本文主要參考的是Android文檔裏的Camera講解。
如果想建立一個簡單的Camera應用程序應該遵循以下的步驟：
檢查和訪問Camera - 檢查是否存在支持的硬件和請求訪問相機。
建立一個預覽的類Class - 建立一個預覽的類，該類是繼承與SurfaceView，並且實現SurfaceHolder的接口。這個類主要是用來實時預覽Camera的圖像。
創建一個預覽佈局 - 預覽類創建好後，需要再創建一個視圖佈局(view layout)。
設置監聽和捕獲圖片 - 監聽用戶拍照或者攝像。
拍照和保存圖片 - 編碼實現拍照並保存所拍的圖片。
釋放相機 - 使用完相機後，你的應用程序一定要釋放Camera。
一 檢測Camera的硬件支持
檢測硬件是否支持Camera，代碼如下：
/** Check if this device has a camera */ private boolean checkCameraHardware(Context context) { if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){ // this device has a camera return true; } else { // no camera on this device return false; } }
二 訪問Camera
使用Camera.open()方法來訪問主Camera，使用該方法也要捕獲異常，代碼如下：
/** A safe way to get an instance of the Camera object. */ public static Camera getCameraInstance(){ Camera c = null; try { c = Camera.open(); // attempt to get a Camera instance } catch (Exception e){ // Camera is not available (in use or does not exist) } return c; // returns null if camera is unavailable }
三 獲取相機有哪些特性
當訪問相機成功時，可以使用函數Camera.getParameters()方法來獲取該相機的詳細特性，該方法返回值是Camera.Parameters
。
四 建立一個預覽類
下面的代碼是如何創建一個基本的相機預覽類。該類要實現SurfaceHolder.Callback。
/** A basic Camera preview class */ public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback { private SurfaceHolder mHolder; private Camera mCamera; public CameraPreview(Context context, Camera camera) { super(context); mCamera = camera; // Install a SurfaceHolder.Callback so we get notified when the // underlying surface is created and destroyed. mHolder = getHolder(); mHolder.addCallback(this); // deprecated setting, but required on Android versions prior to 3.0 mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); } public void surfaceCreated(SurfaceHolder holder) { // The Surface has been created, now tell the camera where to draw the preview. try { mCamera.setPreviewDisplay(holder); mCamera.startPreview(); } catch (IOException e) { Log.d(TAG, "Error setting camera preview: " + e.getMessage()); } } public void surfaceDestroyed(SurfaceHolder holder) { // empty. Take care of releasing the Camera preview in your activity. } public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { // If your preview can change or rotate, take care of those events here. // Make sure to stop the preview before resizing or reformatting it. if (mHolder.getSurface() == null){ // preview surface does not exist return; } // stop preview before making changes try { mCamera.stopPreview(); } catch (Exception e){ // ignore: tried to stop a non-existent preview } // set preview size and make any resize, rotate or // reformatting changes here // start preview with new settings try { mCamera.setPreviewDisplay(mHolder); mCamera.startPreview(); } catch (Exception e){ Log.d(TAG, "Error starting camera preview: " + e.getMessage()); } } }
五 建立一個預覽佈局
預覽的佈局代碼如下：
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="fill_parent" > <FrameLayout android:id="@+id/camera_preview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1" /> <Button android:id="@+id/button_capture" android:text="Capture" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" /> </LinearLayout>
大多數的設備默認的水平方向都是豎屏的，在manifest下修改代碼如下：
<activity android:name=".CameraActivity" android:label="@string/app_name" android:screenOrientation="landscape"> <!-- configure this activity to use landscape orientation --> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>
在應用的相機視圖裏，用元素FrameLayout來使用預覽類。當應用暫停或者關閉後一定要釋放camera。下面的例子就是顯示如何創建一個預覽類。
public class CameraActivity extends Activity { private Camera mCamera; private CameraPreview mPreview; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // Create an instance of Camera mCamera = getCameraInstance(); // Create our Preview view and set it as the content of our activity. mPreview = new CameraPreview(this, mCamera); FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview); preview.addView(mPreview); } }
六 拍照 (Capturing pictures)
使用函數Camera.takePicture()來捕獲圖片。爲了能得到JPEG格式的數據，要實現Camera.PictureCallback接口來保存圖片文件。保存圖片的文件代碼如下：
private PictureCallback mPicture = new PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE); if (pictureFile == null){ Log.d(TAG, "Error creating media file, check storage permissions: " + e.getMessage()); return; } try { FileOutputStream fos = new FileOutputStream(pictureFile); fos.write(data); fos.close(); } catch (FileNotFoundException e) { Log.d(TAG, "File not found: " + e.getMessage()); } catch (IOException e) { Log.d(TAG, "Error accessing file: " + e.getMessage()); } } };
通過調用Camera.takePicture()方法來捕獲圖片。下面的示例代碼顯示的是如何按鈕View.OnClickListener來調用該方法：
// Add a listener to the Capture button Button captureButton = (Button) findViewById(id.button_capture); captureButton.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { // get an image from the camera mCamera.takePicture(null, null, mPicture); } } );
代碼：http://download.csdn.net/detail/yegucheng2618/7631737