Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Don't Reinvent The Wheel ~ For All Android Begi...
Search
Ken Wagatsuma
November 23, 2015
Programming
0
930
Don't Reinvent The Wheel ~ For All Android Beginners ~
Advice for all Android Development Beginners how to learn themself.
Ken Wagatsuma
November 23, 2015
Tweet
Share
More Decks by Ken Wagatsuma
See All by Ken Wagatsuma
Pregel Graph Compute Engines - Supersteps Exampls
kenju
0
210
Kafka on Kubernetes with Strimzi
kenju
0
160
AWS DynamoDB Accelerator (DAX) 101
kenju
2
7.1k
Moden browser introduction
kenju
1
400
Cookpad summer internship 2019 - API
kenju
0
10k
Introduction to Design Patterns
kenju
0
81
GraphQL Asia 2019 "Re-architecture of a decade-old app with BFF/GraphQL"
kenju
0
8.9k
Introduction to TypeScript
kenju
0
720
Introduction to Programmatic Ad
kenju
0
260
Other Decks in Programming
See All in Programming
Advanced Micro Frontends: Multi Version/ Framework Scenarios @WAD 2025, Berlin
manfredsteyer
PRO
0
390
20250708_JAWS_opscdk
takuyay0ne
2
130
DMMを支える決済基盤の技術的負債にどう立ち向かうか / Addressing Technical Debt in Payment Infrastructure
yoshiyoshifujii
3
410
Goで作る、開発・CI環境
sin392
0
260
なぜ「共通化」を考え、失敗を繰り返すのか
rinchoku
1
680
Azure AI Foundryではじめてのマルチエージェントワークフロー
seosoft
0
200
初学者でも今すぐできる、Claude Codeの生産性を10倍上げるTips
s4yuba
16
13k
Deep Dive into ~/.claude/projects
hiragram
14
14k
The Niche of CDK Grant オブジェクトって何者?/the-niche-of-cdk-what-isgrant-object
hassaku63
1
610
Vibe Codingの幻想を超えて-生成AIを現場で使えるようにするまでの泥臭い話.ai
fumiyakume
9
4.1k
AI時代の『改訂新版 良いコード/悪いコードで学ぶ設計入門』 / ai-good-code-bad-code
minodriven
23
9.6k
20250704_教育事業におけるアジャイルなデータ基盤構築
hanon52_
5
1.1k
Featured
See All Featured
Code Review Best Practice
trishagee
69
19k
Adopting Sorbet at Scale
ufuk
77
9.5k
Creating an realtime collaboration tool: Agile Flush - .NET Oxford
marcduiker
30
2.2k
Scaling GitHub
holman
460
140k
GitHub's CSS Performance
jonrohan
1031
460k
The Illustrated Children's Guide to Kubernetes
chrisshort
48
50k
Understanding Cognitive Biases in Performance Measurement
bluesmoon
29
1.8k
Building Applications with DynamoDB
mza
95
6.5k
Evolution of real-time – Irina Nazarova, EuRuKo, 2024
irinanazarova
8
830
VelocityConf: Rendering Performance Case Studies
addyosmani
332
24k
Visualization
eitanlees
146
16k
Keith and Marios Guide to Fast Websites
keithpitt
411
22k
Transcript
Don’t Reinvent The Wheel Kenju Wagatsuma
Agenda: -> ❖ 1m : Introduction ❖ 3m : Main
part ❖ 1m : Conclusion
/** * Introduce Myself * * @kenjuwagatsuma */
'me' = { name : 'Kenju Wagatsuma ( KJ )’,
}
'me' = { name : 'Kenju Wagatsuma ( KJ )’,
company : 'Recruit Technologies Co.,LTD.', }
'me' = { name : 'Kenju Wagatsuma ( KJ )’,
company : 'Recruit Technologies Co.,LTD.', profession : 'Android Development', }
'me' = { name : 'Kenju Wagatsuma ( KJ )’,
company : 'Recruit Technologies Co.,LTD.', profession : 'Android Development', favs : { 'Book' : ‘Soft Skills', 'Music' : ‘The Beatles', 'Hobby' : ‘Acoustic Guitar', 'Sport' : 'Rugby' } }
/** * My Story * * @author me */
```java /** * Validate user id input from a form
* * @param String userID */ private void validateUserId(String userId) { // Validate userId } ```
```java private void validateUserId(String userId) { // Check input field
here if (userId == null || userId.length() == 0) { return; } // Validate userId } ```
```java // Utility class public static class UtilClass { public
static boolean checkStringInput(String str) { if (str == null || str.length() == 0) { return true; } else { return false; } } } // Activity class public void MainActivity extends Activity { private void validateUserId(String userId) { if(UtilClass.checkStringInput(userId)) return; // Validate userId // ... } } ```
/** * @codereview * */
None
None
```java private void validateUserId(String userId) { // Check input field
here if (userId == null || userId.length() == 0) { return; } // Validate userId } ```
```java private void validateUserId(String userId) { // Check input field
here if (TextUtils.isEmpty(userId)) { return; } // Validate userId } ```
Okay, I’ll look at the source code, sir…
```java /** * Returns true if the string is null
or 0-length. * @param str the string to be examined * @return true if str is null or zero length */ public static boolean isEmpty(CharSequence str) { if (str == null || str.length() == 0) return true; else return false; } ```
……
……ʮ͍ͬ͠ΐΜ͚wʯ
```java public static boolean checkStringInput(String str) { if (str ==
null || str.length() == 0) { return true; } else { return false; } } ``` My Code
```java public static boolean isEmpty(CharSequence str) { if (str ==
null || str.length() == 0) return true; else return false; } ``` android.TextUtils
```java public static boolean checkStringInput(String str) { if (str ==
null || str.length() == 0) { return true; } else { return false; } } ``` My Code
```java public static boolean isEmpty(CharSequence str) { if (str ==
null || str.length() == 0) return true; else return false; } ``` android.TextUtils
……ʮ͍ͬ͠ΐΜ͚wʯ(࠶)
/** * Why TextUtils? * (not my own code) *
*/
#47 ʮϥΠϒϥϦʔΛΓɺ ϥΠϒϥϦʔΛ͏ʯ “Effective Java” 2nd Edition
#47 ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ ར̍ ❖ ඪ४ϥΠϒϥϦΛ༻͢Δ͜ͱͰɺͦΕΛॻ͍ ͨઐՈͷࣝͱɺͦΕΛ͋ͳͨΑΓલʹ༻ ͨ͠ਓʑͷܦݧΛར༻͢Δ͜ͱʹͳΓ·͢ɻ “Effective Java” 2nd
Edition
#47 ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ ར̎ ❖ ࣗͷ՝ʹগ͔͠Γؔ࿈͍ͯ͠Δʹର ͢ΔͨΓతͳղܾࡦΛॻ͘͜ͱͰɺ࣌ؒΛແ ବʹ͢Δඞཁ͕ແ͍ɻ “Effective Java” 2nd
Edition
#47 ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ ར̏ ❖ ࣗͰԿ͠ͳͯ͘ɺଟ͘ͷਓʹΑͬͯ܁ Γฦ͠ॻ͖͞ΕΔίʔυɺ࣌ؒͱڞʹύ ϑΥʔϚϯε͕վળ͞ΕΔʢࣗͷίʔυͰͦ ͏͍͔ͳ͍ʣɻ “Effective Java”
2nd Edition
/** * So what? * * @return Conclusion */
#47 ʮϥΠϒϥϦʔΛΓɺϥΠϒϥϦʔΛ͏ʯ For All Beginners,
1. Know Android Library 2. Use Library methods 3. See
& Understand source codes 3 Steps for Learning,
/** * Appendix * */
❖ android.text.format.DateUtils ❖ android.text.format.Formatter ❖ android.text.TextUtils ❖ android.text.util.Linkify ❖ android.util.Pair<F,
S> ❖ android.util.SparseArray<E> ❖ android.util.Log ❖ android.util.LruCache ❖ android.graphics.Color ❖ android.media.ThumbnailUtils android.*
android.text.TextUtils ```java /** * ༩͑ΒΕͨจࣈྻ͕͔ͯ͢Ͳ͏͔Λఆ */ public static boolean isDigitsOnly(CharSequence
str) { final int len = str.length(); for (int i = 0; i< len; i++) { if (!Character.isDigit(str.charAt(i)) { return false; } } return true; } ```
android.text.TextUtils ```java /** * HTMLΤϯίʔυ */ public static boolean htmlEncode(String
s) { StringBuilder sb = new StringBuilder(); char c; for (int i = 0; i < s.length(); i++) { c = s.charAt(i); switch(c) { case '<': sb.append("<"); break; //...ͦͷଞͷΤϯίʔυ͖͢จࣈ default: sb.append(c); } } return sb.toString(); }
android.text.TextUtils ```java /** * trim()Ͱআ͞ΕۭͨനͷΛฦ͠·͢ */ public static int getTrimmedLength(CharSequence
s) { int len = s.length(); int start = 0; while (start < len && s.charAt(start) <= ' ') { start++; } int end = 0; while (end > start && s.charAt(end - 1) <= ' ') { end--; } return end - start; } ```
android.database.DatabaseUtils ```java /** * WHERE۟࡞ͷϔϧύʔϝιου */ public static String concatenateWhere(String
a, String b) { if (TextUtils.isEmpty(a)) { return b; } if (TextUtils.isEmpty(b)) { return a; } return "(" + a + ") AND (" + b + ")"; } ```
android.database.DatabaseUtils ```java /** * CursorͷதΛग़ྗ͢Δσόοά༻ϝιου */ public static void dumpCursor(Cursor
cursor) { dumpCursor(cursor, System.out); } public static void dumpCursor(Cursor cursor, PrintStream stream) { stream.println(">>>>> Dumping cursor " + cursor); if (cursor != null) { int startPos = cursor.getPosition(); cursor.moveToPosition(-1); while (cursor.moveToNext()) { dumpCurrentRow(cursor, stream); } cursor.moveToPosition(startPos); } stream.println("<<<<<"); } ```
android.database.DatabaseUtils ```java /** * CursorͷݱࡏͷߦΛग़ྗ͢Δ */ public static void dumpCurrentRow(Cursor
cursor, PrintStream stream) { String[] cols = cursor.getColumnNames(); stream.println("" + cursor.getPosition() + " {"); int length = cols.length; for (int i = 0; i < length; i++) { String value; try { value = cursor.getString(i); } catch (SQLiteException e) { value = "<unprintable>"; } stream.println(" " + cols[i] + '=' + value); } stream.println("}"); } ```
/** * And Much More! * * Happy Coding! *
*/