【Android】17.4 Activity与IntentService的绑定

分类：C#、Android、VS2015；

创建日期：2016-03-03

一、简介

本示例通过AlarmManager类以固定的时间间隔调用服务（每隔2秒更新一次随机生成的股票数据）。如果将此示例的代码改为定期调用一次Web服务，就能轻松实现股票在线更新的功能。

二、示例3运行截图

本示例在Android 4.4.2（API 19）中运行正常（右侧屏幕中的数据会自动每2秒更新一次），但在Android 6.0（API 23）模拟器中AlarmManager不起作用，原因未知，所以这里截取的是在Android 4.4.2模拟器中运行的效果。

 

三、主要实现步骤

1、添加Json引用

有些股票数据是以JSON格式提供的，如果希望读取JSON格式的数据，需要添加Json引用。

由于本例子实际并未使用它，所以不添加也可以。

具体添加办法如下：鼠标右击项目中的“引用”，然后选择Systm.Json：

2、添加Internet访问权限

股票一般都是通过Internet发布的，如果访问股票的Web服务，还需要添加Internet访问权限（如果已经添加过就不用添加了）：

<uses-permission android:name="android.permission.INTERNET" />

当然，由于这个例子中并没有真正访问Internet，不添加这个权限也可以。

3、添加ch1703_main.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="15dp"
    android:text="test" />

4、添加ch1703SockService.cs

using System;
using System.Collections.Generic;
using Android.App;
using Android.Content;
using Android.OS;

namespace MyDemos.SrcDemos
{
    [Service]
    [IntentFilter(new string[] { StocksUpdatedAction })]
    public class ch1703StockService : IntentService
    {
        IBinder binder;
        public List<Stock> Stocks { get; private set; }
        public const string StocksUpdatedAction = "StocksUpdated";
        List<string> stockSymbols = new List<string>() { "联动A股", "深深B股", "宇平A股", "塔塔B股", "乖乖A股", "果果C股" };
        Random r = new Random();

        protected override void OnHandleIntent(Intent intent)
        {
            UpdateStocks();
            var stocksIntent = new Intent(StocksUpdatedAction);
            SendOrderedBroadcast(stocksIntent, null);
        }

        public override IBinder OnBind(Intent intent)
        {
            binder = new StockServiceBinder(this);
            return binder;
        }

        //此处调用股票的Web服务返回结果，为简化起见，这里用随机数直接返回了模拟的结果
        private void UpdateStocks()
        {
            Stocks = new List<Stock>();
            for (int i = 0; i < stockSymbols.Count; i++)
            {
                Stocks.Add(new Stock() { Symbol = stockSymbols[i], LastPrice = r.Next(10, 151) });
            }
        }
    }

    public class StockServiceBinder : Binder
    {
        public ch1703StockService service { get; private set; }
        public StockServiceBinder(ch1703StockService service)
        {
            this.service = service;
        }
    }

    public class Stock
    {
        public string Symbol { get; set; }
        public float LastPrice { get; set; }
        public override string ToString()
        {
            return string.Format("[Stock: Symbol={0}, LastPrice={1}]", Symbol, LastPrice);
        }
    }
}

5、添加ch1703MainActivity.cs

注意该类继承自ListActivity。

using Android.App;
using Android.Content;
using Android.OS;
using Android.Widget;

namespace MyDemos.SrcDemos
{
    [Activity(Label = "【例17-3】绑定到IntentService")]
    public class ch1703MainActivity : ListActivity
    {
        bool isBound = false;
        StockServiceBinder binder;
        StockServiceConnection stockServiceConnection;
        StockReceiver stockReceiver;
        Intent stockServiceIntent;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            stockReceiver = new StockReceiver(this);

            stockServiceIntent = new Intent(ch1703StockService.StocksUpdatedAction);
            stockServiceConnection = new StockServiceConnection(this);
            BindService(stockServiceIntent, stockServiceConnection, Bind.AutoCreate);

            var intentFilter = new IntentFilter();
            intentFilter.AddAction(ch1703StockService.StocksUpdatedAction);
            intentFilter.Priority = (int)IntentFilterPriority.HighPriority;
            RegisterReceiver(stockReceiver, intentFilter);
            var alarm = (AlarmManager)GetSystemService(AlarmService);
            var a = PendingIntent.GetService(
                this, 0, stockServiceIntent, PendingIntentFlags.UpdateCurrent);
            //每2秒更新一次
            alarm.SetRepeating(AlarmType.Rtc, 0, 2000, a);
        }

        protected override void OnDestroy()
        {
            if (isBound == true)
            {
                UnbindService(stockServiceConnection);
                isBound = false;
            }
            UnregisterReceiver(stockReceiver);
            base.OnDestroy();
        }

        private void UpdateStocks()
        {
            if (isBound)
            {
                var stocks = binder.service.Stocks;
                if (stocks != null)
                {
                    ListAdapter = new ArrayAdapter<Stock>(this,
                        Resource.Layout.ch1703_main, stocks);
                }
            }
        }

        private class StockReceiver : BroadcastReceiver
        {
            ch1703MainActivity activity;
            public StockReceiver(ch1703MainActivity activity)
            {
                this.activity = activity;
            }
            public override void OnReceive(Context context, Intent intent)
            {
                activity.UpdateStocks();
            }
        }

        private class StockServiceConnection : Java.Lang.Object, IServiceConnection
        {
            ch1703MainActivity activity;

            public StockServiceConnection(ch1703MainActivity activity)
            {
                this.activity = activity;
            }

            public void OnServiceConnected(ComponentName name, IBinder service)
            {
                var stockServiceBinder = service as StockServiceBinder;
                if (stockServiceBinder != null)
                {
                    var binder = (StockServiceBinder)service;
                    activity.binder = binder;
                    activity.isBound = true;
                }
            }

            public void OnServiceDisconnected(ComponentName name)
            {
                activity.isBound = false;
            }
        }
    }
}