Category Archives: Fixed problems

reduce macOS Finder memory usage

How to Reduce macOS Finder Memory Usage

If you are experiencing slow performance on memory on macOS (OS X), chances are your memory is running low. While Chrome is notorious for taking up large amount of memory, another culprit is actually the macOS’s own app Finder, which can use up huge amount of RAM. This post will show you how to reduce macOS Finder memory usage from almost a 1GB:

reduce macOS Finder memory usage

Down to a mere 50MB:

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letsencrypt Apache vhost

letsencrypt Apache vhost config on Ubuntu

Solving letsencrypt Apache vhost config issues

Setting up letsencrypt can be tricky with different variations of apache vhost configs. Here is how to set up letsencrypt Apache vhost config correctly:

(Note: letsencrypt is now certbot. The environment I am using is apache2 by DigitalOcean for Ubuntu/Wordpress VPS, single domain name)
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Sony Z3 Top Speaker Noise

[Solved]Sony Z3 Top Speaker Noise Problem

I have recently purchased a Sony Xperia Z3. There seems to be a strange problem with the Sony Z3 top speaker. Most of the time it produces a static background noise when I run any applications that has sound. The noise can still be heard even if I have muted the media volume. But there are occasions where the noise does not occur.

I searched online and found out this a common problem for Sony Z3, the solutions they suggested on the forums(tuning the equalizer settings) did not help me. I have also contacted Sony customer service and they responded that “It happens when you use applications that access Internet.” That seems logical enough first but I soon realized that sometimes the noise does not occur even when I am using the applications that access Internet.

When I tracked down the cases where the noise did not occur, I found out the root cause of it: The Alarm Volume. 

sony z3 sound setting

Alarm volume setting in Sony Z3 sound and notification setting

This is totally strange but it is indeed the cause of the noise. Whenever I lower the alarm volume to below about 60% and reopen the applications, the noise disappears. The alarm volume is not supposed to be related to the sound inside the applications but it seems that Sony Z3 has a software bug that caused them to be linked.

Also note that the global alarm volume in the sound settings will be overwritten by individual alarm volumes that you set in the alarm application.

sony z3 alarm setting

Alarm volume setting in Sony Z3 Alarm app

So in order to make sure the noise does not come back, you need to set both the global alarm volume and individual alarm volumes to below about 60%.

[Solved] onDataChanged not called, Android Wearable

I was doing a school project on Android Wearable for the past few days. A strange bug happened.

I used  Wearable.DataApi.putDataItem(mGoogleApiClient, putDataReq)for triggering  onDataChanged in WearableListenerService. However, I noticed that sometimes  onDataChanged is not called even though the putDataItem method has fired.

The strange thing is this bug only happens on the first call, subsequently the calls trigger normally. More interestingly, the bug only happens sometimes, once in a while, the first call will trigger normally.

Aftering debugging and getting nowhere, I decided to get help from stackoverflow. I found an answer that was relevant:

http://stackoverflow.com/a/24697312/1472186

The answer suggests adding a time field into the DataMap  so that the data is really changed every time. I did not think that was the cause of the problem, because I followed the online tutorial and had a count value in my DataMap, which increments every time. This should have caused the data to change every time.

However, after I added the time field into the DataMap, the bug disappeared. So it was true that my old implementation was not causing any changes. The count value did not work. After thinking through the process again, I figured out why.

The count did increase after each call, from 0 to 1, 2, 3, … However, those values are stored in the DataMap within the wearable device, not on the phone. So it was possible that wearable device already has a DataMap in which there is a data with count 0, although my phone app does not have the DataMap yet. When I send a new DataMap with count 0 from phone to the wearable, that DataMap is already present on the wearable, and hence no change will be detected and onDataChanged will not be triggered.

For time, since the current time is unique and always increasing, there would not be a case where the time in DataMap on the phone already exists on the wearable, hence always triggering onDataChanged.