Theming

Apps customize their look by assigning the process-wide Theme color fields in Application.onCreate and by attaching GradientDrawable backgrounds to individual views. There is no XML resource system — themes are configured in Java and applied imperatively.

Setting the global theme

Theme is a holder of public static int color fields. Assign them before any UI is built — typically the first thing in Application.onCreate:

import picodroid.app.Application;
import picodroid.graphics.Color;
import picodroid.graphics.Theme;

public final class MyApp extends Application {
    @Override
    public void onCreate() {
        Theme.colorPrimary        = Color.rgb(0x6b, 0x4e, 0xc5);
        Theme.colorBackground     = Color.rgb(0x0e, 0x0e, 0x14);
        Theme.colorSurface        = Color.rgb(0x1a, 0x1a, 0x24);
        Theme.colorText           = Color.WHITE;
        Theme.colorTextSecondary  = Color.rgb(0xc8, 0xb8, 0xee);
        Theme.colorOutline        = Color.rgb(0x44, 0x44, 0x55);
        Theme.colorOnPrimary      = Color.WHITE;

        startActivity(new picodroid.content.Intent(MyActivity.class));
    }
}

The palette is process-global (picodroid is single-app), so views read these fields at construction time. Views don’t cascade automatically — a view applies a theme color explicitly, e.g. view.setBackgroundColor(Theme.colorBackground) or label.setTextColor(Theme.colorPrimary).

Theme color fields

Field	Where it shows up
colorPrimary	Active button background, focus rings, accent strokes.
colorBackground	The root window background under all activities.
colorSurface	Container fills (cards, dialogs, list rows).
colorText	Primary text foreground.
colorTextSecondary	De-emphasized text — captions, hints, disabled text.
colorOutline	Borders on EditText, Button outlines, separators.
colorOnPrimary	Foreground on top of colorPrimary (e.g. button label color).

The fields ship with sensible dark-palette defaults; apps that don’t reassign them get those defaults.

Per-widget styling: GradientDrawable

For backgrounds that don’t fit the theme palette directly (rounded cards, gradients, stroked borders), build a GradientDrawable and attach it as the view’s background:

import picodroid.graphics.Color;
import picodroid.graphics.drawable.GradientDrawable;

GradientDrawable bg = new GradientDrawable();
bg.setColor(Color.rgb(0x1a, 0x1a, 0x24));
bg.setCornerRadius(12);
bg.setStroke(2, Color.rgb(0x44, 0x44, 0x55));   // 2 px outline

card.setBackground(bg);

Two-color gradients — there is no gradient constructor; start from new GradientDrawable() and call setGradient(startColor, endColor, orientation) (the setters return the drawable so they chain):

GradientDrawable g = new GradientDrawable()
    .setGradient(Color.rgb(0x6b, 0x4e, 0xc5),
                 Color.rgb(0x2e, 0x1a, 0x4a),
                 GradientDrawable.Orientation.TOP_BOTTOM)
    .setCornerRadius(8);
header.setBackground(g);

Orientation has just two constants: TOP_BOTTOM (1) and LEFT_RIGHT (2). Other angles and radial gradients are not supported.

Worked example

The displaydemo widget sampler ends with a themed-widgets section that walks the full palette + gradient pipeline (gradient header, surface card, pill / ghost buttons). See examples/displaydemo/.

examples/picoenvmon/ is a more realistic application — it customizes the global theme in Application.onCreate and uses gradients sparingly for mood. See examples/picoenvmon/.