行動應用開發筆記#

Table of Contents#

[TOC]

Android (Jetpack Compose)#

可用套件#

Gson

1
com.google.code.gson:gson:2.10

OkHttp

1
com.squareup.okhttp3:okhttp:5.0.0

XML 解析#

1
fun parseXml(parser: XmlPullParser): List<String> {
2
    var eventType = parser.eventType
3
    val list = mutableListOf<String>()
4
    var item = ""
5

6
    while (eventType != XmlPullParser.END_DOCUMENT) {
7
        when (eventType) {
8
            XmlPullParser.START_TAG -> { // <xxx>
9
                when (parser.name) {
10
                    "xxx" -> item = parser.nextText()
11
                }
12
            }
13

14
            XmlPullParser.END_TAG -> { // <xxx/>
15
                when (parser.name) {
16
                    "xxx" -> list.add(item)
17
                }
18
            }
19

20
        }
21
        eventType = parser.next()
22
    }
23
    return list
24
}
25

26
parseXml(context.resources.getXml(R.xml.resourceId))

讀res/raw資料#

通常用來讀取靜態JSON

1
context.resources.openRawResource(R.raw.xxx).bufferedReader().use {
2
    it.readText() }

頁面導航#

因 Navigation 元件需要套件安裝，所以可用下列方法代替 (取自學長)

1
class MainActivity : ComponentActivity() {
2
    override fun onCreate(savedInstanceState: Bundle?) {
3
        super.onCreate(savedInstanceState)
4
        enableEdgeToEdge()
5
        val viewModel by viewModels<MainViewModel>()
6
        setContent {
7
            Crossfade(viewModel.screen, label = "") { screen ->
8
                //若screen為空就退出App
9
                screen?.invoke() ?: finish()
10
            }
11
            // 處理返回鍵
12
            BackHandler(onBack = viewModel::pop)
13
        }
14
    }
15
}

1
class MainViewModel : ViewModel() {
2
    private val screens = mutableStateListOf<@Composable () -> Unit>({ FirstScreen(this) })
3

4
    // 用getter保持最新
5
    val screen get() = screens.lastOrNull()
6

7
    fun push(targetScreen: @Composable () -> Unit) {
8
        screens += targetScreen
9
    }
10

11
    fun pushReplacement(targetScreen: @Composable () -> Unit) {
12
        pop()
13
        screens += targetScreen
14
    }
15

16
    fun pop() {
17
        screens.removeLastOrNull()
18
    }
19
}

Drawer#

1
val drawerState = rememberDrawerState(DrawerValue.Closed) // Closed, Open
2
ModalNavigationDrawer(
3
    drawerContent = {
4
        ModalDrawerSheet {
5
            NavigationDrawerItem(
6
                icon = { Icon(painterResource..., "") },
7
                label = { Text("...") },
8
                selected = false,
9
                onClick = {}
10
            )
11
        }
12
    },
13
    drawerState = drawerState,
14
    gesturesEnabled = true //右滑打開Drawer的手勢
15
)

NOTE
drawerState.open() / close() 為 suspend 方法

HorizontalPager(水平) 適合用來公告輪播亦有 VerticalPager (垂直)

1
val pagerState = rememberPagerState(
2
    initialPage = 0, //Optional
3
    pageCount = { 2 }
4
)
5
HorizontalPager(pagerState) { page ->
6
    when (page) {
7
        0 -> ..
8
    }
9
}

WebView讀取本機HTML#

1
var webView: WebView? = null
2
AndroidView(
3
    factory = { context ->
4
        WebView(context).apply {
5
            loadUrl("file:///android_asset/xxx")
6
            webView = this
7
        }
8
    },
9
)
10

11
//返回鍵回到上一頁
12
BackHandler(onBack = {
13
    webView!!.goBack()
14
})

NOTE
file://android_asset 指向 assets 資料夾

Gson#

toJson#

OkHttp#

GET#

1
val client = OkHttpClient().newBuilder().build()
2

3
val request = Request.Builder()
4
    .url("http://10.0.2.2:8000/reminders/1")
5
    .addHeader("accept","application/json")
6
    .addHeader("X-API-KEY","KEY1")
7
    .build()
8

9
val call = client.newCall(request)
10

11
call.enqueue(object : Callback {
12
    override fun onFailure(call: Call, e: IOException) {
13
        println(e.message)
14
    }
15

16
    override fun onResponse(call: Call, response: Response) {
17
        println(response.body.string())
18
    }
19

20
})

POST (PATCH)#

1
val client = OkHttpClient().newBuilder().build()
2

3
val request = Request.Builder()
4
    .url("http://10.0.2.2:8000/reminders/1")
5
    .patch(Gson().toJson(
6
        mapOf("enabled" to true)
7
    ).toRequestBody("application/json".toMediaType())) //.post() or .patch()
8
    .addHeader("accept","application/json")
9
    .addHeader("X-API-KEY","KEY1")
10
    .build()
11

12
val call = client.newCall(request)
13

14
call.enqueue(object : Callback {
15
    override fun onFailure(call: Call, e: IOException) {
16
        println(e.message)
17
    }
18

19
    override fun onResponse(call: Call, response: Response) {
20
        println(response.body.string())
21
    }
22

23
})

NOTE
可用 call.execute() 做同步請求（不能在UI線程上）

NOTE
10.0.2.2 指向 Host IP

Flutter#

漸層 Paint#

1
final paint = Paint()
2
  ..strokeWidth = 5
3
  ..shader =
4
      LinearGradient(
5
        begin: Alignment.topCenter,
6
        end: Alignment.bottomCenter,
7
        colors: [Color(0x552196F3), Colors.black],
8
      ).createShader(
9
        Rect.fromLTRB(0, 0, size.width, size.height),
10
      );