Android之Service服务实现音乐播放器

Service四大组件之一 没有界面的组件，类似于Window中服务，是android中最重要的组件之一。
Service的实现方式：
继承android.app.service
生命周期：onCreate(只会执行一次)
onStartCoommand（非绑定进入，独立运行）
onDestroy
onBind(绑定，直接进入onBind)
onUnbind
非绑定：如音乐，定位
两种启动方式及区别：
Start:启动服务
Bind：绑定服务
开发步骤：
继承Service
注册Service
在android组件中启动Service
停止服务

public class MainActivity extends Activity {    private Button strat1,strat2,strat3;    private Button stop,stop2;    private Button download,APK;    private MyService myService;    private ServiceConnection serviceConnection=new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            myService=((MyService.MyBinder) service).getService();        }        @Override        public void onServiceDisconnected(ComponentName name) {        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        strat1= (Button) findViewById(R.id.strat1);        strat2= (Button) findViewById(R.id.strat2);        strat3= (Button) findViewById(R.id.strat3);        stop=(Button)findViewById(R.id.stop);        stop2=(Button)findViewById(R.id.stop2);        download=(Button)findViewById(R.id.download);        APK=(Button)findViewById(R.id.APKcheck);       strat1.setOnClickListener(new View.OnClickListener() {           @Override           public void onClick(View v) {               Intent it=new Intent(MainActivity.this,MyService.class);               startService(it);           }       });        stop.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent it=new Intent(MainActivity.this,MyService.class);                stopService(it);            }        });        //绑定        strat2.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent=new Intent(MainActivity.this,MyService.class);               bindService(intent,serviceConnection,BIND_AUTO_CREATE);            }        });        strat3.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                if(myService !=null){                    myService.playMusic();                }            }        });        stop2.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                unbindService(serviceConnection);            }        });        download.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent it=new Intent(MainActivity.this,DownService.class);                startService(it);            }        });        APK.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent it=new Intent(MainActivity.this,DownService.class);                stopService(it);            }        });    }    @Override    protected void onDestroy() {        super.onDestroy();    }}

下面是Service服务的信息，Service服务可以实现异步任务类等；
同时需要注意是绑定与非绑定，以及回调的使用

public class DownService extends Service {    private JSONObject jo;    private int apk;    private DownloadManager.Request request;    private DownloadManager downloadManager;    private Long ids;    public DownService() {    }    @Override    public void onCreate() {        super.onCreate();    }    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        String url= UrlUtil.ROOT_URL+"apk";        new getFile().execute(url);        return START_REDELIVER_INTENT;    }    @Override    public IBinder onBind(Intent intent) {        // TODO: Return the communication channel to the service.        throw new UnsupportedOperationException("Not yet implemented");    }    @Override    public void onDestroy() {        super.onDestroy();        downloadManager.remove(ids);    }    public void downLoad(){        downloadManager=(DownloadManager)getSystemService(Context.DOWNLOAD_SERVICE);        String downUrl=UrlUtil.ROOT_URL+"apk/cc.apk";        request=                new DownloadManager.Request(Uri.parse(downUrl));        request.setDestinationInExternalPublicDir("/" + getPackageName() + "/", "aa.apk");        request.setTitle("...下载");        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);        ids=downloadManager.enqueue(request);        //异步任务类取消//        getFile g=new getFile();//        g.execute();//        g.cancel(true);    }    public class getFile extends AsyncTask<String,Void,String> {        @Override        protected String doInBackground(String... params) {            return HttpUtil.HttpGet(params[0]);        }        @Override        protected void onPostExecute(String s) {            super.onPostExecute(s);            Log.d("==o==", s);            try {                jo = new JSONObject(s);                apk = jo.getInt("vid");            } catch (JSONException e) {                e.printStackTrace();            }            int vid = 0;            try {                vid = getPackageManager().getPackageInfo(getPackageName(), 0).versionCode;            } catch (PackageManager.NameNotFoundException e) {                e.printStackTrace();            }            if (apk > vid) {                downLoad();            }else{                Toast.makeText(getBaseContext(), "已经是最新版本", Toast.LENGTH_SHORT).show();            }        }    }}效果图：