使用CameraX在PreviewView中拍照时相机冻结重启异常排查

• 开发环境：Android 12（API level 31），基于CameraX API开发
• 异常现象：PreviewView可正常显示相机实时画面，但点击拍照按钮后，相机画面出现冻结并重启
• 错误日志：

/ImageCapture: Send image capture request [current, pending] = [0, 1]
D/ImageCapture: issueTakePicture
D/Camera2CameraImpl: {Camera@bcf4c18[id=0]} Issue capture request
D/CaptureSession: Issuing capture request.
D/EGL_emulation: app_time_stats: avg=20.36ms min=1.77ms max=477.02ms count=39
E/CameraCaptureSession: Session 0: Exception while stopping repeating: 
    android.hardware.camera2.CameraAccessException: CAMERA_ERROR (3): cancelRequest:507: Camera 0: Error clearing streaming request: Function not implemented (-38)
        at android.hardware.camera2.CameraManager.throwAsPublicException(CameraManager.java:1179)
...

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.ImageCapture;
import androidx.camera.core.ImageCaptureException;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.view.PreviewView;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import com.google.common.util.concurrent.ListenableFuture;

import java.io.File;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;

public class MainActivity extends AppCompatActivity {

    private PreviewView viewFinder;
    private ProcessCameraProvider cameraProvider;
    private Camera camera;

    private ImageCapture imageCapture;

    private static final int  CAMERA_PERMISSION_CODE = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewFinder = findViewById(R.id.viewFinder);
        startCamera();

        Button takePictureButton = findViewById(R.id.takePictureButton);
        takePictureButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                takePicture();
            }
        });

    }

    private void startCamera() {

        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
            // 权限已授予，打开相机
        } else {
            // 请求权限
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, CAMERA_PERMISSION_CODE);
        }

        ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);
        cameraProviderFuture.addListener(() -> {
            try {
                // 获取可用的相机提供者
                cameraProvider = cameraProviderFuture.get();
                // 配置并启动相机预览
                bindPreview();
            } catch (ExecutionException | InterruptedException e) {
                // 处理错误
            }
        }, ContextCompat.getMainExecutor(this));
    }

    private void bindPreview() {
        imageCapture =
                new ImageCapture.Builder()
                        .setTargetRotation(viewFinder.getDisplay().getRotation())

                        .build();
        Preview preview = new Preview.Builder().build();
        preview.setSurfaceProvider(viewFinder.getSurfaceProvider());
        // 选择后置摄像头
        CameraSelector cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA;
        // 绑定生命周期
        camera = cameraProvider.bindToLifecycle(this, cameraSelector, preview, imageCapture);
    }

    private void takePicture() {
        Executor cameraExecutor = ContextCompat.getMainExecutor(this);
        ImageCapture.OutputFileOptions outputFileOptions =
                new ImageCapture.OutputFileOptions.Builder(new File(getExternalMediaDirs()[0], "photo.jpg")).build();
        imageCapture.takePicture(outputFileOptions, cameraExecutor,
                new ImageCapture.OnImageSavedCallback() {
                    @Override
                    public void onImageSaved(ImageCapture.OutputFileResults outputFileResults) {
                        System.out.println("保存成功");
                        Toast.makeText(MainActivity.this, "照片已保存", Toast.LENGTH_SHORT).show();
                    }
                    @Override
                    public void onError(ImageCaptureException error) {
                        System.out.println("保存失败");
                        Toast.makeText(MainActivity.this, "保存照片出错", Toast.LENGTH_SHORT).show();
                        System.out.println(error);
                    }
                }
        );

    }

}

问题根源分析 #

错误日志中的CAMERA_ERROR (3)和Function not implemented (-38)，结合代码细节，核心问题包括：

1. 权限处理不完整：相机权限申请通过后，未重新触发相机初始化流程
2. 主线程处理拍照操作：主线程执行IO或相机捕获逻辑，易阻塞相机会话导致异常终止
3. ImageCapture配置缺失：未设置适配的捕获模式，与预览会话存在兼容性冲突
4. 文件路径未做空安全校验：getExternalMediaDirs()[0]可能为空，引发潜在异常

修复步骤 #

1. 完善权限回调逻辑
   重写onRequestPermissionsResult方法，在权限授予后重新初始化相机：

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == CAMERA_PERMISSION_CODE) {
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            startCamera();
        } else {
            Toast.makeText(this, "相机权限未授予，无法使用拍照功能", Toast.LENGTH_SHORT).show();
        }
    }
}

2. 使用独立线程Executor处理拍照
   避免主线程阻塞，创建单线程Executor：

private Executor cameraExecutor = Executors.newSingleThreadExecutor();

替换takePicture()中的ContextCompat.getMainExecutor(this)为该Executor

3. 优化ImageCapture配置
   添加捕获模式设置，提升兼容性并降低延迟：

imageCapture = new ImageCapture.Builder()
        .setTargetRotation(viewFinder.getDisplay().getRotation())
        .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
        .build();

4. 文件路径空安全处理
   创建文件前校验存储目录可用性：

private void takePicture() {
    File mediaDir = getExternalMediaDirs()[0];
    if (mediaDir == null || !mediaDir.exists()) {
        Toast.makeText(this, "存储目录不可用", Toast.LENGTH_SHORT).show();
        return;
    }
    File photoFile = new File(mediaDir, "photo.jpg");
    ImageCapture.OutputFileOptions outputFileOptions =
            new ImageCapture.OutputFileOptions.Builder(photoFile).build();
    // 后续拍照逻辑不变
}

5. 升级CameraX依赖版本
   确保使用适配Android 12的稳定版CameraX，在build.gradle中配置：

dependencies {
    def camerax_version = "1.2.3"
    implementation "androidx.camera:camera-core:$camerax_version"
    implementation "androidx.camera:camera-camera2:$camerax_version"
    implementation "androidx.camera:camera-lifecycle:$camerax_version"
    implementation "androidx.camera:camera-view:$camerax_version"
}

内容的提问来源于stack exchange，提问作者Daniel