如何通过SharedPreferences存储登录值的简单解决方案。

您可以扩展MainActivity类或其他存储“想要保留的值”的类。把这些放到作者和读者课程中:

public static final String GAME_PREFERENCES_LOGIN = "Login";

这里InputClass是输入类，OutputClass是输出类。

// This is a storage, put this in a class which you can extend or in both classes:
//(input and output)
public static final String GAME_PREFERENCES_LOGIN = "Login";

// String from the text input (can be from anywhere)
String login = inputLogin.getText().toString();

// then to add a value in InputCalss "SAVE",
SharedPreferences example = getSharedPreferences(GAME_PREFERENCES_LOGIN, 0);
Editor editor = example.edit();
editor.putString("value", login);
editor.commit();

现在你可以在其他地方使用它，比如其他类。下面是OutputClass。

SharedPreferences example = getSharedPreferences(GAME_PREFERENCES_LOGIN, 0);
String userString = example.getString("value", "defValue");

// the following will print it out in console
Logger.getLogger("Name of a OutputClass".class.getName()).log(Level.INFO, userString);

使用这个例子简单明了

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.sairamkrishna.myapplication" >

   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >

      <activity
         android:name=".MainActivity"
         android:label="@string/app_name" >

         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>

      </activity>

   </application>
</manifest>

public class MainActivity extends AppCompatActivity {
   EditText ed1,ed2,ed3;
   Button b1;

   public static final String MyPREFERENCES = "MyPrefs" ;
   public static final String Name = "nameKey";
   public static final String Phone = "phoneKey";
   public static final String Email = "emailKey";

   SharedPreferences sharedpreferences;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);

      ed1=(EditText)findViewById(R.id.editText);
      ed2=(EditText)findViewById(R.id.editText2);
      ed3=(EditText)findViewById(R.id.editText3);

      b1=(Button)findViewById(R.id.button);
      sharedpreferences = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);

      b1.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            String n  = ed1.getText().toString();
            String ph  = ed2.getText().toString();
            String e  = ed3.getText().toString();

            SharedPreferences.Editor editor = sharedpreferences.edit();

            editor.putString(Name, n);
            editor.putString(Phone, ph);
            editor.putString(Email, e);
            editor.commit();
            Toast.makeText(MainActivity.this,"Thanks",Toast.LENGTH_LONG).show();
         }
      });
   }

}

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;
}

}

SharedPreferences的基本思想是将内容存储在XML文件中。

Declare your xml file path.(if you don't have this file, Android will create it. If you have this file, Android will access it.) SharedPreferences prefs = this.getSharedPreferences("com.example.app", Context.MODE_PRIVATE); Write value to Shared Preferences prefs.edit().putLong("preference_file_key", 1010101).apply(); the preference_file_key is the name of shared preference files. And the 1010101 is the value you need to store. apply() at last is to save the changes. If you get error from apply(), change it to commit(). So this alternative sentence is prefs.edit().putLong("preference_file_key", 1010101).commit(); Read from Shared Preferences SharedPreferences sp = this.getSharedPreferences("com.example.app", Context.MODE_PRIVATE); long lsp = sp.getLong("preference_file_key", -1); lsp will be -1 if preference_file_key has no value. If 'preference_file_key' has a value, it will return the value of this.

整个代码是

    SharedPreferences prefs = this.getSharedPreferences("com.example.app", Context.MODE_PRIVATE);    // Declare xml file
    prefs.edit().putLong("preference_file_key", 1010101).apply();    // Write the value to key.

阅读的代码是

    SharedPreferences sf = this.getSharedPreferences("com.example.app", Context.MODE_PRIVATE);    // Declare xml file
    long lsp = sp.getLong("preference_file_key", -1);    // Read the key and store in lsp

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);
  }*/
}

Edit

我从API Demo样本中截取了这个片段。它有一个编辑文本框。在这种情况下，它不是必需的。我也有同样的看法。

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。