有时我们需要知道根据edittext是否有输入内容来改变button的状态，常见的页面就是登录，只要用户没有输入手机号和密码时，button的状态为不可点击，且在UI在表现出来，如何优雅的判断多个edittext的内容呢？

效果

下图的需求是，当用户输入手机号及勾选协议后才能让button处于可点击状态，最简单的做法是分别为edittext和checkbox设置监听，然后设置一个成员变量来进行判断

ezgif.com-video-to-gif.gif

示例代码

这里你只需要将要观察的textview传递给Rule子类即可，Rule是一个抽象类，你可以实现你要判断的规则，我提供了手机号规则（中国），不为空规则和选中规则，使用方式如下。当所有的rule为true或false时会将结果回调给接口，（只有上次的结果与当前结果不同时才会执行回调，即上次为false当前结果也为false时，不执行callback方法）

Watcher.subscribe(new Watcher.Mobile(etMobileNumber), new Watcher.Checked(cbProtocol))
        .setWatcherCallback(enabled -> {
        butNext.setEnabled(enabled);
        tvPasswordLogin.setEnabled(enabled);
    });

源码

public class Watcher {

    public static Watcher subscribe(Rule... rules) {
        return new Watcher(rules);
    }

    private OnWatcherCallback mCallback;
    private boolean mPreWatchResult = false;
    private Map<TextView, Boolean> mObservedMap;

    private Watcher(Rule... rules) {
        mObservedMap = new ArrayMap<>();
        for (Rule rule : rules) {
            mObservedMap.put(rule.mObserved, rule.validation(rule.mObserved.getText()));
            if (rule.mObserved instanceof EditText) {
                rule.mObserved.addTextChangedListener(new EditTextTextWatcher(rule));
            } else if (rule.mObserved instanceof CheckBox) {
                CheckBox checkBox = (CheckBox) rule.mObserved;
                checkBox.setOnCheckedChangeListener(new CheckedChangeListener(rule));
            }
        }
    }

    private void watchResult(Rule rule, boolean result) {
        mObservedMap.put(rule.mObserved, result);
        Collection<Boolean> values = mObservedMap.values();
        if (mCallback != null) {
            boolean watchResult = !values.contains(Boolean.FALSE);
            if (watchResult != mPreWatchResult) {
                mPreWatchResult = watchResult;
                mCallback.callback(watchResult);
            }
        }
    }

    public void setWatcherCallback(OnWatcherCallback callback) {
        this.mCallback = callback;
    }


    private class CheckedChangeListener implements CheckBox.OnCheckedChangeListener {
        private final Rule mRule;

        CheckedChangeListener(Rule rule) {
            this.mRule = rule;
        }

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            watchResult(this.mRule, isChecked);
        }
    }

    private class EditTextTextWatcher extends SimpleTextWatcher {

        private final Rule mRule;

        EditTextTextWatcher(Rule rule) {
            this.mRule = rule;
        }

        @Override
        public void afterTextChanged(Editable s) {
            watchResult(this.mRule, this.mRule.validation(s));
        }
    }


    /**
     * 观察结果回调
     */
    public interface OnWatcherCallback {
        void callback(boolean watch);
    }

    public interface Rule {
         boolean validation(CharSequence charSequence);
    }

    /**
     * 单一规则
     */
    public abstract static class SingleRule implement Rule {

        TextView mObserved;

        public Rule(TextView observed) {
            this.mObserved = observed;
        }
    }

    /**
     * 选中
     */
    public static class Checked extends SingleRule {

        public CheckBox mObserved;

        public Checked(CheckBox observed) {
            super(observed);
            this.mObserved = observed;
        }

        @Override
        public boolean validation(CharSequence charSequence) {
            return this.mObserved.isChecked();
        }
    }

    /**
     * 不为空
     */
    public static class NotEmpty extends SingleRule {
        public NotEmpty(EditText editText) {
            super(editText);
        }

        @Override
        public boolean validation(CharSequence charSequence) {
            return !TextUtils.isEmpty(charSequence);
        }
    }

    /**
     * 手机号
     */
    public static class Mobile extends SingleRule {

        private final String REGEX_MOBILE =
                "^((17[0-9])|(14[0-9])|(13[0-9])|(15[^4,\\D])|(18[0,5-9]))\\d{8}$";

        public Mobile(EditText editText) {
            super(editText);
        }

        @Override
        public boolean validation(CharSequence charSequence) {
            return Pattern.matches(REGEX_MOBILE, this.mObserved.getText());
        }
    }
}