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android摄像头调用

上传者： u011584284 | 上传时间： 2025-06-10 08:55:43 | 文件大小： 942KB | 文件类型： ZIP
在Android平台上，调用摄像头是开发移动应用时常见的功能，主要涉及到系统提供的Camera API或CameraX库。本文将深入探讨如何在Android应用中实现摄像头调用，并将拍照结果保存到SD卡的根目录。 我们需要了解Android的相机权限。在AndroidManifest.xml文件中，必须声明``来获取访问相机的权限，如： ```xml ``` 同时，如果要将图片保存到外部存储（如SD卡），还需声明`WRITE_EXTERNAL_STORAGE`权限，对于Android 6.0及以上版本，还需要在运行时动态请求权限。 接下来，我们讨论如何使用Camera API。Android SDK提供了Camera类，允许开发者直接控制摄像头。以下是一个简单的相机启动示例： ```java // 获取默认的相机ID int cameraId = Camera.getNumberOfCameras() - 1; // 假设最后一个为后置摄像头 Camera.open(cameraId); // 打开指定的相机 // 设置预览显示视图 CameraPreview preview = (CameraPreview) findViewById(R.id.camera_preview); Camera.setPreviewDisplay(preview.getHolder()); // 开始预览 Camera.startPreview(); ``` `CameraPreview`是一个自定义的SurfaceView，用于显示摄像头预览画面。当用户点击拍照按钮时，可以调用`takePicture()`方法进行拍照： ```java Camera.PictureCallback pictureCallback = new Camera.PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { // 处理拍照后的图片数据 File pictureFile = createImageFile(); // 创建图片文件 try { FileOutputStream fos = new FileOutputStream(pictureFile); fos.write(data); fos.close(); } catch (IOException e) { e.printStackTrace(); } // 释放相机资源 camera.release(); } }; // 触发拍照 camera.takePicture(null, null, pictureCallback); ``` `createImageFile()`函数用于在SD卡根目录创建一个图片文件： ```java private File getExternalFilesDir(String type) { return Environment.getExternalStoragePublicDirectory(type); } private File createImageFile() throws IOException { String timestamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date()); String imageFileName = "JPEG_" + timestamp + "_"; File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES); File image = File.createTempFile( imageFileName, /* prefix */ ".jpg", /* suffix */ storageDir /* directory */ ); return image; } ``` 然而，Camera API比较复杂且难以使用，Google在Android X库中推出了CameraX，这是一个现代、易于使用的相机框架。使用CameraX，你可以更简洁地实现相同的功能： ```kotlin val cameraProviderFuture = ProcessCameraProvider.getInstance(this) cameraProviderFuture.addListener({ val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get() val preview = Preview.Builder() .build() .also { it.setSurfaceProvider(binding.previewView.surfaceProvider) } val imageCapture = ImageCapture.Builder() .setTargetRotation(windowManager.defaultDisplay.rotation) .build() val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA cameraProvider.bindToLifecycle(this as LifecycleOwner, cameraSelector, preview, imageCapture) val takePictureButton = findViewById

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