What does top, left, right and bottom mean in Android Rect object

Question

I have an Android project where I should make Apples fall. The apples are painted in a Rect. So I created a function that change the Rect position and repaint. Here's my function :

private void updateApplesPosition() {
    for(Rect rect:fallingDownFruitsList)
        rect.set(rect.left, rect.top +10, rect.right, rect.bottom +10);
}

I have a problem : the Apples don't fall but go from right to left. To make the apples fall I changed the code by this :

private void updateApplesPosition() {
    for(Rect rect:fallingDownFruitsList)
        rect.set(rect.left+10, rect.top, rect.right+10, rect.bottom);
}

they dont go by themselves, you draw them and the bug is there — pskink, Mar 23 '14 at 10:20
`Rect` works just fine, therefore the problem is how you draw them. — Simon, Mar 23 '14 at 10:26

score 221 · Accepted Answer · answered Oct 08 '14 at 09:21

221

This image will explain you in detail:

enter image description here

left The X coordinate of the left side of the rectangle

top The Y coordinate of the top of the rectangle

right The X coordinate of the right side of the rectangle

bottom The Y coordinate of the bottom of the rectangle

enter image description here

answered Oct 08 '14 at 09:21

LOG_TAG

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Thanks alot @Log, I've been breaking my head for two days to understand what left, right and bottom meant. It's unfortunate Android developers documentation is so unexplanatory about this class. – Harisewak Mar 13 '16 at 16:31
@LOG_TAG : The values are in pixels or integers? – Aniruddha Jul 15 '16 at 15:57
rect.top will gives the pixel value or dp value ? – Bhaumik Ghodasara Apr 18 '19 at 05:55
The values are in pixels – Abhriya Roy Jun 17 '19 at 03:57

score 3 · Answer 2 · answered Mar 23 '14 at 10:05

3

From the docs

Parameters

left The X coordinate of the left side of the rectangle

top The Y coordinate of the top of the rectangle

right The X coordinate of the right side of the rectangle

bottom The Y coordinate of the bottom of the rectangle

answered Mar 23 '14 at 10:05

adneal

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I have read the docs but why when I do rect.top +10 it goes to left and not going down – Hunsu Mar 23 '14 at 10:10
@user230137 _setBounds(x-width/2, y-height/2, x+width/2, y+height/2)_ where _int width = getWidth()/10;int height = getHeight()/10;_ – LOG_TAG Oct 08 '14 at 10:29
@adneal : are these values in pixels? – Aniruddha Jul 15 '16 at 15:58
@Aniruddha yes the values are in pixels – Aniruddha K.M Jan 04 '17 at 12:21

score 1 · Answer 3 · answered Jun 29 '20 at 12:45

Adding a crucial information.

The documentation says:

Note that the right and bottom coordinates are exclusive.

So if your rectangle is a single pixel at position 10,10

left = 10 : The X coordinate of the left side of the rectangle

top = 10 : The Y coordinate of the top of the rectangle = 10

right = 11 : The X coordinate of the right side of the rectangle plus one

bottom = 11 : The Y coordinate of the bottom of the rectangle plus one

Note that the right and bottom coordinates are exclusive.

The methods getWidth is declared as such

public final int width() { return right - left; }

Here it will return 11 - 10 = 1, as expected.

https://developer.android.com/reference/android/graphics/Rect

What does top, left, right and bottom mean in Android Rect object

3 Answers3

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