04 calculator

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Programming with Android:Calculator Example

Luca Bedogni Marco Di FeliceDipartimento di Informatica: Scienza e Ingegneria

Universit di Bologna


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Luca Bedogni, Marco Di Felice- Programming with Android Calculator Example

Calculator: Outline

Today:

How to build a Calculator? Define the layout of the application

Create an application that uses this layout

Add some sort of intelligence to the application

Test it


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Calculator: layout

Define the buttons, labels, cells and so on

Place them on the screenPay attention: Android powered phones are very

different in terms of resolutions

Try not to stick with absolute values/positioning (

will see this later)


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Calculator: layout definition


5/18Luca Bedogni, Marco Di Felice- Programming with Android Calculator Example


First Operand




First Operand

Operator




First Operand

Operator

Second Ope




First Operand

Operator

Second Ope

Result


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First Operand

Operator

Second Ope

Result

Operator


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First Operand

Operator

Second Ope

Result

Operator


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Calculator: logic definition

Whenever a user selects a operand cell, a keybo

will pop upPressing an operator button will switch the focus

one operand to another (except for =)

We want to deal with float numbers


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Calculator: events

We want to be warned when a user touches

something on the screen Every time this happens, we will react with a set of ac

The MVC pattern is relaxed that way (pros and cons)

We do not want the result to be focusable


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Calculator: layout building

We will use a set of layouts

Layouts are grouped together following a hierarcWhy not absolute positioning?


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Android has a wide range of devices

Wide range of resolution

Wide range of capabilities


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Android has a wide range of devices

Wide range of resolution

Wide range of capabilities

Need to build dynamic applications that

performs different depending on the device

they're running in.


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Calculator: hierarchy viewer


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Calculator: Recap

Define a Layout

Pay Attention to devices heterogeneityFeatures

Keyboard should pop up when needed

Should not pop up on the result

Switch from one cell to another when pressingoperand

React to Events


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Calculator: start

Let's start developing the calculato

04 calculator

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