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Programming with Android: Calculator Example

Programming with Android: Calculator Example. Luca Bedogni Marco Di Felice Dipartimento di Informatica: Scienza e Ingegneria Università di Bologna. Calculator: Outline. Today: How to build a Calculator? Define the layout of the application

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Programming with Android: Calculator Example

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  1. Programming with Android: Calculator Example Luca Bedogni Marco Di Felice Dipartimento di Informatica: Scienza e Ingegneria Università di Bologna

  2. 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 2

  3. Calculator: layout Define the buttons, labels, cells and so on Place them on the screen Pay attention: Android powered phones are very different in terms of resolutions Try not to stick with absolute values/positioning (we will see this later)

  4. Calculator: layout definition

  5. Calculator: layout definition First Operand

  6. Calculator: layout definition Operator First Operand

  7. Calculator: layout definition Operator Second Operand First Operand

  8. Calculator: layout definition Operator Second Operand First Operand Result

  9. Calculator: layout definition Operator Second Operand First Operand Result Operators

  10. Calculator: layout definition Operator Second Operand First Operand Result Operators

  11. Calculator: logic definition Whenever a user selects a operand cell, a keyboard will pop up Pressing an operator button will switch the focus from one operand to another (except for =) We want to deal with float numbers

  12. 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 actions The MVC pattern is relaxed that way (pros and cons) We do not want the result to be focusable

  13. Calculator: layout building We will use a set of layouts Layouts are grouped together following a hierarchy Why not absolute positioning?

  14. Calculator: layout building We will use a set of layouts Layouts are grouped together following a hierarchy Why not absolute positioning? Android has a wide range of devices Wide range of resolution Wide range of capabilities

  15. Calculator: layout building We will use a set of layouts Layouts are grouped together following a hierarchy Why not absolute positioning? 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.

  16. Calculator: hierarchy viewer

  17. Calculator: Recap Define a Layout Pay Attention to devices heterogeneity Features Keyboard should pop up when needed Should not pop up on the result Switch from one cell to another when pressing operand React to Events

  18. Calculator: start Let's start developing the calculator

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