TextWatcher设置最小值和最大值

Question

im试图使用TextWatcher将输入限制在一个数字范围内，如果用户试图超出范围，则强制输入最小值和最大值。工作几乎如预期，但在删除时，允许视觉上为空的文本。我该怎么避免呢？

inputVal.addTextChangedListener(object:TextWatcher{
override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {}
override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {}
override fun afterTextChanged(s:Editable) {     //s=""
var curVal = s.toString().toIntOrNull()?:5  //curVal=5
if (curVal <  5){
curVal = 5
s.replace(0,s.length,"5")  <- problem here, not replacing cuz s.length=0
}else if (curVal >50){
curVal = 50
s.replace(0,s.length,"50")
}
//some other things to do based on 'curVal'
}})

更新我需要的是，例如，u有一个"20"，并添加一个0(将是200(，将其转换为"50"；如果删除0(为2(，则在输入中强制使用5。

Answer 1

如果s为空，则curVal将为5。

所以它不会触发任何条件。

也许试试：

if (curVal <=  5)

Answer 2

您可以根据自己的喜好进行更改；我们只需要使用source和dest。

source返回在edittext中输入的新输入，如果按退格键则为空dest返回缓冲区中已存在的前一个输入

假设我第一次在edittext中输入6，source返回6，dest返回空，因为第一次在缓冲区中没有输入，如果接下来输入7，那么source将返回7，而dest将返回6。使用这个我们可以检查极限。

class InputRangeFilter(val mMin: Int, val mMax: Int) : InputFilter {
override fun filter(
source: CharSequence?,
start: Int,
end: Int,
dest: Spanned?,
dstart: Int,
dend: Int
): CharSequence? {

val finalValue = (dest.toString().trim() + source.toString().trim()).toInt()

return if (source?.isEmpty() == true && dest?.isEmpty() == true) {
""
} else if (finalValue in (mMin + 1) until mMax) {
null // keep original
} else {
if ((!TextUtils.isEmpty(source) && source.toString().trim().toInt() < mMin)
&& finalValue < mMax
) {
if (source.toString().toInt() == 0) {
""
} else {
source
}
} else {
""
}
}
}
}

用法：

binding.edtText.filters = arrayOf(InputRangeFilter(5, 100))

Answer 3

好吧，经过测试，我可以让它工作了，下面是代码：

class NumberWatcher(private val mMin: Int, private val mMax: Int)
:TextWatcher{
override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {}
override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {}
override fun afterTextChanged(s:Editable) {
Log.d("TextWatcher","Triggered '$s'")
if (s.isEmpty() || s.toString().toInt() < mMin){
s.replace(0, s.length, mMin.toString())
return //will retrigger after the change, to avoid double excecution
}else if (s.toString().toInt() > mMax){
s.replace(0, s.length, mMax.toString())
return //will retrigger after the change, to avoid double excecution
}
Log.d("TextWatcher","Do some things with '$s'")
//do whatever
}
}

用法：

editText.addTextChangedListener(NumberWatcher(5,50))

日志：

D/TextWatcher: Triggered '45'
D/TextWatcher: Do some things with '45'
D/TextWatcher: Triggered '4'
D/TextWatcher: Triggered '5'
D/TextWatcher: Do some things with '5'
D/TextWatcher: Triggered '95'
D/TextWatcher: Triggered '50'
D/TextWatcher: Do some things with '50'
D/TextWatcher: Triggered '0'
D/TextWatcher: Triggered '5'
D/TextWatcher: Do some things with '5'
D/TextWatcher: Triggered '35'
D/TextWatcher: Do some things with '35'
D/TextWatcher: Triggered ''
D/TextWatcher: Triggered '5'
D/TextWatcher: Do some things with '5'