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I'm thinking about the usage of percent, example, in margins.

We can use overlay to separate our layout by DPI sizes, but why can't we use percentage?

Something like that:

Display display = getWindowManager().getDefaultDisplay();

float width = display.getWidth();
float height = display.getHeight();

//20% of left margin
float imageMarginLeft = ( width * 20 ) / 100;

And then set this margin to the image, or whatever element.

Is this bad?

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You can simplify math whenever possible. No reason to multiply by 20 then divide by 100. Just multiply by .20. If you needed a result that was twenty percent in addition to 100 percent of what you already had you could multiply by 1.2. It saves a process making your code just a tad more efficient!

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    \$\begingroup\$ The compiler will probably optimize the expression, but even if it doesn't, the efficiency gain is negligible. \$\endgroup\$ – S.L. Barth - Reinstate Monica Aug 3 '12 at 7:49
  • \$\begingroup\$ @S.L. Barth-Nowadays your right but people used to count processes, and I was taught that inefficient code should never be a supplement for efficient code. Yes, this one computation will never be recognized, but discounting simple math procedures over a million lines of code is arguably incorrect. And for that matter why not? I look at that line and think well that's not very sharp, but to each their own I suppose. \$\endgroup\$ – ChiefTwoPencils Aug 3 '12 at 7:51
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    \$\begingroup\$ Seems we've been taught different things then. I was taught that "It's easier to make correct code go fast, than to make fast code correct". Either way, I do agree that it's good to simplify maths - in general it makes the code more legible, and it may prevent rounding errors. \$\endgroup\$ – S.L. Barth - Reinstate Monica Aug 3 '12 at 8:09
  • \$\begingroup\$ @S.L.Barth- Perfect, that was my true intent in passing the info, the so called efficiency was more of thing to continually think about. I like the quote! Real similar to "cheap blanks aren't good and good blanks aren't cheap"!) \$\endgroup\$ – ChiefTwoPencils Aug 3 '12 at 8:12

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