Lecture 2 Activities

8/13/2019 Lecture 2 Activities

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Lecture 2ACTIVITIES


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Application Life Cycle

Application components life cycle is the cycle from instantiating the component uncompletely destroying it.

Application lifetime is not directly controlled by you. Its determined by the system

How important these components are and how much memory is available are the kprocess


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Activity Life Cycle


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ActivitiesSubclasses of the Activity class

Managed by Activity Manager (managed components)

Each activity is given a window in which to draw its user interface.

The "main" activity is presented to the user when launching the application for the

Running new activity closes the previous one and we get notified by the state via tlife cycle callbacks.


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Activity Life Cycle


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Activity Life Cycle


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Activity Life Cycle


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Creating ActivitiesExtend activity class

Add entry to it the manifest file

open your manifest file and add an element as a child of the


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How to manage Activity Life CycBy implementing callback methods


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Dalvik Debug Monitor Server(DDMS)The android debugging tool

Provides

logging information (logcat ),

Thread and heap information on the device

process, and radio state information

incoming call and SMS spoofing,

location data spoofing, and more


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Running DDMSFrom Eclipse:

Click Window > Open Perspective > Other... > DDMS.


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Using LogCatLogCat outputs the messages that you print out using the Log class along with othmessages such as stack traces when exceptions are thrown.

Filter certain messages with the following buttons:

Verbose

Debug

Info

Warn

Error

You can also setup your own custom filter


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How to use itLog is a logging class that you can utilize in your code to print out messages to theCommon logging methods include:

v(String, String) (verbose)

d(String, String) (debug)

i(String, String) (information)

w(String, String) (warning)

e(String, String) (error)

Example

Log.i(This is an information message );


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Example


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Building UserInterfaces


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How to Build our GUIAll in Java

GUI components, listeners and event handlers are written in Java

All in XML

GUI components and event handler assignment are written in XML

E.g. android:onClick="oClickHandler"

HybridGUI components and resources are described in XML files

All other stuff are written in Java


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Note

Use Java-based for building dynamic guiOtherwise, use the hybrid approach

Easy to maintain

Good separation between Presentation layer and business lo


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Building GUI in Jav


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Building UI in XML


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Building UI in XMLIn Java

In XML


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Building UI in Hybri


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Hybrid


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Link the xml component with theJava Component

findViewById ( View )Use it to get a reference to a view


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Common View Attributesandroid:layout_width="105dp"

android:layout_height="wrap_content"

android:text=Hello"

android:textSize="20sp


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MeasurementsThe small quick advice:

Use sp for fonts

Use dp for every thing else

*dp stands for density pixels or Density-independent pixel


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MeasurementsScreen size

Actual physical size, measured as the screen's diagonal.

E.g. 2.3 inches

Screen density

The quantity of pixels within a physical area of the screen; usually referred to as pper inch).


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View IDEach view you use should have an id

When you are going to refer to this view you will need its id.

To refer to view id inside xml

android:layout_below="@id/label"

To generate an id for a view

android:id="@+id/ok"


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Event ListenersUsing Separate Listener Class

Using Named Inner Class

Using Anonymous inner class

Having the main activity implements the listener onClickListener


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View groupsThey are invisible containers that holds other views.

The base for all layouts like FrameLayout, GridView, List View, Table Layout and ma


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Viewsare the main building blocks for user interface components

The base class for all widgets

Examples are Buttons, Edit Texts, Text Views,

All extends class android.view.View


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Example


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Layouts


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LayoutsYour layout is the architecture for the user interface in an Activity

It defines the layout structure and holds all the elements that appear to the user

Example:

Linear Layout

Frame Layout

Table Layout

Relative Layout


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Linear LayoutLinearLayout is a ViewGroup that displays child View elements in a linear direction

vertically or horizontally.

Via the orientation attribute

supports assigning a weight to children

android:orientation="horizontal"

How Can you build this ?

Linear Layout commonly used


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Linear Layout commonly usedattributesOrientation : horizontal or vertical

fill model: fill_parent, wrap_content

Weight: 1,2,3,.0

Gravity: alignment (left, center, right, top, bottom)

Padding: space from boundaries to content

Margin: space from boundaries to the parents

Android gravity vs. layout_gravity

android:gravity sets the gravity of the content of the View its used on.

android:layout_gravity sets the gravity of the View or Layout in its parent.


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Example


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Relative Layout

Lets child views specify their position relative to the parent

view or to each other (specified by ID)


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Relative LayoutReferring to the container :

android:layout_alignParentTopandroid:layout_alignParentLeft

android:layout_centerInParent

android:layout_centerHorizontal

Referring to other widgets

android:layout_alignTop

android:layout_alignLeft,

android:layout_alignRight

android:layout_below

android:layout_toLeftOf


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Relative LayoutIs a very powerful utility for designing a user interface

It can eliminate nested view groups and keep your layout hierarchy flat, which impperformance.

If you find yourself using several nested LinearLayout groups, you may be able to rwith a single RelativeLayout.

For more about Relative layout

http://developer.android.com/guide/topics/ui/layout/relative.html

http://www.mkyong.com/android/android-relativelayout-example/
http://developer.android.com/guide/topics/ui/layout/relative.htmlhttp://www.mkyong.com/android/android-relativelayout-example/http://www.mkyong.com/android/android-relativelayout-example/http://www.mkyong.com/android/android-relativelayout-example/http://www.mkyong.com/android/android-relativelayout-example/http://www.mkyong.com/android/android-relativelayout-example/http://www.mkyong.com/android/android-relativelayout-example/http://www.mkyong.com/android/android-relativelayout-example/http://developer.android.com/guide/topics/ui/layout/relative.htmlhttp://developer.android.com/guide/topics/ui/layout/relative.html


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Table LayoutViews are grouped in rows and columns

Used in conjunction with TableRow

Columns are determined by Android based on the maximum number of the viewsrow.

Layout_Span attribute can be used to make a view span multiple columns

each column occupies space equal to the size of the largest widget in it.


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Table layout


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Frame Layoutdesigned to block out an area on the screen to display a single item.

FrameLayout should be used to hold a single child view

Multiple inner views will

be overlapped.


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Views


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TextViewandroid:id="@+id/myTextView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:background="#ff0000ff"

android:padding="3px"

android:text="Enter User Name"

android:textSize="16sp"

android:textStyle="bold"

android:gravity="center"


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ImageView


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ImageViewChange Image at runtime

image.setImageResource(R.drawable.myImage);


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Edit Text android:autoText, (true/false) provides automatic spelling assistance

android:capitalize, (words/sentences) automatic capitalization

android:digits, to configure the field to accept only certain digits

android:singleLine, is the field for single-line / multiple-line input

android:passwords, (true/false) controls fields visibility

android:numeric, (integer, decimal, signed) controls numeric format

android:phonenumber, (true/false) Formatting phone numbers


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CheckBoxA checkbox is a specific type of two-states button that can be either checked or un


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Radio Buttons


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END

Lecture 2 Activities

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