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I read Hello Android book and i dont understand some parts of the PuzzleView class of the code. invalidate() function is redrawing only a part of page,not redrawing all the page. this is true?

The following function, why do we use invalidate() twice? what is difference between these two?

private void select(int x, int y) {
    invalidate(selRect);
    selX = Math.min(Math.max(x, 0), 8);
    selY = Math.min(Math.max(y, 0), 8);
    getRect(selX, selY, selRect);
    invalidate(selRect);
}

Please help me .

Cheers

Pariya
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1 Answers1

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Because the rectangle being invalidated has potentially changed between the first call and second

View.invalidate(Rect dirty) will cause the area defined in dirty to be redrawn

gheese
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