android四大组建之Service

Service组件
后台运行的程序
要在AndroidManifest.xml里面配置
<service android:name=".EchoService"></service>
MainActivity添加代码
Intent serviceIntent = new Intent(this,EchoService.class);
startService(serviceIntent);
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onBind 返回IBinder对象，不为null才能connect成功
同时执行Unbind ,Stop 才能关闭service
Bind Service后退，执行onDestroy
Start Service后退，不执行onDestroy
Service之间通信要先绑定

service 是系统组建，由操作系统控制,只能通过bindService请求操作系统，自己不能create

程序实现了启动服务，每隔一秒输出一个数字。可以start,stop,bind,Unbind,通过logcat查看

MainActivity

package com.sammer.l003usingservice;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.ServiceConnection;import android.os.IBinder;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;public class MainActivity extends AppCompatActivity implements View.OnClickListener, ServiceConnection {    private Button btnStartService,btnStopService,btnBindService,btnUnbindService,btnGetCurrentNum;    private Intent serviceIntent;    private  EchoService echoService = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        serviceIntent = new Intent(this,EchoService.class);        btnStartService = (Button) findViewById(R.id.btnStartService);        btnStopService = (Button) findViewById(R.id.btnStopService);        btnBindService = (Button) findViewById(R.id.btnBindService);        btnUnbindService = (Button) findViewById(R.id.btnUnbindService);        btnGetCurrentNum = (Button) findViewById(R.id.btnGetCurrentNum);        btnStartService.setOnClickListener(this);        btnStopService.setOnClickListener(this);        btnBindService.setOnClickListener(this);        btnUnbindService.setOnClickListener(this);        btnGetCurrentNum.setOnClickListener(this);    }    @Override    public void onClick(View view) {        switch (view.getId()){            case R.id.btnStartService:                startService(serviceIntent);                break;            case R.id.btnStopService:                stopService(serviceIntent);                break;            case R.id.btnBindService:                bindService(serviceIntent,this, Context.BIND_AUTO_CREATE);                break;            case R.id.btnUnbindService:                unbindService(this);                echoService = null;                        break;            case R.id.btnGetCurrentNum:                if(echoService != null)                {                    System.out.println("当前服务中数字时："+echoService.getCurrentNum());                }                break;        }    }    @Override    public void onServiceConnected(ComponentName componentName, IBinder binder) {        System.out.println("onServiceConnected");//获取当前服务实例        echoService = ((EchoService.EchoServiceBinder) binder).getService();    }    @Override    public void onServiceDisconnected(ComponentName componentName) {    }}

EchoService.java

package com.sammer.l003usingservice;import android.app.Service;import android.content.Intent;import android.os.Binder;import android.os.IBinder;import android.support.annotation.Nullable;import java.util.Timer;import java.util.TimerTask;/** * Created by Administrator on 2017/8/9. * Weidong Wang 2017 */public class EchoService extends Service {    @Nullable    @Override    public IBinder onBind(Intent intent) {        System.out.println("onBind");        return echoServiceBinder;    }    //自定义一个内部类EchoServiceBinder继承Binder,必须有返回值才能connect    private final EchoServiceBinder echoServiceBinder = new EchoServiceBinder();    public   class EchoServiceBinder extends Binder {        public EchoService getService(){            return  EchoService.this;        }    }    public  int getCurrentNum(){        return  i;    }    @Override    public void onCreate() {        System.out.println("onCreate");        startTimer();        super.onCreate();    }    @Override    public void onDestroy() {        System.out.println("onDestroy");        stopTimer();        super.onDestroy();    }    private  int i = 0;    public void startTimer(){        if(timer == null){            timer = new Timer();            task = new TimerTask(){                @Override                public void run() {                    i++;                    System.out.println(i);                }            };            timer.schedule(task,1000,1000);        }    }    public void  stopTimer(){        if(timer != null){            task.cancel();            timer.cancel();            task = null;            timer = null;        }    }    private Timer timer;    private TimerTask task;}
AndroidManifest.xml添加

 </activity>    <service android:name=".EchoService"></service></application>
activity_main

    <Button        android:id="@+id/btnStartService"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Start Service" />    <Button        android:id="@+id/btnStopService"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Stop Service" />    <Button        android:id="@+id/btnBindService"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Bind Service" />    <Button        android:id="@+id/btnUnbindService"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Unbind Service" />    <Button        android:id="@+id/btnGetCurrentNum"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Get Current Number" />