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Dart for Android Devs
FlutterͱΓ͍͚͋͑ͣͬͯΔΨΠυ
2018/06/26
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Shigehiro Soejima
Android @ DeNA
@highballegg
Flutter Meetup Tokyo
shibuya.apk
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• σʔλܕ
• ม
• ੍ޚจ
• ྫ֎ॲཧ
• Ϋϥε
• ؔ
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DartPad
https://dartpad.dartlang.org/
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σʔλܕ
• numbers
• strings
• booleans
• lists
• maps
• ϓϦϛςΟϒܕͳ͠
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σʔλܕ
numbers
• int
int x = 1;
int hex = 0xDEADBEEF;
• double
double y = 1.1;
double exponents = 1.42e5;
int x = 4 / 2; // error
int y = 5 ~/ 2; // y = 2
• num: int or double
num z = 4 / 2; // z = 2.0 (double)
z = 2; // z = 2 (int), no error
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σʔλܕ
strings
• UTF-16
• Singe/Double ΫΦʔτͲͪΒͰՄ
var str1 = ‘Hello world!’;
var str2 = "Hello world!”;
• Raw จࣈྻ
var raw = r’\t\t\t';
print(raw); // \t\t\t
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• ࿈݁ (վߦɺϒϥϯΫɺʴΛͬͨ3௨Γ)
var s1 = 'Hello '
"world!";
print(s1); // Hello world!
var s2 = 'Hello ' "world!";
print(s2); // Hello world!
var s3 = 'Hello ' + "world!";
print(s3); // Hello world!
σʔλܕ
strings
s1, s2, s3ͷग़ྗ݁Ռͯ͢ಉ͡ɻ
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• 3࿈ΫΦʔτʢ’’’͘͠”””ʣͰғΉ͜ͱͰෳߦΛ
··දݱՄɻ
var str = '''Hello
world!''';
print(str);
var x = 3;
print("number=$x"); // number=3
var str = "Hello world!";
print("length=${str.length}"); // length=12
• ิؒ
σʔλܕ
strings
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σʔλܕ
bool
• true / false
• Javaͱಉ͘͡boolͷtrueͷΈ͕trueɻͦΕҎ֎ͯ͢falseɻ
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σʔλܕ
list = array
var list = [1, 2, 3, 4, 5];
print(list[0]); // 1 (index starts at 0)
list[0] = 0;
print(list); // [0, 2, 3, 4, 5]
list[0] = 2.0; // error
var list2 = const [6, 7, 8, 9, 0];
const list3 = [6, 7, 8, 9, 0];
• ఆʹ͢ΔʹconstΛ͍ͣΕ͔ͷํ๏Ͱ͚Δɻ
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σʔλܕ
map
var map1 = Map(); // new is optional
map1[0] = "zero";
map1[1] = "one";
const map4 = {0: "zero", 1: “one"};
var map3 = const {0: "zero", 1: "one"};
• constԽListܕʹಉ͡ɻ
var map2 = {
"cero": "zero",
"uno": "one",
"dos": "two"};
• key-valueϖΞͰͷఆٛՄೳɻ
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มɾఆ
var num1 = 1;
final num3;
const num4 = 4;
int num2 = 2;
final int num5;
const int num6 = 6;
• var ͘͠໌ࣔతʹܕΛ༩͑ͯఆٛ͢Δɻ
• constͱfinalͲͪΒఆΛఆٛ͢Δ͕ɺ constίϯύΠ
ϧ࣌ʹ͕ඞཁͰɺfinalίϯύΠϧ࣌ʹෆཁ͕ͩҰ
Λ༩͑ΔͱҎ߱มߋෆՄɻ
• _num0ͷΑ͏ʹΞϯμʔείΞΛ͚Δͱprivateͷѻ͍ʹͳ
Δʢϝιουಉ͡ʣɻ
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੍ޚจ
• if else
• for loop
• while loop
• do-while loop
• switch
• forEach
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੍ޚจ
Java
• if else
• for loop
• while loop
• do-while loop
• switch
͜ΕΒJavaʹجຊಉ͡ɻࡾ߲ԋࢉࢠར༻Մɻbreak, continueಉ͡ɻ
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੍ޚจ
forEach
var list = [1, 2, 3, 4, 5];
list.forEach((elm) => print(elm));
• ͏গ͠ෳࡶͳॲཧΛߦ͍͍ͨ߹ؔΛ࡞ͬͯ͢ɻ
void printKeyValue(key, value) {
if (key != null && value != null) {
print("$key:$value");
}
}
Map map = {0: "zero", 1: "one"};
map.forEach(printKeyValue);
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ྫ֎ॲཧ
• ิ͢Δྫ֎ΫϥεΛ໌ࣔతʹॻ͘ͱ͖ try on
• ໌ࣔతʹॻ͔ͳ͍ͱ͖ try catch
• finally Java ʹಉ͡
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try on
try {
var list = [1, 2, 3];
print(list[3]);
} on IndexError {
print("Index out of bounds :(");
}
• catchΛ͚ͭͯྫ֎༰ΛऔΔ͜ͱՄɻ
try {
var list = [1, 2, 3];
print(list[3]);
} on IndexError catch (e) {
print("Index out of bounds: $e");
}
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try catch
try {
somethingGoesWrong();
} on ExceptionA {
// do something here
} on ExceptionB {
// do something here
} catch (e) {
// do something here
}
• Catch-allͰͯ͢ิ͢Δɻ
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Ϋϥε
class Cat {
String breed;
int age;
String name;
Cat(String breed, int age, String name) {
this.breed = breed;
this.age = age;
this.name = name;
}
}
var birman = Cat("Birman", 13,"Ryu");
birman.age = 14;
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Ϋϥε
class Cat {
final String breed;
final int age;
final String name;
Cat(this.breed, this.age, this.name);
}
• Cat(this.breed, this.age, this.name) ͷΑ͏ʹthis.ύϥϝʔ
λ໊ͱ͢Δ͜ͱͰίϯετϥΫλͷೖॲཧͷهड़Λল
ུͰ͖ɺfinalΛ͏͜ͱͰ͖Δɻ
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Ϋϥε
Named Constructor
class AndroidEvent {
String title;
String date;
AndroidEvent(this.title, this.date);
AndroidEvent.shibuyaApk(this.date) {
this.title = "Shibuya.apk";
this.date = date;
}
AndroidEvent.caApk(this.date) {
this.title = “CA.apk";
this.date = date;
}
}
var event = AndroidEvent.shibuyaApk("today");
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Ϋϥε
Factory Constructor
class Series {
final int id;
final String title;
final String url;
Series(this.id, this.title, this.url);
factory Series.fromJson(Map json) {
return new Series(json['id'], json['title'], json['url']);
}
}
• ໊લ͖ίϯετϥΫλʹࣅ͍ͯΔ͕ɺதͰΠϯελϯε
Λ࡞ͬͯฦ͢ඞཁ͕͋Δɻ
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Ϋϥε
Inheritance
class Cat {
String breed;
int age;
String name;
Cat({String breed, int age, String name}) {
this.breed = breed;
this.age = age;
this.name = name;
}
}
var birman = new Cat(breed: "Birman", age: 13, name: "Ryu");
class Birman extends Cat {
Birman(int age, String name) : super(breed: "Birman", age: age, name: name);
Birman.myCat() : this(1, "Shuri");
}
var birman = Birman(1, "Kairi");
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ؔ
var _counter = 0;
void increment() {
_counter++;
}
void increment() => _counter++;
• ؔͷத͕͚ࣜͩͷͷɺলུܗͰهड़Մɻ
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ؔ
getters and setters
var _counter = 0;
void increment() {
_counter++;
}
catName = "Tama";
print(catName); // TAMA
print(name); // Tama
class Cat {
final String breed;
final int age;
final String name;
Cat(this.breed, this.age, this.name);
String get catName => this.name.toUpperCase();
set catName(String name) => this.name = name;
}
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ؔ
Default/Named parameters
void increment(int amount = 1) {
...
}
increment();
• σϑΥϧτύϥϝʔλ
• ໊લ͖ύϥϝʔλ
void enableFlags({bool bold = false, bool hidden = false}) {
...
}
enableFlags(hidden: true);
{}ͰғΉɻશମͰͳ͘ݸผʹғΉ͜ͱՄɻ
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ؔ
Positional parameters
• ϙδγϣφϧύϥϝʔλ
void setName(String last, [String first, String middle]) {
//
}
[]Ͱғͬͨύϥϝʔλ܈ͲΕ͔̍ͭʹΛ༩͑ͨΒɺͦͷύϥϝʔλΑΓॱ
൪͕લͷͷΛ༩͑Δඞཁ͕͋Δɻ
ྫ͑ɺ[a, b, c, d, e] ͱ͋ͬͨͱ͢ΔͱɺdʹΛ༩͑Δ߹a, b, cʹ༩͑
ͳ͚ΕͳΒͳ͍ɻ
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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ɻ
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Flutter Meetup Tokyo #3
2018/07/19
@FlutterTokyo