阅读了多个与我的问题相似的问题后，我认为该问题适用于专业人士！
我正在使用Android Studio。
我正在尝试允许系统定期“隐藏”图片。同时允许用户使用按钮拍照。
尝试解释应该发生的情况-假设您正在打开相机并尝试拍摄完美的照片，那么找到正确的角度需要花费一些时间。显然，一直以来，您都可以预览相机所看到的内容，并且预览一直持续到您按下“拍照” 按钮。我要创建的是在按下“拍摄图片” 按钮之前的时间内，系统正在后台拍摄隐藏的图片。稍后，我将使用用户拍摄的照片以及系统拍摄的照片，并将它们保存在我的设备上以供以后编辑。
[很显然，我无法使用android手机的内置摄像头应用程序]
到目前为止，我一直依靠： https://developer.android.com/guide/topics/media/camera#custom-camera 为我的代码的框架。
注意1：任何建议都将受到欢迎。
注意2：欢迎对我的代码进行任何改进。
注意3：我已经在一些论坛上阅读了可以通过某种方式使用SurfaceTexture的内容，但是我发现这些示例很难理解
注意4：我已经在一些论坛上阅读到可以以某种方式使用Camera2的示例，但是我发现示例难以理解，因此，我目前正在使用已弃用的示例Camera类。
下面提供了我的代码：
public class CameraActivity extends AppCompatActivity {
private Camera mCamera;
private CameraPreview mPreview;
// variable to break the photo taking loop
boolean wasButtonPressed = false;
static int numOfPicturesTakenUpTo25PPS = 0;
boolean isItSafeToTakePicture = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera);
// Create an instance of Camera
mCamera = getCameraInstance();
// Create our Preview view and set it as the content of our activity.
try {
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
} catch (Exception e) {
Log.d(TAG, "error: in the preview creation: " + e.getMessage());
e.printStackTrace();
}
//double check
numOfPicturesTakenUpTo25PPS = 0;
// Add a listener to the Capture button
Button captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
//
wasButtonPressed = true;
if (isItSafeToTakePicture == true) {
mCamera.takePicture(null, null, mPicture);
isItSafeToTakePicture = false; //will be changed later to true by "onPictureTaken"
}
}
}
);
}
@Override
protected void onStart(){
super.onStart();
Toast.makeText(getApplicationContext(), "user - please wait 2 seconds before taking pictures. (should be 2 secs)",Toast.LENGTH_LONG).show();
// note user 2 secs have passed and its ok to use:
Toast.makeText(getApplicationContext(), "You can start taking pictures",Toast.LENGTH_SHORT).show();
// start taking pictures in a loop.
while (wasButtonPressed == false) {
if (isItSafeToTakePicture == true) {
mCamera.takePicture(null, null, mPicture);
isItSafeToTakePicture = false; //will be changed later to true by "onPictureTaken"
}
}
//TODO: do I need to ensure that this [code above] won't be an infinite loop?
}
@Override
protected void onResume(){
super.onResume();
}
@Override
protected void onPause() {
super.onPause();
releaseCamera(); // release the camera immediately on pause event
}
@Override
protected void onStop() {
super.onStop();
releaseCamera(); // release the camera immediately
}
@Override
protected void onDestroy() {
super.onDestroy();
releaseCamera(); // release the camera immediately
}
//----------------------------------------------------------------------------------------------------------------//
//-------------------------end of system functions. beginning of helping functions -------------------------------//
//----------------------------------------------------------------------------------------------------------------//
private void releaseCamera(){
if (mCamera != null){
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
public static Camera getCameraInstance(){
Camera cam1 = null;
try {
int num_of_cameras = Camera.getNumberOfCameras();
for (int i=0; i<num_of_cameras; i++) {
Log.d(TAG, "[My Debugging message] Camera loop: i is " + i + " properties are: ");
}
cam1 = Camera.open(); // attempt to get a Camera instance
}
catch (Exception e){
// Camera is not available (in use or does not exist)
Log.d(TAG, "[My Debugging message] Error Opening the camera !! error message: " + e.getMessage());
e.printStackTrace();
}
//addition: use "camera parameters" or "camera info" to validate information about the camera
// end addition
if (cam1 == null) {
Log.d(TAG, "[My Debugging message] received a NULL camera !!! ");
}
return cam1; // returns null if camera is unavailable
}
private static final String TAG = "CameraActivity";
Context context = this;
private Camera.PictureCallback mPicture = new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
if (numOfPicturesTakenUpTo25PPS >= 25) { ///only 25 pictures per second. so if we want to capture 2 seconds before button pressed - than //TODO: we need to make it 50 PPS
numOfPicturesTakenUpTo25PPS = 0;
}
File pictureFile = new File(getFilesDir() + File.separator + "IMG_" + numOfPicturesTakenUpTo25PPS + ".bmp");
String pictureFilename = "IMG_" + numOfPicturesTakenUpTo25PPS + ".bmp"; //used later for the log.
numOfPicturesTakenUpTo25PPS++;
if (pictureFile == null) {
Log.d(TAG, "[My Debugging message] Error creating media file, check storage permissions");
//no path to picture, return
isItSafeToTakePicture = true;
return;
}
try {
FileOutputStream fos = new FileOutputStream(pictureFile);
fos.write(data);
fos.close();
} catch (FileNotFoundException e) {
Log.d(TAG, "[My Debugging message] File not found: " + e.getMessage());
e.printStackTrace();
} catch (IOException e) {
Log.d(TAG, "[My Debugging message] Error accessing file: " + e.getMessage());
e.printStackTrace();
} catch (Exception e) {
Log.d(TAG, "[My Debugging message] other error: " + e.getMessage());
e.printStackTrace();
}
//if we got here with no exceptions:
Log.d(TAG, "[My Debugging message] File saved [supposedly]: " + pictureFilename + " at " + getFilesDir());
//finished saving picture, it is now safe to take a new picture
isItSafeToTakePicture = true;
//WARNING - these next few lines are a test
camera.release();
camera = null;
}
};
//----------------------------------------------------------------------------------------------------------------//
//------------------------------------------ Camera Preview Section ----------------------------------------------//
//----------------------------------------------------------------------------------------------------------------//
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback { ///TODO: how to fix this shit right here ?:
private SurfaceHolder mHolder;
private Camera mCamera;
// CTOR ?
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();
isItSafeToTakePicture = true;
} catch (IOException e) {
Log.d(TAG, "[My Debugging message] Error starting camera preview: " + e.getMessage());
e.printStackTrace();
} catch (Exception e) {
Log.d(TAG, "[My Debugging message] Error starting camera preview: " + e.getMessage());
e.printStackTrace();
}
}
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
Log.d(TAG, "[My Debugging message] preview surface does not exist [CameraPreview.java]");
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e) {
// ignore: tried to stop a non-existent preview
Log.d(TAG, "[My Debugging message] Error STOPPING camera preview: " + e.getMessage());
e.printStackTrace();
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
isItSafeToTakePicture = true;
} catch (Exception e) {
Log.d(TAG, "[My Debugging message] Error starting camera preview: " + e.getMessage());
e.printStackTrace();
}
}
///-----------------------------------------------------------------------------------------------------///
}
}
谢谢。