Android开发：调用camera API 创建MediaRecorder

1. add below three permission into AndroidManifest.xml file

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

2. get a camera instance

/** 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
}

3. implement a preview for the user to preview the live image for the camera

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

String TAG="CAMERAAPI";

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());
}
}
}

4.initialize MediaRecorder for video recording

private boolean prepareVideoRecorder(){

mCamera = getCameraInstance();
mMediaRecorder = new MediaRecorder();

// Step 1: Unlock and set camera to MediaRecorder
mCamera.unlock();
mMediaRecorder.setCamera(mCamera );

// Step 2: Set sources
mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);

// Step 3: Set a CamcorderProfile (requires API Level 8 or higher)
mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile. QUALITY_HIGH));

// Step 4: Set output file
mMediaRecorder.setOutputFile(getOutputMediaFile( MEDIA_TYPE_VIDEO).toString());

// Step 5: Set the preview output
mMediaRecorder.setPreviewDisplay(mPreview .getHolder().getSurface());

// Step 6: Prepare configured MediaRecorder
try {
mMediaRecorder.prepare();
} catch (IllegalStateException e) {
Log. d(TAG, "IllegalStateException preparing MediaRecorder: " + e.getMessage());
releaseMediaRecorder();
return false ;
} catch (IOException e) {
Log. d(TAG, "IOException preparing MediaRecorder: " + e.getMessage());
releaseMediaRecorder();
return false ;
}
return true ;
}

5.listen for the user operation to start or stop recording, the complete code for MediaRecorder is as below,remember to release the camera and MediaRecord when finished using it.

public class MediaRecorderActivity extends Activity {

public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;

private Camera mCamera;
private CameraPreview mPreview;
private MediaRecorder mMediaRecorder;
String TAG="CAMERAAPI";
boolean isRecording=false ;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout. main);

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);

Button captureButton = (Button) findViewById(id. button_capture);
captureButton.setOnClickListener( new CaptureButtonOnClickListener());
}

public class CaptureButtonOnClickListener implements View.OnClickListener{

public void onClick(View v) {

Button captureButton = (Button)v;

if (isRecording ) {
// stop recording and release camera
mMediaRecorder.stop();  // stop the recording
releaseMediaRecorder(); // release the MediaRecorder object
mCamera.lock();         // take camera access back from MediaRecorder

// inform the user that recording has stopped
captureButton.setText( "Capture");

isRecording = false ;
} else {

try{
// initialize video camera
if (prepareVideoRecorder()) {
// Camera is available and unlocked, MediaRecorder is prepared,
// now you can start recording
mMediaRecorder.start();

// inform the user that recording has started
captureButton.setText( "Stop");
isRecording = true ;
} else {
// prepare didn't work, release the camera
releaseMediaRecorder();
// inform user
}

} catch(Exception ex){

System. out.println(ex.toString());
ex.printStackTrace();
}
}
}
}
/** 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
}

/** Create a File for saving an image or video */
private static File getOutputMediaFile(int type){
// To be safe, you should check that the SDCard is mounted
// using Environment.getExternalStorageState() before doing this.

File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
Environment. DIRECTORY_PICTURES), "MyCameraApp" );
// This location works best if you want the created images to be shared
// between applications and persist after your app has been uninstalled.

// Create the storage directory if it does not exist
if (! mediaStorageDir.exists()){
if (! mediaStorageDir.mkdirs()){
Log. d("MyCameraApp", "failed to create directory");
return null ;
}
}

// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss" ).format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE){
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"IMG_"+ timeStamp + ".jpg" );
} else if (type == MEDIA_TYPE_VIDEO) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"VID_"+ timeStamp + ".mp4" );
} else {
return null ;
}

return mediaFile;
}

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

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
}
}
}

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