Android实现时间倒计时功能

public class MainActivity extends Activity {

 private RelativeLayout countDown;
 // 倒计时
 private TextView daysTv, hoursTv, minutesTv, secondsTv;
 private long mDay = 10;
 private long mHour = 10;
 private long mMin = 30;
 private long mSecond = 00;// 天 ,小时,分钟,秒
 private boolean isRun = true;
 private Handler timeHandler = new Handler() {

  @Override
  public void handleMessage(Message msg) {
   super.handleMessage(msg);
   if (msg.what==1) {
    computeTime();
    daysTv.setText(mDay+"");
    hoursTv.setText(mHour+"");
    minutesTv.setText(mMin+"");
    secondsTv.setText(mSecond+"");
    if (mDay==0&&mHour==0&&mMin==0&&mSecond==0) {
     countDown.setVisibility(View.GONE);
    }
   }
  }
 };

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  countDown = (RelativeLayout) findViewById(R.id.countdown_layout);
  daysTv = (TextView) findViewById(R.id.days_tv);
  hoursTv = (TextView) findViewById(R.id.hours_tv);
  minutesTv = (TextView) findViewById(R.id.minutes_tv);
  secondsTv = (TextView) findViewById(R.id.seconds_tv);

  startRun();
 }

 /**
  * 开启倒计时
  */
 private void startRun() {
  new Thread(new Runnable() {

   @Override
   public void run() {
    // TODO Auto-generated method stub
    while (isRun) {
     try {
      Thread.sleep(1000); // sleep 1000ms
      Message message = Message.obtain();
      message.what = 1;
      timeHandler.sendMessage(message);
     } catch (Exception e) {
      e.printStackTrace();
     }
    }
   }
  }).start();
 }

 /**
  * 倒计时计算
  */
 private void computeTime() {
  mSecond--;
  if (mSecond < 0) {
   mMin--;
   mSecond = 59;
   if (mMin < 0) {
    mMin = 59;
    mHour--;
    if (mHour < 0) {
     // 倒计时结束
     mHour = 23;
     mDay--;
    }
   }
  }
 }
}

<?xml version="1.0" encoding="utf-8"? 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/countdown_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white"
android:gravity="center"  
<RelativeLayout
android:id="@+id/daojishi_rl"
android:layout_width="match_parent"
android:layout_height="40.0dip"
android:layout_marginLeft="10.0dip"
android:layout_marginRight="10.0dip"
android:gravity="center"  
<ImageView
android:id="@+id/describe_iv"
android:layout_width="40.0dip"
android:layout_height="40.0dip"
android:background="@drawable/clock"
android:gravity="center_vertical" / 
<TextView
android:id="@+id/describe_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_marginRight="5.0dip"
android:layout_toRightOf="@+id/describe_iv"
android:text="距离活动还有 "
android:textSize="25sp" / 
<TextView
android:id="@+id/days_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_toRightOf="@+id/describe_tv"
android:textColor="@color/colorAccent"
android:gravity="center"
android:text="20"
android:textSize="20sp" / 
<TextView
android:id="@+id/colon0"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_marginLeft="5.0dip"
android:layout_marginRight="3.0dip"
android:layout_toRightOf="@+id/days_tv"
android:text="天"
android:textSize="20sp"
android:textStyle="bold" / 
</RelativeLayout 
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/daojishi_rl"
android:gravity="center_horizontal"  
<TextView
android:id="@+id/hours_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_toLeftOf="@+id/colon1"
android:textColor="@color/colorAccent"
android:gravity="center"
android:text="23"
android:textSize="20sp" / 
<TextView
android:id="@+id/colon1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_marginLeft="3.0dip"
android:layout_marginRight="3.0dip"
android:layout_toLeftOf="@+id/minutes_tv"
android:text=":"
android:textSize="20sp"
android:textStyle="bold" / 
<TextView
android:id="@+id/minutes_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_toLeftOf="@+id/colon2"
android:textColor="@color/colorAccent"
android:gravity="center"
android:text="59"
android:textSize="20sp" / 
<TextView
android:id="@+id/colon2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_marginLeft="3.0dip"
android:layout_marginRight="3.0dip"
android:layout_toLeftOf="@+id/seconds_tv"
android:text=":"
android:textSize="20sp"
android:textStyle="bold" / 
<TextView
android:id="@+id/seconds_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:gravity="center"
android:text="59"
android:textColor="@color/colorAccent"
android:textSize="20sp" / 
</RelativeLayout 
</RelativeLayout