SharedPreferences 还支持多种不同的数据类型存储，如果存储的数据类型是整型，那么读取出来的数据也是整型的，存储的数据是一个字符串，读取出来的数据仍然是字符串。这样你应该就能明显地感觉到，使用SharedPreferences 来进行数据持久化要比使用文件方便很多。
目录导航
- sharedPreferences简要的说明
- sharedPreferences的使用步骤
- sharedPreferences的项目结构
- sharedPreferences的项目代码
- sharedPreferences的实现原理
- sharedPreferences的友情链接
简单说明
1. SharedPreferences是使用键值对的方式来存储数据的.
2. SharedPreferences保存的数据将持续整个用户会话，即使你的应用程序被杀掉(killed)，直到应用程序卸载
3. SharedPreferences有三种模式：
- Context.MODE_PRIVATE：别的应用不能访问得到SharedPreferences对象
- Context.MODE_WORLD_READABLE：别的应用可以访问，并且是可以读取SharedPreferences中的数据，但不能写入数据
- Context.MODE_WORLD_WRITEABLE:别的应用可以访问，可以在SharedPreferences中写入修改数据
4. Android提供了三种方式得到SharedPreferences 对象：本质上都是调用Context 类中的getSharedPreferences()方法：
- Context类中的getSharedPreferences()：两个参数，第一个指定生成文件的名称，第一个是操作模式。这样可以在一个Activity中创建多个SharedPreferences的文件
- Activity类中的getPreferences()：一个参数，操作模式。使用当前活动的类名作为文件的名称
- PreferenceManager类中的getDefaultSharedPreferences()：一个Context参数，使用当前应用程序的包名作为前缀来命名SharedPreferences文件
使用步骤
1. 向SharedPreferences中写入数据，分为四步：
- 通过上述说明，得到SharedPreferences对象
- 调用SharedPreferences 对象的edit()方法来获取一个SharedPreferences.Editor 对象
- 向SharedPreferences.Editor 对象中添加数据
- 调用commit()方法将添加的数据提交，从而完成数据存储操作
2. 向SharedPreferences中读取数据，分为两步：
- 通过上述说明，得到SharedPreferences对象
- 调用SharedPreferences的getXXX()方法得到数据
项目结构
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+MPVM+adbPrADolNEgYRh+8NWtmTNfPfvB18c/bv/2k5u//eTm8Y/bz37w9cyZr5L0UTb4EAZsKKlBwjD87ocfT1765thy68ib/3v0zPWn32m9fvnb70yLlzLCKRCwo7wGgSTk0zYAw8AgAOAOBgEAdzAIALiDQQDAHQwCAO5gEABwB4MAgDtTM8jbxx9Wti8vnJ5WZwDAjRwZBIkAFI58GcS4TauHAJDKSAZZXFysmlhYWEiti0EA9gEjGaTVahkN0mq1Uuva2OGL8/UvztdH6SEATJRRVzFLS0uKPpaWlmwqJhnk/64e+ubcX935+uhXi3f9ceUvt07++c6Hfy3c37toVPzVlTi2a0iAMQBMglEN0m63a7VapI9ardZut20qJhmk0/jba7/5iztfH738q7s2f33Xu0f+7JtTfyPc35ODIa7HlB4MAJNlDGdSV1dXI4OsrKxY1koyyOrKe889+7S4ra68J9wv60GLDY2yAAnYAtgDxmCQbrdbr9d7E5But2tZa7RVzODWsCCtpN+dBICxMZ5Pc9fX16vV6sbGhn2VUVYxwhJFSg5t+P2o0aBhLAwAY2Zs3wdZXl7OVN74we0X5+tzL/1rhlVMaD5rGi9u8AfAJMnXN8q+OF9PW8UAQI7I3ZV1aasYAMgRuTMIABQIDAIA7mAQAHAHgwCAOxgEANzBIADgDgYBAHcwCAC4U0iDELAKkBP2iUFcJDLsut7RSbqor+FzrQ7sI/aPQTJnrGIQgJHBIBMCg0ApKLBBRi2DQQBGptgG2byxMzu/Nju/tnljJ6mMjByL2DeIlt6sZY4IthEyjaK9howSoU1pv2gQQ0Y0QLEotkFm59eOnDx35OS52fm1pDICSqCZZBDhnmbgDwb0oEY8o2j4nuf16g0EYiivthnvjwxiyogGKBr7xCDH6hYGUZYt8U3DAFZnFYMiDd8Lmg3fC5phM/Di5rRZiNJmdHNgEHNGNEDBKLZBNls7x+prT81/tNmyWMVYGqQZeBX9np4vBHc0BgJJLJ9mEJwBxafYBslYRlzFmMd9v9RgbDcDL6rRDDzP86IZSbSWSSgvVhVviKsYLSMaoGgU2CAun+aK5y6DpFVMvCLxfN8zaSBsBp7pF/KE8s3Aq/i+nvgsnEnll/Wg+JTMIAAwVgppEADICRgEANzBIADgDgYBAHcwCAC4g0EAwB0MAgDuYBAAcAeDAIA7hTQIScsAOWGfGMROIuSDAYyZ/WMQi+tiMAjAmJmaQRYXF6smFhYWUuvm0iDkjEEZmZpBWq2W0SCtViu17gj5IBgEYJxMcxWztLSk6GNpacmmomvS8pBsDinwQwgNEsMI5RBl4e83xGIkj0GZmKZB2u12rVaL9FGr1drttk3FEZKWB/E/ejayHMceZZlKWpEzU8NwSKwhQCmY8pnU1dXVyCArKyuWtRyTluVVTPIvOiRFmQ4cgUEABkzZIN1ut16v9yYg3W7XspZj0nKkhoSM1F6YsvjDDppB+r/ugEEAekz/09z19fVqtbqxsWFfZdQzqQlZymEz8Dzfj3/DQVvFxOHs4i/NYBAoL9M3SBiGy8vLmcqP/GluQpay6ozQfCZVqC9W7+/kTCqUiVwYJCuTS1rmV1wAMlFIg0wKFiIAGcEgfXrLFfwBkAkMAgDuYBAAcAeDAIA7GAQA3MEgAOBOGQ3ycgIXL16cdtcACgYGiZmbm0MiAJkor0H0nZ1O59SpU0gEwB4MIu003uWIHFpke9fYmeCxyJ2FUhpka2tra2sr612ZwSBQAspokN25QzabU9tZL60p9KU4GARKb5ATMwcf+dn9u3OHHn3o/hMzBzFIFjAIlNsgJ2YOHn7wJ9HNww/eJ0pErabFIoZhKAaI3P38S2Le8tV+CLO0iujdGNwlhI/c/fjj5qhnkYZf8YJGvxt+Iz54XFbvpJK5FmhV4nr9GoNA2NTDYRAosUFWXnjgnnsPKCuXe+49sPLCAyaDmMKZ9UAiJTRRjUTTk1aF8oaoZ4WGHw1f8VJisTW9k5JBxCqqovrHV3Lqhx0Og0CJDbI7d+jE0YOHH7xPmoMcTZ6D6G/whpmCySBRuWiPOV1Vi3pWEY+X9Lfxdyz03NdB5qvavjg7ST0cBoFyG6QnkUcfGpwHOZp8HsQYzmxrkH7BeNQm5DOrUc8qaUPa2EkMApOk7Aax/SzGHM4cr2fCsBEoOe5KpLuY4ZyU8K5GPSukDWljJ4cbRFjORJqTdww5NAaBUhrE6fsgCeHM8W41b/mqOr2oyLfM+cz6mRWB1CFt6qSdQYTjRl3FIJBOGQ2SdF3MmL+T6gRRz1AsMEieDCJNW8QfmiDDFXJKGQ2ST4h6hiKCQQDAHQwCAO5gEABwB4MAgDsYBADcwSAA4A4GAQB3CmmQt48/rGxfXjg97U4BlJF9YpDxSGQv40sB9gXTNMibb765u7vrUNFoEOOWrV0MApCRaRqkWq1Wq9WzZ892u91MFSdlEADIyPQNUq1Wa7XapUuX7Cva2AGDAOwBuTBIj4WFhVarZVMxssPmjZ3Z+bXZ+bXNGztJZQTSooPV4J/46lgpiDBr1nFiawCFJ0cG6XHlypXUipEdZufXjpw8d+Tkudn5taQyAmnRwbJBJG+IYcVZs44TWwMoPDkyyPz8/Oeff25TUTfIsbqlQVJzRk3hg+ZkVOus48TWAApPXgxy4cKFO3fuWFaMVzGtnWP1tafmP9psWa9iJmoQY9YxBoH9y/QN8s4773Q6nUwVXc+kZjOInIWqR41aZx0ntgZQeKZpkIWFhe3tbYeKrp/mZpyD+PqpT6es48TWAArP/vlO6li/DzLehQbLFti3FNIgkweDAFiBQYxgEAArMAgAuINBAMAdDAIA7mAQAHAHgwCAOxgEANzBIADgTiENQtIyQE7YJwYZq0QaPt//ArCDpGUdDAJgy/Sv7s9f0jIGAbBl+gbJX9IyBgGwJRcG2ZOkZenHYOIbhmDkgUHEC+Kki+PizGSpQeI/oHzkyCATT1qOI4GEbGVDMPJwg4jBQoO9XHwLZSVHBtm7pGV5wGvTh6EGiecf4jSkt5ffu4PSkReD7EnScl8hzcAT5iJ6MHKaQRJF0XMRHoESMX2D7GHSchg2A8/z/YFAEoKRRYOIqol/MkY4I9IvGZjOlwDse0qVtBxqSenGYOT4s5jobuFe81lTfpAOysn++U7qWJOWAcCKQhoEAHICBgEAdzAIALiDQQDAHQwCAO5gEABw5/8BFg89JackK/8AAAAASUVORK5CYII=" alt="" />
项目代码
一、 AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.linux.sharedpreferencestest"> <application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application> </manifest>
二、 MainActivity.java:
在oncreate方法中初始化一些组件：
private TextView textView; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = (TextView) findViewById(R.id.textView);
}
创建sharedpreference，并且写入数据：
// 在share preference中写入数据
public void write(View view) {
//PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences preferences = this.getPreferences(Context.MODE_PRIVATE);
//SharedPreferences preferences = this.getSharedPreferences("Linux", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit(); Set<String> stringSet = new HashSet<>();
stringSet.add("Huhx");
stringSet.add("Tomhu");
editor.putInt("int", 3);
editor.putString("name", "Linux");
editor.putStringSet("set", stringSet); editor.commit();
Toast.makeText(MainActivity.this, "write to sharde preference success!", Toast.LENGTH_SHORT).show();
}
创建sharedpreference，并且读取数据：
//在share preference中读取数据
public void read(View view) {
SharedPreferences preferences = this.getPreferences(Context.MODE_PRIVATE);
int intData = preferences.getInt("int", 0);
String name = preferences.getString("name", "无名");
Set<String> set = preferences.getStringSet("set", null); StringBuffer stringBuffer = new StringBuffer();
stringBuffer.append("int: " + intData + "\n");
stringBuffer.append("name: " + name + "\n");
int length = set == null ? 0 : set.size();
stringBuffer.append("set size: " + length + "\n"); textView.setText(stringBuffer.toString());
Toast.makeText(MainActivity.this, "read from shared preference success!", Toast.LENGTH_SHORT).show();
}
三、 activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.linux.sharedpreferencestest.MainActivity"> <TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!" /> <Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="write"
android:text="writeToShare" /> <Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="read"
android:text="readFromShare" />
</LinearLayout>
实现原理
- 数据的存储：
public final class EditorImpl implements Editor {
private final Map<String, Object> mModified = Maps.newHashMap();
private boolean mClear = false;
public Editor putString(String key, @Nullable String value) {
synchronized (this) {
mModified.put(key, value);
return this;
}
}
}- 数据的读取：
@Nullable
public String getString(String key, @Nullable String defValue) {
synchronized (this) {
awaitLoadedLocked();
String v = (String)mMap.get(key);
return v != null ? v : defValue;
}
}
- 数据文件：
SharedPreferencesImpl(File file, int mode) {
mFile = file;
mBackupFile = makeBackupFile(file); // 生成bak备份文件
mMode = mode;
mLoaded = false;
mMap = null;
startLoadFromDisk(); //命名文件，解析xml文件，并且将键值对存放到Map中
}- 原理说明：写入：
1. SharedPreferences preferences = this.getPreferences(Context.MODE_PRIVATE);第一次执行的时候，android在/data/data/<package name>/shared_prefs创建了一个xml文件和一个Modifymap：
aaarticlea/png;base64,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" alt="" />
2. SharedPreferences.Editor editor = preferences.edit();生成一个EditorImpl，里面有一个hashmap，代码putXXX()都是存放在这个map里面的：具体代码见上述数据的存储：
3. editor.commit();提交到内存，并且比较modifymap和map，更新map。然后将内存中的内容写入文件当中
for (Map.Entry<String, Object> e : mModified.entrySet()) {
String k = e.getKey();
Object v = e.getValue();
if (v == this || v == null) {
if (!mMap.containsKey(k)) {
continue;
}
mMap.remove(k);
} else {
if (mMap.containsKey(k)) {
Object existingValue = mMap.get(k);
if (existingValue != null && existingValue.equals(v)) {
continue;
}
}
mMap.put(k, v);- 原理说明：读取：
- SharedPreferences preferences = this.getPreferences(Context.MODE_PRIVATE);得到上述的文件，解析成键值对存放在map当中
- String name = preferences.getString(key, defvlue);实际上是执行：String v = (String)mMap.get(key); return v != null ? v : defValue;
- 文件位置: /data/data/<package name>/shared_prefs/文件名.xml: