SharedPreferences

Question

问题1

sp初始化是读取所有的文件，还是指定文件的数据。

问题2

sp读取文件后会把数据保存到map中，如果后续我pusString() 数据了，还需要重新读取文件吗.

启动变慢

sp可能导致启动变慢 :

private void startLoadFromDisk() {
    synchronized (mLock) {
        mLoaded = false;
    }
    new Thread("SharedPreferencesImpl-load") {
        public void run() {
            loadFromDisk();
        }
    }.start();
}

mLock是异步操作
如果启动的时候，主线程读取，会导致启动变慢

@Override
public boolean getBoolean(String key, boolean defValue) {
    synchronized (mLock) {
        awaitLoadedLocked();
        Boolean v = (Boolean)mMap.get(key);
        return v != null ? v : defValue;
    }
}

@GuardedBy("mLock")
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) {
        }
    }
    if (mThrowable != null) {
        throw new IllegalStateException(mThrowable);
    }
}