onTextChanged（）行为不一致

Question

我编写了下面的代码来弄清楚onTextChanged（）方法是如何工作的：

override fun onTextChanged(string: CharSequence?, start: Int, before: Int, count: Int) {
                Log.d(TAG, "onTextChanged triggered.")
                Log.d(TAG, "string = $string")
                Log.d(TAG, "start = $start")
                Log.d(TAG, "before = $before")
                Log.d(TAG, "count = $count")
                Log.d(TAG, "____________________________________________________________")

我注意到：当我只打字时，计数非常简单：

onTextChanged triggered.
string = a
start = 0
before = 0
count = 1
____________________________________________________________
onTextChanged triggered.
string = aa
start = 0
before = 1
count = 2
____________________________________________________________
onTextChanged triggered.
string = aaa
start = 0
before = 2
count = 3
____________________________________________________________
onTextChanged triggered.
string = aaaa
start = 0
before = 3
count = 4
____________________________________________________________
onTextChanged triggered.
string = aaaaa
start = 0
before = 4
count = 5
____________________________________________________________

现在，如果我添加3个（或更多）数字，然后继续键入字母，就会发生以下情况：

onTextChanged triggered.
string = aaaaa2
start = 0
before = 5
count = 6
____________________________________________________________
onTextChanged triggered.
string = aaaaa22
start = 0
before = 6
count = 7
____________________________________________________________
onTextChanged triggered.
string = aaaaa222
start = 0
before = 7     
count = 8
____________________________________________________________
onTextChanged triggered.
string = aaaaa222
start = 0
before = **8**      <---- This is when it gets funny
count = **8**
____________________________________________________________
onTextChanged triggered.
string = aaaaa222a
start = 8
before = 0
count = 1
____________________________________________________________
onTextChanged triggered.
string = aaaaa222aa
start = 9
before = 0
count = 1
 ____________________________________________________________
onTextChanged triggered.
string = aaaaa222aaa
start = 10
before = 0
count = 1
____________________________________________________________
onTextChanged triggered.
string = aaaaa222aaaa
start = 11
before = 0
count = 1
____________________________________________________________
onTextChanged triggered.
string = aaaaa222aaaaa
start = 12
before = 0
count = 1
____________________________________________________________

对我来说，输入3位数字似乎会以某种方式改变TextWatcher的行为，使其将之后的所有内容视为Char而不是CharSequence。

对这种行为有什么解释吗？

Answer 1

虽然我无法解释为什么会出现3位数的情况，但我发现，根本无法保证报价何时会失效。检查这个这个这个

“由于其他afterTextChanged（）方法可能已经进行了其他更改并使偏移量无效，因此不会告诉您更改发生的位置。但是，如果您需要知道这里的情况，可以使用onTextChanged（CharSequence，int，int，int）中的Spannable#setSpan标记您的位置，然后从这里查找范围结束的位置。”

TextWatcher的一个可能的实现就是这个。这样，您将拥有正确的开始和结束索引。