Android实战 - 音心播放器 （MusicActivity - 倒计时 ，进度条实现）

1.背景

    还是音乐播放界面，实现倒计时和进度条功能，基本实现过程: 当打开MusicActivity 的时候，MusicService会发送广播给MusicActivity ，后开始当前播放的时间进度，从而实现倒计时和进度条；

    这里说明下 进度条是 从小到大 ，倒计时是 从大到小 ；

    效果展示 ：

                                               

2.倒计时实现

      实现通过CountDownTimer实现，提供了start()和cancel() 两个方法，可以开始倒计时和取消倒计时，但是，（Android5.0以下）不可以停止，这是非常不给力的；

     （1）解决方法1

              在使用的时候，每次更新，将CountDownTimer 对象先调用cancel()方法，后进行销毁（赋值为null），重新创建和初始化时间，并start();

     （2）解决办法2

              在网上查阅资料后，有人提供了android5.0的CountDownTimmer 源码，使用这个可以cancel(); 但是我没有成功；

        源码分享：

/*
 * 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 cn.labelnet.ui;

import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;

/**
 * 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;

	private boolean mCancelled = false;

	/**
	 * @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.
	 *
	 * Do not call it from inside CountDownTimer threads
	 */
	public final void cancel() {
		mHandler.removeMessages(MSG);
		mCancelled = true;
	}

	/**
	 * Start the countdown.
	 */
	public synchronized final CountDownTimer start() {
		if (mMillisInFuture <= 0) {
			onFinish();
			return this;
		}
		mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture;
		mHandler.sendMessage(mHandler.obtainMessage(MSG));
		mCancelled = false;
		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;

					if (!mCancelled) {
						sendMessageDelayed(obtainMessage(MSG), delay);
					}
				}
			}
		}
	};
}

      （3）倒计时实现

               作用：

                        1）倒计时时间显示

                        2）进度条实时更新显示

                        3）歌词进度显示

                        4）播放结束 ：进度条设置为0，时间设置为总时长，回调LrcView播放结束，进行歌词初始化，显示第一行。

	/**
	 * 倒计时
	 */
	private class CountDownTime extends CountDownTimer {

		private double second = 0;

		public CountDownTime(long millisInFuture, long countDownInterval) {
			super(millisInFuture, countDownInterval);
		}

		@Override
		public void onTick(long millisUntilFinished) {
			//倒计时显示操作
			second = millisUntilFinished / 1000;
			tv_time_sheng.setText(TimeUtil.getMinuteBySecond((int) second));
			// 进度条实现更新操作
			second = (allSecond - second) / allSecond * 100;
			// 
			progressbar_music.setProgress((int) second);
			// 歌词更新操作
			second = allSecond * 1000 - millisUntilFinished;
			// Log.d("MaskMusic", "geci  : "+(long)second);
			lrc.updateTime((long) second);
			// lrcplaytoend.playToPause((long)
			// (allSecond*1000-millisUntilFinished));
		}

		@Override
		public void onFinish() {
			// showToast("MusicActivity 播放完毕");
			lrc.destroyDrawingCache();
			// 播放完毕显示歌词
			// showLrc();
			// 播放完毕需要进行 ，初始化界面 1.进度条初始值，2.歌词回归到第一行 3.时间恢复到总时间
			// 播放中 ，暂停恢复 ： 1.进度条进度保持 2.歌词保持位置 3.时间保持（可以从MusicService获取）
			progressbar_music.setProgress(0);
			tv_time_sheng.setText(TimeUtil.getMinuteBySecond((int) allSecond));
			allSecond = 0;
			lrcplaytoend.playToEnd();
		}
	}

       （4）一个单独的方法来初始化倒计时

	private void CountDown(int allTime) {
		countDown = new CountDownTime(allTime, COUNT_DOWN_INTERVAL);
	}

      （5）初始化倒计时所需要的判断

                 410001不需要看，里面的countDown是CountDownTimmer的对象，清楚该对象，重新重建倒计时，这是这里面使用的；

	if (code == 41001) {
				// 初始化 时间
				if (countDown != null) {
					countDown.cancel();
					countDown = null;
				}
				CountDown(mm.getSeconds() * 1000);
			} else {

				// 销毁上一个对象
				if (countDown != null) {
					countDown.cancel();
					countDown = null;
				}
				// 倒计时同步
				currentTime = intent.getIntExtra(
						MUSIC_SERVICE_TO_ACTIVITY_NOWTIME, 0);
				CountDown(currentTime);
			}

         （6）将秒转化为分

/**
	 * 1.秒转分
	 */
	public static String getMinuteBySecond(int seconds) {

		StringBuffer buffer = new StringBuffer();
		int second = seconds % 60;
		int minute = seconds / 60;

		if (minute <= 9) {
			buffer.append("0" + minute + ":");
		} else {
			buffer.append(minute + ":");
		}
		if (second <= 9) {
			buffer.append("0" + second);
		} else {
			buffer.append(second);
		}
		return buffer.toString();
	}

3.进度条实现

   （1）布局实现

             直接使用的是系统的ProgressBar , 不是很漂亮但很是可以使用的；

    （2）控制实现

             思路是倒计时在执行的时候，总时间减去当前的时间，后将时间换位百分制来使用，实时更新，如倒计时实现；

4.总结

   倒计时和进度条的实现是相对简单的，主要是倒计时的实现，它决定了歌词显示，进度条显示，倒计时显示，三个主要的模块；在使用过程中遇到的问题就是上面的无法cancel() 。当然倒计时也可以自己去封装一个类使用，这里就不实现了。