我有三个活动A, B和C,其中A和B是表单,并在数据库(SQLite)中填充和保存表单数据后。我使用意图从A到B,然后从B到C,我想要的是,每次我打开我的应用程序时,我想要C作为我的主屏幕,而不再是A和B。

我想共享偏好可以解决这个问题,但我找不到一个好的例子来给我一个起点。


当前回答

我只是发现上面所有的例子都太混乱了,所以我自己写了一个。如果您知道自己在做什么,那么代码片段是很好的,但是像我这样不知道的人呢?

想要一个剪切-粘贴的解决方案?好了,就是这里!

创建一个新的java文件并将其称为Keystore。然后粘贴以下代码:

import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.util.Log;

public class Keystore { //Did you remember to vote up my example?
    private static Keystore store;
    private SharedPreferences SP;
    private static String filename="Keys";

private Keystore(Context context) {
    SP = context.getApplicationContext().getSharedPreferences(filename,0);
}

public static Keystore getInstance(Context context) {
    if (store == null) {
        Log.v("Keystore","NEW STORE");
        store = new Keystore(context);
    }
    return store;
}

public void put(String key, String value) {//Log.v("Keystore","PUT "+key+" "+value);
    Editor editor = SP.edit();
    editor.putString(key, value);
    editor.commit(); // Stop everything and do an immediate save!
    // editor.apply();//Keep going and save when you are not busy - Available only in APIs 9 and above.  This is the preferred way of saving.
}

public String get(String key) {//Log.v("Keystore","GET from "+key);
    return SP.getString(key, null);

}

public int getInt(String key) {//Log.v("Keystore","GET INT from "+key);
    return SP.getInt(key, 0);
}

public void putInt(String key, int num) {//Log.v("Keystore","PUT INT "+key+" "+String.valueOf(num));
    Editor editor = SP.edit();

    editor.putInt(key, num);
    editor.commit();
}


public void clear(){ // Delete all shared preferences
    Editor editor = SP.edit();

    editor.clear();
    editor.commit();
}

public void remove(){ // Delete only the shared preference that you want
    Editor editor = SP.edit();

    editor.remove(filename);
    editor.commit();
}
}

现在保存那个文件,忘了它吧。你受够了。现在回到你的活动,像这样使用它:

public class YourClass extends Activity{

private Keystore store;//Holds our key pairs

public YourSub(Context context){
    store = Keystore.getInstance(context);//Creates or Gets our key pairs.  You MUST have access to current context!

    int= store.getInt("key name to get int value");
    string = store.get("key name to get string value");

    store.putInt("key name to store int value",int_var);
    store.put("key name to store string value",string_var);
    }
}

其他回答

共享首选项是XML文件,用于以键-值对存储私有原始数据。数据类型包括布尔型、浮点型、整型、长型和字符串。

当我们想要保存一些在整个应用程序中都可以访问的数据时,一种方法是将其保存在全局变量中。但是一旦应用程序关闭,它就会消失。另一种推荐的方法是保存在SharedPreference中。保存在SharedPreferences文件中的数据在整个应用程序中都可以访问,即使在应用程序关闭或重新启动之后也可以继续保存。

SharedPreferences以键值对的方式保存数据,可以以相同的方式访问。

你可以使用两个方法创建SharedPreferences对象,

1). getsharedpreferences():使用这个方法你可以创建多个SharedPreferences。它的第一个参数名为SharedPreferences。

2). getpreferences():使用这个方法你可以创建Single SharedPreferences。

存储数据

添加变量声明/创建首选项文件

public static final String PREFERENCES_FILE_NAME = "MyAppPreferences";

检索文件名的句柄(使用getSharedPreferences)

SharedPreferences settingsfile= getSharedPreferences(PREFERENCES_FILE_NAME,0);

打开编辑器和添加键值对

SharedPreferences.Editor myeditor = settingsfile.edit(); 
myeditor.putBoolean("IITAMIYO", true); 
myeditor.putFloat("VOLUME", 0.7)
myeditor.putInt("BORDER", 2)
myeditor.putLong("SIZE", 12345678910L)
myeditor.putString("Name", "Amiyo")
myeditor.apply(); 

不要忘记如上所示使用meditor .apply()来应用/保存。

检索数据

 SharedPreferences mysettings= getSharedPreferences(PREFERENCES_FILE_NAME, 0);
IITAMIYO = mysettings.getBoolean("IITAMIYO", false); 
//returns value for the given key. 
//second parameter gives the default value if no user preference found
// (set to false in above case)
VOLUME = mysettings.getFloat("VOLUME", 0.5) 
//0.5 being the default value if no volume preferences found
// and similarly there are get methods for other data types

您可以创建自定义的SharedPreference类

public class YourPreference {   
    private static YourPreference yourPreference;
    private SharedPreferences sharedPreferences;

    public static YourPreference getInstance(Context context) {
        if (yourPreference == null) {
            yourPreference = new YourPreference(context);
        }
        return yourPreference;
    }

    private YourPreference(Context context) {
        sharedPreferences = context.getSharedPreferences("YourCustomNamedPreference",Context.MODE_PRIVATE);
    }

    public void saveData(String key,String value) {
        SharedPreferences.Editor prefsEditor = sharedPreferences.edit();
        prefsEditor .putString(key, value);
        prefsEditor.commit();           
    }

    public String getData(String key) {
        if (sharedPreferences!= null) {
           return sharedPreferences.getString(key, "");
        }
        return "";         
    }
}

你可以像这样获得你的偏好实例:

YourPreference yourPrefrence = YourPreference.getInstance(context);
yourPreference.saveData(YOUR_KEY,YOUR_VALUE);

String value = yourPreference.getData(YOUR_KEY);
public class Preferences {

public static final String PREF_NAME = "your preferences name";

@SuppressWarnings("deprecation")
public static final int MODE = Context.MODE_WORLD_WRITEABLE;

public static final String USER_ID = "USER_ID_NEW";
public static final String USER_NAME = "USER_NAME";

public static final String NAME = "NAME";
public static final String EMAIL = "EMAIL";
public static final String PHONE = "PHONE";
public static final String address = "address";

public static void writeBoolean(Context context, String key, boolean value) {
    getEditor(context).putBoolean(key, value).commit();
}

public static boolean readBoolean(Context context, String key,
        boolean defValue) {
    return getPreferences(context).getBoolean(key, defValue);
}

public static void writeInteger(Context context, String key, int value) {
    getEditor(context).putInt(key, value).commit();

}

public static int readInteger(Context context, String key, int defValue) {
    return getPreferences(context).getInt(key, defValue);
}

public static void writeString(Context context, String key, String value) {
    getEditor(context).putString(key, value).commit();

}

public static String readString(Context context, String key, String defValue) {
    return getPreferences(context).getString(key, defValue);
}

public static void writeFloat(Context context, String key, float value) {
    getEditor(context).putFloat(key, value).commit();
}

public static float readFloat(Context context, String key, float defValue) {
    return getPreferences(context).getFloat(key, defValue);
}

public static void writeLong(Context context, String key, long value) {
    getEditor(context).putLong(key, value).commit();
}

public static long readLong(Context context, String key, long defValue) {
    return getPreferences(context).getLong(key, defValue);
}

public static SharedPreferences getPreferences(Context context) {
    return context.getSharedPreferences(PREF_NAME, MODE);
}

public static Editor getEditor(Context context) {
    return getPreferences(context).edit();
}

}

****使用Preferences写入值使用:-****

Preferences.writeString(getApplicationContext(),
                    Preferences.NAME, "dev");

****使用Preferences读取值使用:-****

Preferences.readString(getApplicationContext(), Preferences.NAME,
                    "");

如何初始化?

// 0 - for private mode`
SharedPreferences pref = getApplicationContext().getSharedPreferences("MyPref", 0); 

Editor editor = pref.edit();

如何在共享偏好中存储数据?

editor.putString("key_name", "string value"); // Storing string

OR

editor.putInt("key_name", "int value"); //Storing integer

别忘了申请:

editor.apply();

如何从共享首选项检索数据?

pref.getString("key_name", null); // getting String

pref.getInt("key_name", 0); // getting Integer

希望这对你有帮助:)

您还可以看看我过去为这个目的编写的示例项目。我在本地保存一个名称,并在用户请求或应用程序启动时检索它。

但是,此时最好使用commit(而不是apply)来持久化数据。更多信息请点击这里。