Android几种持久性储存

SharedPreference

public String getString(String key, @Nullable String defValue) { 
	synchronized (this) { 
 awaitLoadedLocked(); 
 String v = (String)mMap.get(key);
 return v != null ? v : defValue;
 }
}
private void awaitLoadedLocked() {
 while (!mLoaded) {
 try {
 mLock.wait();
 } catch (InterruptedException unused) {
 }
 }
}

private static ArrayMap<String, ArrayMap<File, SharedPreferencesImpl>> sSharedPrefsCache;
public SharedPreferences getSharedPreferences(File file, int mode) {
 synchronized (ContextImpl.class) {
 final ArrayMap<File, SharedPreferencesImpl> cache = getSharedPreferencesCacheLocked();
 sp = cache.get(file);
 if (sp == null) {
 sp = new SharedPreferencesImpl(file, mode);
 cache.put(file, sp);
 return sp;
 }
}

public void apply() {
	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 void handleStopActivity(IBinder token, boolean show, int configChanges, int seq) {
 // 省略无关。。
 // Make sure any pending writes are now committed.
 if (!r.isPreHoneycomb()) {
 QueuedWork.waitToFinish();
 }
 // 省略无关。。
}
public static void waitToFinish() {
 Runnable toFinish;
 while ((toFinish = sPendingWorkFinishers.poll()) != null) {
 toFinish.run();
 }
}

• 强烈建议不要在sp里面存储特别大的key/value, 有助于减少卡顿/anr
• 请不要高频地使用apply, 尽可能地批量提交;commit直接在主线程操作, 更要注意了
• 不要使用MODE_MULTI_PROCESS;
• 高频写操作的key与高频读操作的key可以适当地拆分文件, 由于减少同步锁竞争;
• 不要一上来就执行getSharedPreferences().edit(), 应该分成两大步骤来做, 中间可以执行其他代码.
• 不要连续多次edit(), 应该获取一次获取edit(),然后多次执行putxxx(), 减少内存波动; 经常看到大家喜欢封装方法, 结果就导致这种情况的出现.
• 每次commit时会把全部的数据更新的文件, 所以整个文件是不应该过大的, 影响整体性能;

File

SQLite