本篇文章轉載自馮豐楓《Android EditText 小數(shù)輸入優(yōu)化》。大神使用正則表達式加TextWatcher對EditText小數(shù)輸入進行限制聪富，感覺比使用filter要方便很多凌简，代碼更加簡潔见剩，可讀性更高筋现。

先看一下作者的演示gif：

小數(shù)輸入演示

在需要做限制的EditText上add下面的TextWatcher就好：

public class DecimalInputTextWatcher implements TextWatcher {

    private Pattern mPattern;

    /**
     * 不限制整數(shù)位數(shù)和小數(shù)位數(shù)
     */
    public DecimalInputTextWatcher() {
    }

    /**
     * 限制整數(shù)位數(shù)或著限制小數(shù)位數(shù)
     *
     * @param type   限制類型
     * @param number 限制位數(shù)
     */
    public DecimalInputTextWatcher(Type type, int number) {
        if (type == Type.decimal) {
            mPattern = Pattern.compile("^[0-9]+(\\.[0-9]{0," + number + "})?$");
        } else if (type == Type.integer) {
            mPattern = Pattern.compile("^[0-9]{0," + number + "}+(\\.[0-9]{0,})?$");
        }
    }

    /**
     * 既限制整數(shù)位數(shù)又限制小數(shù)位數(shù)
     *
     * @param integers 整數(shù)位數(shù)
     * @param decimals 小數(shù)位數(shù)
     */

    public DecimalInputTextWatcher(int integers, int decimals) {
        mPattern = Pattern.compile("^[0-9]{0," + integers + "}+(\\.[0-9]{0," + decimals + "})?$");
    }

    @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 editable) {
        String text = editable.toString();

        if (TextUtils.isEmpty(text)) return;

        // 刪除首位無效的“0”
        if ((editable.length() > 1) && (editable.charAt(0) == '0') && editable.charAt(1) != '.') {
            editable.delete(0, 1);
            return;
        }

        // 首位是“.”自動補“0”
        if (text.equals(".")) {
            editable.insert(0, "0");
            return;
        }

        if (mPattern != null && !mPattern.matcher(text).matches() && editable.length() > 0) {
            editable.delete(editable.length() - 1, editable.length());
        }
    }

    public enum Type {
        integer, decimal
    }
}