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:
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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; @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); } @Override public void onFinish() { tv.setText("done"); } @Override public 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:
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<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:
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/* * 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); } } } }; } |
