Android---Service Timer之执行周期任务

我们有时候需要隔一段时间去做一件事，比如检查邮件，检查网络情况等等。本篇文章简单介绍下如何使用Service Timer 去执行周期任务，程序界面上显示一个数字，每隔一秒钟更新 ，每5秒钟显示一个toast。

1.自定义service

public class MyService extends Service {

    private static final long INTERVAL = 5 * 1000;
    private Handler handler = new Handler();
    private Timer mTimer;

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        // 如果已经存在，则先取消
        if (mTimer != null) {
            mTimer.cancel();
        } else {
            mTimer = new Timer();
        }
        mTimer.scheduleAtFixedRate(new MyTimerTask(), 0, INTERVAL);
    }

    private class MyTimerTask extends TimerTask {

        @Override
        public void run() {
            // 新开一个线程执行
            handler.post(runnable);
        }
    }

    private Runnable runnable = new Runnable() {
        @Override
        public void run() {
            Toast.makeText(getApplicationContext(), getTime(),
                    Toast.LENGTH_SHORT).show();
        }

    };

    private String getTime() {
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mTimer.cancel();
    }
}

2.activity_main.xml文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.refreshdemo.MainActivity" >

    <TextView
        android:id="@+id/tvNum"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</RelativeLayout>

3.MainActivity.java

public class MainActivity extends Activity {

    private TextView tvNum;
    private int count = 0; // 计数
    private Handler handler = new Handler();
    private Intent serviceIntent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tvNum = (TextView) findViewById(R.id.tvNum);
        tvNum.setText("0");
        handler.postDelayed(runnable, 1000);
        serviceIntent = new Intent(this, MyService.class);
        this.startService(serviceIntent);
    }

    private Runnable runnable = new Runnable() {
        @Override
        public void run() {
            update();
            handler.postDelayed(this, 1000);
        }
    };

    private void update() {
        count++;
        tvNum.setText(count + "");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        handler.removeCallbacks(runnable);
        this.stopService(serviceIntent);
    }
}

4.最后在AndroidManifest.xml文件中添加Service

<application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.Holo.Light">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        **<service android:name="com.example.refreshdemo.MyService"></service>**
    </application>

运行截图：

源码下载