布局文件main.xml:

<?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" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="5dip"
        android:layout_marginLeft="5dip"
        android:layout_marginRight="5dip"
        android:layout_marginTop="5dip"
        android:gravity="center_vertical"
        android:orientation="horizontal" >

        <EditText
            android:id="@+id/searchEditText"
            android:layout_width="fill_parent"
            android:layout_height="45sp"
            android:layout_weight="1"
            android:hint="搜索"
            android:imeOptions="actionDone"
            android:singleLine="true"
            android:textSize="16sp" />

        <Button
            android:id="@+id/button_clear"
            android:layout_width="40sp"
            android:layout_height="40sp"
            android:layout_marginRight="8dip"
            android:background="@drawable/icon_clear"
            android:visibility="invisible" />
    </LinearLayout>

</LinearLayout>

.java文件如下：

package org.lxh.demo;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class Hello extends Activity {

  EditText searchEditText;
  Button clearButton;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    searchEditText = (EditText) findViewById(R.id.searchEditText);
    clearButton = (Button) findViewById(R.id.button_clear);

    searchEditText.addTextChangedListener(mTextWatcher);
    clearButton.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
        searchEditText.setText("");
      }
    });
  }

  TextWatcher mTextWatcher = new TextWatcher() {
    public void onTextChanged(CharSequence s, int start, int before,
        int count) {
      // TODO Auto-generated method stub
    }

    public void beforeTextChanged(CharSequence s, int start, int count,
        int after) {
      // TODO Auto-generated method stub
    }

    public void afterTextChanged(Editable s) {
      if (searchEditText.getText().toString() != null
          && !searchEditText.getText().toString().equals("")) {
        clearButton.setVisibility(View.VISIBLE);
      } else {
        clearButton.setVisibility(View.INVISIBLE);
      }
    }
  };
}

运行实例如下：

TextWatcher实现一键清空EditText_xml

界面丑的一米，功能是实现了。