EditText实时判断输入字符数

布局文件如下：

<?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:text="Please input the text:"/>
		
	<EditText android:id="@+id/ET" 
    	android:layout_width="match_parent" 
    	android:layout_height="wrap_content"/>
</LinearLayout>

实现如下：

package com.eric.demo;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
    private TextView mTextView;
    private EditText mEditText;
	
    @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 onTextChanged(CharSequence s, int start, int before, int count) {
			// TODO Auto-generated method stub
			 temp = s;
		}
		
		@Override
		public void beforeTextChanged(CharSequence s, int start, int count,
				int after) {
			// TODO Auto-generated method stub
			mTextView.setText(s);	//将输入的内容实时显示
		}
		
		@Override
		public void afterTextChanged(Editable s) {
			// TODO Auto-generated method stub
            editStart = mEditText.getSelectionStart();
            editEnd = mEditText.getSelectionEnd();
			
            mTextView.setText("您输入了" + temp.length() + "个字符");
            if (temp.length() > 10) {
                Toast.makeText(TestActivity.this,
                        "您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);
            }
		}
	};
}