1 Scoala de Vara IP Workshop 2011 – Calimanesti Valcea

AndroidModel View Controller, Observer,

liste, adaptoare si reciclare

Vlad PETRE

vlad@vladpetre.com

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2 Scoala de Vara IP Workshop 2011 – Calimanesti Valcea

Model View Controller (I)• Architectural Pattern• Separa

– Interfata grafica– Programul in sine– Stocarea datelor

• Avantaje– Programare pe componente– Usor de intretinut

• Dezavantaje– Poate fi lent

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Model View Controller (II)

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Model View Controller (III)

• Linie continua – asociere directa• Linie intrerupta – asociere indirecta (ex: Observer)

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Model View Controller (IV)

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Observer (I)

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Observer (II)• Design Pattern• Separa

– Obiectul observat– Observator

• Avantaje– Programare pe componente– Usor de intretinut– Schema generalizata

• Dezavantaje– Poate fi lent

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Observer – Exemplu (I)

Abonarea la Gmail

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Observer – Exemplu (II)

Notificarea

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ListActivity• Activitate specializata pentru o

lista• Poate contine si alte componente• ID-ul listei:

– android:id=“@android:id/list”

• Metode speciale:– onListItemClick(…)– setListAdapter(…)

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Adaptor

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ListView• Container vertical• Optimizat pentru miscare• Implicit, avem componente

identice pe fiecare rand• Rolul adaptorului:

– Genereaza aceste componente

• Evenimente:– setOnItemClickListener(…)– setOnItemLongClickListener(…)

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Adaptor• Poate fi predefinit:

– ArrayAdapter

• Sau customizat de programator:– Prin implementarea ListAdapter– Extinderea BaseAdapter

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Varianta statica cu ArrayAdapter (I)

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Varianta statica cu ArrayAdapter (II)

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Varianta dinamica cu ArrayAdapter (I)

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Varianta dinamica cu ArrayAdapter (II)

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Concluzii implementare cu ArrayAdapter

• ListView– Contine o lista– android:id=“@android:id/list”

• Elementele listei– android.R.layout.simple_list_item_1

• Static– Putem utiliza String[]

• Dinamic– Putem utiliza ArrayList<String>

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Sa incercam ceva mai complex

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Liste cu elemente complexe• Elementele sunt componente de tip container, ce

pot contine:– TextView– ImageView– …

• Adaptor custom-made– Prin implementarea ListAdapter– Extinderea BaseAapter

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Extinderea BaseAdapter (I)• public View getView

(int position, View convertView, ViewGroup list);

• public int getCount ();

• public Object getItem(int position) ;

• public long getItemId(int position);

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Extinderea BaseAdapter (II)

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Extinderea BaseAdapter (III)

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Extinderea BaseAdapter (IV)

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Extinderea BaseAdapter (V)

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Extinderea BaseAdapter (VI)

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Reciclare• Reutilizarea Obiectelor• Evitarea crearii de obiecte

– new is bad for memory!

• Utilizam– buffere

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Optimizare (I)

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Optimizare (II)

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Optimizare (III)

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Tag-uri (pentru View)• public void setTag(Object tag);• public Object getTag();

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Eficient folosind Tag

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Referinte• http://pdm.ipworkshop.ro• http://en.wikipedia.org/wiki/Model%E2%80%93vie

w%E2%80%93controller• http://developer.android.com/guide/tutorials/views

/hello-listview.html

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