Profiling & Performance

Tests confirm RecipeBox behaves correctly. The Android Studio Profiler answers a different question — is it behaving efficiently? A recipe list that scrolls correctly but stutters at 15 frames per second is still a bug users will notice.

The Profiler Tabs

Tab	Shows
CPU	Method call timing and thread activity — which method is eating time on which thread
Memory	Heap allocations over time — object counts, garbage collection events, potential leaks
Network	Every request RecipeBox makes (e.g., fetching a recipe via Retrofit), timing and payload size
Energy	Estimated battery impact of CPU, network, and location usage

Worked Example: A Janky RecyclerView Scroll

Say RecipeBox's recipe list stutters while scrolling. Recording a CPU profile session during the scroll and inspecting the frame timeline shows which frames took too long, and the call chart shows what ran during them.

// RecipeAdapter.java — the culprit
@Override
public void onBindViewHolder(RecipeViewHolder holder, int position) {
    Recipe recipe = recipes.get(position);
    Bitmap fullSizePhoto = BitmapFactory.decodeFile(recipe.photoUri); // decodes a huge file, every bind, on the main thread
    holder.imageView.setImageBitmap(fullSizePhoto);
    holder.titleView.setText(recipe.title);
}

// Fixed: let an image-loading library handle decoding, caching, and sizing off the main thread
@Override
public void onBindViewHolder(RecipeViewHolder holder, int position) {
    Recipe recipe = recipes.get(position);
    Glide.with(holder.itemView.getContext())
        .load(recipe.photoUri)
        .override(200, 200) // decode at thumbnail size, not full resolution
        .into(holder.imageView);
    holder.titleView.setText(recipe.title);
}

Systrace / Perfetto

For a system-wide view spanning the app, the Android framework, and the kernel scheduler at once — useful when a slowdown might not even be RecipeBox's own code — Android Studio can capture a system trace, viewable in Perfetto (the modern successor to the older systrace tool). This lesson only needs the awareness that this deeper level of tracing exists for cases the CPU Profiler's call chart doesn't fully explain.

Common Performance Mistakes