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我对Android相当陌生,我想知道是否可以在相机预览屏幕的中心绘制一个对象,例如圆形或矩形。我目前正在使用纹理视图来预览相机。

我已经查看了以下文章,但努力将其实现到我的代码中:

Android SDK - camera2 - 在 TextureView 上绘制矩形

我该怎么办?我可以使用 Paint 模块来绘制必要的几何图形吗?如果是这样,我会从哪里开始?

https://developer.android.com/reference/android/graphics/Paint

下面的代码打开应用程序并预​​览相机。

package com.example.camerapointer;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import android.Manifest;
import android.content.ActivityNotFoundException;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Camera;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.ImageReader;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.provider.MediaStore;
import android.util.Size;
import android.util.SparseIntArray;
import android.view.Surface;
import android.view.SurfaceView;
import android.view.TextureView;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;

import java.io.File;
import java.util.Arrays;

public class MainActivity extends AppCompatActivity {

    private TextureView textureView;
    private Camera camera;
    private Button Capture, Gallery;
    private String cameraID;

    private CameraDevice cameraDevice;
    private CameraCaptureSession cameraCaptureSession;
    private CaptureRequest captureRequest;
    private CaptureRequest.Builder captureRequestBuilder;

    private Size imageDimensions;
    private ImageReader imageReader;
    private File file;
    private Handler mBackgroundHandler;
    private HandlerThread mBackgroundThread;

    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();


    static {
        ORIENTATIONS.append(Surface.ROTATION_0, 90);
        ORIENTATIONS.append(Surface.ROTATION_90, 0);
        ORIENTATIONS.append(Surface.ROTATION_180, 270);
        ORIENTATIONS.append(Surface.ROTATION_270, 180);
    }

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


        textureView = (TextureView) findViewById(R.id.texture);
        Capture = (Button)findViewById(R.id.btnCapture);
        Gallery = (Button)findViewById(R.id.btnGallery);
        textureView.setSurfaceTextureListener(textureListener);


        Capture.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                takeSnap();
            }
        });

        Gallery.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
             //   startActivity(new Intent(MainActivity.this, Intent.CATEGORY_APP_GALLERY));
            }
        });


    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == 101) {
            if (grantResults[0] == PackageManager.PERMISSION_DENIED) {
                Toast.makeText(getApplicationContext(), "Please allow permissions", Toast.LENGTH_SHORT).show();
            }
        } else {

        }
    }

    TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {

        @Override
        public void onSurfaceTextureAvailable(@NonNull SurfaceTexture surface, int width, int height) {
            try {
                openCamera();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onSurfaceTextureSizeChanged(@NonNull SurfaceTexture surface, int width, int height) {

        }

        @Override
        public boolean onSurfaceTextureDestroyed(@NonNull SurfaceTexture surface) {
            return false;
        }

        @Override
        public void onSurfaceTextureUpdated(@NonNull SurfaceTexture surface) {

        }
    };


    private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            cameraDevice = camera;
            try {
                createCameraPreview();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }

        }

        @Override
        public void onDisconnected(CameraDevice camera) {
            cameraDevice.close();

        }

        @Override
        public void onError(CameraDevice camera, int error) {
            cameraDevice.close();
            cameraDevice = null;
        }
    };

    private void createCameraPreview() throws CameraAccessException {

        SurfaceTexture surfaceTexture = textureView.getSurfaceTexture();
        surfaceTexture.setDefaultBufferSize(imageDimensions.getWidth(), imageDimensions.getHeight());
        Surface surface = new Surface(surfaceTexture);

        captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        captureRequestBuilder.addTarget(surface);

        cameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
            @Override
            public void onConfigured(CameraCaptureSession session) {
                    if(cameraDevice ==  null) {
                        return;
                    }
                    cameraCaptureSession = session;
                try {
                    updatePreview();
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onConfigureFailed(CameraCaptureSession session) {

                Toast.makeText(getApplicationContext(), "Config changed", Toast.LENGTH_SHORT).show();

            }
        }, null);


    }

    private void updatePreview() throws CameraAccessException {
        if(cameraDevice ==  null) {
            return;
        }
        captureRequestBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);

        cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, mBackgroundHandler);


    }

    private void openCamera() throws CameraAccessException {

        CameraManager cameraManager = (CameraManager)getSystemService(Context.CAMERA_SERVICE);
        cameraID = cameraManager.getCameraIdList()[0];

        CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraID);
        StreamConfigurationMap streamConfigurationMap = cameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
        imageDimensions = streamConfigurationMap.getOutputSizes(SurfaceTexture.class)[0];

        if(ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED &&
        ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE}, 101);
            return;
        }
        cameraManager.openCamera(cameraID, stateCallback, null);
    }

    private void takeSnap()
    {

    }

    @Override
    protected void onResume() {

        startBackgroundThread();
        super.onResume();

        if(textureView.isAvailable()) {
            try {
                openCamera();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
        else {
        textureView.setSurfaceTextureListener(textureListener);
        }
    }

    private void startBackgroundThread() {
        mBackgroundThread = new HandlerThread("Cam Background");
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());

    }

    @Override
    protected void onPause() {
        try {
            stopBackgroundThread();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        super.onPause();
    }

    private void stopBackgroundThread() throws InterruptedException {
        mBackgroundThread.quitSafely();

        mBackgroundThread.join();
        mBackgroundThread = null;
        mBackgroundHandler = null;
    }
}
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