干货三：CountDownTimer倒计时工具类

概述

毫无疑问，我们先来看下官方文档中给的介绍

CountDownTimer

官方定义如下：

Schedule a countdown until a time in the future, with regular

notifications on intervals along the way.

同时官方也给出了使用的demo:

构造函数 方法 以及参数含义请参考官方文档，已经很明确的说明了，这里就不重复了~

Code

import android.os.Bundle; import android.os.CountDownTimer; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Button; import com.turing.base.R; /** * 倒计时演示 *

* Android中有个countDownTimer类， * 从名字上就可以看出来，它的功能是记录下载时间， * 将后台线程的创建和Handler队列封装成为了一个方便的调用. *

* CountDownTimer由系统提供,果断抛弃了自己以前使用Handler更新UI的做法 */ public class CountDownActivity extends AppCompatActivity { private MyCountDownTimer mc; private Button countBtn; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_count_down); countBtn = (Button) findViewById(R.id.show); // 共计30S,1S调用一次onTick mc = new MyCountDownTimer(30000, 1000); mc.start(); } public void oncancel(View view) { mc.cancel(); } public void restart(View view) { mc.start(); } /** * 自定义倒计时类 */ 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 onTick(long millisUntilFinished) { countBtn.setText("倒计时(" + millisUntilFinished / 1000 + ")..."); } @Override public void onFinish() { countBtn.setText("done"); } } }

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

运行图

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; /** * 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; /** * boolean representing if the timer was cancelled */ 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. */ public synchronized final void cancel() { mCancelled = true; mHandler.removeMessages(MSG); } /** * Start the countdown. */ public synchronized final CountDownTimer start() { mCancelled = false; 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) { if (mCancelled) { return; } 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); } } } }; }

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。