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
您可以使用以下方法保存值:
public void savePreferencesForReasonCode(Context context,
String key, String value) {
SharedPreferences sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(context);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, value);
editor.commit();
}
使用这个方法，你可以从SharedPreferences中获取值:
public String getPreferences(Context context, String prefKey) {
SharedPreferences sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(context);
return sharedPreferences.getString(prefKey, "");
}
这里prefKey是用来保存特定值的键。谢谢。
其他回答
人们推荐使用SharedPreferences的方法有很多。我在这里做了一个演示项目。示例中的关键点是使用ApplicationContext &单个sharedpreferences对象。本示例演示了如何使用SharedPreferences与以下特性
使用singelton类访问/更新SharedPreferences 不需要总是为读/写SharedPreferences传递上下文 它使用apply()而不是commit() Apply()是异步保存，不返回任何东西，它首先在内存中更新值，然后将更改写入磁盘 asynchronusly。 Commit()是同步保存，它根据结果返回true/false。更改以同步方式写入磁盘 适用于android 2.3+版本
使用示例如下:-
MyAppPreference.getInstance().setSampleStringKey("some_value");
String value= MyAppPreference.getInstance().getSampleStringKey();
点击这里获取源代码 &详细的API可以在developer.android.com上找到
我创建了一个Helper类来简化我的生活。这是一个泛型类，有很多在应用程序中常用的方法，如共享首选项，电子邮件有效性，日期时间格式。在代码中复制这个类，并在任何需要的地方访问它的方法。
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.SharedPreferences;
import android.support.v4.app.FragmentActivity;
import android.view.inputmethod.InputMethodManager;
import android.widget.EditText;
import android.widget.Toast;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
/**
* Created by Zohaib Hassan on 3/4/2016.
*/
public class Helper {
private static ProgressDialog pd;
public static void saveData(String key, String value, Context context) {
SharedPreferences sp = context.getApplicationContext()
.getSharedPreferences("appData", 0);
SharedPreferences.Editor editor;
editor = sp.edit();
editor.putString(key, value);
editor.commit();
}
public static void deleteData(String key, Context context){
SharedPreferences sp = context.getApplicationContext()
.getSharedPreferences("appData", 0);
SharedPreferences.Editor editor;
editor = sp.edit();
editor.remove(key);
editor.commit();
}
public static String getSaveData(String key, Context context) {
SharedPreferences sp = context.getApplicationContext()
.getSharedPreferences("appData", 0);
String data = sp.getString(key, "");
return data;
}
public static long dateToUnix(String dt, String format) {
SimpleDateFormat formatter;
Date date = null;
long unixtime;
formatter = new SimpleDateFormat(format);
try {
date = formatter.parse(dt);
} catch (Exception ex) {
ex.printStackTrace();
}
unixtime = date.getTime();
return unixtime;
}
public static String getData(long unixTime, String formate) {
long unixSeconds = unixTime;
Date date = new Date(unixSeconds);
SimpleDateFormat sdf = new SimpleDateFormat(formate);
String formattedDate = sdf.format(date);
return formattedDate;
}
public static String getFormattedDate(String date, String currentFormat,
String desiredFormat) {
return getData(dateToUnix(date, currentFormat), desiredFormat);
}
public static double distance(double lat1, double lon1, double lat2,
double lon2, char unit) {
double theta = lon1 - lon2;
double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2))
+ Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2))
* Math.cos(deg2rad(theta));
dist = Math.acos(dist);
dist = rad2deg(dist);
dist = dist * 60 * 1.1515;
if (unit == 'K') {
dist = dist * 1.609344;
} else if (unit == 'N') {
dist = dist * 0.8684;
}
return (dist);
}
/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
/* :: This function converts decimal degrees to radians : */
/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
private static double deg2rad(double deg) {
return (deg * Math.PI / 180.0);
}
/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
/* :: This function converts radians to decimal degrees : */
/* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
private static double rad2deg(double rad) {
return (rad * 180.0 / Math.PI);
}
public static int getRendNumber() {
Random r = new Random();
return r.nextInt(360);
}
public static void hideKeyboard(Context context, EditText editText) {
InputMethodManager imm = (InputMethodManager) context
.getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(editText.getWindowToken(), 0);
}
public static void showLoder(Context context, String message) {
pd = new ProgressDialog(context);
pd.setCancelable(false);
pd.setMessage(message);
pd.show();
}
public static void showLoderImage(Context context, String message) {
pd = new ProgressDialog(context);
pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pd.setCancelable(false);
pd.setMessage(message);
pd.show();
}
public static void dismissLoder() {
pd.dismiss();
}
public static void toast(Context context, String text) {
Toast.makeText(context, text, Toast.LENGTH_LONG).show();
}
/*
public static Boolean connection(Context context) {
ConnectionDetector connection = new ConnectionDetector(context);
if (!connection.isConnectingToInternet()) {
Helper.showAlert(context, "No Internet access...!");
//Helper.toast(context, "No internet access..!");
return false;
} else
return true;
}*/
public static void removeMapFrgment(FragmentActivity fa, int id) {
android.support.v4.app.Fragment fragment;
android.support.v4.app.FragmentManager fm;
android.support.v4.app.FragmentTransaction ft;
fm = fa.getSupportFragmentManager();
fragment = fm.findFragmentById(id);
ft = fa.getSupportFragmentManager().beginTransaction();
ft.remove(fragment);
ft.commit();
}
public static AlertDialog showDialog(Context context, String message) {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setMessage(message);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
// TODO Auto-generated method stub
}
});
return builder.create();
}
public static void showAlert(Context context, String message) {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("Alert");
builder.setMessage(message)
.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
}
}).show();
}
public static boolean isURL(String url) {
if (url == null)
return false;
boolean foundMatch = false;
try {
Pattern regex = Pattern
.compile(
"\\b(?:(https?|ftp|file)://|www\\.)?[-A-Z0-9+&#/%?=~_|$!:,.;]*[A-Z0-9+&@#/%=~_|$]\\.[-A-Z0-9+&@#/%?=~_|$!:,.;]*[A-Z0-9+&@#/%=~_|$]",
Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE);
Matcher regexMatcher = regex.matcher(url);
foundMatch = regexMatcher.matches();
return foundMatch;
} catch (PatternSyntaxException ex) {
// Syntax error in the regular expression
return false;
}
}
public static boolean atLeastOneChr(String string) {
if (string == null)
return false;
boolean foundMatch = false;
try {
Pattern regex = Pattern.compile("[a-zA-Z0-9]",
Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE);
Matcher regexMatcher = regex.matcher(string);
foundMatch = regexMatcher.matches();
return foundMatch;
} catch (PatternSyntaxException ex) {
// Syntax error in the regular expression
return false;
}
}
public static boolean isValidEmail(String email, Context context) {
String expression = "^[\\w\\.-]+@([\\w\\-]+\\.)+[A-Z]{2,4}$";
CharSequence inputStr = email;
Pattern pattern = Pattern.compile(expression, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(inputStr);
if (matcher.matches()) {
return true;
} else {
// Helper.toast(context, "Email is not valid..!");
return false;
}
}
public static boolean isValidUserName(String email, Context context) {
String expression = "^[0-9a-zA-Z]+$";
CharSequence inputStr = email;
Pattern pattern = Pattern.compile(expression, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(inputStr);
if (matcher.matches()) {
return true;
} else {
Helper.toast(context, "Username is not valid..!");
return false;
}
}
public static boolean isValidDateSlash(String inDate) {
SimpleDateFormat dateFormat = new SimpleDateFormat("dd/mm/yyyy");
dateFormat.setLenient(false);
try {
dateFormat.parse(inDate.trim());
} catch (ParseException pe) {
return false;
}
return true;
}
public static boolean isValidDateDash(String inDate) {
SimpleDateFormat dateFormat = new SimpleDateFormat("dd-mm-yyyy");
dateFormat.setLenient(false);
try {
dateFormat.parse(inDate.trim());
} catch (ParseException pe) {
return false;
}
return true;
}
public static boolean isValidDateDot(String inDate) {
SimpleDateFormat dateFormat = new SimpleDateFormat("dd.mm.yyyy");
dateFormat.setLenient(false);
try {
dateFormat.parse(inDate.trim());
} catch (ParseException pe) {
return false;
}
return true;
}
}
在任何应用程序中，都有可以通过PreferenceManager实例及其相关方法getDefaultSharedPreferences(Context)访问的默认首选项。
使用SharedPreference实例，可以使用getInt(String key, int defVal)检索任意首选项的int值。在这种情况下，我们更倾向于使用计数器。
在我们的例子中，我们可以使用edit()并使用putInt(String key, int newVal)来修改SharedPreference实例。我们增加了应用程序的计数，这些计数超出了应用程序并相应地显示。
为了进一步演示这一点，再次重新启动应用程序，您将注意到每次重新启动应用程序时计数都会增加。
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
}
}
main。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>
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;
}
}
在这里，我创建了一个Helper类来使用android中的首选项。
这是helper类:
public class PrefsUtil {
public static SharedPreferences getPreference() {
return PreferenceManager.getDefaultSharedPreferences(Applicatoin.getAppContext());
}
public static void putBoolean(String key, boolean value) {
getPreference().edit().putBoolean(key, value)
.apply();
}
public static boolean getBoolean(String key) {
return getPreference().getBoolean(key, false);
}
public static void putInt(String key, int value) {
getPreference().edit().putInt(key, value).apply();
}
public static void delKey(String key) {
getPreference().edit().remove(key).apply();
}
}
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