TextWatcher
16lz
2021-01-26
对于一些需求,如非法字符限制(例如不允许输入#号,如果输入了#给出错误提示),做成动态判断更方便一些,而且容易扩展;
在Android里使用TextWatcher接口可以很方便的对EditText进行监听;TextWatcher中有3个函数需要重载:
public void beforeTextChanged(CharSequence s, int start, int count, int after); public void onTextChanged(CharSequence s, int start, int before, int count); public void afterTextChanged(Editable s);
从函数名就可以知道其意思,每当敲击键盘编辑框的文字改变时,上面的三个函数都会执行,beforeTextChanged可以给出变化之前的内容,onTextChanged和afterTextChanged给出追加上新的字符之后的文本;
class MyWatcher implements TextWatcher{ /**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. * 在s中,从start处开始的count个字符将要被长度为after的文本替代 * s 为变化前的内容; * start 为开始变化位置的索引,从0开始计数; * count 为将要发生变化的字符数 * after 为用来替换旧文本的长度,比如s由1变为12,after为1,由12变为1,after为0; */@Overridepublic void beforeTextChanged(CharSequence s, int start, int count,int after) {// TODO Auto-generated method stubLog.i("test1", "before:s,"+s+",start,"+start+",count,"+count+",after,"+after);} /** * 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 * 在s中,从start处开始的count个字符刚刚替换了原来长度为before的文本 * s 为变化后的内容; * start 为开始变化位置的索引,从0开始计数; * before 为被取代的老文本的长度,比如s由1变为12,before为0,由12变为1,before为1; * count 为将要发生变化的字符数 */@Overridepublic void onTextChanged(CharSequence s, int start, int before,int count) {// TODO Auto-generated method stubLog.i("test1", "ing:s,"+s+",start,"+start+",before,"+before+",count,"+count);} /** * This method is called to notify you that, somewhere within s, the text has been changed. */@Overridepublic void afterTextChanged(Editable s) {// TODO Auto-generated method stubLog.i("test1", "after,s,"+s);}}
注册监听:
EditText mEditor = (EditText)findViewById(R.id.editor_input);mEditor.addTextChangedListener(mTextWatcher);
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