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 Android教程網 >> Android技術 >> 關於Android編程 >> Android倒計時CountDownTimer小記

Android倒計時CountDownTimer小記

編輯:關於Android編程

Android 超簡便的倒計時實現: CountDownTimer

CountDownTimer由系統提供

查資料的時候 發現了CountDownTimer這個類之後 果斷拋棄了以前的倒計時做法


功能:

30秒倒計時 每次間隔1秒


參數:

mc.start();方法開始

mc.cancel();方法結束

new MyCountDownTimer(30000, 1000); 第一個參數表示 總的時間為30000毫秒,間隔1000毫秒



直接上代碼:

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
 * 
 * 倒計時的類  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有顯示時間延遲
		mc.cancel();
	}

	public void restart(View view) {
		Toast.makeText(MainActivity.this, "重新開始", Toast.LENGTH_LONG).show();// toast有顯示時間延遲
		mc.start();
	}

	/**
	 * 繼承 CountDownTimer 防范
	 * 
	 * 重寫 父類的方法 onTick() 、 onFinish()
	 */

	class MyCountDownTimer extends CountDownTimer {
		/**
		 * 
		 * @param millisInFuture
		 *            表示以毫秒為單位 倒計時的總數
		 * 
		 *            例如 millisInFuture=1000 表示1秒
		 * 
		 * @param countDownInterval
		 *            表示 間隔 多少微秒 調用一次 onTick 方法
		 * 
		 *            例如: countDownInterval =1000 ; 表示每1000毫秒調用一次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("倒計時(" + millisUntilFinished / 1000 + ")...");
		}
	}
}
//┏┓   ┏┓
//┏┛┻━━━┛┻┓
//┃       ┃  
//┃   ━   ┃
//┃ ┳┛ ┗┳ ┃
//┃       ┃
//┃   ┻   ┃
//┃       ┃
//┗━┓   ┏━┛
//┃   ┃   神獸保佑        
//┃   ┃   代碼無BUG!
//┃   ┗━━━┓
//┃       ┣┓
//┃       ┏┛
//┗┓┓┏━┳┓┏┛
//  ┃┫┫ ┃┫┫
//  ┗┻┛ ┗┻┛

布局:



    

    


附:

CountDownTimer源碼:

/*
 * 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:
 *
 * 
 * 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); } } } }; }

每日精進 前進一步


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