Question

我正在阅读Android编程中的 TextWatcher 。我无法理解afterTextChanged和onTextChanged之间的区别。

虽然我提到过 Differences between TextWatcher 's onTextChanged, beforeTextChanged and afterTextChanged但是当我需要使用onTextChanged而不是afterTextChanged时，我仍然无法想到这种情况。

Answer 1

我在Android Dev Portal上找到了对此的解释

http://developer.android.com/reference/android/text/TextWatcher.html

**abstract void afterTextChanged(Editable s)**
This method is called to notify you that, somewhere within s, the text has been changed.

**abstract void beforeTextChanged(CharSequence s, int start, int count, int after)**
This method is called to notify you that, within s, the count characters beginning at start are about to be replaced by new text with length after.

**abstract void onTextChanged(CharSequence s, int start, int before, int count)**
This method is called to notify you that, within s, the count characters beginning at start have just replaced old text that had length before.

所以，两者之间的区别是：

我可以使用afterTextChanged 更改我的文字，而onTextChanged不允许我这样做
onTextChanged给出了改变位置的偏移，而afterTextChanged没有

Answer 2

在评论中添加一些内容给Pratik Dasa的回答以及与@SimpleGuy的讨论，因为我没有足够的声誉来发表评论。

这三种方法也由else if触发。这将使长度为16（在这种情况下），因此EditText.setText("your string here")不总是count。

请注意，三种方法的参数列表不同：

这就是abstract void afterTextChanged(Editable s) abstract void beforeTextChanged(CharSequence s, int start, int count, int after) abstract void onTextChanged(CharSequence s, int start, int before, int count)和afterTextChanged之间的差异：参数。

请同时查看此主题中接受的答案：Android TextWatcher.afterTextChanged vs TextWatcher.onTextChanged

Answer 3

这里有解释：

onTextChanged：这意味着当你开始打字时，就像你想写“体育”一样，这将调用每个角色，就像你按下“s”然后再按“p”然后“o”时调用等......

afterTextChanged：这会在你停止输入时调用，它会在你完全写下“sport”之后调用，这是主要的差异。

YOUR_EDIT_TEXT.addTextChangedListener(new TextWatcher() {

                    @Override
                    public void onTextChanged(CharSequence s, int start, int before, int count) {

                    //Your query to fetch Data
                    }

                    @Override
                    public void beforeTextChanged(CharSequence s, int start, int count, int after) {

                    }

                    @Override
                    public void afterTextChanged(Editable s) {
                        if (s.length() > 0) {

                            //Your query to fetch Data
                        }
                    }
                });

onTextChanged vs Android中的afterTextChanged - 需要实时示例

3 个答案: