The document provides a comprehensive guide on enhancing Android app interfaces through tips on image handling, animations, and list management. It emphasizes the importance of caching images for performance, utilizing smooth animations with various techniques, and implementing efficient list structures using view holders and background tasks. Additionally, it addresses best practices for layout design and improving user experience with features like smart scrollbars.

1. Android UI Tips & Tricks
Shem Magnezi

2. Making your good app great
Know your app
Understand
what you need
No magic/ generic
solutions
You know how to
write a good app
Looks good Feel slick
Not gonna talk
about viral/
design/
downloads etc...

3. Agenda
● Working with images
● Bring your views into life with animations
● Upgrade your lists views

4. Working with images

5. Images in memory
Bitmap memory size:
Bitmap.getWidth() * Bitmap.getHeight() * Bitmap.config
Determine how much the bitmap gonna take:
Image.width * Image.height * Options.config / Options.sampleSize

6. Cache Cache Cache
● Use cache for performance
● Be careful not using too much memory

7. Determine your cache size
● Approximate per-application memory:
getSystemService(Context.ACTIVITY_SERVICE).getMemoryClass()
● Pay attention to: onTrimMemory(int level) on your
Application
● Profile your memory
usage live

8. Loading the proper image type
For small image views work with thumbnails:
MediaStore.Images.Thumbnails.getThumbnail(
..., int kind, ...)
MINI_KIND: 512 x 384
MICRO_KIND: 96 x 96

9. Sample size
Original size is probably too big, so load smaller size.
Original
inSampleSize=2

10. Determine the right sample size
● Get the original image size using:
options.inJustDecodeBounds = true;
● Get the view that gonna present the image
● Find the minimum sample_size so:
o image.width / sample_size > view.width
o image.height / sample_size > view.height
o it also prefer that sample_size will be power of 2 for faster/
easier decoding

11. Find your view size
Sometimes your view size is 0 (cause is not yet drawn), so
you should wait until the system will draw it:
view.getViewTreeObserver().addOnGlobalLayoutListener(
new OnGlobalLayoutListener() {
public void onGlobalLayout() {
//load image for the right size
}
});
}

12. Determine image size
CENTER_CROP
float scale = Math.max(viewW / imgW, viewH / imgH)
float scaledWidth = scaale * viewW;
float scaledHeight = scale * viewHt;
CENTER_INSIDE
float scale = Math.min(viewW / imgW, viewH / imgH)
float scaledWidth = scaale * viewW;
float scaledHeight = scale * viewHt;

13. Make your cache a bit smarter
get(Item image, Size size) {
cached = getImage(image);
if (cached != null) {
if (cached.size >=
size) {
//saved
time!
} else {
//maybe
display a lower
//resolution until loading
//the full image
}
} else {
//photo not in cache, but we
//did our best
}
}
put(Item image, Size size) {
if (size < MICRO_KIND_SIZE) {
//load micro kind
thumbnail
} else if (size <
MINI_KIND_SIZE) {
//load mini kind
thumbnail
} else {
//read the full image
with the
//right sample size
}
}

14. Bitmap config
ARG_565 has no alpha channel
and is it in lower quality
But:
● It’s ~x2 faster to load
● It consume half of the
memory
● Most of the time you won’t
see any difference
source: Romain Guy

15. Animations

16. Interpolator
Sometimes you can use interpolator instead of
couple of sequenced animations.
For example, the built-in bounce animation on
android.

17. Between-activities animationsSet activity style:
<item name="android:windowBackground">@android:color/transparent</item>
When moving to this activity:
startActivity(intent);
overridePendingTransition(0, 0);
Do the animation:
ViewTreeObserver observer = animationImage.getViewTreeObserver();
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
public boolean onPreDraw() {
animationImage.getViewTreeObserver().removeOnPreDrawListener(this);
runEnterAnimation(back, startBounds);
}
});

18. Pre drawer listener?
Very useful for animations!
● Create enter animation to your activity
● Create animation to your view when it’s
added to the screen
● Animate list items when the list changes

19. Smart image animation

20. Case #1
Scaling animation for the image view:
ObjectAnimator.ofFloat(image_1, "scaleY", 1,
1.5f);
<ImageView
android:id="@+id/image_1"
android:layout_width="225dp"
android:layout_height="150dp"
android:scaleType="centerCrop"
/>
When animating the
view there is no re-
layout and the image
not preserving it’s
scale type

21. Case #2
Use a frame and do a reverse scaling to the inner
image:
<RelativeLayout android:id="@+id/image_2"
android:layout_width="225dp"
android:layout_height="150dp">
<ImageView android:id="@+id/inner_image"
android:layout_width="225dp"
android:layout_height="300dp"
android:layout_marginTop="-75dp"
android:layout_marginBottom="-75dp"/>
</RelativeLayout>
anim.playTogether(
ObjectAnimator.ofFloat(image_2, "scaleY", 1, 1.5f),
ObjectAnimator.ofFloat(inner, "scaleY", 1f,
0.6666f));
● Lots of
calculations
● The animation is
not linear
● Need an extra
view

22. Case #3
Use an extra image as the target view:
anim.playTogether(
ObjectAnimator.ofFloat(image_3, "scaleY", 0.6666f, 1f),
ObjectAnimator.ofFloat(image_3, "alpha", 0, 1));
<ImageView
android:id="@+id/image_3"
android:layout_width="225dp"
android:layout_height="225dp"
android:scaleType="centerCrop"
/>
● You are losing the
original view
● The animation
isn’t smooth

23. Case #4
Implement you own Animation:
public class ExpandAnimation extends Animation {
protected void applyTransformation(float inp ...) {
...
if (inp < 1.0f) {
lp.height =(int)(start + (end - start)* inp);
mAnimatedView.requestLayout();
}
}
<ImageView android:id="@+id/image_4"
android:layout_width="225dp"
android:layout_height="150dp"
android:scaleType="centerCrop" />

24. Working with Lists

25. The basic things
● Reuse items
● ViewHolder pattern
● Long tasks should run in background with
AsyncTask
● Cancel view loading tasks using
RecyclerListener
● Use ListFragment

26. Profile your drawing
● Design your layout as flat as you can
● Avoid over drawing or nested weights
● Profile your list using GPU overdraw and
GPU Rendering in developer options

27. Empty view in your ListFragment
Use
android:id="@android:id/empty"
for the case the list is empty
<ListView
android:id="@android:id/list"
… />
<RelativeLayout
android:id="@android:id/empty"
... />

28. Save each item state
In your adapter:
Set<Integer> opened = HashSet<Integer>();
On widget opened:
opened.add(item.getId());
In getView():
view.setOpened(opened.contains(item.getId());

29. Scrolled view inside ListView
You sometime want to put a view that can be scrolled by himself as one of your
listview items- for example putting a grid view of images.
For doing it you must let layout manager that this view must take it’s full size:
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int heightSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2,
MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, heightSpec);
getLayoutParams().height = getMeasuredHeight();
}
source: stackoverflow.com

30. Smart scrollbar for easy navigation
● Put a relative view that contains your list view and set
him as a OnScrollListener
● On onScroll calc the right position of your scroller
view using totalItemCount and
visibleItemCount
● On draw put your scroller view using
setTranslationY

31. Smart scrollbar for easy navigation
You can even add a behavior for dragging the scroller
using onTouchEvent:
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
if (//event in scroll bar view)
mDragging = true;
} else if (me.getAction() == MotionEvent.ACTION_UP) {
if (mDragging)
mDragging = false;
} else if (me.getAction() == MotionEvent.ACTION_MOVE) {
if (mDragging)
mList.setSelectionFromTop(//calc the right item index, 0);
}
}

32. </presentation>
Thank you.