类设计

namespace NetworkAssistant
{
    //声明按键事件监听委托接口
    public delegate void OnKeyDown_callback(int keyCode);
    //按键事件发布者
    public class MyKeyEventPublish
    {
        private int KeyCode;
        public Action<int> OnKeyDown { set; get; }
        public int OnKeyDownChanged
        {
            get { return KeyCode; }
            set
            {
                KeyCode = value;
                OnKeyDown?.Invoke(value);
            }
        }
    }
    //按键事件订阅者
    public class MyKeyEventSubscribe
    {
        OnKeyDown_callback cb;
        public MyKeyEventSubscribe(OnKeyDown_callback _cb)
        {
            cb = _cb;
        }

        public void OnKeyDown( int newKeyCode)
        {
            Console.WriteLine($"[{newKeyCode}]");
            cb?.Invoke(newKeyCode);
        }
    }
}

 

2、MainActivity.cs

//按键事件发布者
MyKeyEventPublish myKeyEventPublish;
protected override void OnCreate(Bundle savedInstanceState)
{
    //实例化按键事件发布者
    myKeyEventPublish = new MyKeyEventPublish();
    TabLayoutResource = Resource.Layout.Tabbar;
    ToolbarResource = Resource.Layout.Toolbar;

    base.OnCreate(savedInstanceState);

    Xamarin.Essentials.Platform.Init(this, savedInstanceState);
    global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
                
    LoadApplication(new App(myKeyEventPublish));
}

public override bool OnKeyDown([GeneratedEnum]Keycode keyCode, KeyEvent e)
{
    //键值更改事件发布方法
    myKeyEventPublish.OnKeyDown((int)keyCode);

    //switch (keyCode)
    //{
    //    case Keycode.VolumeUp:
    //        Message.ShortAlert("音量上");
    //        break;
    //    case Keycode.VolumeDown:
    //        Message.ShortAlert("音量下");
    //        break;
    //    default:break;
    //}

    return true;//屏蔽按键原有功能
    //return base.OnKeyDown(keyCode, e);//不屏蔽原有功能
}

 

3、App.cs

namespace NetworkAssistant
{
    public partial class App : Application
    {
        public App(MyKeyEventPublish myKeyEventPublish)
        {
            InitializeComponent();

            MainPage = new MainPage(myKeyEventPublish);
        }

        protected override void OnStart()
        {
            // Handle when your app starts
        }

        protected override void OnSleep()
        {
            // Handle when your app sleeps
        }

        protected override void OnResume()
        {
            // Handle when your app resumes
        }
    }
}

 

4、MainPage.cs

//按键事件发布者
MyKeyEventPublish myKeyEventPublish;
//按键事件接收者
MyKeyEventSubscribe myKeyEventSubscribe;
public MainPage(MyKeyEventPublish mkp)
{
    //实例化按键事件发布者
    myKeyEventPublish = mkp;
    //实例化按键事件接收者
    myKeyEventSubscribe = new MyKeyEventSubscribe(OnKeyDownCallBack);
    //增加订阅
    myKeyEventPublish.OnKeyDown += myKeyEventSubscribe.OnKeyDown;

    InitializeComponent();
}
void OnKeyDownCallBack(int keyCode)
{
    if (keyCode == 24)
    {//音量键上
        //Message.ShortAlert("音量键上");
        SendData("VU");
    }
    else if (keyCode == 25)
    {//音量键下
        //Message.ShortAlert("音量键下");
        SendData("VD");
    }
    else
    {
        Console.WriteLine("按键按下:"+keyCode);
    }
}

 

欢迎讨论,非常感谢

 





本文转自博客园,原文地址:https://www.cnblogs.com/sethnie/p/11332571.html