Android addTextChangedListener方法介绍

最新推荐文章于 2021-05-26 18:41:09 发布

茈男子淡漠

最新推荐文章于 2021-05-26 18:41:09 发布

阅读量2w

点赞数 6

CC 4.0 BY-SA版权

分类专栏： Android开发文章标签： addTextChangedListener TextWatcher beforeTextChanged onTextChanged afterTextChanged

本文链接：https://blog.youkuaiyun.com/w1070216393/article/details/83214646

Android开发专栏收录该内容

23 篇文章

订阅专栏

本文详细解析了在Android开发中，如何使用TextWatcher监听EditText文本变化，包括beforeTextChanged、onTextChanged和afterTextChanged三个关键方法的作用及其实现细节。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

文本变化监听器addTextChangedListener中TextWatcher方法三个方法意义

EditText editText = findViewById(R.id.et_test);
editText.addTextChangedListener(new TextWatcher() {
    // charSequence为在你按键之前显示的字符串  start为新字符串与charSequence开始出现差异的下标  count表示原字符串的count个字符  after表示将会被after个字符替换
    @Override
    public void beforeTextChanged(CharSequence charSequence, int start, int count, int after) {
        Log.i(TAG, "beforeTextChanged: charSequence=" + charSequence + ", start=" + start + ", count=" + count + ", after=" + after);
    }

    // 按键之前字符串的start位置的before个字符已经被count个字符替换形成新字符串charSequence
    @Override
    public void onTextChanged(CharSequence charSequence, int start, int before, int count) {
        Log.i(TAG, "onTextChanged: charSequence=" + charSequence + ", start=" + start + ", before=" + before + ", count=" + count);
    }

    // afterTextChanged中 editable为EditText显示的内容
    @Override
    public void afterTextChanged(Editable editable) {
        Log.i(TAG, "afterTextChanged: editable=" + editable);
    }
});

通过上面注释已经可以理解了,此处附上测试log

// 输入a
com.nan.myapplication I/breeze: beforeTextChanged: s=, start=0, count=0, after=1
com.nan.myapplication I/breeze: onTextChanged: s=a, start=0, before=0, count=1
// 继续输入b
com.nan.myapplication I/breeze: beforeTextChanged: s=a, start=1, count=0, after=1
com.nan.myapplication I/breeze: onTextChanged: s=ab, start=1, before=0, count=1
// 继续输入GG
com.nan.myapplication I/breeze: beforeTextChanged: s=ab, start=2, count=0, after=2
com.nan.myapplication I/breeze: onTextChanged: s=abGG, start=2, before=0, count=2
// 删除最后一个G
com.nan.myapplication I/breeze: beforeTextChanged: s=abGG, start=3, count=1, after=0
com.nan.myapplication I/breeze: onTextChanged: s=abG, start=3, before=1, count=0
// 将bG选中替换为嘿嘿
com.nan.myapplication I/breeze: beforeTextChanged: s=abG, start=1, count=2, after=2
com.nan.myapplication I/breeze: onTextChanged: s=a嘿嘿, start=1, before=2, count=2

此处省略了afterTextChanged中的log,这个方法没有任何疑问,能少一句log就少一句,清爽!