曾经做过一个项目，其中登录界面的交互令人印象深刻。交互设计师给出了一个非常作的设计，要求做出包含根据情况可变色的下划线，左侧有可变图标，右侧有可变删除标志的输入框，如图

记录制作过程：

第一版本

public class LineEditText extends EditText {

private Paint mPaint;
private int color;
public static final int STATUS_FOCUSED = 1;
public static final int STATUS_UNFOCUSED = 2;
public static final int STATUS_ERROR = 3;
private int status = 2;
private Drawable del_btn;
private Drawable del_btn_down;
private int focusedDrawableId = R.drawable.user_select;// 默认的
private int unfocusedDrawableId = R.drawable.user;
private int errorDrawableId = R.drawable.user_error;
Drawable left = null;
private Context mContext;
public LineEditText(Context context) {

 super(context);
 mContext = context;
 init();
}
public LineEditText(Context context, AttributeSet attrs) {

 super(context, attrs);
 mContext = context;
 init();

}
public LineEditText(Context context, AttributeSet attrs, int defStryle) {

 super(context, attrs, defStryle);
 mContext = context;
 TypedArray a = context.obtainStyledAttributes(attrs,
   R.styleable.lineEdittext, defStryle, 0);
 focusedDrawableId = a.getResourceId(
   R.styleable.lineEdittext_drawableFocus, R.drawable.user_select);
 unfocusedDrawableId = a.getResourceId(
   R.styleable.lineEdittext_drawableUnFocus, R.drawable.user);
 errorDrawableId = a.getResourceId(
   R.styleable.lineEdittext_drawableError, R.drawable.user_error);
 a.recycle();
 init();
}
/** * 2014/7/31 * * @author Aimee.ZHANG */

private void init() {
 mPaint = new Paint();
 // mPaint.setStyle(Paint.Style.FILL);
 mPaint.setStrokeWidth(3.0f);
 color = Color.parseColor("#bfbfbf");
 setStatus(status);
 del_btn = mContext.getResources().getDrawable(R.drawable.del_but_bg);
 del_btn_down = mContext.getResources().getDrawable(R.drawable.del_but_bg_down);
 addTextChangedListener(new TextWatcher() {

  @Override
  public void onTextChanged(CharSequence arg0, int arg1, int arg2,
    int arg3) {
  }

  @Override
  public void beforeTextChanged(CharSequence arg0, int arg1,
    int arg2, int arg3) {
  }

  @Override
  public void afterTextChanged(Editable arg0) {
   setDrawable();
  }
 });
 setDrawable();
}

@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 mPaint.setColor(color);
 canvas.drawLine(0, this.getHeight() - 1, this.getWidth(),
   this.getHeight() - 1, mPaint);
}

// 删除图片
private void setDrawable() {
 if (length() < 1) {
  setCompoundDrawablesWithIntrinsicBounds(left, null, del_btn, null);
 } else {
  setCompoundDrawablesWithIntrinsicBounds(left, null, del_btn_down,null);
 }
}

// 处理删除事件
@Override
public boolean onTouchEvent(MotionEvent event) {
 if (del_btn_down != null && event.getAction() == MotionEvent.ACTION_UP) {
  int eventX = (int) event.getRawX();
  int eventY = (int) event.getRawY();
  Log.e("eventXY", "eventX = " + eventX + "; eventY = " + eventY); 
  Rect rect = new Rect();
  getGlobalVisibleRect(rect);
  rect.left = rect.right - 50;
  if (rect.contains(eventX, eventY))
  setText("");
 }
 return super.onTouchEvent(event);
}

public void setStatus(int status) {
 this.status = status;


 if (status == STATUS_ERROR) {
  try {
   left = getResources().getDrawable(errorDrawableId);
  } catch (NotFoundException e) {
   e.printStackTrace();
  }
  setColor(Color.parseColor("#f57272"));
 } else if (status == STATUS_FOCUSED) {
  try {
   left = getResources().getDrawable(focusedDrawableId);
  } catch (NotFoundException e) {
   e.printStackTrace();
  }
  setColor(Color.parseColor("#5e99f3"));
 } else {
  try {
   left = getResources().getDrawable(unfocusedDrawableId);
  } catch (NotFoundException e) {
   e.printStackTrace();
  }
  setColor(Color.parseColor("#bfbfbf"));
 }
 if (left != null) {
// left.setBounds(0, 0, 30, 40);

// this.setCompoundDrawables(left, null, null, null);

  setCompoundDrawablesWithIntrinsicBounds(left,null,del_btn,null);
 }
 postInvalidate();
}

public void setLeftDrawable(int focusedDrawableId, int unfocusedDrawableId,
  int errorDrawableId) {
 this.focusedDrawableId = focusedDrawableId;
 this.unfocusedDrawableId = unfocusedDrawableId;
 this.errorDrawableId = errorDrawableId;
 setStatus(status);
}

@Override
protected void onFocusChanged(boolean focused, int direction,
  Rect previouslyFocusedRect) {
 super.onFocusChanged(focused, direction, previouslyFocusedRect);
 if (focused) {
  setStatus(STATUS_FOCUSED);
 } else {
  setStatus(STATUS_UNFOCUSED);
 }
}

@Override
protected void finalize() throws Throwable {
 super.finalize();
};

public void setColor(int color) {
 this.color = color;
 this.setTextColor(color);
 invalidate();
}
}

效果图：

代码解释：

变量名 STATUS_FOCUSED,STATUS_UNFOCUSED,STATUS_ERROR 标示了三种状态，选中状况为蓝色，未选中状态为灰色，错误状态为红色。 focusedDrawableId unfocusedDrawableId errorDrawableId 存放三种状态的图片，放置于最左侧。

canvas.drawLine(0, this.getHeight() - 1, this.getWidth(),this.getHeight() - 1, mPaint); //画editText 最下方的线 setCompoundDrawablesWithIntrinsicBounds(left, null, del_btn, null); //放置左边的和右边的图片（左，上，右，下） 相当于 android:drawableLeft="" android:drawableRight=""

1、onTouchEvent 当手机点击时，第一个先执行的函数，当点击右侧删除图标是清空 edittext
2、setStatus 根据不同的状态，左边的图片不一样
存在的问题： 这版本虽然基本功能已经实现，但是不符合需求，设计中要求文本框中无文字时，右侧删除按钮不显示，不点击删除按钮，删除按钮要保持灰色，点击时才可以变蓝色。

因此有了第二个版本

public class LineEditText extends EditText implements TextWatcher, <br /> OnFocusChangeListener{

private Paint mPaint;
private int color;
public static final int STATUS_FOCUSED = 1;
public static final int STATUS_UNFOCUSED = 2;
public static final int STATUS_ERROR = 3;
private int status = 2;
private Drawable del_btn;
private Drawable del_btn_down;
private int focusedDrawableId = R.drawable.user_select;// 默认的
private int unfocusedDrawableId = R.drawable.user;
private int errorDrawableId = R.drawable.user_error;
Drawable left = null;
private Context mContext;
/** 
 * 是否获取焦点，默认没有焦点 
 */ 
private boolean hasFocus = false; 
/** 
 * 手指抬起时的X坐标 
 */ 
private int xUp = 0; 

public LineEditText(Context context) {
 super(context);
 mContext = context;
 init();
}

public LineEditText(Context context, AttributeSet attrs) {
 super(context, attrs);
 mContext = context;
 init();

}

public LineEditText(Context context, AttributeSet attrs, int defStryle) {
 super(context, attrs, defStryle);
 mContext = context;
 TypedArray a = context.obtainStyledAttributes(attrs,
   R.styleable.lineEdittext, defStryle, 0);
 focusedDrawableId = a.getResourceId(
   R.styleable.lineEdittext_drawableFocus, R.drawable.user_select);
 unfocusedDrawableId = a.getResourceId(
   R.styleable.lineEdittext_drawableUnFocus, R.drawable.user);
 errorDrawableId = a.getResourceId(
   R.styleable.lineEdittext_drawableError, R.drawable.user_error);
 a.recycle();
 init();
}

/**
 * 2014/7/31
 * 
 * @author Aimee.ZHANG
 */
private void init() {
 mPaint = new Paint();
 // mPaint.setStyle(Paint.Style.FILL);
 mPaint.setStrokeWidth(3.0f);
 color = Color.parseColor("#bfbfbf");
 setStatus(status);
 del_btn = mContext.getResources().getDrawable(R.drawable.del_but_bg);
 del_btn_down = mContext.getResources().getDrawable(R.drawable.del_but_bg_down);
 addListeners();
 setCompoundDrawablesWithIntrinsicBounds(left, null, null, null);
}

@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 mPaint.setColor(color);
 canvas.drawLine(0, this.getHeight() - 1, this.getWidth(),
   this.getHeight() - 1, mPaint);
}

// 删除图片
// private void setDrawable() { // if (length() < 1) { // setCompoundDrawablesWithIntrinsicBounds(left, null, null, null); // } else { // setCompoundDrawablesWithIntrinsicBounds(left, null, del_btn,null); // } // }

// 处理删除事件
@Override
public boolean onTouchEvent(MotionEvent event) {
 if (del_btn != null && event.getAction() == MotionEvent.ACTION_UP) {
  // 获取点击时手指抬起的X坐标 
  xUp = (int) event.getX(); 
  Log.e("xUp", xUp+""); 
  /*Rect rect = new Rect();
  getGlobalVisibleRect(rect);
  rect.left = rect.right - 50;*/
   // 当点击的坐标到当前输入框右侧的距离小于等于 getCompoundPaddingRight() 的距离时，则认为是点击了删除图标 
  if ((getWidth() - xUp) <= getCompoundPaddingRight()) { 
   if (!TextUtils.isEmpty(getText().toString())) {
    setText(""); 
   } 
  }
 }else if(del_btn != null && event.getAction() == MotionEvent.ACTION_DOWN && getText().length()!=0){
  setCompoundDrawablesWithIntrinsicBounds(left,null,del_btn_down,null);
 }else if(getText().length()!=0){
  setCompoundDrawablesWithIntrinsicBounds(left,null,del_btn,null);
 }
 return super.onTouchEvent(event);
}

public void setStatus(int status) {
 this.status = status;


 if (status == STATUS_ERROR) {
  try {
   left = getResources().getDrawable(errorDrawableId);
  } catch (NotFoundException e) {
   e.printStackTrace();
  }
  setColor(Color.parseColor("#f57272"));
 } else if (status == STATUS_FOCUSED) {
  try {
   left = getResources().getDrawable(focusedDrawableId);
  } catch (NotFoundException e) {
   e.printStackTrace();
  }
  setColor(Color.parseColor("#5e99f3"));
 } else {
  try {
   left = getResources().getDrawable(unfocusedDrawableId);
  } catch (NotFoundException e) {
   e.printStackTrace();
  }
  setColor(Color.parseColor("#bfbfbf"));
 }
 if (left != null) {
// left.setBounds(0, 0, 30, 40); // this.setCompoundDrawables(left, null, null, null); setCompoundDrawablesWithIntrinsicBounds(left,null,null,null); } postInvalidate(); }

public void setLeftDrawable(int focusedDrawableId, int unfocusedDrawableId,
  int errorDrawableId) {
 this.focusedDrawableId = focusedDrawableId;
 this.unfocusedDrawableId = unfocusedDrawableId;
 this.errorDrawableId = errorDrawableId;
 setStatus(status);
}
 private void addListeners() { 
  try { 
   setOnFocusChangeListener(this); 
   addTextChangedListener(this); 
  } catch (Exception e) { 
   e.printStackTrace(); 
  } 
 } 
@Override
protected void onFocusChanged(boolean focused, int direction,
  Rect previouslyFocusedRect) {
 super.onFocusChanged(focused, direction, previouslyFocusedRect);
 this.hasFocus=focused;
 if (focused) {
  setStatus(STATUS_FOCUSED);
 } else {
  setStatus(STATUS_UNFOCUSED);
  setCompoundDrawablesWithIntrinsicBounds(left,null,null,null);
 }
}

@Override
protected void finalize() throws Throwable {
 super.finalize();
};

public void setColor(int color) {
 this.color = color;
 this.setTextColor(color);
 invalidate();
}



@Override
public void afterTextChanged(Editable arg0) {
 // TODO Auto-generated method stub
 postInvalidate();
}

@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
  int arg3) {
 // TODO Auto-generated method stub
  if (TextUtils.isEmpty(arg0)) { 
   // 如果为空，则不显示删除图标 
   setCompoundDrawablesWithIntrinsicBounds(left, null, null, null); 
  } else { 
   // 如果非空，则要显示删除图标 
   setCompoundDrawablesWithIntrinsicBounds(left, null, del_btn, null); 
  } 
}
@Override
 public void onTextChanged(CharSequence s, int start, int before, int after) { 
 if (hasFocus) { 
  if (TextUtils.isEmpty(s)) { 
   // 如果为空，则不显示删除图标 
   setCompoundDrawablesWithIntrinsicBounds(left, null, null, null); 
  } else { 
   // 如果非空，则要显示删除图标 
   setCompoundDrawablesWithIntrinsicBounds(left, null, del_btn, null); 
  } 
 } 
}

@Override
public void onFocusChange(View arg0, boolean arg1) {
 // TODO Auto-generated method stub
 try { 
  this.hasFocus = arg1; 
 } catch (Exception e) { 
  e.printStackTrace(); 
 } 
} 
}

比较关键的方法是：onTouchEvent

当进入界面，点击输入框，要判断输入框中是否已有文字，如果有则显示灰色的删除按钮，如果没有则不显示，如果点击了删除按钮，删除按钮变蓝色

存在的问题： 这个版本依旧存在问题，就是输入长度超过输入框，所画的线不会延伸，如图

解决方法：

@Override

protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 mPaint.setColor(color);
 int x=this.getScrollX();
 int w=this.getMeasuredWidth();
 canvas.drawLine(0, this.getHeight() - 1, w+x,
   this.getHeight() - 1, mPaint);
}

w：获取控件长度

X：延伸后的长度

最终效果：

以上就是Android实现自定义的EditText下划线的方法，希望对大家的学习有所帮助。