8.Media and Camera/Media Camera

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

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context="mirror.android.cameratest.CameraTest" >

    <!-- 4.Palcing preview in a layout -->
    <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:gravity="center"/>

</LinearLayout>

package mirror.android.cameratest;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.CameraInfo;
import android.hardware.Camera.Parameters;
import android.hardware.Camera.PictureCallback;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.FrameLayout;

public class CameraTest extends Activity {

    private Camera camera;
    private CameraPreview mPreview;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera_test);
        
        if(checkCameraHardware(getApplication())){
            camera = getCameraInstance();
            Parameters p = camera.getParameters();
            //Log.d("Camera--->getParameters",p.toString());//--->android.hardware.Camera$Parameters@41757e0
            
            // get camera information of the device
            int cameraCount = Camera.getNumberOfCameras();
            CameraInfo cameraInfo = new CameraInfo();
            for(int i = 0; i < cameraCount ; i++){
                Camera.getCameraInfo(i, cameraInfo);
                //get information from cameraInfo object
                //such as cameraInfo.orientation
            }
            
            //Create our Preview view and set it as the content of our activity.
            mPreview = new CameraPreview(getApplication(), camera);
            FrameLayout preview = (FrameLayout)findViewById(R.id.camera_preview);
            preview.addView(mPreview);
        }
        
        Button captureButton = (Button)findViewById(R.id.button_capture);
        captureButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                camera.takePicture(null, null, mPicture);
            }
        });
    }
    
    
    //1.check if the 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;
    }
    
    //2.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)
            e.printStackTrace();
        }
        return c; // returns null if camera is unavailable
    }
    
    //5. implements a PictureCallback to save image
    private PictureCallback mPicture = new PictureCallback() {
        @Override
        public void onPictureTaken(final byte[] data, Camera camera) {
            
            camera.stopPreview();
            new Thread(
                new Runnable(){
                    @Override
                    public void run() {
                        File pictureFile = new File(Environment.getExternalStorageDirectory(), System.currentTimeMillis() + ".jpg");
                        try{
                            FileOutputStream fos = new FileOutputStream(pictureFile);
                            fos.write(data);
                            fos.close();
                        }catch (FileNotFoundException e) {
                            Log.d("Camera Error","File not found: " + e.getMessage());
                        }catch (IOException e) {
                            Log.d("Camera Error","Error accessing file: " + e.getMessage());
                        }
                    }
                }
            ).start();
            camera.startPreview();
        }
    };

    //6. realese the camera obkect
    @Override
    protected void onDestroy() {
        if(camera != null){
            camera.stopPreview();
            camera.release();
            camera = null;
        }
        super.onDestroy();
    }
}

package mirror.android.cameratest;

import java.io.IOException;

import android.content.Context;
import android.hardware.Camera;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

//3. Creating a 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;
        mHolder = getHolder();
        
        //Install a SurfaceHolder.Callback so we get notified when the underlying surface is created and destroyed.
        mHolder.addCallback(this);
    }

    @Override
    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("Camera Error", "Error setting camera preview: " + e.getMessage());
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        // 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
        mCamera.stopPreview();
        
        // set preview size and make any resize, rotate or
        // reformatting changes here
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d("Camera Error", "Error setting camera preview: " + e.getMessage());
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }
}

1. Manifest Declarations

　　<uses-permission android:name="android.permission.CAMERA" />      permission to use a device camera

　　<uses-feature android:name="android.hardware.camera" />　　　　　 declare use of camera features

　　<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />　　saves images to the external storage (SD Card),

　　<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />　　      tags images with GPS location information

2. Detecting camera hardware

　　Check for the existence of cameras and request access.

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;
    }
}

　　get an instance of Camera by open() method

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
}

　

3. Checking camera features

　　get further information about its capabilities using the getParameters() method and checking the returned Parameters object for supported

　　　　capabilities.

　　use getcameraInfo() to determine if a camera is on the front or back of the device, and the orientation of the image.

4. Creating a preview class

　　A camera preview class is a SurfaceView that can display the live image data coming from a camera

　　implements SurfaceHolder.Calback to captrue the callback events for creating and destroying the view

/** 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);

    }

    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());
        }
    }
}

5. Placing preview in a layput

<?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>

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>

6. Capturing pictures

　　In order to retrieve a picture, use the takePicture() method.

　　This method takes three parameters which receive data from the camera.

　　　　<1>

　　　　<2>

　　　　<3>

　　In order to receive data in a JPEG format, you must implement an PictureCallback interface to receive the image data and write it to a file.

// 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);
        }
    }
);

private PictureCallback mPicture = new PictureCallback() {

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE); //参照上面的总例程修改
        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());
        }
    }
};

7. Releasing the camera

　　release the camera object when your application stops using it, and as soon as your application is paused

protected void onPause() {
    super.onPause();
    if (mCamera != null){
        mCamera.release();  // release the camera for other applications
        mCamera = null;
    }
}

8. Saving Media Files

　　pictures and videos should be saved to a device's external storage directory (SD Card) to conserve system space and to allow users

　　　　to access these files without their device

　　<1>Enviroment.getExternalStoragePublicDirectory(Evironment.DIRECTORY_PICTURE)

　　　　 This method returns the standard, shared and recommended location for saving pictures and videos.

　　　　 This directory is shared (public), so other applications can easily discover, read, change and delete files saved in this location.

　　　　 If your application is uninstalled by the user, media files saved to this location will not be removed.

　　<2>Context.getExternalFileDir(Environment.DIRECTORY_PICTURE)

　　　　 standard location for saving pictures and videos which are associated with your application

　　　　 If your application is uninstalled, any files saved in this location are removed.

9. Camera Features

　　9.1 Checking feature availabity

　　　　Check the availabilty of camera features by getting an instance of a camera’s parameters object, and checking the relevant methods.　

// get Camera parameters
Camera.Parameters params = mCamera.getParameters();

List<String> focusModes = params.getSupportedFocusModes();
if (focusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)) {
  // Autofocus mode is supported
}

　　9.2 Using camera features

// get Camera parameters
Camera.Parameters params = mCamera.getParameters();
// set the focus mode
params.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
// set Camera parameters
mCamera.setParameters(params);

　　　　9.2.1 Metering and focus areas

http://my.oschina.net/madmatrix/blog/204333