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The knowledge of this article "Android how to achieve a countdown custom control" is not understood by most people, so the editor summarizes the following content, detailed content, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "Android how to achieve a countdown custom control" article.

(1) Preface

Android actually provides a countdown control called CountDownTimer, which is easy to use, but it's more tedious to do it in the countdown style we want. For example, we want the countdown to display styles such as HH:MM:SS or HH-MM-SS according to the style we want, or we want to show as follows:

The work to be done will be more tedious, not that it can not be realized, but it is more expensive to achieve, so if we make it into a custom view, we can do the countdown style display according to the style passed by the user (Note: the code in this article does not do the function of these styles, but based on this article code is easy to achieve this function), let's take a look at the countdown custom control I implemented.

(note The code of this article can not be directly used in the project. If you need to use it in the project, you also need to deal with the code, such as fixed time to display width, otherwise the display time will jump and display incompletely, for example, you can measure the width of "00:00:00" and set a display view, or the reader can choose the solution, and whether the inner margin of the font needs to be removed when displaying. It's up to the reader to decide for himself, and it's easy to remove the inner margin, which is just a method of TextView setIncludeFontPadding (false).

(2) effect display

The countdown is accurate to milliseconds, but it can also be modified according to your own needs. It's simple to change the format from "HH:MM:SS SSS" to "HH:MM:SS".

(3) ideas for realization

The idea of implementation is actually very simple, inherited from a TextView, with reference to the system countdown control to do a package on it.

First initialize the countdown time required:

Public void init (long timeInFuture, long timeInterval) {mTimeInFuture = timeInFuture; mTimeInterval = timeInterval; mStopTimeInFuture = SystemClock.elapsedRealtime () + mTimeInFuture; updateText (mStopTimeInFuture);}

TimeInFuture means the length of time you want to count down, such as 10 seconds, 3 days, 5 days, etc. TimeInterval represents the interval, that is, how much time each countdown decreases, which can be 1 second, 2 seconds, 3 seconds. ElapsedRealtime means to get the time value experienced from the device boot, and by adding our length of time, we can be ready to start the countdown.

Public void start () {mStarted = true; updateTimer ();}

When the user calls the start () function, the updateTimer () function is called, which performs the logic of the countdown:

Private void updateTimer () {boolean running = mVisible & & mStarted & & isShown (); if (running! = mRunning) {if (running) {doCountDownTimer ();} else {removeCallbacks (mTickRunnable);} mRunning = running;}}

As you can see from the code, the countdown is done only if the control is visible and mStarted. The countdown execution function doCountDownTimer is as follows:

Private void doCountDownTimer () {final long millisLeft = mStopTimeInFuture-SystemClock.elapsedRealtime (); if (millisLeft

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