Using Vector Drawables for Icons in Kotlin XML Android Apps: A Comprehensive Guide

In Android development, using Vector Drawables as icons offers several advantages over traditional raster images (like PNGs or JPGs). Vector Drawables are resolution-independent, meaning they look crisp and clear on any screen size and density. This makes them ideal for icons and simple graphics that need to scale without losing quality. In this article, we’ll explore how to effectively use Vector Drawables as icons in your Kotlin XML-based Android applications.

What are Vector Drawables?

Vector Drawables are XML files that describe images using a set of points, lines, and curves, rather than storing pixel data. Because of this, they can be scaled without any loss in quality, making them perfect for icons, logos, and simple graphics in your app. The file format is typically .xml and can be created or edited using Android Studio’s Vector Asset Studio or other vector graphics editors.

Benefits of Using Vector Drawables

• Resolution Independence: Scales perfectly to any screen size without losing quality.
• Smaller App Size: Vector files are generally smaller than raster images, reducing the overall app size.
• Easy Theming: Can be tinted programmatically to match your app’s theme.
• Reduced Asset Management: No need to create multiple versions of the same icon for different screen densities (hdpi, mdpi, xhdpi, etc.).

Step-by-Step Guide to Using Vector Drawables in Kotlin XML Android Apps

Step 1: Importing Vector Drawables into Your Project

The easiest way to import Vector Drawables is by using Android Studio’s built-in Vector Asset Studio. This tool helps you import Material Design icons, SVG files, or create custom vector graphics.

1. Right-click on the res directory in the Project view.
2. Select New > Vector Asset.
3. Choose an icon from the Material Design icons library, or import your own SVG or PSD file.
4. Configure the properties like name, size, and density compatibility.
5. Click Next and then Finish to import the Vector Drawable into your project’s drawable directory.

Here’s a sample XML Vector Drawable file (e.g., ic_baseline_settings_24.xml):

<vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:width="24dp"
    android:height="24dp"
    android:viewportWidth="24"
    android:viewportHeight="24"
    android:tint="#333333">
    <path
        android:fillColor="@android:color/white"
        android:pathData="M19.14,12.94c0.04,-0.3 0.06,-0.59 0.06,-0.88s-0.02,-0.58 -0.06,-0.88l2.2,-1.7c0.19,-0.15 0.24,-0.42 0.12,-0.64l-2,-3.46c-0.12,-0.22 -0.39,-0.3 -0.61,-0.22l-2.42,1.95c-0.51,-0.4 -1.06,-0.76 -1.68,-1.07l-0.3,-2.52C12.7,-2.8 12.43,-3 12.1,-3h-2c-0.32,0 -0.59,0.19 -0.71,0.49l-0.3,2.52c-0.62,0.31 -1.17,0.67 -1.68,1.07l-2.42,-1.95c-0.22,-0.08 -0.49,0 -0.61,0.22l-2,3.46c-0.13,0.22 -0.07,0.49 0.12,0.64l2.2,1.7c-0.04,0.3 -0.06,0.58 -0.06,0.88s0.02,0.58 0.06,0.88l-2.2,1.7c-0.19,0.15 -0.24,0.42 -0.12,0.64l2,3.46c0.12,0.22 0.39,0.3 0.61,0.22l2.42,-1.95c0.51,0.4 1.06,0.76 1.68,1.07l0.3,2.52c0.12,0.3 0.39,0.49 0.71,0.49h2c0.32,0 0.59,-0.19 0.71,-0.49l0.3,-2.52c0.62,-0.31 1.17,-0.67 1.68,-1.07l2.42,1.95c0.22,0.08 0.49,0 0.61,-0.22l2,-3.46c0.13,-0.22 0.07,-0.49 -0.12,-0.64l-2.2,-1.7zM12,15.5c-1.93,0 -3.5,-1.57 -3.5,-3.5s1.57,-3.5 3.5,-3.5 3.5,1.57 3.5,3.5 -1.57,3.5 -3.5,3.5z" />
</vector>

Step 2: Using Vector Drawables in XML Layouts

To use the Vector Drawable in your layout XML file, reference it using the android:src attribute in an ImageView or the android:drawableLeft, android:drawableRight, android:drawableTop, and android:drawableBottom attributes in a TextView or Button.

<!-- ImageView Example -->
<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/ic_baseline_settings_24"
    android:contentDescription="@string/settings_icon" />

<!-- TextView Example -->
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:drawableLeft="@drawable/ic_baseline_settings_24"
    android:text="Settings"
    android:gravity="center_vertical" />

<!-- Button Example -->
<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:drawableLeft="@drawable/ic_baseline_settings_24"
    android:text="Settings" />

Step 3: Tinting Vector Drawables

One of the advantages of Vector Drawables is the ability to tint them programmatically or via XML to match your app’s theme or provide visual feedback to user interactions.

Tinting in XML

Use the app:tint attribute in your XML layout file. Note that you’ll need to add the xmlns:app namespace to your root layout element:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_baseline_settings_24"
        app:tint="@color/colorPrimary"
        android:contentDescription="@string/settings_icon" />
</LinearLayout>

Tinting Programmatically in Kotlin

In your Kotlin code, you can use setColorFilter to tint the Vector Drawable:

import android.graphics.PorterDuff
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.ImageView
import androidx.core.content.ContextCompat

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val imageView: ImageView = findViewById(R.id.settingsIcon)
        val color = ContextCompat.getColor(this, R.color.colorPrimary)
        imageView.setColorFilter(color, PorterDuff.Mode.SRC_IN)
    }
}

Step 4: Handling Compatibility Issues

Vector Drawables are supported natively from Android 5.0 (API level 21) and higher. For backward compatibility with older versions of Android, use the app:srcCompat attribute instead of android:src and ensure that you have included vectorDrawables.useSupportLibrary = true in your app’s build.gradle file.

Update build.gradle

android {
    defaultConfig {
        vectorDrawables.useSupportLibrary = true
    }
}

Use app:srcCompat in XML

<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:srcCompat="@drawable/ic_baseline_settings_24"
    android:contentDescription="@string/settings_icon" />

Best Practices

• Keep it Simple: Vector Drawables are best suited for simple icons and graphics. Complex vector images can become large and impact performance.
• Optimize: Use tools like SVGOMG to optimize your SVG files before importing them into Android Studio.
• Test: Always test your app on different devices and screen densities to ensure your Vector Drawables are rendering correctly.
• Use Theme Attributes: To automatically adapt the tint color of your Vector Drawables based on the current theme, use theme attributes in your app:tint.

Conclusion

Using Vector Drawables as icons in Kotlin XML Android apps is an effective way to create resolution-independent, themable, and smaller-sized applications. By following the steps outlined in this guide, you can seamlessly integrate Vector Drawables into your projects, improving the overall quality and performance of your app.