SharedPreferences详细介绍
作用
SharedPreferences是一种轻型的数据存储方式，它的本质是基于XML文件存储key-value键值对数据。格式如下：
<xml version='1.0' encoding='utf-8' standalone='yes' ?>
<string name="STRING_KEY">string</string>
<boolean name="BOOLEAN_KEY" value="true" /> 模式
Context.MODE_PRIVATE = 0
Context.MODE_APPEND = 32768
Context.MODE_WORLD_READABLE = 1
Context.MODE_WORLD_WRITEABLE = 2
Context.MODE_PRIVATE：为默认操作模式，代表该文件是私有数据，只能被应用本身访问，在该模式下，写入的内容会覆盖原文件的内容，如果想把新写入的内容追加到原文件中。可以使用Context.MODE_APPEND
Context.MODE_APPEND：模式会检查文件是否存在，存在就往文件追加内容，否则就创建新文件。
Context.MODE_WORLD_READABLE和Context.MODE_WORLD_WRITEABLE用来控制其他应用是否有权限读写该文件。
MODE_WORLD_READABLE：表示当前文件可以被其他应用读取；MODE_WORLD_WRITEABLE：表示当前文件可以被其他应用读写。
另外Activity还提供了另一个getPreferences(mode)方法操作SharedPreferences，这个方法默认使用当前类不带包名的类名作为文件的名称。
相关类
- SharedPreferences （接口）实现类 SharedPreferencesImpl
- Eidtor （接口） 实现类 EditorImpl
public interface SharedPreferences {
public interface OnSharedPreferenceChangeListener {
void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key);
}
public interface Editor {
// 存放字符串
Editor putString(String key, @Nullable String value);
// 存放字符串Set集合
Editor putStringSet(String key, @Nullable Set<String> values);
// 存放int
Editor putInt(String key, int value);
// 存放long
Editor putLong(String key, long value);
// 存放float
Editor putFloat(String key, float value);
// 存放boolean
Editor putBoolean(String key, boolean value);
// 根据key移除
Editor remove(String key);
// 移除所有数据
Editor clear();
// 提交事务 前面所有Eidtor的操作只能commit()再回生效
boolean commit();
// 提交事务 作用与commit()方法一样。区别
void apply();
}
Map<String, ?> getAll();
@Nullable
Set<String> getStringSet(String key, @Nullable Set<String> defValues);
int getInt(String key, int defValue);
long getLong(String key, long defValue);
float getFloat(String key, float defValue);
boolean getBoolean(String key, boolean defValue);
boolean contains(String key);
Editor edit();
void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener);
void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener);
}从上面的代码可知，SharedPreferences 是一个接口，里面有一个Eidtor接口。有一定编程经验的人都知道，put一般是存放数据的，get是获取数据。在这里也确实如此。所以SharedPreferences只具备获取数据的能力，而存储、删除使用的是Eidtor类。细心的同志可能注意到上图使用put的对象就是Eidtor类的对象。
存储的数据类型
从上面这张图片可以看出SharedPreferences可以存储boolean、String、int、long、和String类型的Set集合。从上面的Eidtor的源码也可以看出了。
存储位置
首先要使用SharedPreferences存储数据据需要获取到SharedPreferences的对象。怎么获取？使用Context的getSharedPreferences(String fileName , int mode);方法获取。看源码：
public abstract SharedPreferences getSharedPreferences(String name, @PreferencesMode int mode);这是一个抽象的方法，所以必有继承了Context的类重写了这个方法。看代码：
class ContextImpl extends Context {
private ArrayMap<String, File> mSharedPrefsPaths; // key 为文件的名字 Vuler为文件
/** *根绝这段代码产生大胆的猜想，一个应用可以产生多个SheradPrefrences，文件的名字作为唯一的标识符。事实也确实如此，自己去证明。 */
@Override
public SharedPreferences getSharedPreferences(String name, int mode) {
if (mPackageInfo.getApplicationInfo().targetSdkVersion <
Build.VERSION_CODES.KITKAT) {
if (name == null) {
name = "null";
}
}
File file;
synchronized (ContextImpl.class) {
if (mSharedPrefsPaths == null) {
mSharedPrefsPaths = new ArrayMap<>();
}
//根据文件的名 获取文件。若file为null则说明此应用还没创建以这个名字的文件。
file = mSharedPrefsPaths.get(name);
if (file == null) {
// 根据传进来的name 生成文件
file = getSharedPreferencesPath(name);
// 把文件的 存放带Map集合中
mSharedPrefsPaths.put(name, file);
}
}
return getSharedPreferences(file, mode);
}
/** *创建xml文件 **/
@Override
public File getSharedPreferencesPath(String name) {
return makeFilename(getPreferencesDir(), name + ".xml");
}
private File getPreferencesDir() {
synchronized (mSync) {
if (mPreferencesDir == null) {
mPreferencesDir = new File(getDataDir(), "shared_prefs");
}
return ensurePrivateDirExists(mPreferencesDir);
}
}
@Override
public File getDataDir() {
if (mPackageInfo != null) {
File res = null;
if (isCredentialProtectedStorage()) {
res = mPackageInfo.getCredentialProtectedDataDirFile();
} else if (isDeviceProtectedStorage()) {
res = mPackageInfo.getDeviceProtectedDataDirFile();
} else {
res = mPackageInfo.getDataDirFile();
}
if (res != null) {
if (!res.exists() && android.os.Process.myUid() == android.os.Process.SYSTEM_UID) {
Log.wtf(TAG, "Data directory doesn't exist for package " + getPackageName(),
new Throwable());
}
return res;
} else {
throw new RuntimeException(
"No data directory found for package " + getPackageName());
}
} else {
throw new RuntimeException(
"No package details found for package " + getPackageName());
}
}
private static File ensurePrivateDirExists(File file) {
return ensurePrivateDirExists(file, 0771, -1, null);
}
private static File ensurePrivateDirExists(File file, int mode, int gid, String xattr) {
if (!file.exists()) {
final String path = file.getAbsolutePath();
try {
Os.mkdir(path, mode);
Os.chmod(path, mode);
if (gid != -1) {
Os.chown(path, -1, gid);
}
} catch (ErrnoException e) {
if (e.errno == OsConstants.EEXIST) {
// We must have raced with someone; that's okay
} else {
Log.w(TAG, "Failed to ensure " + file + ": " + e.getMessage());
}
}
if (xattr != null) {
try {
final StructStat stat = Os.stat(file.getAbsolutePath());
final byte[] value = new byte[8];
Memory.pokeLong(value, 0, stat.st_ino, ByteOrder.nativeOrder());
Os.setxattr(file.getParentFile().getAbsolutePath(), xattr, value, 0);
} catch (ErrnoException e) {
Log.w(TAG, "Failed to update " + xattr + ": " + e.getMessage());
}
}
}
return file;
}
}经过上面的源码分析SharedPrefrences的文件的位置在/data/data/<应用的包名>/sgared-prefes 目录下。
SharedPrefrences 和 Eidtor 的实现类SharedPreferencesImpl 和 EidtorImpl 操作数据的实体类
看源码：
final class SharedPreferencesImpl implements SharedPreferences {
private static final String TAG = "SharedPreferencesImpl";
private static final boolean DEBUG = false;
private static final Object CONTENT = new Object();
private static final long MAX_FSYNC_DURATION_MILLIS = 256;
private final File mFile;
private final File mBackupFile;
private final int mMode;
private final Object mLock = new Object();
private final Object mWritingToDiskLock = new Object();
@GuardedBy("mLock")
private Map<String, Object> mMap; // 调用SharedPrefrences 的get方法时，实际是从这个Map集合中取值。
@GuardedBy("mLock")
private int mDiskWritesInFlight = 0;
@GuardedBy("mLock")
private boolean mLoaded = false;
@GuardedBy("mLock")
private long mStatTimestamp;
@GuardedBy("mLock")
private long mStatSize;
@GuardedBy("mLock")
private final WeakHashMap<OnSharedPreferenceChangeListener, Object> mListeners =
new WeakHashMap<OnSharedPreferenceChangeListener, Object>();
/** Current memory state (always increasing) */
@GuardedBy("this")
private long mCurrentMemoryStateGeneration;
/** Latest memory state that was committed to disk */
@GuardedBy("mWritingToDiskLock")
private long mDiskStateGeneration;
/** Time (and number of instances) of file-system sync requests */
@GuardedBy("mWritingToDiskLock")
private final ExponentiallyBucketedHistogram mSyncTimes = new ExponentiallyBucketedHistogram(16);
private int mNumSync = 0;
// 创建SharedPreferences对象调用的构造方法
SharedPreferencesImpl(File file, int mode) {
mFile = file;
mBackupFile = makeBackupFile(file);
mMode = mode;
mLoaded = false;
mMap = null;
// 重要的方法
startLoadFromDisk();
}
private void startLoadFromDisk() {
synchronized (mLock) {
mLoaded = false;
}
new Thread("SharedPreferencesImpl-load") {
public void run() {
loadFromDisk();
}
}.start();
}
private void loadFromDisk() {
synchronized (mLock) {
if (mLoaded) {
return;
}
if (mBackupFile.exists()) {
mFile.delete();
mBackupFile.renameTo(mFile);
}
}
// Debugging
if (mFile.exists() && !mFile.canRead()) {
Log.w(TAG, "Attempt to read preferences file " + mFile + " without permission");
}
Map map = null;
StructStat stat = null;
try {
stat = Os.stat(mFile.getPath());
if (mFile.canRead()) {
BufferedInputStream str = null;
try {
str = new BufferedInputStream(
new FileInputStream(mFile), 16*1024);
// 把文件中的内容 读取后存放在Map集合中。
map = XmlUtils.readMapXml(str);
} catch (Exception e) {
Log.w(TAG, "Cannot read " + mFile.getAbsolutePath(), e);
} finally {
IoUtils.closeQuietly(str);
}
}
} catch (ErrnoException e) {
/* ignore */
}
synchronized (mLock) {
mLoaded = true;
if (map != null) {
mMap = map; // 使mMap引用指向map引用指向的对象。
mStatTimestamp = stat.st_mtime;
mStatSize = stat.st_size;
} else {
mMap = new HashMap<>();
}
mLock.notifyAll();
}
}
static File makeBackupFile(File prefsFile) {
return new File(prefsFile.getPath() + ".bak");
}
void startReloadIfChangedUnexpectedly() {
synchronized (mLock) {
// TODO: wait for any pending writes to disk?
if (!hasFileChangedUnexpectedly()) {
return;
}
startLoadFromDisk();
}
}
// Has the file changed out from under us? i.e. writes that
// we didn't instigate.
private boolean hasFileChangedUnexpectedly() {
synchronized (mLock) {
if (mDiskWritesInFlight > 0) {
// If we know we caused it, it's not unexpected.
if (DEBUG) Log.d(TAG, "disk write in flight, not unexpected.");
return false;
}
}
final StructStat stat;
try {
/* * Metadata operations don't usually count as a block guard * violation, but we explicitly want this one. */
BlockGuard.getThreadPolicy().onReadFromDisk();
stat = Os.stat(mFile.getPath());
} catch (ErrnoException e) {
return true;
}
synchronized (mLock) {
return mStatTimestamp != stat.st_mtime || mStatSize != stat.st_size;
}
}
public void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
synchronized(mLock) {
mListeners.put(listener, CONTENT);
}
}
public void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
synchronized(mLock) {
mListeners.remove(listener);
}
}
private void awaitLoadedLocked() {
if (!mLoaded) {
// Raise an explicit StrictMode onReadFromDisk for this
// thread, since the real read will be in a different
// thread and otherwise ignored by StrictMode.
BlockGuard.getThreadPolicy().onReadFromDisk();
}
while (!mLoaded) {
try {
mLock.wait();
} catch (InterruptedException unused) {
}
}
}
// 从mMap中获取所有值
public Map<String, ?> getAll() {
synchronized (mLock) {
awaitLoadedLocked();
//noinspection unchecked
return new HashMap<String, Object>(mMap);
}
}
// 从mMap中获取String值
@Nullable
public String getString(String key, @Nullable String defValue) {
synchronized (mLock) {
awaitLoadedLocked();
String v = (String)mMap.get(key);
return v != null ? v : defValue;
}
}
// 从mMap中获取String Set集合值
@Nullable
public Set<String> getStringSet(String key, @Nullable Set<String> defValues) {
synchronized (mLock) {
awaitLoadedLocked();
Set<String> v = (Set<String>) mMap.get(key);
return v != null ? v : defValues;
}
}
// 从mMap中获取int值
public int getInt(String key, int defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Integer v = (Integer)mMap.get(key);
return v != null ? v : defValue;
}
}
// 从mMap中获取long 值
public long getLong(String key, long defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Long v = (Long)mMap.get(key);
return v != null ? v : defValue;
}
}
// 从mMap中获取float 值
public float getFloat(String key, float defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Float v = (Float)mMap.get(key);
return v != null ? v : defValue;
}
}
// 从mMap中获取boolean 值
public boolean getBoolean(String key, boolean defValue) {
synchronized (mLock) {
awaitLoadedLocked();
Boolean v = (Boolean)mMap.get(key);
return v != null ? v : defValue;
}
}
// mMap中是否包含Key
public boolean contains(String key) {
synchronized (mLock) {
awaitLoadedLocked();
return mMap.containsKey(key);
}
}
// 获取Editor类对象
public Editor edit() {
context.getSharedPreferences(..).edit().putString(..).apply()
synchronized (mLock) {
awaitLoadedLocked();
}
return new EditorImpl();
}
private static class MemoryCommitResult {
final long memoryStateGeneration;
@Nullable final List<String> keysModified;
@Nullable final Set<OnSharedPreferenceChangeListener> listeners;
final Map<String, Object> mapToWriteToDisk;
final CountDownLatch writtenToDiskLatch = new CountDownLatch(1);
@GuardedBy("mWritingToDiskLock")
volatile boolean writeToDiskResult = false;
boolean wasWritten = false;
private MemoryCommitResult(long memoryStateGeneration, @Nullable List<String> keysModified,
@Nullable Set<OnSharedPreferenceChangeListener> listeners,
Map<String, Object> mapToWriteToDisk) {
this.memoryStateGeneration = memoryStateGeneration;
this.keysModified = keysModified;
this.listeners = listeners;
this.mapToWriteToDisk = mapToWriteToDisk;
}
void setDiskWriteResult(boolean wasWritten, boolean result) {
this.wasWritten = wasWritten;
writeToDiskResult = result;
writtenToDiskLatch.countDown();
}
}
// Eidtor的实现类
public final class EditorImpl implements Editor {
private final Object mLock = new Object();
@GuardedBy("mLock")
private final Map<String, Object> mModified = Maps.newHashMap();
@GuardedBy("mLock")
private boolean mClear = false;
// 存储String 值
public Editor putString(String key, @Nullable String value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
// 存储String Set集合
public Editor putStringSet(String key, @Nullable Set<String> values) {
synchronized (mLock) {
mModified.put(key,
(values == null) ? null : new HashSet<String>(values));
return this;
}
}
// 存储int 值
public Editor putInt(String key, int value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
// 存储long
public Editor putLong(String key, long value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
//存储float
public Editor putFloat(String key, float value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
// 存储boolean
public Editor putBoolean(String key, boolean value) {
synchronized (mLock) {
mModified.put(key, value);
return this;
}
}
// 根据key移除
public Editor remove(String key) {
synchronized (mLock) {
mModified.put(key, this);
return this;
}
}
public Editor clear() {
synchronized (mLock) {
mClear = true;
return this;
}
}
public void apply() {
final long startTime = System.currentTimeMillis();
final MemoryCommitResult mcr = commitToMemory();
final Runnable awaitCommit = new Runnable() {
public void run() {
try {
mcr.writtenToDiskLatch.await();
} catch (InterruptedException ignored) {
}
if (DEBUG && mcr.wasWritten) {
Log.d(TAG, mFile.getName() + ":" + mcr.memoryStateGeneration
+ " applied after " + (System.currentTimeMillis() - startTime)
+ " ms");
}
}
};
QueuedWork.addFinisher(awaitCommit);
Runnable postWriteRunnable = new Runnable() {
public void run() {
awaitCommit.run();
QueuedWork.removeFinisher(awaitCommit);
}
};
SharedPreferencesImpl.this.enqueueDiskWrite(mcr, postWriteRunnable);
notifyListeners(mcr);
}
private MemoryCommitResult commitToMemory() {
long memoryStateGeneration;
List<String> keysModified = null;
Set<OnSharedPreferenceChangeListener> listeners = null;
Map<String, Object> mapToWriteToDisk;
synchronized (SharedPreferencesImpl.this.mLock) {
if (mDiskWritesInFlight > 0) {
mMap = new HashMap<String, Object>(mMap);
}
mapToWriteToDisk = mMap;
mDiskWritesInFlight++;
boolean hasListeners = mListeners.size() > 0;
if (hasListeners) {
keysModified = new ArrayList<String>();
listeners = new HashSet<OnSharedPreferenceChangeListener>(mListeners.keySet());
}
synchronized (mLock) {
boolean changesMade = false;
if (mClear) {
if (!mMap.isEmpty()) {
changesMade = true;
mMap.clear();
}
mClear = false;
}
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);
}
changesMade = true;
if (hasListeners) {
keysModified.add(k);
}
}
mModified.clear();
if (changesMade) {
mCurrentMemoryStateGeneration++;
}
memoryStateGeneration = mCurrentMemoryStateGeneration;
}
}
return new MemoryCommitResult(memoryStateGeneration, keysModified, listeners,
mapToWriteToDisk);
}
public boolean commit() {
long startTime = 0;
if (DEBUG) {
startTime = System.currentTimeMillis();
}
MemoryCommitResult mcr = commitToMemory();
SharedPreferencesImpl.this.enqueueDiskWrite(
mcr, null /* sync write on this thread okay */);
try {
mcr.writtenToDiskLatch.await();
} catch (InterruptedException e) {
return false;
} finally {
if (DEBUG) {
Log.d(TAG, mFile.getName() + ":" + mcr.memoryStateGeneration
+ " committed after " + (System.currentTimeMillis() - startTime)
+ " ms");
}
}
notifyListeners(mcr);
return mcr.writeToDiskResult;
}
private void notifyListeners(final MemoryCommitResult mcr) {
if (mcr.listeners == null || mcr.keysModified == null ||
mcr.keysModified.size() == 0) {
return;
}
if (Looper.myLooper() == Looper.getMainLooper()) {
for (int i = mcr.keysModified.size() - 1; i >= 0; i--) {
final String key = mcr.keysModified.get(i);
for (OnSharedPreferenceChangeListener listener : mcr.listeners) {
if (listener != null) {
listener.onSharedPreferenceChanged(SharedPreferencesImpl.this, key);
}
}
}
} else {
// Run this function on the main thread.
ActivityThread.sMainThreadHandler.post(new Runnable() {
public void run() {
notifyListeners(mcr);
}
});
}
}
}
private void enqueueDiskWrite(final MemoryCommitResult mcr,
final Runnable postWriteRunnable) {
final boolean isFromSyncCommit = (postWriteRunnable == null);
final Runnable writeToDiskRunnable = new Runnable() {
public void run() {
synchronized (mWritingToDiskLock) {
writeToFile(mcr, isFromSyncCommit);
}
synchronized (mLock) {
mDiskWritesInFlight--;
}
if (postWriteRunnable != null) {
postWriteRunnable.run();
}
}
};
if (isFromSyncCommit) {
boolean wasEmpty = false;
synchronized (mLock) {
wasEmpty = mDiskWritesInFlight == 1;
}
if (wasEmpty) {
writeToDiskRunnable.run();
return;
}
}
QueuedWork.queue(writeToDiskRunnable, !isFromSyncCommit);
}
private static FileOutputStream createFileOutputStream(File file) {
FileOutputStream str = null;
try {
str = new FileOutputStream(file);
} catch (FileNotFoundException e) {
File parent = file.getParentFile();
if (!parent.mkdir()) {
Log.e(TAG, "Couldn't create directory for SharedPreferences file " + file);
return null;
}
FileUtils.setPermissions(
parent.getPath(),
FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
-1, -1);
try {
str = new FileOutputStream(file);
} catch (FileNotFoundException e2) {
Log.e(TAG, "Couldn't create SharedPreferences file " + file, e2);
}
}
return str;
}
private void writeToFile(MemoryCommitResult mcr, boolean isFromSyncCommit) {
long startTime = 0;
long existsTime = 0;
long backupExistsTime = 0;
long outputStreamCreateTime = 0;
long writeTime = 0;
long fsyncTime = 0;
long setPermTime = 0;
long fstatTime = 0;
long deleteTime = 0;
if (DEBUG) {
startTime = System.currentTimeMillis();
}
boolean fileExists = mFile.exists();
if (DEBUG) {
existsTime = System.currentTimeMillis();
// Might not be set, hence init them to a default value
backupExistsTime = existsTime;
}
if (fileExists) {
boolean needsWrite = false;
if (mDiskStateGeneration < mcr.memoryStateGeneration) {
if (isFromSyncCommit) {
needsWrite = true;
} else {
synchronized (mLock) {
if (mCurrentMemoryStateGeneration == mcr.memoryStateGeneration) {
needsWrite = true;
}
}
}
}
if (!needsWrite) {
mcr.setDiskWriteResult(false, true);
return;
}
boolean backupFileExists = mBackupFile.exists();
if (DEBUG) {
backupExistsTime = System.currentTimeMillis();
}
if (!backupFileExists) {
if (!mFile.renameTo(mBackupFile)) {
Log.e(TAG, "Couldn't rename file " + mFile
+ " to backup file " + mBackupFile);
mcr.setDiskWriteResult(false, false);
return;
}
} else {
mFile.delete();
}
}
try {
FileOutputStream str = createFileOutputStream(mFile);
if (DEBUG) {
outputStreamCreateTime = System.currentTimeMillis();
}
if (str == null) {
mcr.setDiskWriteResult(false, false);
return;
}
XmlUtils.writeMapXml(mcr.mapToWriteToDisk, str);
writeTime = System.currentTimeMillis();
FileUtils.sync(str);
fsyncTime = System.currentTimeMillis();
str.close();
ContextImpl.setFilePermissionsFromMode(mFile.getPath(), mMode, 0);
if (DEBUG) {
setPermTime = System.currentTimeMillis();
}
try {
final StructStat stat = Os.stat(mFile.getPath());
synchronized (mLock) {
mStatTimestamp = stat.st_mtime;
mStatSize = stat.st_size;
}
} catch (ErrnoException e) {
// Do nothing
}
if (DEBUG) {
fstatTime = System.currentTimeMillis();
}
// Writing was successful, delete the backup file if there is one.
mBackupFile.delete();
if (DEBUG) {
deleteTime = System.currentTimeMillis();
}
mDiskStateGeneration = mcr.memoryStateGeneration;
mcr.setDiskWriteResult(true, true);
if (DEBUG) {
Log.d(TAG, "write: " + (existsTime - startTime) + "/"
+ (backupExistsTime - startTime) + "/"
+ (outputStreamCreateTime - startTime) + "/"
+ (writeTime - startTime) + "/"
+ (fsyncTime - startTime) + "/"
+ (setPermTime - startTime) + "/"
+ (fstatTime - startTime) + "/"
+ (deleteTime - startTime));
}
long fsyncDuration = fsyncTime - writeTime;
mSyncTimes.add(Long.valueOf(fsyncDuration).intValue());
mNumSync++;
if (DEBUG || mNumSync % 1024 == 0 || fsyncDuration > MAX_FSYNC_DURATION_MILLIS) {
mSyncTimes.log(TAG, "Time required to fsync " + mFile + ": ");
}
return;
} catch (XmlPullParserException e) {
Log.w(TAG, "writeToFile: Got exception:", e);
} catch (IOException e) {
Log.w(TAG, "writeToFile: Got exception:", e);
}
// Clean up an unsuccessfully written file
if (mFile.exists()) {
if (!mFile.delete()) {
Log.e(TAG, "Couldn't clean up partially-written file " + mFile);
}
}
mcr.setDiskWriteResult(false, false);
}
}通过上面的源码可以看出 getXXX()获取值的时候是SharedPrefrencesImpi 获取的，其余的操作都是通过EidtorImpi 类的对象操作的。获取值的时候是直接从SharedPrefrencesImpi类的mMap集合中获取的，一开始已经把xml文件中的值读取保存到mMap集合中了。
