👀 Views: 55 💬 Answers: 1 📅 Created: 2025-06-05

android custom-view performance canvas Kotlin

I've searched everywhere and can't find a clear answer. I'm working with a frustrating scenario with custom view rendering in my Android app targeting API level 34. My custom view is supposed to draw a pattern on the canvas, but it seems to hang the UI thread whenever the drawing logic is executed, especially when I zoom in on the pattern. I have implemented the `onDraw` method as follows: ```kotlin override fun onDraw(canvas: Canvas) { super.onDraw(canvas) val paint = Paint().apply { color = Color.RED; style = Paint.Style.FILL } if (zoomLevel > 1) { for (i in 0 until width step 20) { for (j in 0 until height step 20) { // Simulate complex drawing logic here canvas.drawCircle(i * zoomLevel, j * zoomLevel, 5f * zoomLevel, paint) } } } } ``` I've tried optimizing the drawing code by caching bitmaps and using `invalidate()` judiciously, but the app still becomes unresponsive with an ANR (Application Not Responding) behavior after a few seconds of interaction. The stack trace points to the `onDraw` method being the culprit. I've also checked for any potential issues in my layout that might be causing excessive redraws. Here’s how I set my custom view in the layout: ```xml <com.example.CustomView android:id="@+id/custom_view" android:layout_width="match_parent" android:layout_height="match_parent" /> ``` I suspect the nested loops are too heavy for real-time drawing, but I want to keep the rendering smooth, especially on devices with lower specs. Is there a recommended approach to handle such rendering tasks without blocking the UI thread? Any insights or optimizations would be greatly appreciated! For context: I'm using Kotlin on macOS.