我想储存一个时间值并且需要检索和编辑它。我该如何使用SharedPreferences
实现这个目的?
我想储存一个时间值并且需要检索和编辑它。我该如何使用SharedPreferences
实现这个目的?
要获取共享参数,请使用以下方法 在您的Activity中:
SharedPreferences prefs = this.getSharedPreferences(
"com.example.app", Context.MODE_PRIVATE);
读取偏好设置:
String dateTimeKey = "com.example.app.datetime";
// use a default value using new Date()
long l = prefs.getLong(dateTimeKey, new Date().getTime());
编辑和保存偏好设置。Date dt = getSomeDate();
prefs.edit().putLong(dateTimeKey, dt.getTime()).apply();
Android SDK的示例目录中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
Edit==>
我注意到,同样需要在这里解释commit()
和apply()
之间的区别。
commit()
在成功保存值时返回true
,否则返回false
。它会同步地将值保存到SharedPreferences中。
apply()
从2.3开始添加,无论成功或失败都没有返回值。它会立即将值保存到SharedPreferences中,但是会启动一个异步的提交。
更多细节请参见此处。
this.getSharedPreferences
给我返回以下错误:The method getSharedPreferences(String, int) is undefined for the type MyActivity
。 - Si8要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();
要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*/
}
编辑sharedpreference
中的数据
SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();
editor.putString("text", mSaved.getText().toString());
editor.putInt("selection-start", mSaved.getSelectionStart());
editor.putInt("selection-end", mSaved.getSelectionEnd());
editor.apply();
从 sharedpreference
中检索数据
SharedPreferences prefs = getPreferences(MODE_PRIVATE);
String restoredText = prefs.getString("text", null);
if (restoredText != null)
{
//mSaved.setText(restoredText, TextView.BufferType.EDITABLE);
int selectionStart = prefs.getInt("selection-start", -1);
int selectionEnd = prefs.getInt("selection-end", -1);
/*if (selectionStart != -1 && selectionEnd != -1)
{
mSaved.setSelection(selectionStart, selectionEnd);
}*/
}
编辑
我从API Demo示例中获取了这段代码片段。它包含一个EditText
文本框,在这个context
中是不必要的。我正在对此进行评论。
写作:
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", "");
单例共享首选项类。将来可能有助于他人。
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
public class SharedPref
{
private static SharedPreferences mSharedPref;
public static final String NAME = "NAME";
public static final String AGE = "AGE";
public static final String IS_SELECT = "IS_SELECT";
private SharedPref()
{
}
public static void init(Context context)
{
if(mSharedPref == null)
mSharedPref = context.getSharedPreferences(context.getPackageName(), Activity.MODE_PRIVATE);
}
public static String read(String key, String defValue) {
return mSharedPref.getString(key, defValue);
}
public static void write(String key, String value) {
SharedPreferences.Editor prefsEditor = mSharedPref.edit();
prefsEditor.putString(key, value);
prefsEditor.commit();
}
public static boolean read(String key, boolean defValue) {
return mSharedPref.getBoolean(key, defValue);
}
public static void write(String key, boolean value) {
SharedPreferences.Editor prefsEditor = mSharedPref.edit();
prefsEditor.putBoolean(key, value);
prefsEditor.commit();
}
public static Integer read(String key, int defValue) {
return mSharedPref.getInt(key, defValue);
}
public static void write(String key, Integer value) {
SharedPreferences.Editor prefsEditor = mSharedPref.edit();
prefsEditor.putInt(key, value).commit();
}
}
只需在MainActivity
上调用SharedPref.init()
一次即可。
SharedPref.init(getApplicationContext());
写入数据
SharedPref.write(SharedPref.NAME, "XXXX");//save string in shared preference.
SharedPref.write(SharedPref.AGE, 25);//save int in shared preference.
SharedPref.write(SharedPref.IS_SELECT, true);//save boolean in shared preference.
读取数据
String name = SharedPref.read(SharedPref.NAME, null);//read string in shared preference.
int age = SharedPref.read(SharedPref.AGE, 0);//read int in shared preference.
boolean isSelect = SharedPref.read(SharedPref.IS_SELECT, false);//read boolean in shared preference.
最简单的方法:
保存:
getPreferences(MODE_PRIVATE).edit().putString("Name of variable",value).commit();
获取:
your_variable = getPreferences(MODE_PRIVATE).getString("Name of variable",default value);
存储信息
SharedPreferences preferences = getSharedPreferences(PREFS_NAME,Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("username", username.getText().toString());
editor.putString("password", password.getText().toString());
editor.putString("logged", "logged");
editor.commit();
重置您的偏好设置
SharedPreferences.Editor editor = preferences.edit();
editor.clear();
editor.commit();
//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);
}
}
//saving a boolean into prefs
SharedPrefs.savePref(this, SharedPrefs.KEY_MY_SHARED_BOOLEAN, booleanVar);
您可以通过以下方式检索您的SharedPreferences
//getting a boolean from prefs
booleanVar = SharedPrefs.getBoolean(this, SharedPrefs.KEY_MY_SHARED_BOOLEAN);
在任何应用程序中,都可以通过PreferenceManager
实例及其相关方法getDefaultSharedPreferences(Context)
访问默认偏好设置。
使用SharedPreference
实例,可以使用getInt(String key, int defVal)检索任何首选项的int值。在这种情况下,我们感兴趣的首选项是counter。
在我们的情况下,我们可以使用edit()修改SharedPreference
实例,并使用putInt(String key, int newVal)
将计数器递增到我们的应用程序中,使其持久存在应用程序之外并相应地显示。
要进一步演示此功能,请重新启动您的应用程序,您将注意到每次重新启动应用程序时计数器都会增加。
PreferencesDemo.java
代码:
package org.example.preferences;
import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.widget.TextView;
public class PreferencesDemo extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Get the app's shared preferences
SharedPreferences app_preferences =
PreferenceManager.getDefaultSharedPreferences(this);
// Get the value for the run counter
int counter = app_preferences.getInt("counter", 0);
// Update the TextView
TextView text = (TextView) findViewById(R.id.text);
text.setText("This app has been started " + counter + " times.");
// Increment the counter
SharedPreferences.Editor editor = app_preferences.edit();
editor.putInt("counter", ++counter);
editor.commit(); // Very important
}
}
主要文件.xml
代码:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:id="@+id/text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />
</LinearLayout>
要将值存储在共享首选项中:
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = sp.edit();
editor.putString("Name","Jayesh");
editor.commit();
要从共享首选项中检索值:
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this);
String name = sp.getString("Name", ""); // Second parameter is the default value.