evPwd = (EditText) findViewById(R.id.ev_password);
evPwd.addTextChangedListener(new TextWatcher() {
  @Override
  public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

  }

  @Override
  public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
    String editable = evPwd.getText().toString();
    String regEx = "[^a-zA-Z0-9]"; //只能输入字母或数字
    Pattern p = Pattern.compile(regEx);
    Matcher m = p.matcher(editable);
    String str = m.replaceAll("").trim();  //删掉不是字母或数字的字符
    if(!editable.equals(str)){
      evPwd.setText(str); //设置EditText的字符
      evPwd.setSelection(str.length()); //因为删除了字符，要重写设置新的光标所在位置
    }
  }

public abstract CharSequence filter ( 
  CharSequence source, //输入的文字 
  int start, //开始位置 
  int end, //结束位置 
  Spanned dest, //当前显示的内容 
  int dstart, //当前开始位置 
  int dend //当前结束位置 
);

evPwd.setFilters(new InputFilter[]{
  new InputFilter() {
    @Override
    public CharSequence filter(CharSequence charSequence, int i, int i1, Spanned spanned, int i2, int i3) {
      String regex = "^[\u4E00-\u9FA5]+$";
      boolean isChinese = Pattern.matches(regex, charSequence.toString());
      if (!Character.isLetterOrDigit(charSequence.charAt(i)) || isChinese) {
        return "";
      }
      return null;
    }
  }
});

public class LimitEditText extends EditText {
  public LimitEditText(Context context) {
    super(context);
  }

  public LimitEditText(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public LimitEditText(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
  }

  /**
   * 输入法
   * @param outAttrs
   * @return
   */
  @Override
  public InputConnection onCreateInputConnection(EditorInfo outAttrs) {
    return new InnerInputConnecttion(super.onCreateInputConnection(outAttrs),
        false);
  }

  class InnerInputConnecttion extends InputConnectionWrapper implements InputConnection {

    public mInputConnecttion(InputConnection target, boolean mutable) {
      super(target, mutable);
    }

    /**
     * 对输入的内容进行拦截
     *
     * @param text
     * @param newCursorPosition
     * @return
     */
    @Override
    public boolean commitText(CharSequence text, int newCursorPosition) {
      // 只能输入字母或者数字
      if (!Character.isLetterOrDigit(charSequence.charAt(i)) || isChinese) {
        return false;
      }
      return super.commitText(text, newCursorPosition);
    }

    @Override
    public boolean sendKeyEvent(KeyEvent event) {
      return super.sendKeyEvent(event);
    }

    @Override
    public boolean setSelection(int start, int end) {
      return super.setSelection(start, end);
    }
  }
}