Android TextWatcher监控EditText中的输入内容并限制其输入字符个数

color=blue]    布局中EditText在android布局中经常用到，对EditText中输入的内容也经常需要进行限制，我们可以通过TextWatcher去观察输入框中输入的内容，作个笔记。

主布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="fill_parent"    android:layout_height="fill_parent">
<TextView  android:id="@+id/tv"    android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:textColor="@android:color/white"     android:ellipsize="marquee"    
android:focusable="true"     android:marqueeRepeatLimit="marquee_forever"     android:focusableInTouchMode="true"     android:scrollHorizontally="true"       
android:text="Please input the text:"/>
<EditText android:id="@+id/ET"     android:layout_width="match_parent"     android:layout_height="wrap_content"   
android:inputType="number"/>
</LinearLayout>

java代码：
package com.android.text;
import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class TextWatcherDemo extends Activity {   
private TextView mTextView;   
private EditText mEditText;   
/** Called when the activity is first created. */   
@Override   
public void onCreate(Bundle savedInstanceState)
{       
  super.onCreate(savedInstanceState);       
  setContentView(R.layout.main);       
  mTextView = (TextView)findViewById(R.id.tv);       
  mEditText = (EditText)findViewById(R.id.ET);             mEditText.addTextChangedListener(mTextWatcher);   
}   

TextWatcher mTextWatcher = new TextWatcher()
{       
  private CharSequence temp;       
  private int editStart ;       
  private int editEnd ;       
  @Override       
  public void beforeTextChanged(CharSequence s, int arg1, int arg2, int arg3) {
            temp = s;
}              

@Override       
public void onTextChanged(CharSequence s, int arg1, int arg2, int arg3) {          
     mTextView.setText(s);       
}              

@Override       
public void afterTextChanged(Editable s) {           
  editStart = mEditText.getSelectionStart();           
  editEnd = mEditText.getSelectionEnd();           
  if (temp.length() > 10) {               
  Toast.makeText(TextWatcherDemo.this,"你输入的字数已经超过了限制！",    Toast.LENGTH_SHORT).show();               
  s.delete(editStart-1, editEnd);               
  int tempSelection = editStart;               
  mEditText.setText(s);               
  mEditText.setSelection(tempSelection);           
}       
}   
};
}[/color]