android.util.AtomicFile#exists ( )源码实例Demo

private void readEvents() {
    synchronized (mEventsLock) {
        // Read might prune events so mark as dirty.
        mEventsDirty = true;
        mEvents.clear();
        final AtomicFile readFrom = mInjector.getFile(EVENTS_FILE);
        if (readFrom != null && readFrom.exists()) {
            FileInputStream input = null;
            try {
                input = readFrom.openRead();
                readEventsLocked(input);
            } catch (IOException e) {
                readFrom.delete();
                Slog.e(TAG, "Failed to read change mEvents.", e);
            } finally {
                IoUtils.closeQuietly(input);
            }
        }
    }
}
 

private void readAmbientBrightnessStats() {
    mAmbientBrightnessStatsTracker = new AmbientBrightnessStatsTracker(mUserManager, null);
    final AtomicFile readFrom = mInjector.getFile(AMBIENT_BRIGHTNESS_STATS_FILE);
    if (readFrom != null && readFrom.exists()) {
        FileInputStream input = null;
        try {
            input = readFrom.openRead();
            mAmbientBrightnessStatsTracker.readStats(input);
        } catch (IOException e) {
            readFrom.delete();
            Slog.e(TAG, "Failed to read ambient brightness stats.", e);
        } finally {
            IoUtils.closeQuietly(input);
        }
    }
}
 

private void writeEvents() {
    synchronized (mEventsLock) {
        if (!mEventsDirty) {
            // Nothing to write
            return;
        }

        final AtomicFile writeTo = mInjector.getFile(EVENTS_FILE);
        if (writeTo == null) {
            return;
        }
        if (mEvents.isEmpty()) {
            if (writeTo.exists()) {
                writeTo.delete();
            }
            mEventsDirty = false;
        } else {
            FileOutputStream output = null;
            try {
                output = writeTo.startWrite();
                writeEventsLocked(output);
                writeTo.finishWrite(output);
                mEventsDirty = false;
            } catch (IOException e) {
                writeTo.failWrite(output);
                Slog.e(TAG, "Failed to write change mEvents.", e);
            }
        }
    }
}