This document discusses creating custom UI components in Android. It begins by explaining that widgets and layouts are used to construct user interfaces. It then discusses reasons for building custom components, such as having more control over the UI. It provides examples of creating simple custom components by extending existing widgets and layouts. It also covers creating more complex "compound" custom components using layout inflation. The document discusses techniques for debugging and optimizing custom components. Finally, it discusses how to package custom components in a library project so they can be shared across applications.

1. Custom UI Components

3. Widgets and Layouts are
used to construct a UI.
• A Widget is a UI element, like a text field or button
• Layouts are invisible containers, like LinearLayout or
RelativeLayout

4. Widget != Widget

5. Widget

6. Layout

7. View Hierarchy

8. Why build custom
components? Isn't
there enough already?

9. Free

10. 37 SEK

11. public void onCreate(Bundle savedInstanceState) {
....
mPriceTextView = (TextView) findViewById(R.id.price);
mPriceTextView.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence s, int start,
int before, int count) {
if (getText(R.string.free).equals(s.toString())) {
mPriceTextView.setTextColor(
getResources().getColor(R.color.free));
} else {
mPriceTextView.setTextColor(
getResources().getColor(R.color.rent));
}
}
@Override
public void beforeTextChanged(CharSequence s, int start,
int count, int after) { }
@Override
public void afterTextChanged(Editable s) { }
});
}

12. We can solve this
problem with custom
components.

13. When building a fully
customized component
extend View.

14. Need to override onDraw
to be able to show
something.
• 2D graphics
• Text in different variations
• Other components
• Or pretty much anything else

15. onMeasure should be
overridden by subclasses
to provide measurement
of their contents.

16. Custom widgets can
really be as complicated
as you need them to be.

17. Not so fully customized
components.

19. PriceView
public class PriceView extends TextView implements TextWatcher {
public PriceView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public void onTextChanged(CharSequence s, int start,
int before, int count) {
if (!TextUtils.isEmpty(s) && getResources()
.getText(R.string.free).equals(s.toString())) {
setTextColor(getResources().getColor(R.color.free));
} else {
setTextColor(getResources().getColor(R.color.rent));
}
}
@Override
public void afterTextChanged(Editable s) {
}
@Override
public void beforeTextChanged(CharSequence s, int start,
int count, int after) {
}
}

20. <TextView
android:id="@+id/price"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/free"
android:textSize="30sp"
/>
<com.markupartist.demo.ao11.demo2.PriceView
android:id="@+id/price"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/free"
android:textSize="30sp"
/>

21. Demo

22. Compound Components
priceView.setPrice(
new Price(amount, currency)
);

23.
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
>
<TextView
android:id="@+id/amount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="@color/rent"
android:textSize="30sp"
/>
<TextView
android:id="@+id/currency"
android:paddingLeft="5dip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="30sp"
/>
</LinearLayout>

24. public class PriceView extends LinearLayout {
private TextView mAmount;
private TextView mCurrency;
public PriceView(Context context, AttributeSet attrs) {
super(context, attrs);
LayoutInflater inflater = (LayoutInflater) context.getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
LinearLayout priceView = (LinearLayout) inflater.inflate(
R.layout.priceview, null);
mAmount = (TextView) priceView.findViewById(R.id.amount);
mCurrency = (TextView) priceView.findViewById(R.id.currency);
}
public void setPrice(Price price) {
mAmount.setText(price.getAmount());
mCurrency.setText(price.getCurrency());
}
}

25. Demo

26. How to debug and
optimize the UI?

27. $ ./tools/layoutopt

28. $ ./tools/hierarchyviewer

29. Demo
Hiearchy Viewer

30. Reduce the number of
views in the view tree
with <merge>

31. <LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<TextView
android:id="@+id/amount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="@color/rent"
android:textSize="30sp"/>
<TextView
android:id="@+id/currency"
android:paddingLeft="5dip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="30sp"/>
</LinearLayout>

32. <merge
<TextView
android:id="@+id/amount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="@color/rent"
android:textSize="30sp"/>
<TextView
android:id="@+id/currency"
android:paddingLeft="5dip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="30sp"/>
</merge>

33. And...
inflater.inflate(
R.layout.priceview,
null
this,
);
true
);

34. Demo
Hiearchy Viewer

35. isInEditMode()

36. Photo by anarchosyn, http://www.flickr.com/photos/24293932@N00/4530523480/

37. Sets of properties that specifies the
look of a Widget. This can be
properties such a width, height and
colors. The concept is similar to
CSS and separates presentation
from the content.

38. Styles and Themes
• Custom attributes
• Styles
• Themes

39. Custom attributes
<com.markupartist.demo.ao11.demo5.PriceView
android:id="@+id/price"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:amountText="37"
app:currencyText="SEK"
/>

40. Goes into
res/values/attrs.xml
• Declared in the top <resources or in the <declare-stylable>
element
• The <attr> element has two attributes name and format
– Name is used when referring from code e.g.
R.stylable.PriceView_amountText
– Format defines the value it represents
• Reference
• Color
• String
• Boolean
• And a few more

41. Custom Attributes
<resources>
<attr name="amountStyle" format="reference" />
<declare-styleable name="PriceView">
<attr name="amountText" format="string" />
</declare-styleable>
</resources>
public PriceView(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray array = context.obtainStyledAttributes(
attrs, R.styleable.PriceView, 0, 0);
String amountText =
array.getString(R.styleable.PriceView_amountText);
// Set amount to the view...
array.recycle();
}

42. Styles goes into
res/values/styles.xml
<merge>
<TextView android:id="@+id/amount" style="@style/AmountText"/>
<TextView android:id="@+id/currency" style="@style/CurrencyText"/>
</merge>
<style name="PriceText" parent="android:style/Widget.TextView">
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:textSize">30sp</item>
</style>
<style name="AmountText" parent="@style/PriceText">
<item name="android:textColor">@color/rent</item>
</style>
<style name="CurrencyText" parent="@style/PriceText">
<item name="android:paddingLeft">5dip</item>
</style>

43. A problem with styles is
that it's hard to change
the style of an View
that's included within a
compound component.
And we can't change the
style in runtime.

44. Themes, a style that’s
applied to a whole
Activity or Application
• With custom attributes we can provide a way to
style views within compound components
• Makes it easier for others to override default styles
• This can be hooks for styles, dimensions, colors...

45. <attr name="amountStyle" format="reference" />
<TextView android:id="@+id/priceview_amount"
style="?attr/amountStyle" />
<style name="AO11Theme" parent="android:style/Theme">
<item name="amountStyle">@style/AmountText</item>
</style>
android:theme="@style/AO11Theme"
<style name="AO11ThemeCustom"
parent="android:style/Theme.Light">
<item name="amountStyle">@style/CustomAmountText</item>
</style>
android:theme="@style/AO11ThemeCustom"

46. How do we make a custom
component available for
other applications.
• We can't use JAR
• We don't want to copy-paste resources

47. Library Projects
• Holds shared code and resources
• Resources are merged at build time
• Can be used for
– Custom components
– White label apps
– Paid and free versions of the same app

48. Thank you
https://github.com/johannilsson/ao11