public abstract class ErrorTextWatcher implements TextWatcher {

  private TextInputLayout mTextInputLayout;
  private String errorMessage;

  protected ErrorTextWatcher(@NonNull final TextInputLayout textInputLayout, @NonNull final String errorMessage) {
    this.mTextInputLayout = textInputLayout;
    this.errorMessage = errorMessage;
  }

public final boolean hasError() {
  return mTextInputLayout.getError() != null;
}

protected String getEditTextValue() {
  return mTextInputLayout.getEditText().getText().toString();
}

public abstract boolean validate();

protected void showError(final boolean error) {
  if (!error) {
    mTextInputLayout.setError(null);
    mTextInputLayout.setErrorEnabled(false);
  } else {
    if (!errorMessage.equals(mTextInputLayout.getError())) {
      // Stop the flickering that happens when setting the same error message multiple times
      mTextInputLayout.setError(errorMessage);
    }
    mTextInputLayout.requestFocus();
  }
}

public class MinimumLengthTextWatcher extends ErrorTextWatcher {

  private final int mMinLength;
  private boolean mReachedMinLength = false;

  public MinimumLengthTextWatcher(final TextInputLayout textInputLayout, final int minLength) {
    this(textInputLayout, minLength, R.string.error_too_few_characters);
  }

  public MinimumLengthTextWatcher(final TextInputLayout textInputLayout, final int minLength, @StringRes final int errorMessage) {
    super(textInputLayout, String.format(textInputLayout.getContext().getString(errorMessage), minLength));
    this.mMinLength = minLength;
  }

@Override
public void onTextChanged(final CharSequence text…) {
  if (mReachedMinLength) {
    validate();
  }
  if (text.length() >= mMinLength) {
    mReachedMinLength = true;
  }
}

@Override
public boolean validate() {
  mReachedMinLength = true; // This may not be true but now we want to force the error to be shown
  showError(getEditTextValue().length() < mMinLength);
  return !hasError();
}

mPasswordView = (TextInputLayout) findViewById(R.id.password_text_input_layout);
mValidPasswordTextWatcher = new MinimumLengthTextWatcher(mPasswordView, getResources().getInteger(R.integer.min_length_password));
mPasswordView.getEditText().addTextChangedListener(mValidPasswordTextWatcher);

public class ValidEmailTextWatcher extends ErrorTextWatcher {

  private final EmailAddressValidator mValidator = new EmailAddressValidator();
  private boolean mValidated = false;


  public ValidEmailTextWatcher(@NonNull final TextInputLayout textInputLayout) {
    this(textInputLayout, R.string.error_invalid_email);
  }

  public ValidEmailTextWatcher(@NonNull final TextInputLayout textInputLayout, @StringRes final int errorMessage) {
    super(textInputLayout, textInputLayout.getContext().getString(errorMessage));
  }

  @Override
  public void onTextChanged(…) {
    if (mValidated) {
      validate();
    }
  }

  @Override
  public boolean validate() {
    showError(!mValidator.isValid(getEditTextValue()));
    mValidated = true;
    return !hasError();
  }

mEmailView = (TextInputLayout) findViewById(R.id.email_text_input_layout);
mValidEmailTextWatcher = new ValidEmailTextWatcher(mEmailView);
mEmailView.getEditText().addTextChangedListener(mValidEmailTextWatcher);

private boolean allFieldsAreValid() {
  /**
   * Since the text watchers automatically focus on erroneous fields, do them in reverse order so that the first one in the form gets focus
   * &= may not be the easiest construct to decipher but it's a lot more concise. It just means that once it's false it doesn't get set to true
   */
  boolean isValid = mValidPasswordTextWatcher.validate();
  isValid &= mValidEmailTextWatcher.validate();
  return isValid;
}

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 {  
  /** 
   * 刪除按鈕的引用 
   */ 
  private Drawable mClearDrawable;  
  /** 
   * 控件是否有焦點(diǎn) 
   */ 
  private boolean hasFoucs; 
  
  public ClearEditText(Context context) {  
    this(context, null);  
  }  
  
  public ClearEditText(Context context, AttributeSet attrs) {  
    //這里構(gòu)造方法也很重要，不加這個(gè)很多屬性不能再XML里面定義 
    this(context, attrs, android.R.attr.editTextStyle);  
  }  
   
  public ClearEditText(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
    init(); 
  } 
   
   
  private void init() {  
    //獲取EditText的DrawableRight,假如沒(méi)有設(shè)置我們就使用默認(rèn)的圖片 
    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());  
    //默認(rèn)設(shè)置隱藏圖標(biāo) 
    setClearIconVisible(false);  
    //設(shè)置焦點(diǎn)改變的監(jiān)聽 
    setOnFocusChangeListener(this);  
    //設(shè)置輸入框里面內(nèi)容發(fā)生改變的監(jiān)聽 
    addTextChangedListener(this);  
  }  
  
  
  /** 
   * 因?yàn)槲覀儾荒苤苯咏oEditText設(shè)置點(diǎn)擊事件，所以我們用記住我們按下的位置來(lái)模擬點(diǎn)擊事件 
   * 當(dāng)我們按下的位置 在 EditText的寬度 - 圖標(biāo)到控件右邊的間距 - 圖標(biāo)的寬度 和 
   * EditText的寬度 - 圖標(biāo)到控件右邊的間距之間我們就算點(diǎn)擊了圖標(biāo)，豎直方向就沒(méi)有考慮 
   */ 
  @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); 
  } 
  
  /** 
   * 當(dāng)ClearEditText焦點(diǎn)發(fā)生變化的時(shí)候，判斷里面字符串長(zhǎng)度設(shè)置清除圖標(biāo)的顯示與隱藏 
   */ 
  @Override  
  public void onFocusChange(View v, boolean hasFocus) {  
    this.hasFoucs = hasFocus; 
    if (hasFocus) {  
      setClearIconVisible(getText().length() > 0);  
    } else {  
      setClearIconVisible(false);  
    }  
  }  
  
  
  /** 
   * 設(shè)置清除圖標(biāo)的顯示與隱藏，調(diào)用setCompoundDrawables為EditText繪制上去 
   * @param visible 
   */ 
  protected void setClearIconVisible(boolean visible) {  
    Drawable right = visible ? mClearDrawable : null;  
    setCompoundDrawables(getCompoundDrawables()[0],  
        getCompoundDrawables()[1], right, getCompoundDrawables()[3]);  
  }  
    
   
  /** 
   * 當(dāng)輸入框里面內(nèi)容發(fā)生變化的時(shí)候回調(diào)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) {  
      
  }  
   
   
  /** 
   * 設(shè)置晃動(dòng)動(dòng)畫 
   */ 
  public void setShakeAnimation(){ 
    this.setAnimation(shakeAnimation(5)); 
  } 
   
   
  /** 
   * 晃動(dòng)動(dòng)畫 
   * @param counts 1秒鐘晃動(dòng)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; 
  } 
  
  
} 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  android:background="#95CAE4"> 
 
 
  <com.example.clearedittext.ClearEditText 
    android:id="@+id/username" 
    android:layout_marginTop="60dp" 
    android:layout_width="fill_parent" 
    android:background="@drawable/login_edittext_bg"  
    android:drawableLeft="@drawable/icon_user" 
    android:layout_marginLeft="10dip" 
    android:layout_marginRight="10dip" 
    android:singleLine="true" 
    android:drawableRight="@drawable/delete_selector" 
    android:hint="輸入用戶名" 
    android:layout_height="wrap_content" > 
 
  </com.example.clearedittext.ClearEditText> 
 
  <com.example.clearedittext.ClearEditText 
    android:id="@+id/password" 
    android:layout_marginLeft="10dip" 
    android:layout_marginRight="10dip" 
    android:layout_marginTop="10dip" 
    android:drawableLeft="@drawable/account_icon" 
    android:hint="輸入密碼" 
    android:singleLine="true" 
    android:password="true" 
    android:drawableRight="@drawable/delete_selector" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/username" 
    android:background="@drawable/login_edittext_bg" > 
  </com.example.clearedittext.ClearEditText> 
 
  <Button 
    android:id="@+id/login" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:layout_marginLeft="10dip" 
    android:layout_marginRight="10dip" 
    android:background="@drawable/login_button_bg" 
    android:textSize="18sp" 
    android:textColor="@android:color/white" 
    android:layout_below="@+id/password" 
    android:layout_marginTop="25dp" 
    android:text="登錄" /> 
 
</RelativeLayout> 

package com.example.clearedittext; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.text.TextUtils; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.Toast; 
 
public class MainActivity extends Activity { 
  private Toast mToast; 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
     
    final ClearEditText username = (ClearEditText) findViewById(R.id.username); 
    final ClearEditText password = (ClearEditText) findViewById(R.id.password); 
     
    ((Button) findViewById(R.id.login)).setOnClickListener(new OnClickListener() { 
       
      @Override 
      public void onClick(View v) { 
        if(TextUtils.isEmpty(username.getText())){ 
          //設(shè)置晃動(dòng) 
          username.setShakeAnimation(); 
          //設(shè)置提示 
          showToast("用戶名不能為空"); 
          return; 
        } 
         
        if(TextUtils.isEmpty(password.getText())){ 
          password.setShakeAnimation(); 
          showToast("密碼不能為空"); 
          return; 
        } 
      } 
    }); 
  } 
   
  /** 
   * 顯示Toast消息 
   * @param msg 
   */ 
  private void showToast(String msg){ 
    if(mToast == null){ 
      mToast = Toast.makeText(this, msg, Toast.LENGTH_SHORT); 
    }else{ 
      mToast.setText(msg); 
    } 
    mToast.show(); 
  } 
 
 
}