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05 Compose - Layout – Box and Modifier Functions 1

one_past_last_jedi profile image One Past Last Jedi Updated on ・5 min read

Introduction:

In this Lecture we will talk about the most used Modifier Function.

Modifier.Background():

First, some function has overload function like this one has 2 overloads function.

1/

fun Modifier.background(
    color: Color, 
    shape: Shape = RectangleShape
): Modifier
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2/

fun Modifier.background(
    brush: Brush, 
    shape: Shape = RectangleShape, 
    alpha: Float = 1.0f
): Modifier
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color:

we can choose color by one of the following method.

1/ By choose from default color like this:

.background(Color.Green)
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2/ Or by choose red, green, blue alpha as Float number [0f, 1f] like this:

.background(Color(red = 0.5f, green = 0.2f, blue = 0.7f, alpha = 1.0f))
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3/ Or by choose red, green, blue alpha as Int number [0, 255] like this:

.background(Color(red = 50, green = 100, blue = 200, alpha = 255))
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4/ Or by choose Hex-Format like this:

.background(Color(0xFFaa9911))
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Shape:

Can be RectangleShape or CircleShape or more advanced Shape that you need to use advanced function to do it. Here an example of CircleShape:

.background(Color(0xFFaa9911), shape = CircleShape,)
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brush:

1/

horizontalGradient(
colors: List<Color>, 
startX: Float = 0.0f, 
endX: Float = Float.POSITIVE_INFINITY, 
tileMode: TileMode = TileMode.Clamp)
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Creates a horizontal gradient with the given colors evenly dispersed within the gradient.
Example:

.background(brush=
                Brush.horizontalGradient(
                colors = listOf(Color.Red, Color.Blue, Color.Green),
                startX = 100.5f,
                endX = Float.POSITIVE_INFINITY,
                tileMode = TileMode.Mirror,)
                       )
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2/

horizontalGradient(vararg colorStops: Pair<Float, Color>, 
startX: Float = 0.0f, 
endX: Float = Float.POSITIVE_INFINITY, 
tileMode: TileMode = TileMode.Clamp)
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Creates a horizontal gradient with the given colors dispersed at the provided offset defined in the colorstop pair.
Example:

.background(brush=
                Brush.horizontalGradient(
                    (0.2f to Color.Red),
                    (0.4f to Color.Blue),
                    (0.9f to Color.Green),
                startX = 0.0f,
                endX = Float.POSITIVE_INFINITY,
                tileMode = TileMode.Clamp,)
                       )
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3/

linearGradient(vararg colorStops: Pair<Float, Color>, 
start: Offset = Offset.Zero, 
end: Offset = Offset.Infinite, 
tileMode: TileMode = TileMode.Clamp)
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Creates a linear gradient with the provided colors along the given start and end coordinates.
Example:

.background(brush=
                Brush.linearGradient(
                    (0.2f to Color.Red),
                    (0.4f to Color.Blue),
                    (0.9f to Color.Green),
                tileMode= TileMode.Clamp,)
                       )
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4/

linearGradient(colors: List<Color>, 
start: Offset = Offset.Zero, 
end: Offset = Offset.Infinite, 
tileMode: TileMode = TileMode.Clamp)
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Creates a linear gradient with the provided colors along the given start and end coordinates.

5/

radialGradient(colors: List<Color>, 
center: Offset = Offset.Unspecified, 
radius: Float = Float.POSITIVE_INFINITY, 
tileMode: TileMode = TileMode.Clamp)
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Creates a radial gradient with the given colors evenly dispersed within the gradient.
Example:

.background(brush=
                Brush.radialGradient(
                    colors= listOf(Color.Green, Color.Blue, Color.Yellow),
                    center= Offset.Unspecified,
                    radius= Float.POSITIVE_INFINITY,
                    tileMode= TileMode.Clamp),
                       )
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6/

radialGradient(vararg colorStops: Pair<Float, Color>, 
center: Offset = Offset.Unspecified, 
radius: Float = Float.POSITIVE_INFINITY, 
tileMode: TileMode = TileMode.Clamp)
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Creates a radial gradient with the given colors at the provided offset defined in the colorstop pair.

7/

sweepGradient(colors: List<Color>, 
center: Offset = Offset.Unspecified)
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Creates a sweep gradient with the given colors dispersed evenly around the center.
Example:

.background(brush=
                Brush.sweepGradient(
                    colors= listOf(Color.Green, Color.Blue, Color.Yellow),
                    center= Offset.Unspecified,
                                   ),
                       )
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8/

sweepGradient(vararg colorStops: Pair<Float, Color>, 
center: Offset = Offset.Unspecified)
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Creates a sweep gradient with the given colors dispersed around the center with offsets defined in each colorstop pair.

9/

verticalGradient(colors: List<Color>, 
startY: Float = 0.0f, 
endY: Float = Float.POSITIVE_INFINITY, 
tileMode: TileMode = TileMode.Clamp)
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Creates a vertical gradient with the given colors evenly dispersed within the gradient.
Example:

.background(brush=
                Brush.verticalGradient(
                    colors= listOf(Color.Green, Color.Blue, Color.Yellow),
                                   ),
                       )
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10/

verticalGradient(vararg colorStops: Pair<Float, Color>, 
startY: Float = 0f, 
endY: Float = Float.POSITIVE_INFINITY, 
tileMode: TileMode = TileMode.Clamp)
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Creates a vertical gradient with the given colors at the provided offset defined in the PairFloat,Color.

Modifier.fillMaxSize(fraction: Float = 1f)

It make the Box() or the widget as big as the available to it. For example if we apply it to our Box(), the box will take the whole screen:

@Composable
fun MyBox()
{
    Box(
        contentAlignment = Alignment.TopEnd,
        modifier = Modifier
            .background(color = Color.Yellow)
            .fillMaxSize()
            .padding(all = 30.dp)
       )
    {
        Text(text = "Hello Box 1")
    }
}
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We notice that contentAlignment

is Alignment the Child of the Box inside the Box.

We can also make it to fill some percent of max size like this:

.fillMaxSize(fraction = 0.5f)
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Bact to the Box():

Box can have more than one Child but children will be stacked one on top of the other.
A box with no content that can participate in layout, drawing, pointer input due to the modifier applied to it. For example:

Box {
    Box(Modifier.fillMaxSize().background(Color.Cyan))
    Box(
        Modifier.matchParentSize()
            .padding(top = 20.dp, bottom = 20.dp)
            .background(Color.Yellow)
    )
    Box(
        Modifier.matchParentSize()
            .padding(40.dp)
            .background(Color.Magenta)
    )
    Box(
        Modifier.align(Alignment.Center)
            .size(300.dp, 300.dp)
            .background(Color.Green)
    )
    Box(
        Modifier.align(Alignment.TopStart)
            .size(150.dp, 150.dp)
            .background(Color.Red)
    )
    Box(
        Modifier.align(Alignment.BottomEnd)
            .size(150.dp, 150.dp)
            .background(Color.Blue)
    )
}
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Finally:

We will continue discover more Modifier Functions because most those functions can be applied to most widgets (Composable function).
See you 😄

================================================

You can join us in the discord server
https://discord.gg/TWnnBmS
and ask me any questions in (#kotlin-and-compose) channel.

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