Android使用CountDownTimer类实现倒计时闹钟

package com.home.brewclock; 
 
import android.app.Activity; 
import android.media.MediaPlayer; 
import android.os.Bundle; 
import android.os.CountDownTimer; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.TextView; 
 
public class MainActivity extends Activity implements OnClickListener { 
  private Button addTimeBtn; 
  private Button decreaseTimeBtn; 
  private Button startBtn; 
  private Button closeMusicBtn; 
  private TextView timeText; 
 
  private int brewTime = 3; 
  private CountDownTimer countDownTimer; 
  private boolean isBrewing = false; 
  private MediaPlayer alarmMusic; 
 
  @Override 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
 
    addTimeBtn = (Button) findViewById(R.id.main_btn_up); 
    decreaseTimeBtn = (Button) findViewById(R.id.main_btn_down); 
    startBtn = (Button) findViewById(R.id.main_start); 
    closeMusicBtn = (Button) findViewById(R.id.main_btn_close_music); 
    timeText = (TextView) findViewById(R.id.main_tv); 
    addTimeBtn.setOnClickListener(this); 
    decreaseTimeBtn.setOnClickListener(this); 
    startBtn.setOnClickListener(this); 
    closeMusicBtn.setOnClickListener(this); 
    setBrewTime(3); 
  } 
 
  /** 
   * 设置闹钟倒计时初始值 
   * 
   * @param minutes 
   */ 
  public void setBrewTime(int minutes) { 
    if (isBrewing) 
      return; 
    brewTime = minutes; 
 
    if (brewTime < 1) { 
      brewTime = 1; 
    } 
    timeText.setText(String.valueOf(brewTime) + "m"); 
  } 
 
  /** 
   * 开启闹钟 
   */ 
  public void startBrew() { 
    // 创建一个CountDownTimer对象记录闹钟时间 
    countDownTimer = new CountDownTimer(brewTime * 60 * 1000, 1000) { 
      @Override 
      public void onTick(long millisUntilFinished) { 
        timeText.setText(String.valueOf(millisUntilFinished / 1000) 
            + "s"); 
      } 
 
      @Override 
      public void onFinish() { 
        isBrewing = false; 
        timeText.setText(brewTime + "m"); 
        startBtn.setText("Start"); 
        // 加载指定音乐，并为之创建MediaPlayer对象 
        alarmMusic = MediaPlayer.create(MainActivity.this, R.raw.music); 
        // 设置为循环播放 
        alarmMusic.setLooping(true); 
        // 播放音乐 
        alarmMusic.start(); 
        closeMusicBtn.setVisibility(0); 
      } 
    }; 
    countDownTimer.start(); 
    startBtn.setText("Stop"); 
    isBrewing = true; 
  } 
 
  /** 
   * 停止计时 
   */ 
  public void stopBrew() { 
    if (countDownTimer != null) { 
      countDownTimer.cancel(); 
    } 
    isBrewing = false; 
    startBtn.setText("Start"); 
  } 
 
  @Override 
  public void onClick(View v) { 
    if (v == addTimeBtn) { 
      setBrewTime(brewTime + 1); 
    } else if (v == decreaseTimeBtn) { 
      setBrewTime(brewTime - 1); 
    } else if (v == startBtn) { 
      if (isBrewing) { 
        stopBrew(); 
      } else { 
        startBrew(); 
      } 
    } else if (v == closeMusicBtn) { 
      if (alarmMusic != null) { 
        alarmMusic.stop(); 
        closeMusicBtn.setVisibility(8); 
      } 
    } 
  } 
} 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" > 
 
  <Button 
    android:id="@+id/main_btn_close_music" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="关闭音乐" 
    android:visibility="gone" /> 
 
  <LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_centerInParent="true" 
    android:gravity="center" 
    android:orientation="horizontal" > 
 
    <Button 
      android:id="@+id/main_btn_down" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="-" 
      android:textSize="40dp" /> 
 
    <TextView 
      android:id="@+id/main_tv" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:padding="10dp" 
      android:text="0:00" 
      android:textSize="40dp" /> 
 
    <Button 
      android:id="@+id/main_btn_up" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="+" 
      android:textSize="40dp" /> 
  </LinearLayout> 
 
  <Button 
    android:id="@+id/main_start" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_alignParentBottom="true" 
    android:text="Start" /> 
 
</RelativeLayout>