TextWatcher实现一键清空EditText

布局文件main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://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><?xml version="1.0" encoding="utf-8"