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;
}
}