我想存储一个时间值,需要检索和编辑它。我如何使用SharedPreferences来做到这一点?


当前回答

要获得共享首选项,请使用以下方法 在活动中:

SharedPreferences prefs = this.getSharedPreferences(
      "com.example.app", Context.MODE_PRIVATE);

读取首选项:

String dateTimeKey = "com.example.app.datetime";

// use a default value using new Date()
long l = prefs.getLong(dateTimeKey, new Date().getTime()); 

编辑和保存首选项

Date dt = getSomeDate();
prefs.edit().putLong(dateTimeKey, dt.getTime()).apply();

android sdk的示例目录包含一个检索和存储共享首选项的示例。它位于:

<android-sdk-home>/samples/android-<platformversion>/ApiDemos directory

编辑= = >

我注意到,在这里写commit()和apply()之间的区别也很重要。

如果保存成功,Commit()返回true,否则返回false。它同步保存值到SharedPreferences。

Apply()是在2.3中添加的,无论成功还是失败都不返回任何值。它会立即将值保存到SharedPreferences,但会启动异步提交。 更多细节在这里。

其他回答

如果你正在与团队中的其他开发人员一起开发一个大型应用程序,并打算让所有内容都很好地组织起来,而不是分散的代码或不同的SharedPreferences实例,你可以这样做:

//SharedPreferences manager class
public class SharedPrefs {

    //SharedPreferences file name
    private static String SHARED_PREFS_FILE_NAME = "my_app_shared_prefs";

    //here you can centralize all your shared prefs keys
    public static String KEY_MY_SHARED_BOOLEAN = "my_shared_boolean";
    public static String KEY_MY_SHARED_FOO = "my_shared_foo";

    //get the SharedPreferences object instance
    //create SharedPreferences file if not present


    private static SharedPreferences getPrefs(Context context) {
        return context.getSharedPreferences(SHARED_PREFS_FILE_NAME, Context.MODE_PRIVATE);
    }

    //Save Booleans
    public static void savePref(Context context, String key, boolean value) {
        getPrefs(context).edit().putBoolean(key, value).commit();       
    }

    //Get Booleans
    public static boolean getBoolean(Context context, String key) {
        return getPrefs(context).getBoolean(key, false);
    }

    //Get Booleans if not found return a predefined default value
    public static boolean getBoolean(Context context, String key, boolean defaultValue) {
        return getPrefs(context).getBoolean(key, defaultValue);
    }

    //Strings
    public static void save(Context context, String key, String value) {
        getPrefs(context).edit().putString(key, value).commit();
    }

    public static String getString(Context context, String key) {
        return getPrefs(context).getString(key, "");
    }

    public static String getString(Context context, String key, String defaultValue) {
        return getPrefs(context).getString(key, defaultValue);
    }

    //Integers
    public static void save(Context context, String key, int value) {
        getPrefs(context).edit().putInt(key, value).commit();
    }

    public static int getInt(Context context, String key) {
        return getPrefs(context).getInt(key, 0);
    }

    public static int getInt(Context context, String key, int defaultValue) {
        return getPrefs(context).getInt(key, defaultValue);
    }

    //Floats
    public static void save(Context context, String key, float value) {
        getPrefs(context).edit().putFloat(key, value).commit();
    }

    public static float getFloat(Context context, String key) {
        return getPrefs(context).getFloat(key, 0);
    }

    public static float getFloat(Context context, String key, float defaultValue) {
        return getPrefs(context).getFloat(key, defaultValue);
    }

    //Longs
    public static void save(Context context, String key, long value) {
        getPrefs(context).edit().putLong(key, value).commit();
    }

    public static long getLong(Context context, String key) {
        return getPrefs(context).getLong(key, 0);
    }

    public static long getLong(Context context, String key, long defaultValue) {
        return getPrefs(context).getLong(key, defaultValue);
    }

    //StringSets
    public static void save(Context context, String key, Set<String> value) {
        getPrefs(context).edit().putStringSet(key, value).commit();
    }

    public static Set<String> getStringSet(Context context, String key) {
        return getPrefs(context).getStringSet(key, null);
    }

    public static Set<String> getStringSet(Context context, String key, Set<String> defaultValue) {
        return getPrefs(context).getStringSet(key, defaultValue);
    }
}

在您的活动中,您可以这样保存SharedPreferences

//saving a boolean into prefs
SharedPrefs.savePref(this, SharedPrefs.KEY_MY_SHARED_BOOLEAN, booleanVar);

你可以这样检索你的SharedPreferences

//getting a boolean from prefs
booleanVar = SharedPrefs.getBoolean(this, SharedPrefs.KEY_MY_SHARED_BOOLEAN);

写:

SharedPreferences preferences = getSharedPreferences("AUTHENTICATION_FILE_NAME", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("Authentication_Id",userid.getText().toString());
editor.putString("Authentication_Password",password.getText().toString());
editor.putString("Authentication_Status","true");
editor.apply();

阅读:

SharedPreferences prfs = getSharedPreferences("AUTHENTICATION_FILE_NAME", Context.MODE_PRIVATE);
String Astatus = prfs.getString("Authentication_Status", "");

我为sharedpreferences写了一个helper类:

import android.content.Context;
import android.content.SharedPreferences;

/**
 * Created by mete_ on 23.12.2016.
 */
public class HelperSharedPref {

Context mContext;

public HelperSharedPref(Context mContext) {
    this.mContext = mContext;
}

/**
 *
 * @param key Constant RC
 * @param value Only String, Integer, Long, Float, Boolean types
 */
public void saveToSharedPref(String key, Object value) throws Exception {
    SharedPreferences.Editor editor = mContext.getSharedPreferences(key, Context.MODE_PRIVATE).edit();
    if (value instanceof String) {
        editor.putString(key, (String) value);
    } else if (value instanceof Integer) {
        editor.putInt(key, (Integer) value);
    } else if (value instanceof Long) {
        editor.putLong(key, (Long) value);
    } else if (value instanceof Float) {
        editor.putFloat(key, (Float) value);
    } else if (value instanceof Boolean) {
        editor.putBoolean(key, (Boolean) value);
    } else {
        throw new Exception("Unacceptable object type");
    }

    editor.commit();
}

/**
 * Return String
 * @param key
 * @return null default is null
 */
public String loadStringFromSharedPref(String key) throws Exception {
    SharedPreferences prefs = mContext.getSharedPreferences(key, Context.MODE_PRIVATE);
    String restoredText = prefs.getString(key, null);

    return restoredText;
}

/**
 * Return int
 * @param key
 * @return null default is -1
 */
public Integer loadIntegerFromSharedPref(String key) throws Exception {
    SharedPreferences prefs = mContext.getSharedPreferences(key, Context.MODE_PRIVATE);
    Integer restoredText = prefs.getInt(key, -1);

    return restoredText;
}

/**
 * Return float
 * @param key
 * @return null default is -1
 */
public Float loadFloatFromSharedPref(String key) throws Exception {
    SharedPreferences prefs = mContext.getSharedPreferences(key, Context.MODE_PRIVATE);
    Float restoredText = prefs.getFloat(key, -1);

    return restoredText;
}

/**
 * Return long
 * @param key
 * @return null default is -1
 */
public Long loadLongFromSharedPref(String key) throws Exception {
    SharedPreferences prefs = mContext.getSharedPreferences(key, Context.MODE_PRIVATE);
    Long restoredText = prefs.getLong(key, -1);

    return restoredText;
}

/**
 * Return boolean
 * @param key
 * @return null default is false
 */
public Boolean loadBooleanFromSharedPref(String key) throws Exception {
    SharedPreferences prefs = mContext.getSharedPreferences(key, Context.MODE_PRIVATE);
    Boolean restoredText = prefs.getBoolean(key, false);

    return restoredText;
}

}

在共享首选项中存储值:

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("Name","Harneet");
editor.apply();

从共享首选项中检索值:

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
String name = preferences.getString("Name", "");
if(!name.equalsIgnoreCase(""))
{
    name = name + "  Sethi";  /* Edit the value here*/
}

简单的方法:

保存:

getPreferences(MODE_PRIVATE).edit().putString("Name of variable",value).commit();

检索:

your_variable = getPreferences(MODE_PRIVATE).getString("Name of variable",default value);