Android写一个拍照并且显示在屏幕上面的程序

以下是一个Android拍照并显示在屏幕上的示例代码：

XML布局文件：

<FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<Button
    android:id="@+id/button_capture"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Capture"
    android:layout_gravity="center_horizontal|bottom" />

MainActivity.java文件：

public class MainActivity extends AppCompatActivity {
    private Camera mCamera;
    private CameraPreview mPreview;
    private Button mCaptureButton;

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

        // 创建一个Camera实例
        mCamera = getCameraInstance();

        // 创建一个预览视图并将其设置为FrameLayout中的子视图
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);

        // 设置拍照按钮的点击监听器
        mCaptureButton = (Button) findViewById(R.id.button_capture);
        mCaptureButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 拍照
                mCamera.takePicture(null, null, mPicture);
            }
        });
    }

    /** 获取Camera实例 */
    private Camera getCameraInstance() {
        Camera c = null;
        try {
            c = Camera.open();
        } catch (Exception e) {
            // 打开相机失败
        }
        return c;
    }

    /** 在屏幕上显示拍摄的照片 */
    private void displayCapturedPhoto(byte[] data) {
        // 将数据转换为位图
        Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);

        // 创建一个ImageView并将位图设置为其图像
        ImageView imageView = new ImageView(this);
        imageView.setImageBitmap(bitmap);

        // 创建一个AlertDialog并将ImageView设置为其视图
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setView(imageView)
                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // 关闭对话框
                        dialog.dismiss();
                    }
                });
        AlertDialog dialog = builder.create();
        dialog.show();
    }

    /** 拍照后保存照片数据的回调函数 */
    private Camera.PictureCallback mPicture = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            // 显示拍摄的照片
            displayCapturedPhoto(data);

            // 重新启动预览
            camera.startPreview();
        }
    };

    @Override
    protected void onPause() {
        super.onPause();
        // 释放相机资源
        releaseCamera();
    }

    /** 释放相机资源 */
    private void releaseCamera() {
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }
}

CameraPreview.java文件：

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // 获取SurfaceHolder并设置其回调
        mHolder = getHolder();
        mHolder.addCallback(this);

        // 预览视图为透明
        mHolder.setFormat(PixelFormat.TRANSPARENT);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // 将预览视图与相机关联起来
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            // 开始相机预览失败
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // 如果预览视图发生变化，先停止预览
        if (mHolder.getSurface() == null) {
            return;
        }
        try {
            mCamera.stopPreview();
        } catch (Exception e) {
            // 无法停止相机预览
        }

        // 启动相机预览
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();
        } catch (Exception e) {
            // 开始相机预览失败
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // 释放相机资源
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }
}