Hello YuSEO禅最近在看CameraX的资料，看到一个系列文章，讲解的挺好，打算翻译成中文，顺便学习下，这个系列会分解成4篇小文章，每个文章都有自己的主题，分别是：
- 《在Jetpack Compose中使用Accompanist获取设备权限》(本文)
- 《在Jetpack Compose中使用CameraX进行照相预览》
- 《在Jetpack Compose中使用CameraX对相机截图操作》
- 《在Jetpack Compose中从图库选择照片》
Manifest添加权限配置
Android在使用设备功能的时候，都要进行权限的申请，我们可以通过配置AndroidManifest.xml文件来注册软件所需要的功能权限，比如我们要使用相机功能，可以添加如下配置：
<uses-feature android:name="android.hardware.camera" />
<uses-permission android:name="android.permission.CAMERA" /><uses-feature android:name="android.hardware.camera" />
<uses-permission android:name="android.permission.CAMERA" />动态权限获取Accompanist
这种方式并不一定保险，因为用户可能在安装软件的时候，选择了不授权给软件相应的功能，所以我们还要增加一个软件运行时，能够动态判断和动态获取权限的能力，这时候我们就可以用到Accompanist这个库，其中提供了accompanist-permissions子库，我们可以用这个库来实现动态获取权限，首先我们要加载这个库，在Module级别的build.gradle文件写入：
implementation "com.google.accompanist:accompanist-permissions:0.23.1" implementation "com.google.accompanist:accompanist-permissions:0.23.1"写这篇文章的时候，最新版本是0.31.3-beta，但是新建的compose项目使用的是1.1.1的compose版本，所以要选0.23.1的兼容版本，你们根据自己的兼容版本自行选择：
之后创建一个Permission的方法，方便获取权限：
kotlin
@Composable
private fun Rationale(
text: String,
onRequestPermission: () -> Unit
) {
AlertDialog(
onDismissRequest = { /* Don't */ },
title = {
Text(text = "Permission request")
},
text = {
Text(text)
},
confirmButton = {
Button(onClick = onRequestPermission) {
Text("Ok")
}
}
)
}
@OptIn(ExperimentalPermissionsApi::class)
@Composable
fun Permission(
permission: String = android.Manifest.permission.CAMERA,
rationale: String = "This permission is important for this app. Please grant the permission.",
permissionNotAvailableContent: @Composable () -> Unit = { },
content: @Composable () -> Unit = { }
) {
val permissionState = rememberPermissionState(permission)
PermissionRequired(
permissionState = permissionState,
permissionNotGrantedContent = {
Rationale(
text = rationale,
onRequestPermission = { permissionState.launchPermissionRequest() }
)
},
permissionNotAvailableContent = permissionNotAvailableContent,
content = content
)
}@Composable
private fun Rationale(
text: String,
onRequestPermission: () -> Unit
) {
AlertDialog(
onDismissRequest = { /* Don't */ },
title = {
Text(text = "Permission request")
},
text = {
Text(text)
},
confirmButton = {
Button(onClick = onRequestPermission) {
Text("Ok")
}
}
)
}
@OptIn(ExperimentalPermissionsApi::class)
@Composable
fun Permission(
permission: String = android.Manifest.permission.CAMERA,
rationale: String = "This permission is important for this app. Please grant the permission.",
permissionNotAvailableContent: @Composable () -> Unit = { },
content: @Composable () -> Unit = { }
) {
val permissionState = rememberPermissionState(permission)
PermissionRequired(
permissionState = permissionState,
permissionNotGrantedContent = {
Rationale(
text = rationale,
onRequestPermission = { permissionState.launchPermissionRequest() }
)
},
permissionNotAvailableContent = permissionNotAvailableContent,
content = content
)
}Rationale的方法这里面就是一个Dialog的提示，主要是Permission中的rememberPermissionState和PermissionRequired两个方法，这两个方法是Accompanist提供的，可以自己看看API文档,之后我们在项目中调用我们的Permission方法请求权限就行：
kotlin
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
PhotoAppWithCameraX_ComposeTheme {
// A surface container using the 'background' color from the theme
Surface(modifier = Modifier.fillMaxSize(),
color = MaterialTheme.colors.background) {
val context = LocalContext.current
Permission(
permission = android.Manifest.permission.CAMERA,
rationale = "You said you wanted a picture, so I'm going to have to ask for permission.",
permissionNotAvailableContent = {
Column() {
Text("O noes! No Camera!")
Spacer(modifier = Modifier.height(8.dp))
Button(onClick = {
context.startActivity(Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
data = Uri.fromParts("package", context.packageName, null)
})
}) {
Text("Open Settings")
}
}
}
) {
Text("It worked!")
}
}
}
}
}
}class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
PhotoAppWithCameraX_ComposeTheme {
// A surface container using the 'background' color from the theme
Surface(modifier = Modifier.fillMaxSize(),
color = MaterialTheme.colors.background) {
val context = LocalContext.current
Permission(
permission = android.Manifest.permission.CAMERA,
rationale = "You said you wanted a picture, so I'm going to have to ask for permission.",
permissionNotAvailableContent = {
Column() {
Text("O noes! No Camera!")
Spacer(modifier = Modifier.height(8.dp))
Button(onClick = {
context.startActivity(Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
data = Uri.fromParts("package", context.packageName, null)
})
}) {
Text("Open Settings")
}
}
}
) {
Text("It worked!")
}
}
}
}
}
}运行之后会有如下图示结果：
一开始会提示请求权限，如果不成功会提示打开设置菜单，进行手动开启权限，如果成功会显示成功提示。到这里我们就算使用Accompanist成功请求到照相机的权限，下一篇文章我们尝试在Compose中预览相机实时取景的功能。