EditText 小数位位数限制

一、方案：

@1、addTextChangedListener
缺点：保留指定位数后，还是会执行其他附加的TextChangedListener


@2、InputFilter
完美解决addTextChangedListener实现的缺点

二、基于InputFilter实现

1、InputFilter 工具类

/**
 * ggband
 * 限制 小数和整数的位数
 */
public class InputNumLengthFilter implements InputFilter {

    private int maxPoint;
    private int maxInteger;
    public InputNumLengthFilter(int maxPoint, int maxInteger) {
        this.maxPoint = maxPoint;
        this.maxInteger = maxInteger;
    }

    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        int maxLength = maxInteger + maxPoint + 1;
        // 删除等特殊字符，直接返回
        if (nullFilter(source)) return null;
        String dValue = dest.toString();
        String[] splitArray = dValue.split("\.");//在点前后分开两段
        if (splitArray.length > 0) {
            String intValue = splitArray[0];
            int errorIndex = dValue.indexOf(".");
            if (errorIndex == -1) {
                errorIndex = dValue.length();
            }
            if (intValue.length() >= maxLength - maxPoint - 1 && dstart <= errorIndex) {
                if (".".equals(source.toString())) {
                    return null;
                }
                return "";
            }
        }
        if (splitArray.length > 1 && dstart == dValue.length()) {
            String dotValue = splitArray[1];
            int diff = dotValue.length() + 1 - maxPoint;
            if (diff > 0) {
                try {
                    return source.subSequence(start, end - diff);
                } catch (IndexOutOfBoundsException e) {
                    return source;
                }
            }
        }
        if (dest.length() == maxLength - 1 && ".".equals(source.toString())) {
            return "";
        }
        if (dest.length() >= maxLength) {
            return "";
        }
        return null;
    }

    //  第一个参数是小数部分的位数，第二个参数是总长度（包括小数点）

    private boolean nullFilter(CharSequence source) {
       return source.toString().isEmpty();
    }
}

　2、ViewHelper工具类：

/**
 * 让一个输入框只能输入指定位数小数 和整数位
 *
 * @param editText   EditText
 * @param maxInteger 最大整数位数
 * @param maxPoint   最大小数位数
 *  create by ggband
 */
public static void setPricePointWithInteger(final EditText editText, final int maxPoint, final int maxInteger, InputFilter... inputFilters) {
    if (inputFilters == null || inputFilters.length == 0) {
        editText.setFilters(new InputFilter[]{new InputNumLengthFilter(maxPoint, maxInteger)});
    } else {
        InputFilter[] newInputFilters = new InputFilter[inputFilters.length + 1];
        System.arraycopy(inputFilters, 0, newInputFilters, 0, inputFilters.length);
        newInputFilters[inputFilters.length] = new InputNumLengthFilter(maxPoint, maxInteger);
        editText.setFilters(newInputFilters);
    }

}

3、使用：

ViewHelper.setPricePointWithInteger(etCpu, 4, 10)

ggband