camerax——uesecase之preview

Posted 2021-06-06 灵剑山真人

1. 添加依赖

   def camerax_version = "1.0.0"
   // CameraX core library using camera2 implementation
   implementation "androidx.camera:camera-camera2:$camerax_version"
   // CameraX Lifecycle Library
   implementation "androidx.camera:camera-lifecycle:$camerax_version"
   // CameraX View class
   implementation "androidx.camera:camera-view:1.0.0-alpha24"

    

2. 创建预览previewView布局

   <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="match_parent">
   
       <androidx.camera.view.PreviewView
           android:id="@+id/viewFinder"
           android:layout_width="match_parent"
           android:layout_height="match_parent" />
       
   </FrameLayout>

    

3. 申请相机权限：

   manifest中添加：
   <uses-feature android:name="android.hardware.camera.any" />
       <uses-permission android:name="android.permission.CAMERA" />
   
   
   fragment或activity中使用registerforactivityresult

    

4. 请求cameraProvider:

   import androidx.camera.lifecycle.ProcessCameraProvider
   import com.google.common.util.concurrent.ListenableFuture
   
   class MainActivity : AppCompatActivity() {
       private lateinit var cameraProviderFuture : ListenableFuture<ProcessCameraProvider>//定义一个字段
       override fun onCreate(savedInstanceState: Bundle?) {
        startCamera()
       }
   
   　　private fun startCamera(){
      cameraProviderFuture = ProcessCameraProvider.getInstance(this)
   }
   }

    

5. 剩余的配置

    private fun startCamera() {
          cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())//创建 ProcessCameraProvider 的实例。这用于将相机的生命周期绑定到生命周期所有者。这消除了打开和关闭相机的任务，因为 CameraX 具有生命周期感知能力。
   
           cameraProviderFuture.addListener(Runnable {//----------1
               val cameraProvider = cameraProviderFuture.get()//用来把相机的生命周期绑定到fragment
               bindPreview(cameraProvider)
           }, ContextCompat.getMainExecutor(requireContext()))
       }
   
       private fun bindPreview(cameraProvider : ProcessCameraProvider) {
           val preview : Preview = Preview.Builder()//构建preview-----------------2
               .build().also {
                   it.setSurfaceProvider(previewView.surfaceProvider)//和androidx.camera.view.PreviewView控件绑定
               }
   
           val cameraSelector : CameraSelector = CameraSelector.Builder()//选择前后相机----------------3
               .requireLensFacing(CameraSelector.LENS_FACING_BACK)//可选择前相机或后相机
               .build()
   
   
           var camera = cameraProvider.bindToLifecycle(this as LifecycleOwner, cameraSelector, preview)//把相机的生命周期绑定到fragment---------4
                                                                                                       //目前只有preview这一个usecase
       }