我正在制作一个自定义相机，只需拍照并预览图像。我无法预览图像。即使我在拍照后调用了stopPreview方法，也会显示图片，但是当我按下主页并再次恢复应用程序时相机会重置。
public class CameraActivity extends ActionBarActivity {
Camera camera;
private static final String TAG = CameraActivity.class.getName();
private Button captureImageButton;
private Button retakeImageButton;
private Button nextImageButton;
private Button doneButton;
static final String IS_NEW_IMAGE = "isNewImage";
private CameraSurfaceView cameraPreview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera);
captureImageButton = (Button) findViewById(R.id.button_capture);
retakeImageButton = (Button) findViewById(R.id.retakeImage);
nextImageButton = (Button) findViewById(R.id.nextImage);
doneButton = (Button) findViewById(R.id.done);
}
@Override
protected void onResume() {
super.onResume();
camera = getCameraInstance();
if (camera != null) {
cameraPreview = new CameraSurfaceView(this, camera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(cameraPreview);
}
captureImageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (camera != null) {
camera.takePicture(null, null, mPicture);
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_camera, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private Camera getCameraInstance() {
Camera c = null;
try {
int backCameraId = findBackFacingCamera();
if (backCameraId >= 0) {
c = Camera.open(backCameraId); // attempt to get a Camera instance
}
} catch (Exception e) {
final Snackbar snackBar = Snackbar.make(findViewById(android.R.id.content), "Please shut down all the background applications and try again", Snackbar.LENGTH_LONG);
ViewGroup snackBarView = (ViewGroup) snackBar.getView();
snackBarView.setBackgroundColor(getResources().getColor(R.color.PrimaryOrange));
snackBar.setAction("Go Back", new View.OnClickListener() {
@Override
public void onClick(View v) {
if (getApplicationContext() != null) {
snackBar.dismiss();
finish();
}
}
});
snackBar.show();
}
return c; // returns null if camera is unavailable
}
private Camera.PictureCallback mPicture = new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
enablePreviewMode();
camera.stopPreview();
File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
if (pictureFile == null) {
Log.d(TAG, "Error creating media file, check storage permissions: ");
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());
}
}
};
public static final int MEDIA_TYPE_IMAGE = 1;
/**
* Create a file Uri for saving an image or video
*/
private static Uri getOutputMediaFileUri(int type) {
return Uri.fromFile(getOutputMediaFile(type));
}
/**
* 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", Locale.US).format(new Date());
File mediaFile;
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"IMG_" + timeStamp + ".png");
return mediaFile;
}
private void enablePreviewMode() {
if (captureImageButton != null && retakeImageButton != null && doneButton != null & nextImageButton != null) {
captureImageButton.setVisibility(View.GONE);
retakeImageButton.setVisibility(View.VISIBLE);
retakeImageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent retakeIntent = getIntent();
if (retakeIntent != null) {
finish();
retakeIntent.putExtra(IS_NEW_IMAGE, true);
startActivity(retakeIntent);
}
}
});
doneButton.setVisibility(View.VISIBLE);
doneButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
nextImageButton.setVisibility(View.VISIBLE);
nextImageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent retakeIntent = getIntent();
if (retakeIntent != null) {
finish();
retakeIntent.putExtra(IS_NEW_IMAGE, false);
startActivity(retakeIntent);
}
}
});
}
}
private void releaseCamera() {
if (camera != null) {
camera.release();
}
if (cameraPreview != null) {
cameraPreview.getHolder().removeCallback(cameraPreview);
}
}
private int findBackFacingCamera() {
int cameraId = -1;
//Search for the back facing camera
//get the number of cameras
int numberOfCameras = Camera.getNumberOfCameras();
//for every camera check
for (int i = 0; i < numberOfCameras; i++) {
Camera.CameraInfo info = new Camera.CameraInfo();
Camera.getCameraInfo(i, info);
if (info.facing == Camera.CameraInfo.CAMERA_FACING_BACK) {
cameraId = i;
break;
}
}
return cameraId;
}
@Override
protected void onPause() {
super.onPause();
releaseCamera();
}
@Override
protected void onStop() {
super.onStop();
releaseCamera();
}
}
SurfaceView
public class CameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
private static final String TAG = CameraSurfaceView.class.getName();
public CameraSurfaceView(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.setDisplayOrientation(90);
mCamera.setPreviewDisplay(holder);
Camera.Parameters params = mCamera.getParameters();
params.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
mCamera.setParameters(params);
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.
mCamera.release();
}
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());
}
}
}
即使普通相机也不能像这样工作。另一种方法是使用2个片段并传递图像但我想它如果android有一些规定。
答案 0 :(得分：0)
您是否将CameraSurfaceView放入activity_camera.xml？
如果答案是真的，我想我知道如何解决你的问题
您只需要将CameraSurfaceView xml定义提取到独立的xml布局文件中，并在onResume()回调Activity时对其进行充气，然后将其附加到布局根目录，例如调用top level {{ 1}}对象的Layout方法并将您的虚增addChild传递进去，并在CameraSurfaceView onPause()回调时将其分开，例如从顶层移除Activity CameraSurfaceView对象。
总结：
1.膨胀（每次重新充气）并将Layout添加到CameraSurfaceView中的视图层次结构中;
2.从视图层次结构中删除onResume()并将其取消。