安卓倒计时

public class MainActivity extends Activity {

private TextView  tvtime;
private  long  time=600;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvtime=(TextView)findViewById(R.id.tvtime);
handler.postDelayed(runnable, 1000);
}

Handler handler = new Handler();
Runnable runnable = new Runnable() {
@Override
public void run() {
time--;
tvtime.setText("" + formatLongToTimeStr(time));
if(time>0){
handler.postDelayed(this, 1000);
}
}
};

public  String formatLongToTimeStr(Long l) {
int minute = 0;
int second = 0;
second = l.intValue() ;
if (second > 60) {
minute = second / 60;
second = second % 60;
}

if (minute > 60) {

minute = minute % 60;
}
String strtime =minute+"分"+second+"秒";
return strtime;

}
}

<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="custom.community.com.deomtime.MainActivity">

<TextView
android:id="@+id/tvtime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
/>
</RelativeLayout>