Android programming introduction

Android ProgrammingReading “The Big Nerd Ranch Guide” Bruce Tsai

Activity States

Resumed (Running)

Paused

Stopped

2

Text

Activity LifecycleBack? Home?

3

Text

Back StackIntact Last in, first out

4

Multitasks

Task is cohesive unit that can move to “background” when user begins a new task or go to Home screen

5

Text

Start Other ActivityVia ActivityManager

6

Intent

Object that component uses to communicate with OS

Explicit intent — start activities within application

create Intent with Context and Class

Implicit intent — start activities in another application

7

Intent i = new Intent(QuizActivity.this, CheatActivity.class);!

startActivity(i);

8

Put Intent Extras (parent)

Intent i = new Intent(QuizActivity.this, CheatActivity.class);!

i.putExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE, true);!

startActivity(i);

9

Use Intent Extra (child)mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);

10

11

Get Activity Result

Intent i = new Intent(QuizActivity.this, CheatActivity.class);!

i.putExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE, true);!

startActivity(i);!

startActivityForResult(i, 0);

12

Set Result (child)Intent data = new Intent();!

data.putExtra(EXTRA_ANSWER_SHOWN, true);!

setResult(RESULT_OK, data);

13

Handle Result (parent)protected void onActivityResult(int requestCode, int resultCode, Intent data) {!

! if (data == null) return;!

! mIsCheater = !data.getBooleanExtra(CheatActivity.EXTRA_ANSWER_SHOWN, false);!

}

14

FragmentController object that activity can deputize to perform tasks

15

Support LibraryFragment is introduced from API level 11

16

Fragment HostActivity defines a spot in its layout for fragment’s view

Activity manage lifecycle of fragment instance

Hosting approaches: add to layout or add to code

17

Fragment Manager

18

Fragment Transaction

Usages of fragment in activities are add, remove, replace and perform other actions

Each set of changes that is committed to activity is fragment transaction

19

FragmentManager fm = getSupportFragmentManager();!

Fragment fragment = fm.findFragmentById(R.id.fragmentContainer);!

if (fragment == null) {!

! fragment = new CrimeFragment();!

! fm.beginTransaction()! .add(R.id.fragmentContainer)! .commit();!

}

20

SDK Versions

Minimum SDK version — hard floor below which the OS should refuse to install the app

Target SDK version — API level the app is designed to run on

Build SDK version — private information between you and compiler

21

dp (dip) — density-independent pixel

sp — scale-independent pixel

22

<Button ! android:layout_width=“wrap_content”! android:layout_weight=“1” />!

<CheckBox ! android:layout_width=“wrap_content”! android:layout_weight=“1” />