Android应用中怎么实现一个带清除功能的输入框

package com.example.clearedittext; 
 
import android.content.Context; 
import android.graphics.drawable.Drawable; 
import android.text.Editable; 
import android.text.TextWatcher; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.View.OnFocusChangeListener; 
import android.view.animation.Animation; 
import android.view.animation.CycleInterpolator; 
import android.view.animation.TranslateAnimation; 
import android.widget.EditText; 
 
public class ClearEditText extends EditText implements  
    OnFocusChangeListener, TextWatcher {  
  /** 
   * 删除按钮的引用 
   */ 
  private Drawable mClearDrawable;  
  /** 
   * 控件是否有焦点 
   */ 
  private boolean hasFoucs; 
  
  public ClearEditText(Context context) {  
    this(context, null);  
  }  
  
  public ClearEditText(Context context, AttributeSet attrs) {  
    //这里构造方法也很重要，不加这个很多属性不能再XML里面定义 
    this(context, attrs, android.R.attr.editTextStyle);  
  }  
   
  public ClearEditText(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
    init(); 
  } 
   
   
  private void init() {  
    //获取EditText的DrawableRight,假如没有设置我们就使用默认的图片 
    mClearDrawable = getCompoundDrawables()[2];  
    if (mClearDrawable == null) {  
//     throw new NullPointerException("You can add drawableRight attribute in XML"); 
      mClearDrawable = getResources().getDrawable(R.drawable.delete_selector);  
    }  
     
    mClearDrawable.setBounds(0, 0, mClearDrawable.getIntrinsicWidth(), mClearDrawable.getIntrinsicHeight());  
    //默认设置隐藏图标 
    setClearIconVisible(false);  
    //设置焦点改变的监听 
    setOnFocusChangeListener(this);  
    //设置输入框里面内容发生改变的监听 
    addTextChangedListener(this);  
  }  
  
  
  /** 
   * 因为我们不能直接给EditText设置点击事件，所以我们用记住我们按下的位置来模拟点击事件 
   * 当我们按下的位置 在 EditText的宽度 - 图标到控件右边的间距 - 图标的宽度 和 
   * EditText的宽度 - 图标到控件右边的间距之间我们就算点击了图标，竖直方向就没有考虑 
   */ 
  @Override  
  public boolean onTouchEvent(MotionEvent event) { 
    if (event.getAction() == MotionEvent.ACTION_UP) { 
      if (getCompoundDrawables()[2] != null) { 
 
        boolean touchable = event.getX() > (getWidth() - getTotalPaddingRight()) 
            && (event.getX() < ((getWidth() - getPaddingRight()))); 
         
        if (touchable) { 
          this.setText(""); 
        } 
      } 
    } 
 
    return super.onTouchEvent(event); 
  } 
  
  /** 
   * 当ClearEditText焦点发生变化的时候，判断里面字符串长度设置清除图标的显示与隐藏 
   */ 
  @Override  
  public void onFocusChange(View v, boolean hasFocus) {  
    this.hasFoucs = hasFocus; 
    if (hasFocus) {  
      setClearIconVisible(getText().length() > 0);  
    } else {  
      setClearIconVisible(false);  
    }  
  }  
  
  
  /** 
   * 设置清除图标的显示与隐藏，调用setCompoundDrawables为EditText绘制上去 
   * @param visible 
   */ 
  protected void setClearIconVisible(boolean visible) {  
    Drawable right = visible ? mClearDrawable : null;  
    setCompoundDrawables(getCompoundDrawables()[0],  
        getCompoundDrawables()[1], right, getCompoundDrawables()[3]);  
  }  
    
   
  /** 
   * 当输入框里面内容发生变化的时候回调的方法 
   */ 
  @Override  
  public void onTextChanged(CharSequence s, int start, int count,  
      int after) {  
        if(hasFoucs){ 
          setClearIconVisible(s.length() > 0); 
        } 
  }  
  
  @Override  
  public void beforeTextChanged(CharSequence s, int start, int count,  
      int after) {  
      
  }  
  
  @Override  
  public void afterTextChanged(Editable s) {  
      
  }  
   
   
  /** 
   * 设置晃动动画 
   */ 
  public void setShakeAnimation(){ 
    this.setAnimation(shakeAnimation(5)); 
  } 
   
   
  /** 
   * 晃动动画 
   * @param counts 1秒钟晃动多少下 
   * @return 
   */ 
  public static Animation shakeAnimation(int counts){ 
    Animation translateAnimation = new TranslateAnimation(0, 10, 0, 0); 
    translateAnimation.setInterpolator(new CycleInterpolator(counts)); 
    translateAnimation.setDuration(1000); 
    return translateAnimation; 
  } 
  
  
}