package iflab.test;import android.app.Activity;import android.os.Bundle;import android.text.Editable;import android.text.TextWatcher;import android.widget.TextView;import android.widget.Toast;public class firstActivity extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        TextView myTextView = null; // 声明变量        myTextView = (TextView) findViewById(R.id.myTextView); // 获取对象        myTextView.addTextChangedListener(new TextWatcher() { // 添加监听器                    @Override                    public void afterTextChanged(Editable s) { // 文本改变后                        // TODO Auto-generated method stub                    }                    @Override                    public void beforeTextChanged(CharSequence s, int start,                            int count, int after) {                        // TODO Auto-generated method stub //文本改变前                    }                    @Override                    public void onTextChanged(CharSequence s, int start,                            int before, int count) {                        // TODO Auto-generated method stub //文本改变时                        Toast.makeText(                                getApplicationContext(),                                "原字符串共" + String.valueOf(before) + "个字符。"                                        + "从第" + String.valueOf(start)                                        + "个字符开始更改为字符串：" + s + "。共"                                        + String.valueOf(count) + "字符。",                                Toast.LENGTH_LONG).show(); // 显示提示信息                    }                });        myTextView.setText("1234567890"); // 重设文本内容    }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <TextView        android:id="@+id/myTextView"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="@string/hello" /></LinearLayout>