Android PreferenceActivity：将值保存为整数

PreferenceActivity: save value as integer

提问by Laimoncijus

Using a simple EditTextPreferencein my preferences activity:

EditTextPreference在我的偏好活动中使用一个简单的：

<EditTextPreference
    android:key="SomeKey"
    android:title="@string/some_title"
    android:summary="..."
    android:numeric="integer"
    android:maxLength="2"
/>

Is there a way that this configuration value would be saved as integer? Seems now it just allows to enter numbers, but the value is still saved as string:

有没有办法将此配置值保存为整数？现在似乎它只允许输入数字，但该值仍保存为字符串：

Calling:

调用：

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
int value = preferences.getInt("SomeKey", -1);

throws me java.lang.ClassCastException: java.lang.String, and:

抛出我java.lang.ClassCastException: java.lang.String，并且：

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
String value = preferences.getString("SomeKey", "-1");

retrieves the value successfully.

成功检索值。

How to make PreferenceActivityto save value as integer by default?

PreferenceActivity默认情况下如何将值保存为整数？

回答by broot

You could extend EditTextPreference:

您可以扩展 EditTextPreference：

public class IntEditTextPreference extends EditTextPreference {

    public IntEditTextPreference(Context context) {
        super(context);
    }

    public IntEditTextPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public IntEditTextPreference(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected String getPersistedString(String defaultReturnValue) {
        return String.valueOf(getPersistedInt(-1));
    }

    @Override
    protected boolean persistString(String value) {
        return persistInt(Integer.valueOf(value));
    }
}

It would be better to overwrite onSetInitialValue() and setText() methods, but then you would have to copy some code from a base class. Above solution is simplier, but it's quite tricky - "string" methods do something with ints. Try to not extend this class further ;-)

最好覆盖 onSetInitialValue() 和 setText() 方法，但是您必须从基类复制一些代码。上面的解决方案更简单，但它非常棘手 - “字符串”方法对整数做一些事情。尽量不要进一步扩展这个类;-)

You could use it from XML by:

您可以通过以下方式从 XML 使用它：

<package.name.IntEditTextPreference
    android:key="SomeKey"
    android:title="@string/some_title"
    android:summary="..."
    android:numeric="integer"
    android:maxLength="2"
/>

回答by broot

Even if you set android:numeric="integer" it'll be text preference - as its name suggest. You could easily convert string value to int using Integer.valueOf(). Also you could overwrite PreferenceActivity to do conversion automatically on exit.

即使您设置了 android:numeric="integer" 它也将是文本首选项 - 顾名思义。您可以使用 Integer.valueOf() 轻松地将字符串值转换为 int。您也可以覆盖 PreferenceActivity 以在退出时自动进行转换。

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I think the best solution is to write simple method to get this value from preferences. Something like:

我认为最好的解决方案是编写简单的方法来从偏好中获取这个值。就像是：

public static int getSomePref(Context context) {
    SharedPreferences prefs =
        PreferenceManager.getDefaultSharedPreferences(context);
    String value = prefs.getString("SomeKey", null);
    return value == null ? -1 : Integer.valueOf(value);
}

Then you could very easily use it from your code.

然后你可以很容易地从你的代码中使用它。

回答by Arnab Jain

Even though an Answer has been parked accepted I would like to share one more shorter way to achieve this :

即使已经接受了一个答案，我还是想分享一种更短的方法来实现这一目标：

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
int value = Integer.parseInt(preferences.getString("SomeKey", "-1"));

Since you have already set that only numbers can be entered this won't through any exception. yet to complete my answer :

由于您已经设置只能输入数字，因此不会出现任何异常。尚未完成我的回答：

<EditTextPref
    android:key="SomeKey"
    android:title="@string/some_title"
    android:summary="..."
    android:numeric="integer"
    android:maxLength="2" />

回答by Jadeye

I think this is the shortest one I could come up with:

我认为这是我能想到的最短的一个：

int CheckInterval = Integer.parseInt(sharedPreferences.getString("check_frequency","60"));

回答by cartok

I had the same Problem. (I wanted SharedPreference to give me a port number that i stored in a preferences xml file as defaultValue).

我有同样的问题。（我希望 SharedPreference 给我一个端口号，我将其作为 defaultValue 存储在首选项 xml 文件中）。

Implementing all the SharedPreferences methods would be much effort, so writing a custom method in the class that instanced the SharedPreferences, as brootsuggested would be best i think.

实现所有 SharedPreferences 方法会很费力，所以在实例化 SharedPreferences 的类中编写一个自定义方法，正如broot建议的那样，我认为最好。

You can aswell just use the Static method of Integer in the line where you need it:

您也可以在需要的行中使用 Integer 的静态方法：

int number = Integer.valueOf(settings.getString("myNumberString", "0"));