【移动应用开发技术】怎么在Android中实现列表倒计时

【移动应用开发技术】怎么在Android中实现列表倒计时

怎么在Android中实现列表倒计时？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。CountDownTimer类用法

private

CountDownTimer

timer

=

new

CountDownTimer(30000,

1000)

{

//根据间隔时间来不断回调此方法，这里是每隔1000ms调用一次

@Override

public

void

onTick(long

millisUntilFinished)

{

//todo

millisUntilFinished为剩余时间，也就是30000

-

n*1000

}

//结束倒计时调用

@Override

public

void

onFinish()

{

//todo

}

};

//开始倒计时

timer.start();

//取消倒计时（译者：取消后，再次启动会重新开始倒计时）

timer.cancel();;代码实现先看核心，也就是CountDownAdapter类，这里就简化UI，每个item只有一个textView来显示倒计时，布局XML就不放了，直接放代码class

CountDownAdapter(private

var

activity:

ListActivity,

private

var

data:

ArrayList<Date>,

private

var

systemDate:

Date)

:

BaseAdapter()

{

private

val

timeMap

=

HashMap<TextView,

MyCountDownTimer>()

private

val

handler

=

Handler()

private

val

runnable

=

object

:

Runnable

{

override

fun

run()

{

if

(systemDate

!=

null)

{

systemDate.time

=

systemDate.time

+

1000

Log.i("xujf",

"服务器时间线程==="

+

systemDate

+

"==for=="

+

this)

handler.postDelayed(this,

1000)

}

}

}

init

{

handler.postDelayed(runnable,

1000)

}

override

fun

getView(position:

Int,

convertView:

View?,

parent:

ViewGroup?):

View

{

var

v:

View

var

tag:

ViewHolder

var

vo

=

data[position]

if

(null

==

convertView)

{

v

=

activity.layoutInflater.inflate(R.layout.item_count_down,

null)

tag

=

ViewHolder(v)

v.tag

=

tag

}

else

{

v

=

convertView

tag

=

v.tag

as

ViewHolder

}

//获取控件对应的倒计时控件是否存在,

存在就取消,

解决时间重叠问题

var

tc:

MyCountDownTimer?

=

timeMap[tag.tvTime]

if

(tc

!=

null)

{

tc.cancel()

tc

=

null

}

//计算时间差

val

time

=

getDistanceTimeLong(systemDate,

vo)

//创建倒计时，与控件绑定

val

cdu

=

MyCountDownTimer(position,

time,

1000,

tag.tvTime)

cdu.start()

//[醒目]此处需要map集合将控件和倒计时类关联起来

timeMap.put(tag.tvTime,

cdu)

return

v

}

/**

*

退出时清空所有item的计时器

*/

fun

cancelAllTimers()

{

var

s:

Set<MutableMap.MutableEntry<TextView,

MyCountDownTimer>>?

=

timeMap.entries

var

it:

Iterator<*>?

=

s!!.iterator()

while

(it!!.hasNext())

{

try

{

val

pairs

=

it.next()

as

MutableMap.MutableEntry<*,

*>

var

cdt:

MyCountDownTimer?

=

pairs.value

as

MyCountDownTimer

cdt!!.cancel()

cdt

=

null

}

catch

(e:

Exception)

{

}

}

it

=

null

s

=

null

timeMap.clear()

}

fun

removeTimer(){

handler?.removeCallbacks(runnable)

}

fun

reSetTimer(date:

Date)

{

removeTimer()

systemDate

=

date

handler.postDelayed(runnable,

1000)

}

override

fun

getItem(position:

Int):

Any

=

data[position]

override

fun

getItemId(position:

Int):

Long

=

0L

override

fun

getCount():

Int

=

data.size

internal

inner

class

ViewHolder(view:

View)

{

var

tvTime

=

view.findViewById<TextView>(R.id.tv_time)

}

/**

*

倒计时类，每间隔countDownInterval时间调用一次onTick()

*

index参数可去除，在这里只是为了打印log查看倒计时是否运行

*/

private

inner

class

MyCountDownTimer(internal

var

index:

Int,

millisInFuture:

Long,

internal

var

countDownInterval:

Long,

internal

var

tv:

TextView

)

:

CountDownTimer(millisInFuture,

countDownInterval)

{

override

fun

onTick(millisUntilFinished:

Long)

{

//millisUntilFinished为剩余时间长

Log.i("xujf",

"====倒计时还活着===第

$index

项item======")

//设置时间格式

val

m

=

millisUntilFinished

/

countDownInterval

val

hour

=

m

/

(60

*

60)

val

minute

=

(m

/

60)

%

60

val

s

=

m

%

60

tv.text

=

"倒计时

(${hour}小时${minute}分${s}秒)"

}

override

fun

onFinish()

{

tv.text

=

"倒计时结束"

//todo

可以做一些刷新动作

}

}

/**

*

时间工具，返回间隔时间长

*/

fun

getDistanceTimeLong(one:

Date,

two:

Date):

Long

{

var

diff

=

0L

try

{

val

time1

=

one.time

val

time2

=

two.time

if

(time1

<

time2)

{

diff

=

time2

-

time1

}

else

{

diff

=

time1

-

time2

}

}

catch

(e:

Exception)

{

e.printStackTrace()

}

return

diff

}

}这里主要的创建一个线程来保持服务器时间和N个item倒计时的“走”动。保持服务器时间没什么好说的，就是Handler配合Runnable的循环调用，注意的是，当activity销毁时，别忘了调用CountDownAdapter的removeTimer()方法来取消handler的回调，防止内存泄漏。重点就是item里的倒计时的线程控制，这里参照网上的一个比较好的方法，就是用HashMap<TextView,MyCountDownTimer>()来让MyCountDownTimer和item里的TextView关联起来，也就是每个item对应一个CountDownTimer，当关闭页面时或者刷新list时，可利用cancelAllTimers()方法来清除所有关联，避免内存泄漏。以下是ListActivity，伪造一些时间数据class

ListActivity

:

AppCompatActivity()

{

private

val

list:

ArrayList<Date>

=

ArrayList()

private

var

countDownAdapter:

CountDownAdapter?

=

null

override

fun

onCreate(savedInstanceState:

Bundle?)

{

super.onCreate(savedInstanceState)

setContentView(R.layout.activity_list)

getDate()

setDate()

}

private

fun

setDate()

{

if

(countDownAdapter

==

null)

{

countDownAdapter

=

CountDownAdapter(this,

list,

Date())

lv_count_down.adapter

=

countDownAdapter

lv_count_down.onItemClickListener

=

AdapterView.OnItemClickListener

{

adapterView,

view,

i,

l

->

val

intent

=

Intent(ListActivity@this,

Main2Activity::class.java)

startActivity(intent)

}

}

else

{

//刷新数据时，重置本地服务器时间

countDownAdapter!!.reSetTimer(Date())

countDownAdapter!!.notifyDataSetChanged()

}

}

private

fun

getDate()

{

for

(i

in

1..20)

{

var

date

=

Date(Date().time

+

i

*

1000

*

60

*

30)

list.add(date)

}

}

override

fun

onDestroy()

{

countDownAdapter?.cancelAllTimers()

countDownAdapter?.removeTimer()

super.onDestroy()

}

}这