编写Android 调用摄像头

好的，您可以参考以下步骤：

1. 添加权限

首先，在AndroidManifest.xml中添加以下权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

这将允许您的应用程序访问设备上的摄像头和存储。

2. 创建布局

然后，在您的布局文件中添加一个SurfaceView和一个按钮，以便用户可以启动摄像头。

<SurfaceView
    android:id="@+id/surfaceView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Take Picture" />

3. 实现启动摄像头的方法

在您的活动中，您需要实现启动摄像头并将预览显示在SurfaceView上的方法。您可以使用Camera类来实现这一点。

private Camera camera;
private SurfaceView surfaceView;
private Button button;

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

    surfaceView = findViewById(R.id.surfaceView);
    button = findViewById(R.id.button);

    // Add button click listener
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            // Start the camera
            startCamera();
        }
    });
}

private void startCamera() {
    try {
        // Get the camera object
        camera = Camera.open();

        // Create a new surface holder
        SurfaceHolder holder = surfaceView.getHolder();

        // Set the surface holder callback
        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {
                // Set the camera preview display
                try {
                    camera.setPreviewDisplay(surfaceHolder);
                    camera.startPreview();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
                // Do nothing
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
                // Stop the camera preview
                camera.stopPreview();

                // Release the camera
                camera.release();
            }
        });
    } catch (Exception e) {
        e.printStackTrace();
    }
}

这个方法使用Camera.open()方法来获取摄像头对象。然后，它创建一个SurfaceHolder对象，并将它添加到SurfaceView上。使用SurfaceHolder.Callback，我们在SurfaceHolder创建和销毁时启动和停止摄像头预览。

4. 实现拍照的方法

最后，您需要实现一个方法，以便用户可以拍照并将图像保存到设备存储中。您可以使用Camera.takePicture()方法来实现这一点。

private void takePicture() {
    // Create a new picture callback
    Camera.PictureCallback pictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] bytes, Camera camera) {
            // Save the image to external storage
            File file = new File(Environment.getExternalStorageDirectory(), "picture.jpg");
            try {
                FileOutputStream fos = new FileOutputStream(file);
                fos.write(bytes);
                fos.close();
            } catch (Exception e) {
                e.printStackTrace();
            }

            // Restart the camera preview
            camera.startPreview();
        }
    };

    // Take the picture
    camera.takePicture(null, null, pictureCallback);
}

这个方法将创建一个Camera.PictureCallback对象，并将其传递给Camera.takePicture()方法。在PictureCallback的回调方法中，我们将保存图像到设备存储，并通过camera.startPreview()方法重新启动摄像头预览。

5. 完成

现在，您的Android应用程序可以使用摄像头拍照了。您可以使用以下代码将它们组合在一起。

private Camera camera;
private SurfaceView surfaceView;
private Button button;

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

    surfaceView = findViewById(R.id.surfaceView);
    button = findViewById(R.id.button);

    // Add button click listener
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            // Take the picture
            takePicture();
        }
    });

    // Start the camera
    startCamera();
}

private void startCamera() {
    try {
        // Get the camera object
        camera = Camera.open();

        // Create a new surface holder
        SurfaceHolder holder = surfaceView.getHolder();

        // Set the surface holder callback
        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {
                // Set the camera preview display
                try {
                    camera.setPreviewDisplay(surfaceHolder);
                    camera.startPreview();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
                // Do nothing
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
                // Stop the camera preview
                camera.stopPreview();

                // Release the camera
                camera.release();
            }
        });
    } catch (Exception e) {
        e.printStackTrace();
    }
}

private void takePicture() {
    // Create a new picture callback
    Camera.PictureCallback pictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] bytes, Camera camera) {
            // Save the image to external storage
            File file = new File(Environment.getExternalStorageDirectory(), "picture.jpg");
            try {
                FileOutputStream fos = new FileOutputStream(file);
                fos.write(bytes);
                fos.close();
            } catch (Exception e) {
                e.printStackTrace();
            }

            // Restart the camera preview
            camera.startPreview();
        }
    };

    // Take the picture
    camera.takePicture(null, null, pictureCallback);
}

希望对您有所帮助！