NumTextWatcher Edittext 监听输入的小数位

主要是针对 需要限制小数位数的输入框做的监听处理

public class NumTextWatcher implements TextWatcher {
private int defaultRetain = 2;
private EditText edit;

public NumTextWatcher(@NonNull EditText edit, int retainDecimal, AfterTextChange chang) {
    this.defaultRetain = retainDecimal;
    this.edit = edit;
    this.mChange = chang;
}
 @Override
  public void beforeTextChanged(CharSequence s, int start, int count, int after) {

}

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {

}

@Override
public void afterTextChanged(Editable s) {
    CharSequence afterChange = s.toString();
    if (TextUtils.isEmpty(afterChange)) {
        if (mChange != null)
            mChange.afterText(afterChange);
        return;
    }
    //删除“.”后面超过2位后的数据
    if (afterChange.toString().contains(".")) {
        int first = afterChange.toString().indexOf(".");
        int last = afterChange.toString().lastIndexOf(".");
        if (first == last) {
            if (afterChange.length() - 1 - first > defaultRetain) {
                afterChange=afterChange.subSequence(0, first + defaultRetain + 1);
                this.edit.setText(afterChange);
                this.edit.setSelection(afterChange.length()); //光标移到最后
            }
        } else {
            afterChange=afterChange.subSequence(0, last);
            this.edit.setText(afterChange.subSequence(0, last));
            this.edit.setSelection(afterChange.length()); //光标移到最后
        }

    }
    //如果"."在起始位置,则起始位置自动补0
    if (afterChange.toString().trim().substring(0).equals(".")) {
        afterChange = "0" + afterChange;
        this.edit.setText(afterChange);
        this.edit.setSelection(2); //光标移到最后
    }
    //如果起始位置为0,且第二位跟的不是".",则无法后续输入
    if (afterChange.toString().startsWith("0") && afterChange.toString().trim().length() > 1) {
        if (!afterChange.toString().substring(1, 2).equals(".")) {
            this.edit.setText(afterChange.subSequence(0, 1));
            this.edit.setSelection(1);
            return;
        }
    }

    if (mChange != null)
        mChange.afterText(afterChange);
}

private AfterTextChange mChange;

 public interface AfterTextChange {
    void afterText(CharSequence after);
}
}