Android实现极简打开摄像头

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <SurfaceView
        android:id="@+id/surfaceView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback{

    private SurfaceHolder holder;
    private Camera camera;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_main);
        SurfaceView surfaceView = findViewById(R.id.surfaceView);
        holder = surfaceView.getHolder();
        holder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        if(camera == null){
            try {
                camera = Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK);
                camera.setPreviewDisplay(holder);
                camera.startPreview();
                Camera.Parameters parameters = camera.getParameters();
                parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
                parameters.setFlashMode(Camera.Parameters.FLASH_MODE_AUTO);
                camera.setParameters(parameters);
                camera.setDisplayOrientation(90);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextureView
        android:id="@+id/surfaceView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

public class MainActivity extends AppCompatActivity implements TextureView.SurfaceTextureListener {

    private TextureView textureView;

    private CaptureRequest.Builder builder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textureView = findViewById(R.id.surfaceView);
        textureView.setSurfaceTextureListener(this);
    }

    @Override
    public void onSurfaceTextureAvailable(final SurfaceTexture surface, int width, int height) {
        CameraManager manager = (CameraManager) getSystemService(CAMERA_SERVICE);
        if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA)
                != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        try {
            manager.openCamera("0", new CameraDevice.StateCallback() {
                @Override
                public void onOpened(@NonNull CameraDevice camera) {
                    try {
                    SurfaceTexture surfaceTexture = textureView.getSurfaceTexture();
                    surfaceTexture.setDefaultBufferSize(1440,1080);
                    Surface surface = new Surface(surfaceTexture);
                    builder = camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
                    builder.addTarget(surface);

                    camera.createCaptureSession(Arrays.asList(surface),
                            new CameraCaptureSession.StateCallback() {
                        @Override
                        public void onConfigured(@NonNull CameraCaptureSession session) {
                            try {
                                session.setRepeatingRequest(builder.build(), null, null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onConfigureFailed(@NonNull CameraCaptureSession session) {

                        }
                    }, null);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

                @Override
                public void onDisconnected(@NonNull CameraDevice camera) {

                }

                @Override
                public void onError(@NonNull CameraDevice camera, int error) {

                }
            }, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }
}