程序包 ohos.data.preferences

接口 Preferences

public interface Preferences

Provides interfaces to obtain and modify preference data.

The preference data is stored in a file, which matches only one Preferences instance in the memory. You can use DatabaseHelper.getPreferences(java.lang.String) to obtain the Preferences instance matching the file that stores preference data, and use DatabaseHelper.removePreferencesFromCache(java.lang.String) to remove the Preferences instance from the memory.

从以下版本开始:

1

SystemCapability

SystemCapability.Data#DATA_APPDATAMGR

嵌套类概要

嵌套类

限定符和类型	接口	说明
static interface	Preferences.PreferencesObserver	Provides an interface to listen for preference data changes.

字段概要

字段

限定符和类型	字段	说明
static int	MAX_KEY_LENGTH	Indicates the maximum length of a key (80 characters).
static int	MAX_VALUE_LENGTH	Indicates the maximum length of a string (8192 characters).

方法概要

限定符和类型	方法	说明
Preferences	clear()	Clears all preferences from the Preferences object.
Preferences	delete(String key)	Deletes the preference with a specified key from the Preferences object.
void	flush()	Asynchronously saves the Preferences object to the file.
boolean	flushSync()	Synchronously saves the Preferences object to the file.
Map<String,?>	getAll()	Obtains all preferences from this Preferences object.
boolean	getBoolean(String key, boolean defValue)	Obtains the value of a preference in the boolean format.
float	getFloat(String key, float defValue)	Obtains the value of a preference in the float format.
int	getInt(String key, int defValue)	Obtains the value of a preference in the int format.
long	getLong(String key, long defValue)	Obtains the value of a preference in the long format.
String	getString(String key, String defValue)	Obtains the value of a preference in the string format.
Set<String>	getStringSet(String key, Set<String> defValue)	Obtains the value of a preference in the string set format.
boolean	hasKey(String key)	Checks whether the Preferences object contains a preference matching a specified key.
Preferences	putBoolean(String key, boolean value)	Sets a boolean value for the key in the Preferences object.
Preferences	putFloat(String key, float value)	Sets a float value for the key in the Preferences object.
Preferences	putInt(String key, int value)	Sets an int value for the key in the Preferences object.
Preferences	putLong(String key, long value)	Sets a long value for the key in the Preferences object.
Preferences	putString(String key, String value)	Sets a string value for the key in the Preferences object.
Preferences	putStringSet(String key, Set<String> value)	Sets a string set value for the key in the Preferences object.
void	registerObserver(Preferences.PreferencesObserver preferencesObserver)	Registers an observer to listen for the change of a Preferences object.
void	unregisterObserver(Preferences.PreferencesObserver preferencesObserver)	Unregisters an existing observer.

字段详细资料

MAX_KEY_LENGTH

static final int MAX_KEY_LENGTH

Indicates the maximum length of a key (80 characters).

另请参阅:

常量字段值

MAX_VALUE_LENGTH

static final int MAX_VALUE_LENGTH

Indicates the maximum length of a string (8192 characters).

另请参阅:

常量字段值

方法详细资料

getInt

int getInt(String key,
           int defValue)

Obtains the value of a preference in the int format.

If the value is null or not in the int format, the default value is returned.

参数:

key - Indicates the key of the preference. It cannot be null or empty.

defValue - Indicates the default value to return.

返回:

Returns the value matching the specified key if it is found; returns the default value otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

getString

String getString(String key,
                 String defValue)

Obtains the value of a preference in the string format.

If the value is null or not in the string format, the default value is returned.

参数:

key - Indicates the key of the preference. It cannot be null or empty.

defValue - Indicates the default value to return.

返回:

Returns the value matching the specified key if it is found; returns the default value otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

getBoolean

boolean getBoolean(String key,
                   boolean defValue)

Obtains the value of a preference in the boolean format.

If the value is null or not in the boolean format, the default value is returned.

参数:

key - Indicates the key of the preference. It cannot be null or empty.

defValue - Indicates the default value to return.

返回:

Returns the value matching the specified key if it is found; returns the default value otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

getFloat

float getFloat(String key,
               float defValue)

Obtains the value of a preference in the float format.

If the value is null or not in the float format, the default value is returned.

参数:

key - Indicates the key of the preference. It cannot be null or empty.

defValue - Indicates the default value to return.

返回:

Returns the value matching the specified key if it is found; returns the default value otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

getLong

long getLong(String key,
             long defValue)

Obtains the value of a preference in the long format.

If the value is null or not in the long format, the default value is returned.

参数:

key - Indicates the key of the preference. It cannot be null or empty.

defValue - Indicates the default value to return.

返回:

Returns the value matching the specified key if it is found; returns the default value otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

getStringSet

Set<String> getStringSet(String key,
                         Set<String> defValue)

Obtains the value of a preference in the string set format.

If the value is null or not in the string set format, the default value is returned.

参数:

key - Indicates the key of the preference. It cannot be null or empty.

defValue - Indicates the default value to return.

返回:

Returns the value matching the specified key if it is found; returns the default value otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

getAll

Map<String,?> getAll()

Obtains all preferences from this Preferences object.

Do not modify any of the returned preferences; otherwise, data inconsistency will occur.

返回:

Returns all preferences in this Preferences object.

从以下版本开始:

3

putInt

Preferences putInt(String key,
                   int value)

Sets an int value for the key in the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to modify. It cannot be null or empty.

value - Indicates the value of the preference.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

putString

Preferences putString(String key,
                      String value)

Sets a string value for the key in the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to modify. It cannot be null or empty.

value - Indicates the value of the preference.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

putBoolean

Preferences putBoolean(String key,
                       boolean value)

Sets a boolean value for the key in the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to modify. It cannot be null or empty.

value - Indicates the value of the preference.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

putLong

Preferences putLong(String key,
                    long value)

Sets a long value for the key in the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to modify. It cannot be null or empty.

value - Indicates the value of the preference.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

putFloat

Preferences putFloat(String key,
                     float value)

Sets a float value for the key in the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to modify. It cannot be null or empty.

value - Indicates the value of the preference.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

putStringSet

Preferences putStringSet(String key,
                         Set<String> value)

Sets a string set value for the key in the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to modify. It cannot be null or empty.

value - Indicates the value of the preference.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

delete

Preferences delete(String key)

Deletes the preference with a specified key from the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

参数:

key - Indicates the key of the preference to delete. It cannot be null or empty.

返回:

Returns this Preferences object.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

clear

Preferences clear()

Clears all preferences from the Preferences object.

You can call the flush() or flushSync() method to save the Preferences object to the file.

返回:

Returns this Preferences object.

从以下版本开始:

1

flush

void flush()

Asynchronously saves the Preferences object to the file.

从以下版本开始:

1

flushSync

boolean flushSync()

Synchronously saves the Preferences object to the file.

返回:

Returns true if the Preferences instance is saved successfully; returns false otherwise.

从以下版本开始:

1

hasKey

boolean hasKey(String key)

Checks whether the Preferences object contains a preference matching a specified key.

参数:

key - Indicates the key of the preference to check for.

返回:

Returns true if the Preferences object contains a preference with the specified key; returns false otherwise.

抛出:

IllegalArgumentException - Throws this exception if key.length() exceeds MAX_KEY_LENGTH.

从以下版本开始:

1

registerObserver

void registerObserver(Preferences.PreferencesObserver preferencesObserver)

Registers an observer to listen for the change of a Preferences object.

The observer of Preferences must implement the PreferencesObserver interface. When the preference data changes, PreferencesObserver#onChange will be called.

参数:

preferencesObserver - Indicates the observer to be registered.

从以下版本开始:

1

unregisterObserver

void unregisterObserver(Preferences.PreferencesObserver preferencesObserver)

Unregisters an existing observer.

The observer of Preferences must implement the PreferencesObserver interface.

参数:

preferencesObserver - Indicates the observer to be unregistered.

从以下版本开始:

1