Android - how to draw text with background color using canvas

To draw text with a background color using a Canvas in Android, you can use the drawText() method for the text and drawRect() for the background. Here's how you can do it:

Example Code

1. Custom View Class: Create a custom view by extending View.

   import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Rect; import android.util.AttributeSet; import android.view.View; public class CustomTextView extends View { private Paint textPaint; private Paint backgroundPaint; private String text = "Hello, World!"; private Rect textBounds; public CustomTextView(Context context) { super(context); init(); } public CustomTextView(Context context, AttributeSet attrs) { super(context, attrs); init(); } private void init() { textPaint = new Paint(); textPaint.setColor(Color.WHITE); // Text color textPaint.setTextSize(50); // Text size textPaint.setAntiAlias(true); // Smooth edges backgroundPaint = new Paint(); backgroundPaint.setColor(Color.BLUE); // Background color textBounds = new Rect(); textPaint.getTextBounds(text, 0, text.length(), textBounds); // Calculate text bounds } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); // Draw background rectangle canvas.drawRect( 0, 0, textBounds.width() + 20, // Add padding textBounds.height() + 20, // Add padding backgroundPaint ); // Draw the text canvas.drawText(text, 10, textBounds.height() + 10, textPaint); // Draw text with padding } } 

2. Using the Custom View in Layout: Add your custom view to your XML layout file.

   <your.package.name.CustomTextView android:layout_width="wrap_content" android:layout_height="wrap_content" /> 

Explanation

• Paint: Two Paint objects are created: one for the text and another for the background.
• Rect: A Rect is used to calculate the bounds of the text, which helps to size the background rectangle appropriately.
• onDraw: In the onDraw method, first, the background rectangle is drawn, followed by the text.

Summary

This approach allows you to draw text with a background color on a Canvas. You can adjust the colors, sizes, and positions according to your needs.

Examples

1. Android Canvas: Draw text with background color

   • Description: Drawing text on a Canvas with a background color using Paint.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.BLACK); // Text color paint.setTextSize(30); // Text size Rect rect = new Rect(100, 100, 300, 200); // Background rectangle paint.setStyle(Paint.Style.FILL); paint.setColor(Color.YELLOW); // Background color canvas.drawRect(rect, paint); paint.setColor(Color.BLACK); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

2. Android Canvas: Draw text with rounded background

   • Description: Drawing text with a rounded background using Canvas and Paint.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size RectF rectF = new RectF(100, 100, 300, 200); // Background rounded rectangle paint.setStyle(Paint.Style.FILL); paint.setColor(Color.BLUE); // Background color canvas.drawRoundRect(rectF, 10, 10, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

3. Android Canvas: Draw text with background gradient

   • Description: Drawing text with a gradient background using Canvas and Paint.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size LinearGradient gradient = new LinearGradient(0, 0, 0, 200, Color.RED, Color.YELLOW, Shader.TileMode.CLAMP); paint.setShader(gradient); Rect rect = new Rect(100, 100, 400, 200); // Background rectangle paint.setStyle(Paint.Style.FILL); canvas.drawRect(rect, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

4. Android Canvas: Draw text with background using Path

   • Description: Drawing text with a background shape using Path and Canvas.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.BLACK); // Text color paint.setTextSize(30); // Text size Path path = new Path(); path.addCircle(200, 150, 100, Path.Direction.CW); // Circle background paint.setStyle(Paint.Style.FILL); paint.setColor(Color.YELLOW); // Background color canvas.drawPath(path, paint); paint.setColor(Color.BLACK); // Reset text color canvas.drawText("Hello, World!", 150, 170, paint); // Draw text 

5. Android Canvas: Draw text with transparent background

   • Description: Drawing text with a transparent background using Canvas and Paint.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size Rect rect = new Rect(100, 100, 300, 200); // Background rectangle paint.setStyle(Paint.Style.FILL); paint.setColor(Color.argb(128, 255, 0, 0)); // Transparent red background canvas.drawRect(rect, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

6. Android Canvas: Draw text with background using PorterDuff

   • Description: Drawing text with a background using PorterDuff mode in Paint.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size Rect rect = new Rect(100, 100, 300, 200); // Background rectangle paint.setStyle(Paint.Style.FILL); paint.setColor(Color.BLUE); // Background color canvas.drawRect(rect, paint); paint.setColor(Color.WHITE); // Reset text color paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

7. Android Canvas: Draw text with background using Path and LinearGradient

   • Description: Drawing text with a gradient background using Path and LinearGradient.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size Path path = new Path(); path.addRect(100, 100, 300, 200, Path.Direction.CW); // Rectangle background paint.setStyle(Paint.Style.FILL); int[] colors = {Color.RED, Color.YELLOW}; float[] positions = {0, 1}; LinearGradient gradient = new LinearGradient(0, 0, 0, 200, colors, positions, Shader.TileMode.CLAMP); paint.setShader(gradient); canvas.drawPath(path, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

8. Android Canvas: Draw text with rounded background using Path

   • Description: Drawing text with a rounded background shape using Path and Canvas.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size Path path = new Path(); RectF rectF = new RectF(100, 100, 300, 200); // Background rounded rectangle path.addRoundRect(rectF, 20, 20, Path.Direction.CW); paint.setStyle(Paint.Style.FILL); paint.setColor(Color.GREEN); // Background color canvas.drawPath(path, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

9. Android Canvas: Draw text with background using RadialGradient

   • Description: Drawing text with a radial gradient background using Canvas and RadialGradient.
   • Code:

     Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size RadialGradient gradient = new RadialGradient(200, 150, 100, new int[]{Color.RED, Color.YELLOW}, new float[]{0, 1}, Shader.TileMode.CLAMP); paint.setShader(gradient); Rect rect = new Rect(100, 100, 400, 200); // Background rectangle paint.setStyle(Paint.Style.FILL); canvas.drawRect(rect, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

10. Android Canvas: Draw text with background using LinearGradient

    • Description: Drawing text with a linear gradient background using Canvas and LinearGradient.
    • Code:

      Paint paint = new Paint(); paint.setColor(Color.WHITE); // Text color paint.setTextSize(30); // Text size LinearGradient gradient = new LinearGradient(0, 0, 0, 200, new int[]{Color.RED, Color.YELLOW}, new float[]{0, 1}, Shader.TileMode.CLAMP); paint.setShader(gradient); Rect rect = new Rect(100, 100, 400, 200); // Background rectangle paint.setStyle(Paint.Style.FILL); canvas.drawRect(rect, paint); paint.setColor(Color.WHITE); // Reset text color canvas.drawText("Hello, World!", 120, 170, paint); // Draw text 

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