<?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/activity_main" 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="yascn.com.timecalc.MainActivity"> <TextView  android:textSize="20dp"  android:layout_centerInParent="true"  android:id="@+id/tv_remaintime"  android:layout_width="wrap_content"  android:layout_height="wrap_content"  android:textColor="#000000"  /></RelativeLayout>

package yascn.com.timecalc;import android.os.Handler;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.TextView;import android.widget.Toast;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;public class MainActivity extends AppCompatActivity { TextView tv_remaintime;//倒計時 private long countdownTime;//倒計時的總時間(單位:毫秒) private String timefromServer;//從服務器獲取的訂單生成時間 private long chaoshitime;//從服務器獲取訂單有效時長(單位:毫秒) @Override protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_main);  tv_remaintime = (TextView) findViewById(R.id.tv_remaintime);  getTimeDuring(); } Handler handler = new Handler(); Runnable runnable = new Runnable() {  @Override  public void run() {   countdownTime -= 1000;//倒計時總時間減1   SimpleDateFormat minforamt = new SimpleDateFormat("mm:ss");   String hms = minforamt.format(countdownTime);//格式化倒計時的總時間   tv_remaintime.setText("還剩下" + hms);   handler.postDelayed(this, 1000);  } }; private void getTimeDuring() {  chaoshitime = 30 * 60 * 1000;//應該從服務器獲取  timefromServer = "2017-01-23 11:40:50";//應該從服務器獲取  SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  try {   Date serverDate = df.parse(timefromServer);   long duringTime = new Date().getTime() - serverDate.getTime();//計算當前時間和從服務器獲取的訂單生成時間的時間差   countdownTime = chaoshitime - duringTime;//計算倒計時的總時間   handler.postDelayed(runnable, 1000);  } catch (ParseException e) {   e.printStackTrace();  } }}