Android倒计时CountDownTimer小记

Android 超简便的倒计时实现:  CountDownTimer

CountDownTimer由系统提供

查资料的时候 发现了CountDownTimer这个类之后 果断抛弃了以前的倒计时做法

功能:

30秒倒计时 每次间隔1秒

参数:

mc.start();方法开始

mc.cancel();方法结束

new MyCountDownTimer(30000, 1000); 第一个参数表示 总的时间为30000毫秒,间隔1000毫秒

直接上代码:

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 + ")...");
		}
	}
}
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//┗━┓　　　┏━┛
//┃　　　┃   神兽保佑　　　　　　　　
//┃　　　┃   代码无BUG！
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布局:

<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=".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>

附: 

CountDownTimer源码:

/*
 * 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
 *
 *      http://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:
 *
 * <pre class="prettyprint">
 * new CountDownTimer(30000, 1000) {
 *
 *     public void onTick(long millisUntilFinished) {
 *         mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
 *     }
 *
 *     public void onFinish() {
 *         mTextField.setText("done!");
 *     }
 *  }.start();
 * </pre>
 *
 * 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);
                }
            }
        }
    };
}

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