Android倒计时CountDownTimer小记
16lz
2021-12-04
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;@Overrideprotected 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);}@Overridepublic void onFinish() {tv.setText("done");}@Overridepublic void onTick(long millisUntilFinished) {Log.i("MainActivity", millisUntilFinished + "");tv.setText("倒计时(" + millisUntilFinished / 1000 + ")...");}}}//┏┓ ┏┓//┏┛┻━━━┛┻┓//┃ ┃ //┃ ━ ┃//┃ ┳┛ ┗┳ ┃//┃ ┃//┃ ┻ ┃//┃ ┃//┗━┓ ┏━┛//┃ ┃ 神兽保佑 //┃ ┃ 代码无BUG!//┃ ┗━━━┓//┃ ┣┓//┃ ┏┛//┗┓┓┏━┳┓┏┛// ┃┫┫ ┃┫┫// ┗┻┛ ┗┻┛
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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