Android Camera

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文档 %ANDROID_SDK%/docs/guide/topics/media/camera.html

Considerations

• 硬件是否支持摄像头 有2种方式检查: mainfest中

  <uses-feature android:name="android.hardware.camera" />

  或者 

  context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)

   

• 使用手机自带Camera App还是定制App
• Storage App存储的图片或者视频是否只有本App可以看

Manifest

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />

定义了uses-feature之后，不支持Camera的设备(不一定是手机)，Google Play会阻止该程序安装。如果Camera是可选的，在后面加上 android:required="false"即可。

<uses-feature android:name="android.hardware.camera" android:required="false" />

如果需要存储图片、视频或者地理位置信息，则需要加上

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

使用自带Camera App

1. 使用Intent 
2. startActivityForResult()
3. onActivityResult()

例子

Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE); // create a file to save the image
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri); // set the image file name

// start the image capture Intent
startActivityForResult(intent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);

详见文档

定制App

• Detect and Access Camera - Create code to check for the existence of cameras and request access.
• Create a Preview Class - Create a camera preview class that extends SurfaceView and implements theSurfaceHolder interface. This class previews the live images from the camera.
• Build a Preview Layout - Once you have the camera preview class, create a view layout that incorporates the preview and the user interface controls you want.
• Setup Listeners for Capture - Connect listeners for your interface controls to start image or video capture in response to user actions, such as pressing a button.
• Capture and Save Files - Setup the code for capturing pictures or videos and saving the output.
• Release the Camera - After using the camera, your application must properly release it for use by other applications.

 mainfest上面已经讲过了，不再赘述

Detect and Access Camera

如果mainfest里没有检查设备是否支持Camera，在运行期间应该检查:

/** 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;
    }
}

 Android 2.3 (API Level 9) 之后，可以通过Camera.getNumberOfCameras()获取Camera个数。

Accessing cameras

/** 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
}

Android 2.3 (API Level 9)之后，可以使用Camera.open(int)打开指定的Camera

Android 5.0(API Level 21)之后， android.hardware.camera is deprecated，需要使用 android.hardware.camera2

if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
     // your code using Camera API here - is between 1-20
} else if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
     // your code using Camera2 API here - is api 21 or higher
}

Checking camera features

继上一步(Camera.open)之后，可以使用Camera.getParameters()获取Camera的相关信息。Android 2.3 (API Level 9)之后，还可以使用Camera.getCameraInfo()来判断是前置还是后置Camera以及获取Image的方向。

Creating a preview class

例子:

/** 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());
        }
    }
}

可以在surfaceChanged()方法中设置Camera支持的size——getSupportedPreviewSizes()，找到上面代码中//set preview size

mCamera.getParameters().setPreviewSize

layout

例子:

<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>

Activity

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);
    }
}

其中getCameraInstance在上文有提到。

释放

释放例子:

public class CameraActivity extends Activity {
    private Camera mCamera;
    private SurfaceView mPreview;
    private MediaRecorder mMediaRecorder;

    ...

    @Override
    protected void onPause() {
        super.onPause();
        releaseMediaRecorder();       // if you are using MediaRecorder, release it first
        releaseCamera();              // release the camera immediately on pause event
    }

    private void releaseMediaRecorder(){
        if (mMediaRecorder != null) {
            mMediaRecorder.reset();   // clear recorder configuration
            mMediaRecorder.release(); // release the recorder object
            mMediaRecorder = null;
            mCamera.lock();           // lock camera for later use
        }
    }

    private void releaseCamera(){
        if (mCamera != null){
            mCamera.release();        // release the camera for other applications
            mCamera = null;
        }
    }
}

 

转载于:https://my.oschina.net/shanlilaideyu/blog/704609