java 使用 TextWatcher 进行 EditText 验证

EditText validation with TextWatcher

提问by Tivie

I have a Dialog with a EditTextand a button. This EditTextwill name the database table I will create so its of the utmost importance it is validated. So i would like to pose 2 questions:

我有一个 DialogEditText和一个按钮。这EditText将命名我将创建的数据库表，因此对其进行验证至关重要。所以我想提出两个问题：

1) This is quite simple, but i couldn't fin it anywhere: what characters can a database table name accept? Can it accept numbers? And can a number be the first character?

1）这很简单，但我在任何地方都找不到：数据库表名可以接受哪些字符？它可以接受数字吗？数字可以是第一个字符吗？

2) I've managed to validate the EditTextusing TextWtacher. Here's the code:

2）我已经设法验证EditText使用TextWtacher. 这是代码：

et_name.addTextChangedListener(new TextWatcher() {

public void afterTextChanged(Editable s) {

    String filtered_str = s.toString();

        if (filtered_str.matches(".*[^a-z^0-9].*")) {

        filtered_str = filtered_str.replaceAll("[^a-z^0-9]", "");

        s.clear();

        // s.insert(0, filtered_str);

        Toast.makeText(context,
            "Only lowercase letters and numbers are allowed!",
            Toast.LENGTH_SHORT).show();

    }

}

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

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

Currently, if the user inserts any character other than lowercase letters and numbers, the textbox is cleared. If I uncomment s.insert(0, filtered_str);in order to to replace the EditText with the filtered string, my app hangs. And guess what I find in the debug?

目前，如果用户插入小写字母和数字以外的任何字符，则文本框将被清除。如果我取消注释s.insert(0, filtered_str);以便用过滤后的字符串替换 EditText，我的应用程序会挂起。猜猜我在调试中发现了什么？

ERROR/AndroidRuntime(2454): java.lang.StackOverflowError=D

错误/AndroidRuntime（2454）：java.lang.StackOverflowError=D

The question is... how can I replace the s text?

问题是...如何替换 s 文本？

-> s.replace(0, s.toString().length(), filtered_str);(remove s.clear, of course) doesn't seem to work either.

-> s.replace(0, s.toString().length(), filtered_str);（当然，删除 s.clear）似乎也不起作用。

采纳答案by Tivie

After some headbanging, I finally found the solution. Seems s.append(filtered_str) after s.clear() works. Dunno why it hasn't work before.

经过一番折腾，终于找到了解决办法。在 s.clear() 工作之后似乎 s.append(filtered_str) 。不知道为什么它以前不起作用。

回答by El David

private TextWatcher listenerTextChangedFiltro = new TextWatcher() {
        public void afterTextChanged(Editable editable) {

                final String textoFiltrado = StaticString.filterTextCustom(String.valueOf(editable.toString().toLowerCase()));
                if (!textoFiltrado.equals(editable.toString().toLowerCase())) {
                    editable.clear();
                    editable.append(textoFiltrado);
                }
         }
};

回答by Sheshadri Mantha

hey! i'm trying similar thing with forcing the input text to be all lowercase; s.clear() followed by s.append() causes a StackOverflow for me too (or still).

嘿！我正在尝试类似的事情，强制输入文本全部为小写；s.clear() 后跟 s.append() 也会（或仍然）对我造成 StackOverflow。

wonder why Android puts us thru' hoops to force conversion to lowercase ?

想知道为什么 Android 会让我们陷入困境以强制转换为小写？

Since using TextWatcher was crashing for me (rightly so... and i couldn't figure out how to work spans), i looked at TransformationMethod.

由于使用 TextWatcher 对我来说崩溃了（这是正确的......而且我无法弄清楚如何工作跨度），我查看了 TransformationMethod。

1st try was to do an inline TransformationMethod on the EditText with something like this:

第一次尝试是在 EditText 上使用以下内容执行内联 TransformationMethod：

et.setTransformationMethod(new TransformationMethod() {

        public void onFocusChanged(View view, CharSequence sourceText, boolean focused, int direction,
                Rect previouslyFocusedRect) {
        }

        public CharSequence getTransformation(CharSequence source, View view) {
            String ret = source.toString().toLowerCase();
            System.out.println(ret);
            return ret;
        }
    });

This caused crash due to IndexArrayOutOfBounds as soon as i typed a single char in the ET... could not figure out why.

一旦我在 ET 中输入一个字符，这就会由于 IndexArrayOutOfBounds 导致崩溃......无法弄清楚原因。

So, i checked the code for PasswordTransformation and then ReplacementTransformation -- both seem very complicated and i didn't want to bother with all that ?stuff?.

所以，我检查了 PasswordTransformation 和 ReplacementTransformation 的代码——两者看起来都很复杂，我不想打扰所有这些？东西？。

Then in checked out the SinglelineTransformation subclass which was simple... so i created LowerCaseTransformation as subclass of ReplacementTransformation as follows:

然后检查了简单的 SinglelineTransformation 子类……所以我创建了 LowerCaseTransformation 作为 ReplacementTransformation 的子类，如下所示：

public class LowerCaseReplacement extends ReplacementTransformationMethod {
private static final char[] ORIG = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
        'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
private static final char[] REPS = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
        'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
private static LowerCaseReplacement singleton;

@Override
protected char[] getOriginal() {
    return ORIG;
}

@Override
protected char[] getReplacement() {
    return REPS;
}

public static LowerCaseReplacement getInstance() {
    if (singleton == null)
        singleton = new LowerCaseReplacement();
    return singleton;
}

}

}

and adding this xform to et... as in et.setTransformationMethod(LowerCaseReplacement.getInstnace())...

并将这个 xform 添加到 et... 就像 et.setTransformationMethod(LowerCaseReplacement.getInstnace())...

This works!!

这有效！！

If anyone has a better solution, then please enlighten!

如果有人有更好的解决方案，那么请赐教！

回答by kgiannakakis

The problem is that when you call the insert method, the text changed method is called again. This results in a vicious circle, thus the stack overflow. You can avoid this by not replacing a string that is properly formatted.

问题是当你调用insert方法时，又调用了text changed方法。这导致恶性循环，从而堆栈溢出。您可以通过不替换格式正确的字符串来避免这种情况。