Android中EditText的filter过滤(kotlin版)

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class SpaceAndLineInputFilter : InputFilter {
    override fun filter(
        source: CharSequence?,//即将要输入的字符串
        start: Int,//source的start
        end: Int,//source的end
        dest: Spanned?,//输入框中原来的内容
        dstart: Int,//光标所在位置
        dend: Int//光标终止位置
    ): CharSequence {
        var result = dest.toString()
        var resultInput = source.toString()
        //不能连续空格,只限定在开始和结尾
        if ((" ") == resultInput && result.startsWith(" ") && (dstart == 0 || dstart == 1)) {
            return ""
        }
        if ((" ") == resultInput && result.endsWith(" ") && (dstart == result.length || dstart == result.length - 1)) {
            return ""
        }
        //不能连续换行,只限定在结尾
        if (("n") == resultInput && result.endsWith("n") && dstart == result.length) {
            return ""
        }
        return resultInput
    }
}

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 et_filter.filters = arrayOf(SpaceAndLineInputFilter())

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/**
 * @Anthor:Tian
 * @Date:2020/10/5
 * @Description: 限制最大字数
 */
class MaxLengthInputFilter(maxLen: Int, isChineseChar: Boolean, message: String) : InputFilter {
    private var maxCount: Int = maxLen //最长的字符数
    private var message: CharSequence? = message //要提示的信息
    private var isChinese2Char = isChineseChar //是否汉字相当于两个字符(在名字中)

    companion object {
        //Unicode编码中文的范围
         const val regEx = "[\u4e00-\u9fa5]"
        //表情的范围
         const val regEm = "[\ud83d-\ude3d]"
    }


    //过滤规则
    override fun filter(source: CharSequence?, start: Int, end: Int, dest: Spanned?, dstart: Int, dend: Int): CharSequence {
        //如果一个汉字相当于两个字符,则额外加一遍中文个数
        //当前已有的字符数
        val curCount = dest.toString().length + (if (isChinese2Char) getChineseCount(dest.toString()) else 0)
        //输入框的字符数
        val inputCount = source.toString().length + (if (isChinese2Char) getChineseCount(source.toString()) else 0)
        //用于保存可以放下的字符串
        var result: String = ""
        //超出最大字符数
        if (curCount + inputCount > maxCount) {
            var restCount = maxCount - curCount
            var index = 0
            while (restCount > 0) {
                val c = source?.get(index)
                if (isChinese2Char and isChinese(c.toString())
                        or isEmojiCharacter(c.toString())) { //当为汉字或者表情
                    if (restCount >= 2) {
                        restCount -= 2
                        result += c
                    }
                } else {
                    result += c
                    restCount -= 1
                }
                index++
            }
            //当达到最大字符数时提示
            Toast.makeText(BaseApplication.getContext(), message, Toast.LENGTH_SHORT).show()
            return result
        } else {
            return source.toString()
        }
    }

    private fun isChinese(str: String): Boolean {
        return Pattern.matches(regEx, str)
    }

    //判断是否为表情
    private fun isEmojiCharacter(str : String) : Boolean {
        return Pattern.matches(regEm, str);
    }

    // 计算中文字符的个数
    private fun getChineseCount(str: String?): Int {
        var count = 0
        val p = Pattern.compile(regEx)
        val m = p.matcher(str)
        while (m.find()) {
            for (i in 0..m.groupCount()) {
                count += 1
            }
        }
        return count
    }

}

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et_filter.filters = arrayOf(MaxLengthInputFilter(10,true,"已达到最大字数"))