{"id":31843,"date":"2019-10-31T21:43:27","date_gmt":"2019-10-31T18:43:27","guid":{"rendered":"https:\/\/prohoster.info\/blog\/sozdanie-kalkulyatora-chaevyh-na-kotlin-kak-eto-rabotaet\/"},"modified":"2019-10-31T21:43:27","modified_gmt":"2019-10-31T18:43:27","slug":"sozdanie-kalkulyatora-chaevyh-na-kotlin-kak-eto-rabotaet","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/sozdanie-kalkulyatora-chaevyh-na-kotlin-kak-eto-rabotaet","title":{"rendered":"Vytv\u00e1\u0159en\u00ed kalkul\u00e1toru spropitn\u00e9ho v Kotlinu: jak to funguje?","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"Vytv\u00e1\u0159en\u00ed
\n
\nPopisujeme, jak vytvo\u0159it jednoduchou aplikaci pro v\u00fdpo\u010det spropitn\u00e9ho v jazyce Kotlin. Konkr\u00e9tn\u011b, Kotlin 1.3.21, Android 4, Android Studio 3. Tento \u010dl\u00e1nek bude zaj\u00edmav\u00fd p\u0159edev\u0161\u00edm pro ty, kte\u0159\u00ed za\u010d\u00ednaj\u00ed svou cestu ve v\u00fdvoji aplikac\u00ed pro Android. Umo\u017e\u0148uje pochopit, co a jak funguje uvnit\u0159 aplikace. <\/p>\n

Takov\u00fd kalkul\u00e1tor se hod\u00ed, kdy\u017e je pot\u0159eba spo\u010d\u00edtat \u010d\u00e1stku spropitn\u00e9ho pro skupinu, kter\u00e1 se rozhodla str\u00e1vit \u010das v restauraci nebo kav\u00e1rn\u011b. Samoz\u0159ejm\u011b, ne v\u0161ichni a ne v\u017edy nech\u00e1vaj\u00ed \u010d\u00ed\u0161n\u00edk\u016fm spropitn\u00e9, je to sp\u00ed\u0161e z\u00e1padn\u00ed tradice, ale proces v\u00fdvoje takov\u00e9 aplikace je ka\u017edop\u00e1dn\u011b zaj\u00edmav\u00fd.
\n<\/a><\/noindex><\/p>\n

P\u0159ipom\u00edn\u00e1me:<\/b> pro v\u0161echny \u010dten\u00e1\u0159e \"Habra\" \u2013 sleva 10 000 korun p\u0159i registraci na jak\u00fdkoli kurz Skillbox s promok\u00f3dem \"Habr\".<\/i><\/p>\n

Skillbox doporu\u010duje:<\/b> Praktick\u00fd kurz Mobiln\u00ed v\u00fdvoj\u00e1\u0159 PRO<\/a><\/noindex>.\n<\/p><\/blockquote>\n

\nTakto aplikace vypad\u00e1 b\u011bhem pr\u00e1ce:<\/p>\n

\"Vytv\u00e1\u0159en\u00ed
\n
\nZad\u00e1te po\u017eadovan\u00fd procentu\u00e1ln\u00ed pod\u00edl z celkov\u00e9 \u010d\u00e1stky, po\u010det \u00fa\u010dastn\u00edk\u016f setk\u00e1n\u00ed a dostanete v\u00fdsledek \u2014 \u010d\u00e1stku spropitn\u00e9ho, kterou byste m\u011bli nechat.<\/p>\n

Za\u010d\u00edn\u00e1me<\/h3>\n

\nCelkov\u00fd vzhled aplikace vypad\u00e1 n\u00e1sledovn\u011b:
\n\"Vytv\u00e1\u0159en\u00ed
\n
\n\"Vytv\u00e1\u0159en\u00ed
\n
\nPrvn\u00ed krok \u2014 nahr\u00e1n\u00ed z\u00e1klad\u016f projektu<\/a><\/noindex>. Otev\u0159eme ji v Android Studio 3.0 nebo nov\u011bj\u0161\u00ed verzi. Sestav\u00edme a spust\u00edme projekt a vid\u00edme b\u00edlou obrazovku. To je v po\u0159\u00e1dku, tak to m\u00e1 b\u00fdt.<\/p>\n

\"Vytv\u00e1\u0159en\u00ed
\n
\n\"Vytv\u00e1\u0159en\u00ed
\n
\nAkce u\u017eivatele jsou v projektu naps\u00e1ny chronologicky, aby v\u0161echno d\u00e1valo smysl. Pro jejich zobrazen\u00ed otev\u0159eme View -> Tool Windows -> TODO.<\/p>\n

Zkoum\u00e1me projekt a otev\u00edr\u00e1me colors.xml pro posouzen\u00ed barevn\u00e9 palety. V strings.xml jsou um\u00edst\u011bna textov\u00e1 data (popisky) a v styles.xml jsou n\u011bkter\u00e9 \u0161ablony p\u00edsem.<\/p>\n

V\u00fdvoj sekce n\u00e1klad\u016f<\/h3>\n

\nOtev\u0159eme activity_main.xml a p\u0159id\u00e1me n\u00ed\u017ee uveden\u00fd k\u00f3d do LinearLayout (#1):<\/p>\n

<\/code><\/pre>\n
\nNyn\u00ed m\u016f\u017eete nastavit styl adres\u00e1\u0159e values nebo si hr\u00e1t s barvami pomoc\u00ed n\u00e1stroje material.io<\/a><\/noindex>.<\/p>\n
Te\u010f projekt vypad\u00e1 takto:<\/p>\n
\"Vytv\u00e1\u0159en\u00ed
\n Jak vid\u00edte, v\u00fdpo\u010det n\u00e1klad\u016f se prov\u00e1d\u00ed na z\u00e1klad\u011b \u00fadaj\u016f, kter\u00e9 zad\u00e1v\u00e1 u\u017eivatel. <\/i><\/p>\n
V\u00fdvoj sekce \u00fa\u010dt\u016f<\/h3>\n
\nP\u0159id\u00e1v\u00e1me n\u00ed\u017ee uveden\u00fd k\u00f3d do LinearLayout po Expense Section (#2):<\/p>\n
<! \u2014 TODO #3: Vytvo\u0159it sekci \u00fa\u010dt\u016f \u2192\n \n\u2026<\/code><\/pre>\n
\nUzav\u00edr\u00e1me LinearLayout po seznamu \u00fakol\u016f a pot\u00e9 p\u0159id\u00e1v\u00e1me nov\u00fd k\u00f3d, kter\u00fd um\u00edst\u00edme do LinearLayout (#3):<\/p>\n
<\/code><\/pre>\n
\nJeliko\u017e hlavn\u00edm c\u00edlem aplikace je v\u00fdpo\u010det individu\u00e1ln\u00edch n\u00e1klad\u016f pro ka\u017ed\u00e9ho z \u00fa\u010dastn\u00edk\u016f ve\u010de\u0159e v restauraci, hraje kl\u00ed\u010dovou roli costPerPersonTextView. <\/p>\n
EditText omezuje vstup na jeden \u0159\u00e1dek, tento parametr by m\u011bl m\u00edt hodnotu NumberDecimal inputType.<\/p>\n
\"Vytv\u00e1\u0159en\u00ed
\n Spou\u0161t\u00edme projekt pro testov\u00e1n\u00ed a zad\u00e1v\u00e1me parametry celkov\u00fdch \u0161kod (rozbit\u00e9 \u0161\u00e1lky, tal\u00ed\u0159e atd.)<\/i><\/p>\n
V\u00fdvoj sekce \u201eLid\u00e9 a spropitn\u00e9\u201c<\/h3>\n
\nAbychom p\u0159idali mo\u017enost v\u00fdb\u011bru v\u00fd\u0161e spropitn\u00e9ho, vlo\u017e\u00edme n\u00ed\u017ee uveden\u00fd k\u00f3d do nov\u00e9 sekce LinearLayout (#4):<\/p>\n
<\/code><\/pre>\n
\nTento \u00fasek k\u00f3du je nezbytn\u00fd pro p\u0159esn\u00fd v\u00fdpo\u010det \u010d\u00e1stky spropitn\u00e9ho. V\u00fdchoz\u00ed hodnota textu je 20. ImageButtons jsou vybaveny ikonami v adres\u00e1\u0159i s pr\u00e1vy pro z\u00e1pis.<\/p>\n
\u00dapln\u011b kop\u00edrujeme sekci a p\u0159id\u00e1me n\u00e1sleduj\u00edc\u00ed (#5):<\/p>\n