Your First Android Project! презентация

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7+ years of Android, 9+ years total
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@colriot

Checklist
Android Studio, Java, Git are ready to use
Checked-in on Eventbrite
Joined slack (android-academy-msk) https://bit.ly/2NIR0x0
Android Studio, Kotlin, Git are ready to use

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

Android Studio & First Project

File >> New Project

File >> New Project

https://developer.android.com/about/dashboards/index.html

What’s an Activity?
Activity - a component with a screen with which users can interact in order to do something.
https://developer.android.com/guide/components/activities.html

API 28
Alchaka
Art of Movement
Breath control
Center of Being
Detoxify Poison
Flashburn
Force Body
Force Enlightenment
Force ghost
Force healing[1]
Force speed
Force stealth (Also known as Force Concealment)
Hibernation trance
Morichro
Tapas
Cloak of Shadow

API 21
Alchaka
Art of Movement
Breath control
Center of Being
Detoxify Poison
Flashburn
Force Body
Force Enlightenment
Force ghost
Force healing[1]
Force speed
Force stealth (Also known as Force Concealment)
Hibernation trance
Morichro
Tapas
Cloak of Shadow
Alchaka
Art of Movement
Breath control
Center of Being
Detoxify Poison
Flashburn
Force Body
Force Enlightenment
Force ghost
Force healing[1]
Force speed
Force stealth (Also known as Force Concealment)
Hibernation trance
Morichro
Tapas
Cloak of Shadow

Alchaka
Art of Movement
Breath control
Center of Being
Detoxify Poison
Flashburn
Force Body
Force Enlightenment
Force ghost
Force healing[1]
Force speed
Force stealth (Also known as Force Concealment)
Hibernation trance
Morichro
Tapas
Cloak of Shadow
Alchaka
Art of Movement
Breath control
Center of Being
Detoxify Poison
Flashburn
Force Body
Force Enlightenment
Force ghost
Force healing[1]
Force speed
Force stealth (Also known as Force Concealment)
Hibernation trance
Morichro
Tapas
Cloak of Shadow
Alchaka
Art of Movement
Breath control
Center of Being
Detoxify Poison
Flashburn
Force Body
Force Enlightenment
Force ghost
Force healing[1]
Force speed
Force stealth (Also known as Force Concealment)
Hibernation trance
Morichro
Tapas
Cloak of Shadow
min API 21
Support Library (AppCompat, androidx)

AndroidManifest.xml
MainActivity.java
activity_main.xml
3 Interesting Things:

How Does An Activity Look?

Android Application Structure for now
Application
Activity
A
Activity
B
...
… Manifest ...
Activity
C
https://developer.android.com/guide/topics/manifest/manifest-intro.html

How to run the app?
Push the tempo!

How to run the app?
We need to choose a device.

Option 1: A Real Device
Allow USB Debugging.
It’s in the Developer Options setting,
which might be hidden
Read more:
https://developer.android.com/tools/device.html
https://developer.android.com/studio/debug/dev-options.html

Android developer in 30 seconds
Android developer

Confirm popup and run

Option 2: A Virtual Device
Open the AVD manager
and create a virtual device.
The run dialog will offer you to start it.

I click “Run”, You say Ho!
Android Studio Builds the project

*.java
*.xml
images, videos
AndroidManifest.xml
Android Asset Packaging Tool (aapt)
R.java
Java Compiler
Compiled Resources
*.class
*.dex
Dex
Compiler
APK Builder
foo.apk

What does it take to build the project?
But Gradle helps us with it.
https://developer.android.com/studio/build/

I click “Run”, You say Ho!
Android Studio Builds the project
http://developer.android.com/tools/help/adb.html

How is it run?
Android looks through the application’s manifest
Finds an Activity with special “marker”
Launches it

It’s ALIVE!

Build config
Project’s build.gradle
App’s build.gradle

Any Questions?

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

A Little Bit On Layouts

Views
Everything in that XML file is a View.
A View:
Knows to draw itself
Used for user interaction
Has (at least) width and height (match_parent / wrap_content/fixed)

ViewGroup (Layout)
A special kind of view.
Knows to position its children views on the screen.

LinearLayout
Lays items in a row or a column.
Can also divide existing space by weight.
https://developer.android.com/guide/topics/ui/layout/linear.html

How does the layout look?

1
2
3

Any Questions?

BTC Miner

activity_main.xml android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>

LinearLayout orientation

activity_main.xml android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>

**making things prettier**

Change Text Size (editor)

Change Text Size (code)
...
android:textSize="70sp" />
...
android:textSize="70sp" />

Save Size
We have set up the value 70sp twice!
Repetition in code?? Not for me!

Save Size in dimens.xml
70sp

dimens.xml

Use Size From dimen.xml
...
android:textSize="@dimen/btc_text_size"/>

Saving String Resources
...
android:text="ADD BTC"/>

Saving String Resources
...
android:text="@string/add_btc"/>

Saving String on strings.xml
BTC Miner
ADD BTC
0

strings.xml

Resources
Layouts
Drawable (images, vectors, shapes)
Animations
Colors
Themes & Styles
Booleans / Integers / Dimens /…
Other XMLs
Raw (everything else)
https://developer.android.com/guide/topics/resources/providing-resources

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

BTC Miner
Does nothing...

Activity
public class MainActivity extends AppCompatActivity {
}

Activity
public class MainActivity extends AppCompatActivity {
}

Activity
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); }
}

Activity
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); }
}

setContentView
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);
}
}

Let’s make it mine!
Access Views declared in XML from Java code
Change text in TextView
Set onClickListener for the Button
Increment BTC counter & update text

Reference to the view on code
public class MainActivity extends AppCompatActivity {
private TextView btcText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btcText = findViewById(/*...*/);
}
}

Assign view ID
...
android:id="@+id/btc_text"/>

Reference to the view on code
public class MainActivity extends AppCompatActivity {
private TextView btcText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btcText = findViewById(R.id.btc_text);
}
}

*.java
*.xml
images, videos
AndroidManifest.xml
Android Asset Packaging Tool (aapt)
R.java
Java Compiler
Compiled Resources
*.class
*.dex
Dex
Compiler
APK Builder
foo.apk

Mighty (Tho)R
Autogenerated
Each resource type becomes
a static nested class
Each resource becomes
an int ID with the same name

Change text in TextView
btcText = findViewById(R.id.btc_text);
btcText.setText("Hello World!");

Change text in TextView
btcText = findViewById(R.id.btc_text);
btcText.setText("Hello World!");

Change text in TextView
btcText = findViewById(R.id.btc_text);
btcText.setText(R.string.initial_btc);

Find a button and setOnClickListener
Button addBtcButton = findViewById(R.id.add_btc_button);
addBtcButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO : update BTC count
}
});

Find a button and setOnClickListener
Button addBtcButton = findViewById(R.id.add_btc_button);
addBtcButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO : update BTC count
}
});

Let’s make a BTC counter!
We’ll need a BTC counter variable. Let’s add an int and set it to 0.
public class MainActivity extends AppCompatActivity {
private int btcCounter = 0;
//...
}

Setting onClickListener
addBtcButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
btcCounter++;
String btc = String.valueOf(btcCounter);
btcText.setText(btc);
}
});

Not xml?
android:id="@+id/add_btc_button"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:onClick="onButtonClick"/>
public void onButtonClick(View view) {
}

OMG, It looks great!

Questions?

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

Rotate the device

WHERE ARE...
MY BTC?????...

Is it a bug or feature?

Rotate the device

Create a different layout for landscape

activity_main.xml (#2)

Now: Rotate the device

setContentView
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);
}
}

First android device
HTC Dream
320x480px (2:3)
180 ppi
3.2” (81mm)
http://en.wikipedia.org/wiki/HTC_Dream

Current Android Device
Pixel 2 XL
2880x1440px (18:9)
538 ppi
6.0” (152mm)
https://en.wikipedia.org/wiki/Pixel_2

Big Android Device
Nexus 10 (Tablet)
2560x1600px
300ppi
10.1”
http://en.wikipedia.org/wiki/Nexus_10

Small Android Device
LG G Watch
Most
Same techniques apply
http://en.wikipedia.org/wiki/Android_Wear

The difference is Big

Differences
Pixel Density
Screen size
Orientation
OS version
Locale
Device type
...
https://developer.android.com/guide/topics/manifest/activity-element#config
https://developer.android.com/guide/topics/resources/providing-resources#AlternativeResources

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

We need more Activities!

Creating another Activity
Using Android Studio, use Alt + Insert -or- Command + N to create something new. This shortcut is also context aware.
Let’s create a new activity and call it SecondActivity.
https://developer.android.com/training/basics/firstapp/starting-activity.html

File >> New Project

File >> New Project

You can’t just open an activity on your own -
Android does it for you.
And this is done by using an Intent.
How to open SecondActivity

Intents have...
used for Explicit Intents
used for Implicit Intents
used to tell things to the recipient
used to tell things to the messenger
Component Name
Action
Data (and Type)
Category
Extras
Flags

How to open SecondActivity
MainActivity.java:
public void openSecondActivity() {
Intent secondActivityIntent = new Intent(this, SecondActivity.class);
startActivity(secondActivityIntent);
}

Invoke opening SecondActivity
Let’s open it on every 5th BTC mined!
addBtcButton.setOnClickListener(new View.OnClickListener() { @Override
public void onClick(View v) {
// ...
if (btcCounter % 5 == 0) {
openSecondActivity();
}
}
});

Intents have...
used for Explicit Intents
used for Implicit Intents
used to tell things to the recipient
used to tell things to the messenger
Component Name
Action
Data (and Type)
Category
Extras
Flags

MainActivity.java:
private void openSecondActivity() {
Intent secondActivityIntent = new Intent(this, SecondActivity.class);
secondActivityIntent.putExtra("KEY_BTC", btcCounter);
startActivity(secondActivityIntent);
}
Pass arguments to next activity

Pass arguments to next activity
SecondActivity.java:
public static final String KEY_BTC = "KEY_BTC";
MainActivity.java:
private void openSecondActivity() {
Intent secondActivityIntent = new Intent(this, SecondActivity.class);
secondActivityIntent.putExtra(KEY_BTC, btcCounter);
startActivity(secondActivityIntent);
}

Get the data passed by the caller
See that the data passed
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
int btcCount = getIntent().getIntExtra(KEY_BTC, 0);
}

activity_second.xml
The whole Activity is just a TextView with ID:
android:id="@+id/status_text" android:layout_width="match_parent"
android:layout_height="match_parent" />

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
int btcCount = getIntent().getIntExtra(KEY_BTC, 0);
}
Use the data in UI

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
int btcCount = getIntent().getIntExtra(KEY_BTC, 0);
TextView statusText = findViewById(R.id.status_text);
statusText.setText(getString(R.string.btc_status, btcCounter));
}
Use the data in UI

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
int btcCount = getIntent().getIntExtra(KEY_BTC, 0);
TextView statusText = findViewById(R.id.status_text);
statusText.setText(getString(R.string.btc_status, btcCounter));
}
Use the data in UI

String with format
BTC Miner
ADD BTC
0
Wow! You already have %d BTC

SecondActivity

Best Practice: Start Activity Statically
SecondActivity.java:
private static final String KEY_BTC = "KEY_BTC";
public static void start(Activity activity, int btcCounter) {
Intent intent = new Intent(activity, SecondActivity.class);
intent.putExtra(KEY_BTC, btcCounter);
activity.startActivity(intent);
}

Best Practice: Start Activity Statically
SecondActivity.java:
private static final String KEY_BTC = "KEY_BTC";
public static void start(Activity activity, int btcCounter) {
Intent intent = new Intent(activity, SecondActivity.class);
intent.putExtra(KEY_BTC, btcCounter);
activity.startActivity(intent);
}

Best Practice: Start Activity Statically
MainActivity.java:
public void openSecondActivity() {
SecondActivity.start(this, btcCounter);
}

Any Questions?

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

Activity Lifecycle

The Activity Lifecycle
https://developer.android.com/guide/components/activities/activity-lifecycle

The Activity Lifecycle
When activity lifecycle state changes,
Android lets us know with a callback: onCreate() -> onDestroy()
onStart() -> onStop().
onResume() -> onPause().

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

Logging

Logging
Definition:
A logfile is a file that records either events that occur in an operating system or other software.
Code:
Log.i(TAG, "Ahtung");

Log level
Verbose Log.v()
Debug Log.d()
Info Log.i()
Warn Log.w()
Error Log.e()

Log level
Verbose Log.v()
Debug Log.d()
Info Log.i()
Warn Log.w()
Error Log.e()
Fatal Log.wtf()

Logging

private static final String TAG = "MainActivity";
@Override
protected void onResume() {
super.onResume();
Log.i(TAG, "onResume");
}
@Override
protected void onPause() {
super.onPause();
Log.i(TAG, "onPause");
}
Log lifecycle

private static final String TAG = "MainActivity";
@Override
protected void onResume() {
super.onResume();
Log.i(TAG, "onResume");
}
@Override
protected void onPause() {
super.onPause();
Log.i(TAG, "onPause");
}
Log lifecycle

Any Questions?

Agenda
Android Studio & First Project
Activity & Layouts
Resources
Java & XML works together
Different configurations
Intents
Activity Lifecycle
Logs

Recap
What’s an Activity? Describe Activity Lifecycle methods.
What’s the Manifest?
Which resource types do we have?
What are View, ViewGroup and LinearLayout?
Which class helps us to open another Activity? How to pass data between Activities?
Which types of Intents do we have? What’s the difference?
How to print information to Android log file?

git - getting today’s code
If you want to grab the code for this lecture, you should clone this GitHub repository:
https://bit.ly/2x2mqHy

And now….Exercise!
https://goo.gl/phRktb

Fundamentals #2: Views