Compose 和其他程式庫

 可以用Compose 加入一些最為實用的程式庫。

取得 Activity 結果

rememberLauncherForActivityResult() API 可助您從可組合項中取得 Activity 結果

@Composable
fun Greeting(name: String) {
	var imageUri by remember { mutableStateOf<Uri?>(null) }
    val launcher = rememberLauncherForActivityResult(GetContent()) { uri: Uri? ->
        imageUri = uri
    }
    Column {
        Button(onClick = { launcher.launch("image/*") }) {
            Text(text = "Load Image")
        }
        Image(
            painter = rememberImagePainter(imageUri),
            contentDescription = "My Image"
        )
    }
}

顯示結果:

處理系統返回按鈕

可組合項可以使用 BackHandler 以攔截 Back key 事件

@Composable
fun Greeting(name: String) {
	...	
    var backHandlingEnabled by remember { mutableStateOf(true) }
    BackHandler(backHandlingEnabled) {
        // Handle back press
        Log.d("kevin","press back key")
    }
	...
}

顯示結果:

圖片載入

Instacart 的 Coil 程式庫提供透過外部來源載入圖片的可組合函式，例如透過網路載入遠端圖片。

權限

 <uses-permission android:name="android.permission.INTERNET" />
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

build.gradle

implementation("io.coil-kt:coil-compose:2.2.1")

@Composable
fun Greeting(name: String) {
	...	
       val painter = rememberAsyncImagePainter(
        ImageRequest.Builder(LocalContext.current).data(data = "https://picsum.photos/300/300")
            .apply(block = fun ImageRequest.Builder.() {
                crossfade(true)
            }).build()
    )

    Box {
        Image(
            painter = painter,
            contentDescription = stringResource(R.string.image_content_desc),
            modifier = Modifier.align(Alignment.Center)
        )

        when (painter.state) {
            is AsyncImagePainter.State.Loading -> {
                // Display a circular progress indicator whilst loading
                Log.d("kevin","load image ...")
            }
            is AsyncImagePainter.State.Error -> {
                // If you wish to display some content if the request fails
            }
        }
    }	...
}

顯示結果:

參考:

https://developer.android.com/jetpack/compose/libraries

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裡面也有蠻多 operator 的介紹，歡迎大家有興趣的參考看看
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