Android Programming

Using Selection Widgets

Lesson 3

NGUYEN The Linh

Android Programming

Contents

Introducing Adapters 1

Using Selection Widgets 2

Exercise 3 3

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Android Programming

Using Selection Widgets

Introducing Adapters

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Android Programming

Introducing Adapters

Adapters are bridging classes that bind data to user-interface Views.

Using ArrayAdapter The ArrayAdapter is a generic class that binds AdapterViews to an array of

objects.

By default, the ArrayAdapter binds the toString() value of each object to a

TextView control defined within a layout.

To apply an Adapter to an AdapterView-derived class, you call the View’s

setAdapter() method, passing in an Adapter instance, as shown in the snippet

below:

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Android Programming

Introducing Adapters

Using ArrayAdapter (cont.)

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Android Programming

Introducing Adapters

Example 3.1

Using Basic ArrayAdapter

Example 3.1 project

• MainActivity.java

• activity_main.xml

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Introducing Adapters

Custom ArrayAdapter

You can subclass ArrayAdapter and override getView() to “roll

your own” views:

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Using Selection Widgets

Using Selection Widgets

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Using Selection Widgets

ListView

The classic Android ListView is a plain list of text.

However, you can have a list whose rows are made up of icons,

or icons and text, or check-boxes and text, or whatever you

want.

Update Example 3.1 project

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Using Selection Widgets

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Using Selection Widgets

ListView (cont.)

Custom ArrayAdapter for binding more data

See Example 3.2

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Using Selection Widgets

Example 3.2

Custom ArrayAdapter

Example 3.2 project

• MainActivity.java

• Person.java

• MyArrayAdapter.java

• activity_main.xml

• list_item.xml

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Using Selection Widgets

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Using Selection Widgets

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Better. Stronger. Faster.

Using convertView

Android Programming

Using Selection Widgets

GridView

As the name suggests, GridView gives you a two-dimensional

grid of items to choose from.

You have moderate control over the number and size of the

columns; the number of rows is dynamically determined based

on the number of items the supplied adapter says are available

for viewing.

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Using Selection Widgets

GridView (cont.)

Properties

• android:numColumns spells out how many columns there are, or, if you

supply a value of auto_fit, Android will compute the number of columns

based on available space and the following properties.

• android:verticalSpacing and its counterpart android:horizontalSpacing

indicate how much whitespace there should be between items in the grid.

• android:columnWidth indicates how many pixels wide each column should

be.

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Using Selection Widgets

GridView (cont.)

Properties (cont.)

• android:stretchMode; this should be columnWidth to have the columns

take up available space or spacingWidth to have the whitespace between

columns absorb extra space.

Otherwise, the GridView works much like any other selection

widget—use setAdapter() to provide the data and child views.

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Using Selection Widgets

Example 3.3

GridView

Example 3.3 project

• MainActivity.java

• MyArrayAdapter.java

• activity_main.xml

• gridview_item.xml

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Using Selection Widgets

Spinners

Spinners provide a quick way to select one value from a set.

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Using Selection Widgets

Spinners (cont.)

The choices you provide for the spinner can come from any

source, but must be provided through an SpinnerAdapter, such

as an ArrayAdapter

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Exercise 3

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