android开发分享使用CountDownTimer类轻松实现倒计时功能

  package com.example.daojishi;      import android.app.activity;   import android.os.bundle;   import android.os.countdowntimer;   import android.util.log;   import android.view.view;   import android.widget.textview;   import android.widget.toast;      /**    *    * @author baozi    *    * 倒计时的类 countdowntimer    *    */   public class mainactivity extends activity {        private mycountdowntimer mc;     private textview tv;        @override     protected void oncreate(bundle savedinstancestate) {       super.oncreate(savedinstancestate);       setcontentview(r.layout.activity_main);       tv = (textview) findviewbyid(r.id.show);       mc = new mycountdowntimer(30000, 1000);       mc.start();     }        public void oncancel(view view) {       toast.maketext(mainactivity.this, "取消", toast.length_long).show();// toast有显示时间延迟       mc.cancel();     }        public void restart(view view) {       toast.maketext(mainactivity.this, "重新开始", toast.length_long).show();// toast有显示时间延迟       mc.start();     }        /**      * 继承 countdowntimer 防范      *      * 重写 父类的方法 ontick() 、 onfinish()      */        class mycountdowntimer extends countdowntimer {       /**        *        * @param millisinfuture        *      表示以毫秒为单位 倒计时的总数        *        *      例如 millisinfuture=1000 表示1秒        *        * @param countdowninterval        *      表示 间隔 多少微秒 调用一次 ontick 方法        *        *      例如: countdowninterval =1000 ; 表示每1000毫秒调用一次ontick()        *        */       public mycountdowntimer(long millisinfuture, long countdowninterval) {         super(millisinfuture, countdowninterval);       }          @override       public void onfinish() {         tv.settext("done");       }          @override       public void ontick(long millisuntilfinished) {         log.i("mainactivity", millisuntilfinished + "");         tv.settext("倒计时(" + millisuntilfinished / 1000 + ")...");       }     }   }   //┏┓　　　┏┓   //┏┛┻━━━┛┻┓   //┃　　　　　　　┃ 　   //┃　　　━　　　┃   //┃　┳┛　┗┳　┃   //┃　　　　　　　┃   //┃　　　┻　　　┃   //┃　　　　　　　┃   //┗━┓　　　┏━┛   //┃　　　┃  神兽保佑　　　　　　　　   //┃　　　┃  代码无bug！   //┃　　　┗━━━┓   //┃　　　　　　　┣┓   //┃　　　　　　　┏┛   //┗┓┓┏━┳┓┏┛   // ┃┫┫　┃┫┫   // ┗┻┛　┗┻┛     

  <relativelayout xmlns:android="https://schemas.android.com/apk/res/android"     xmlns:tools="https://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=".mainactivity" >        <textview       android:id="@+id/show"       android:layout_width="wrap_content"       android:layout_height="wrap_content"       android:text="@string/hello_world" />        <button       android:id="@+id/button1"       android:onclick="oncancel"       android:layout_width="wrap_content"       android:layout_height="wrap_content"       android:layout_alignleft="@+id/show"       android:layout_below="@+id/show"       android:layout_marginleft="50dp"       android:layout_margintop="106dp"       android:text="cancel" />        <button       android:id="@+id/button2"       android:layout_width="wrap_content"       android:layout_height="wrap_content"       android:layout_alignleft="@+id/button1"       android:layout_below="@+id/button1"       android:layout_margintop="63dp"       android:onclick="restart"       android:text="restart" />      </relativelayout>     

  /*    * copyright (c) 2008 the android open source project    *    * licensed under the apache license, version 2.0 (the "license");    * you may not use this file except in compliance with the license.    * you may obtain a copy of the license at    *    *   https://www.apache.org/licenses/license-2.0    *    * unless required by applicable law or agreed to in writing, software    * distributed under the license is distributed on an "as is" basis,    * without warranties or conditions of any kind, either express or implied.    * see the license for the specific language governing permissions and    * limitations under the license.    */      package android.os;      import android.util.log;      /**    * schedule a countdown until a time in the future, with    * regular notifications on intervals along the way.    *    * example of showing a 30 second countdown in a text field:    *    *    * new countdowntimer(30000, 1000) {    *    *   public void ontick(long millisuntilfinished) {    *     mtextfield.settext("seconds remaining: " + millisuntilfinished / 1000);    *   }    *    *   public void onfinish() {    *     mtextfield.settext("done!");    *   }    * }.start();    *    *    * the calls to {@link #ontick(long)} are synchronized to this object so that    * one call to {@link #ontick(long)} won't ever occur before the previous    * callback is complete. this is only relevant when the implementation of    * {@link #ontick(long)} takes an amount of time to execute that is significant    * compared to the countdown interval.    */   public abstract class countdowntimer {        /**      * millis since epoch when alarm should stop.      */     private final long mmillisinfuture;        /**      * the interval in millis that the user receives callbacks      */     private final long mcountdowninterval;        private long mstoptimeinfuture;        /**      * @param millisinfuture the number of millis in the future from the call      *  to {@link #start()} until the countdown is done and {@link #onfinish()}      *  is called.      * @param countdowninterval the interval along the way to receive      *  {@link #ontick(long)} callbacks.      */     public countdowntimer(long millisinfuture, long countdowninterval) {       mmillisinfuture = millisinfuture;       mcountdowninterval = countdowninterval;     }        /**      * cancel the countdown.      */     public final void cancel() {       mhandler.removemessages(msg);     }        /**      * start the countdown.      */     public synchronized final countdowntimer start() {       if (mmillisinfuture <= 0) {         onfinish();         return this;       }       mstoptimeinfuture = systemclock.elapsedrealtime() + mmillisinfuture;       mhandler.sendmessage(mhandler.obtainmessage(msg));       return this;     }           /**      * callback fired on regular interval.      * @param millisuntilfinished the amount of time until finished.      */     public abstract void ontick(long millisuntilfinished);        /**      * callback fired when the time is up.      */     public abstract void onfinish();           private static final int msg = 1;           // handles counting down     private handler mhandler = new handler() {          @override       public void handlemessage(message msg) {            synchronized (countdowntimer.this) {           final long millisleft = mstoptimeinfuture - systemclock.elapsedrealtime();              if (millisleft <= 0) {             onfinish();           } else if (millisleft < mcountdowninterval) {             // no tick, just delay until done             sendmessagedelayed(obtainmessage(msg), millisleft);           } else {             long lasttickstart = systemclock.elapsedrealtime();             ontick(millisleft);                // take into account user's ontick taking time to execute             long delay = lasttickstart + mcountdowninterval - systemclock.elapsedrealtime();                // special case: user's ontick took more than interval to             // complete, skip to next interval             while (delay < 0) delay += mcountdowninterval;                sendmessagedelayed(obtainmessage(msg), delay);           }         }       }     };   }