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

 

  <?
  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);
            }
        }
    };
}