Android自定义输入手机号自动添加分隔符

public class AccountTxtView extends android.support.v7.widget.AppCompatEditText {
  private final char CUT = '-';
  public AccountTxtView(Context context) {
    super(context);
  }
  public AccountTxtView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }
  public AccountTxtView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
  }
  @Override
  protected void onTextChanged(CharSequence text, int start, int lengthBefore, int lengthAfter) {
    if (text == null || text.length() == 0)
      return;
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i