Applying Shadow Effect on Android TextView

Overview

Text shadow enhances text legibility and visual depth by adding a soft outline or offset layer behind a TextView. Shadow effects are commonly used to make text stand out over images, gradients, or complex backgrounds. Android provides built-in support for shadow rendering via APIs and XML attributes.

This document explains how to apply shadow effects on text in Android using both XML and programmatic approaches, along with design considerations and advanced usage patterns.

Shadow in Typography — Why It Matters

Shadow in typography can:

• Improve online readability in low-contrast areas
• Add visual hierarchy to UI elements
• Provide subtle design accents without heavy graphics
• Simulate depth in flat layouts
• Support multi-layered text styling

In mobile UI design, a carefully tuned shadow can reduce eye strain and increase clarity when text overlays busy backgrounds.

Basic Shadow Using XML Attributes

Android’s TextView supports the android:shadowLayer attribute, which defines the radius, offset, and color of the shadow.

Shadow Attributes

Example: XML Shadow

<TextView
    android:id="@+id/textShadow"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Elevated Text"
    android:textSize="28sp"
    android:textColor="#FFFFFF"
    android:shadowColor="#80000000"
    android:shadowDx="2"
    android:shadowDy="2"
    android:shadowRadius="4" />

Here:

• A semi-transparent black shadow (#80000000) adds depth
• Offsets position the shadow below and to the right
• A moderate blur radius smooths the edge

Shadow values can be scaled based on screen density to ensure consistent rendering across devices.

Programmatic Shadow in Java/Kotlin

Applying shadow at runtime enables dynamic effects based on app state, theme, or user preferences.

Java

TextView textView = findViewById(R.id.textShadow);
textView.setShadowLayer(
        6f,   // radius
        4f,   // dx
        4f,   // dy
        Color.parseColor("#66000000")  // shadow color
);

Kotlin

val textView: TextView = findViewById(R.id.textShadow)
textView.setShadowLayer(
    6f,
    4f,
    4f,
    Color.parseColor("#66000000")
)

Programmatic shadow application is useful when themes or user control determine the visual style.

Advanced Shadow Techniques

Multi-Layered Text Shadow

To simulate richer depth or “neon glow” effects, you can stack shadows by drawing multiple TextView’s or customizing drawing in a Canvas.

textView.setShadowLayer(8f, 0f, 0f, Color.parseColor("#FF5722"));
textView.setShadowLayer(12f, 2f, 2f, Color.parseColor("#E91E63"));

Because setting multiple shadow layers on the same text replaces the previous one, a custom view with multiple drawn text passes can achieve layered visuals.

Custom Drawing with Canvas

When shadows require precise control (e.g., layered colored glows or animating shadow properties), override onDraw() in a custom TextView:

public class ShadowTextView extends androidx.appcompat.widget.AppCompatTextView {

    public ShadowTextView(Context context) {
        super(context);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // Draw shadow pass
        getPaint().setShadowLayer(10f, 5f, 5f, Color.BLACK);
        super.onDraw(canvas);
        // Draw primary text on top
        getPaint().setShadowLayer(0f, 0f, 0f, Color.TRANSPARENT);
        super.onDraw(canvas);
    }
}

Custom drawing offers complete control over the sequence and rendering, allowing you to combine shadow with animations or state changes.

Design Considerations

Color and Contrast

• Select a shadow color with appropriate opacity; pure black isn’t always best
• Mid-tone backgrounds may benefit from lighter, blurred shadows

Performance Impacts

• Excessive shadow radius and high blur values can increase rendering cost
• On large text blocks or lists, consider limiting shadows to headers or key elements

Accessibility

• Ensure that text remains legible without shadow for users with contrast requirements
• Shadows should not replace contrast — they should augment readability

Cross-Device Consistency

Device pixel densities vary across Android screens. To ensure consistent shadow appearance:

• Use dp or sp for shadow properties when calculating offsets
• Scale shadow attributes based on DisplayMetrics.density

Example:

float scale = getResources().getDisplayMetrics().density;
textView.setShadowLayer(4 * scale, 2 * scale, 2 * scale, Color.DKGRAY);

This ensures similar visual weight across phones and tablets.