EditText View 限制输入字符数，并倒计还能输入多少字符，兼容中英文字符

EditTextCountWatch.java

/**
* EditText View 限制输入字符数，并倒计还能输入多少字符，兼容中英文字符
* author  : ruibin1 (ruibin1@staff.weibo.com)
* create  : 2019/3/28 - 2:12 PM.
* thanks  : https://github.com/FJ917/FJEditTextCount
*/
public class EditTextCountWatch {
    private EditText mEtContent;
    private TextView mTvNum;
    //最大字符
    private int mMaxNum = 10;
    //支持输入的最多字符数量，如支持最多 10 个
    private int mMaxLenChar = mMaxNum * 2;
    private int mStartCountNum = 0;
    private Callback mCallback;

    private InputFilter filter = new InputFilter() {

        @Override
        public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
            int dindex = 0;
            int count = 0;

            while (count <= mMaxLenChar && dindex < dest.length()) {
                char c = dest.charAt(dindex++);
                if (c < 128) {
                    count = count + 1;
                } else {
                    count = count + 2;
                }
            }

            if (count > mMaxLenChar) {
                return dest.subSequence(0, dindex - 1);
            }

            int sindex = 0;
            while (count <= mMaxLenChar && sindex < source.length()) {
                char c = source.charAt(sindex++);
                if (c < 128) {
                    count = count + 1;
                } else {
                    count = count + 2;
                }
            }

            if (count > mMaxLenChar) {
                sindex--;
            }

            return source.subSequence(0, sindex);
        }
    };

    /**
     *
     * @param etContent 输入 View
     */
    public EditTextCountWatch(EditText etContent) {
        this.mEtContent = etContent;
    }


    /**
     * 倒计数显示对应的 view
     * @param tvNumCount
     * @return
     */
    public EditTextCountWatch numCountView(TextView tvNumCount){
        this.mTvNum = tvNumCount;
        return this;
    }

    public EditTextCountWatch callback(Callback callback){
        this.mCallback = callback;
        return this;
    }

    /**
     * 设置最大输入的字符数，不考虑中英文
     * @param maxNum
     * @return
     */
    public EditTextCountWatch maxNum(int maxNum){
        this.mMaxNum = maxNum;
        this.mMaxLenChar = maxNum*2;
        return this;
    }

    /**
     * 开始计数的字符数，比如可以输入 30 个字符，但是一开始并不倒计数，直到 输入 20 个才开始计数
     * @param startCountNum
     * @return
     */
    public EditTextCountWatch startCountNum(int startCountNum){
        this.mStartCountNum = startCountNum * 2;
        return this;
    }

    public void build(){
        if(mTvNum == null){
            throw new IllegalStateException("tvNumCount view can not be null");
        }
        //设置长度
        mEtContent.setFilters(new InputFilter[]{filter});
        //监听输入
        mEtContent.addTextChangedListener(mTextWatcher);
    }

    /** 刷新剩余输入字数 */
    private void setLeftCount() {
        //到目标位置才开始计数
        long inputCount = getInputCount();
        if (mStartCountNum > inputCount) {
            mTvNum.setText("");
        }else{
            mTvNum.setTextColor(Color.parseColor("#cccccc"));
            int leftNum = mMaxNum - calculateTextCharacterLength(mEtContent.getText().toString());
            mTvNum.setText(String.valueOf(leftNum));
            if (leftNum <= 0) {
                mTvNum.setTextColor(Color.parseColor("#F31212"));
            }
        }
    }

    /**
     * 计算输入文字长度
     * 引用自前版本的计算方式
     * @param text
     * @return 返回文字长度的字节数 如果最终要计算字符数需要/2取整
     */
    private static int calculateTextLength(String text) {

        if(TextUtils.isEmpty(text)){
            return 0;
        }
        int totle = 0;
        boolean isEmptyText = true;
        char ch;
        for (int i = 0, len = text.length(); i < len; i++) {
            ch = (char) text.codePointAt(i);
            if (isEmptyText && ch != ' ' && ch != '\n') { // 文本含有不是空格和回车的字符
                isEmptyText = false;
            }
            totle += ch > 255 ? 2 : 1;
        }

        // 文本只含有空格和回车
        if (isEmptyText) {
            return 0;
        }

        return totle;
    }

    /** 获取用户输入内容字数 */
    private long getInputCount() {
        return calculateTextLength(mEtContent.getText().toString());
    }

    private TextWatcher mTextWatcher = new TextWatcher() {
        private int editStart;
        private int editEnd;
        public void afterTextChanged(Editable s) {
            editStart = mEtContent.getSelectionStart();
            editEnd = mEtContent.getSelectionEnd();
            // 先去掉监听器，否则会出现栈溢出
            mEtContent.removeTextChangedListener(mTextWatcher);
            // 注意这里只能每次都对整个EditText的内容求长度，不能对删除的单个字符求长度
            // 因为是中英文混合，单个字符而言，calculateLength函数都会返回1
            while (mMaxNum - calculateTextCharacterLength(s.toString()) < 0 ) { // 当输入字符个数超过限制的大小时，进行截断操作
                s.delete(editStart - 1, editEnd);
                editStart--;
                editEnd--;
            }
            // 恢复监听器
            mEtContent.addTextChangedListener(mTextWatcher);
            setLeftCount();
            if(mCallback != null){
                mCallback.onTextChanged(mEtContent.getText().toString());
            }
        }

        public void beforeTextChanged(CharSequence s, int start, int count,int after) {}

        public void onTextChanged(CharSequence s, int start, int before,int count) {}
    };

    private static int calculateTextCharacterLength(String text) {
        int byteLength = calculateTextLength(text);
        return (int)Math.ceil(byteLength/2.0);
    }

    public interface Callback{
        void onTextChanged(String content);
    }
}