为了在 Jetpack Compose 环境下开发一个使用后置摄像头采集视频，并在帧差异检测的基础上自动录制的 Android 应用，我们可以使用 CameraX 和 ViewModel，同时结合 FTP 上传功能。
下面这个完整示例展示了如何使用 Jetpack Compose 和 CameraX 编写这个应用。
添加依赖
在 build.gradle 中添加所需的依赖：
dependencies {
implementation "androidx.compose.ui:ui:1.3.0"
implementation "androidx.compose.material:material:1.3.0"
implementation "androidx.lifecycle:lifecycle-viewmodel-compose:2.5.1"
implementation "androidx.camera:camera-camera2:1.1.0"
implementation "androidx.camera:camera-lifecycle:1.1.0"
implementation "androidx.camera:camera-video:1.0.0-alpha28"
implementation "androidx.camera:camera-view:1.1.0"
implementation 'commons-net:commons-net:3.6'
implementation 'androidx.activity:activity-compose:1.3.1'
}
权限配置
在 AndroidManifest.xml 中添加所需的权限：
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.INTERNET" />
创建 ViewModel
我们需要一个 ViewModel 来管理摄像头的操作、视频帧分析和录像控制。
创建 CameraViewModel.kt：
import android.content.Context
import android.net.Uri
import android.os.Handler
import android.os.Looper
import android.util.Log
import androidx.camera.core.*
import androidx.camera.lifecycle.ProcessCameraProvider
import androidx.camera.video.*
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.core.content.ContextCompat
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import java.io.File
import java.text.SimpleDateFormat
import java.util.*
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
class CameraViewModel : ViewModel() {
var isRecording = mutableStateOf(false)
var previewUri = mutableStateOf<Uri?>(null)
private var videoCapture: VideoCapture<Recorder>? = null
private var recording: Recording? = null
private lateinit var cameraExecutor: ExecutorService
fun startCamera(context: Context, previewView: PreviewView) {
val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
cameraProviderFuture.addListener({
val cameraProvider = cameraProviderFuture.get()
val preview = Preview.Builder().build().also {
it.setSurfaceProvider(previewView.surfaceProvider)
}
val recorder = Recorder.Builder()
.setQualitySelector(QualitySelector.from(Quality.HIGHEST))
.build()
videoCapture = VideoCapture.withOutput(recorder)
val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
try {
cameraProvider.unbindAll()
cameraProvider.bindToLifecycle(
context as androidx.lifecycle.LifecycleOwner,
cameraSelector,
preview,
videoCapture
)
} catch (exc: Exception) {
Log.e("CameraViewModel", "Use case binding failed", exc)
}
detectMotionAndRecord(context) // Start detecting motion and recording
}, ContextCompat.getMainExecutor(context))
cameraExecutor = Executors.newSingleThreadExecutor()
}
private fun detectMotionAndRecord(context: Context) {
var prevFrame: ImageProxy? = null
val handler = Handler(Looper.getMainLooper())
val delayMillis = 100L
val captureRunnable = object : Runnable {
override fun run() {
if (isRecording.value) {
recording?.stop()
isRecording.value = false
}
// Capture frame
videoCapture?.takePicture(cameraExecutor, ContextCompat.getMainExecutor(context), object : ImageCapture.OnImageCapturedCallback() {
override fun onCaptureSuccess(image: ImageProxy) {
if (prevFrame == null) {
prevFrame = image
} else {
// Compare frames
val isDifferent = compareFrames(prevFrame!!, image)
prevFrame?.close()
prevFrame = image
if (isDifferent) {
if (!isRecording.value) {
startRecording(context)
isRecording.value = true
}
} else {
if (System.currentTimeMillis() - recordingStartTime > 5000) {
recording?.stop()
isRecording.value = false
}
}
}
handler.postDelayed(this, delayMillis)
}
override fun onError(exception: ImageCaptureException) {
Log.e("CameraViewModel", "Image capture failed", exception)
}
})
}
}
handler.post(captureRunnable)
}
private var recordingStartTime = 0L
private fun compareFrames(frame1: ImageProxy, frame2: ImageProxy): Boolean {
// Implement frame comparison logic (e.g., by comparing pixel values)
return true // example return, implement actual comparison
}
private fun startRecording(context: Context) {
val fileName = SimpleDateFormat("yyyyMMdd_HHmmss", Locale.US)
.format(System.currentTimeMillis()) + ".mp4"
val file = File(context.externalMediaDirs.first(), fileName)
val outputOptions = VideoCapture.OutputFileOptions.Builder(file).build()
recordingStartTime = System.currentTimeMillis()
videoCapture?.startRecording(
outputOptions,
ContextCompat.getMainExecutor(context),
object : VideoCapture.OnVideoSavedCallback {
override fun onVideoSaved(outputFileResults: VideoCapture.OutputFileResults) {
val savedUri = Uri.fromFile(file)
previewUri.value = savedUri
uploadToFTP(file)
}
override fun onError(videoCaptureError: Int, message: String, cause: Throwable?) {
Log.e("CameraViewModel", "Video capture failed: $message", cause)
}
})
}
private fun uploadToFTP(file: File) {
viewModelScope.launch(Dispatchers.IO) {
FTPUpload.uploadFile(
file.path,
"192.168.10.100", 21,
"yyy", "xxx"
)
}
}
}
创建UI
在MainActivity.kt中设置UI：
import android.Manifest
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.result.contract.ActivityResultContracts
import androidx.activity.viewModels
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.core.content.ContextCompat
import com.google.accompanist.permissions.ExperimentalPermissionsApi
import com.google.accompanist.permissions.rememberMultiplePermissionsState
import com.google.accompanist.permissions.shouldShowRationale
import java.util.*
class MainActivity : ComponentActivity() {
private val cameraViewModel: CameraViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
JetpackComposeCameraTheme {
Surface(modifier = Modifier.fillMaxSize()) {
val context = remember { this }
val permissionState = rememberMultiplePermissionsState(
permissions = listOf(
Manifest.permission.CAMERA,
Manifest.permission.RECORD_AUDIO,
Manifest.permission.WRITE_EXTERNAL_STORAGE,
Manifest.permission.READ_EXTERNAL_STORAGE
)
)
if (permissionState.allPermissionsGranted) {
CameraPreview(cameraViewModel)
} else {
Column(
Modifier
.fillMaxSize()
.padding(16.dp)
) {
Text("Permissions need to be granted to use the camera")
Spacer(modifier = Modifier.height(8.dp))
if (permissionState.shouldShowRationale) {
Text("Please allow the permissions.")
} else {
OutlinedButton(onClick = { permissionState.launchMultiplePermissionRequest() }) {
Text("Allow")
}
}
}
}
}
}
}
}
}
@Composable
fun CameraPreview(cameraViewModel: CameraViewModel) {
val context = LocalContext.current
val isRecording = cameraViewModel.isRecording.collectAsState()
Column(modifier = Modifier.fillMaxSize()) {
Box(modifier = Modifier
.weight(1f)
.fillMaxSize()) {
AndroidView(
factory = { ctx ->
val previewView = PreviewView(ctx)
cameraViewModel.startCamera(ctx, previewView)
previewView
},
modifier = Modifier.fillMaxSize()
)
}
Row(modifier = Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.Center) {
Button(onClick = { /* Trigger cameraViewModel logic here */ },
modifier = Modifier.padding(16.dp)) {
Text("Start Recording")
}
Button(onClick = { /* Trigger cameraViewModel logic here */ },
modifier = Modifier.padding(16.dp)) {
Text("Stop Recording")
}
}
}
}
实现FTP上传功能
创建FTPUpload.kt以实现FTP上传功能：
import org.apache.commons.net.ftp.FTP
import org.apache.commons.net.ftp.FTPClient
import java.io.File
import java.io.FileInputStream
import java.io.IOException
object FTPUpload {
fun uploadFile(filePath: String, server: String, port: Int, user: String, pass: String) {
val ftpClient = FTPClient()
try {
ftpClient.connect(server, port)
ftpClient.login(user, pass)
ftpClient.enterLocalPassiveMode()
ftpClient.setFileType(FTP.BINARY_FILE_TYPE)
val dateFolder = SimpleDateFormat("yyyyMMdd", Locale.US).format(System.currentTimeMillis())
ftpClient.makeDirectory(dateFolder)
ftpClient.changeWorkingDirectory(dateFolder)
val firstRemoteFile = File(filePath).name
val inputStream = FileInputStream(filePath)
println("Start uploading first file")
val done = ftpClient.storeFile(firstRemoteFile, inputStream)
inputStream.close()
if (done) {
println("File is uploaded successfully.")
}
} catch (ex: IOException) {
ex.printStackTrace()
} finally {
try {
if (ftpClient.isConnected) {
ftpClient.logout()
ftpClient.disconnect()
}
} catch (ex: IOException) {
ex.printStackTrace()
}
}
}
}
通过这些代码片段，可以使用Jetpack Compose开发一个能够通过手机后置主摄像头录制视频、检测画面差异、实时预览并将视频上传至FTP服务器的Android应用。
个人博客：visen123.github.io
