addTextChangedListener

btn1 = (Button)findViewById(R.id.btn1);
txt1 = (TextView)findViewById(R.id.txt1);
etxt1 = (EditText)findViewById(R.id.etxt1);

btn1.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
txt1.setText(etxt1.getText());
}
});

//添加监听器

txt1.addTextChangedListener(new TextWatcher() {
public void afterTextChanged(Editable arg0) {
String str = arg0.toString();
String strTo = "";


if (str.equals("123"))
strTo = "haha";
else if (str.equals("456"))
strTo = "hihi";
else
strTo = str;

//*注意：如果是监听当前控件就用bUseFlag变量控制，否则系统多重监控导致无限修改最后系统崩溃
if (bUseFlag == false)
{
bUseFlag = true;
arg0.replace(0, arg0.length(),strTo);
bUseFlag = false;
}
}


//两个override是不用的
@Override
public void beforeTextChanged(CharSequence arg0, int arg1,
int arg2, int arg3) {
}


@Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
}
});