Performance degradation in Android app due to GC?

Question

Android

In a typical piece of code, I have a performance drop of 5 seconds.

for (int i = 0; i < list.size(); i++){        \\ size ~ 30k
        String str = list.get(i);
        float strWidth = paint.measureText (str);
}

Tested in gyenni motion emulator. In a real device, processing takes as much as 50 seconds. But if I do this:

for (int i = 0; i < list.size(); i++){        \\ size ~ 30k
        String str = list.get(i);
         
        str = "a very very very long string";
        float strWidth = paint.measureText (str);
}

That, there are no problems. How can this be explained? Help me please.

Answer 1

If accuracy is not important, then you can do this:

float symWidth = paint.measureText("X");
for (int i = 0; i < list.size(); i++){        \\ size ~ 30k
        String str = list.get(i);
        float strWidth = symWidth * str.length;
}

Accuracy is far from ideal if the font is not monospaced, but fast.

Answer 2

The problem is most likely all the same in get and the loop. And the second example does not slow down because get does not happen - optimization. The cycle itself may not even occur.

Answer 3

I'll comment out the line with measureText in 1 example and everything is ok, it works fast.
Rendered Strings str; and int size = list.size() per loop - didn't help. I parallelized the code using AsyncTask, it did not help (each thread processed a separate part of the list). I also tried an array for the place of the list, and the file stream.readLine () does not help.
Is the measureText function slow?

Answer 4

measureText is very slow!
I have no idea why to consider the size for all rows at once ...
Maybe an error in the logic?