Develop Reference

Android executes task sequentially or not?

I am getting a very interesting behavior by Android Studio in my project. The calls to different activities are not executing sequentially!
I am building a project where in the calls are like this:
button.setOnClickListener()
{
(1) call to cusom camera acivity
(2) call to activity showing preview of latest captured image
(3) call to a doCrop() function
}
But when executed, the actual flow is:
(1) call to the doCrop() function
(2) call to activity showing preview of image captured
(3) call to cusom camera acivity
The custom camera activity handles all the necessary SurfaceHolder and SurfaceView operations.
Is this effect happening as the SurfaceView layout creation and destroying takes more time and android switches to easier one task first?
Even so, it should skip to preview activity and not to doCrop() call.
What is happening here? Please give some pointers !
Thank you!
EDIT:
The naming is:
MainActivity - main activity
Preview - creates camera instance
CameraPreview - Handles SurfaceView etc
ImagePreview -Shows specified image
Main activity code:
photo.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
File temp = new File(//path to store image);
imageUri=Uri.fromFile(temp);
Intent intent = new Intent(MainActivity.this,Preview.class);
startActivity(intent);
// Image Preview Activity
Intent intent1=new Intent(MainActivity.this,ImagePreview.class);
startActivity(intent1);
//Crop function
doCrop();
}
});
The preview activity code:
public class Preview extends Activity {
private static final String TAG = "CamTestActivity";
CameraPreview preview;
Button buttonClick;
Camera camera;
Activity act;
Context ctx;
Uri uri;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ctx = this;
act = this;
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_preview);
preview = new CameraPreview(this, (SurfaceView)findViewById(R.id.surfaceView));
preview.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
((FrameLayout) findViewById(R.id.layout)).addView(preview);
preview.setKeepScreenOn(true);
buttonClick = (Button) findViewById(R.id.btnCapture);
buttonClick.setOnClickListener(new OnClickListener()
{
public void onClick(View v) {
camera.takePicture(shutterCallback, rawCallback, pngCallback);
}
});
}
#Override
protected void onResume() {
super.onResume();
int numCams = Camera.getNumberOfCameras();
if(numCams > 0){
try{
camera = Camera.open(0);
camera.startPreview();
preview.setCamera(camera);
} catch (RuntimeException ex){
Toast.makeText(ctx, getString(R.string.camera_not_found), Toast.LENGTH_LONG).show();
}
}
}
#Override
protected void onPause() {
if(camera != null) {
camera.stopPreview();
preview.setCamera(null);
camera.release();
camera = null;
}
super.onPause();
}
private void resetCam() {
camera.startPreview();
preview.setCamera(camera);
}
private void refreshGallery(File file) {
Intent mediaScanIntent = new Intent( Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
mediaScanIntent.setData(Uri.fromFile(file));
sendBroadcast(mediaScanIntent);
}
ShutterCallback shutterCallback = new ShutterCallback() {
public void onShutter() {
}
};
PictureCallback rawCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
}
};
PictureCallback pngCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
new SaveImageTask().execute(data);
resetCam();
Log.d(TAG, "onPictureTaken - png");
}
};
private class SaveImageTask extends AsyncTask<byte[], Void, Void> {
#Override
protected Void doInBackground(byte[]... data) {
// save the image
}
catch (Exception e) { e.printStackTrace();}
return null;
}
}
}
CameraPreview code:
class CameraPreview extends ViewGroup implements SurfaceHolder.Callback {
private final String TAG = "Preview";
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
CameraPreview(Context context, SurfaceView sv) {
super(context);
mSurfaceView = sv;
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
requestLayout();
// get Camera parameters
Camera.Parameters params = mCamera.getParameters();
List<String> focusModes = params.getSupportedFocusModes();
if (focusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)) {
// set the focus mode
params.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
// set Camera parameters
mCamera.setParameters(params);
}
}
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null) {
mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
}
}
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if (changed && getChildCount() > 0) {
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null) {
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth) {
final int scaledChildWidth = previewWidth * height / previewHeight;
child.layout((width - scaledChildWidth) / 2, 0,
(width + scaledChildWidth) / 2, height);
} else {
final int scaledChildHeight = previewHeight * width / previewWidth;
child.layout(0, (height - scaledChildHeight) / 2,
width, (height + scaledChildHeight) / 2);
}
}
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell it where
// to draw.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null) {
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null) return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the requirement
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
if(mCamera != null) {
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.startPreview();
}
}
}

I think this is more of a design issue.
Should you really be opening more than one activity at once?
When an activity is started, it's put on top of the history stack, which could give the illusion that it's happening the other way round.
But I can't comment any further until I see code.
UPDATE: Yep, design issue.
This is the way it should work:
Onclick action in MainActivity should ONLY open Preview activity using startActivityForResult().
User takes photo, triggering setResult() and closing the camera activity.
Result gets returned to MainActivity, triggering onActivityResult()
Code in onActivityResult starts ImagePreview activity.
onCreate function in ImagePreview triggers doCrop();
I do suggest you have a good read of the Android Documentation here:
http://developer.android.com/guide/components/activities.html
Android is less flexible (or more helpful) than other platforms and it's essential that you have a good understanding of the API.

Activity startup code is asynchronous, and if you launch several activities simultaneously, like this:
startActivity(intent1);
startActivity(intent2);
startActivity(intent3);
it is not guaranteed, that they'll be shown to user sequentially, that is, in "launch order".
This is expected behaviour, and you normally should not do such a thing, as it is indication of your application design flaw

So what you are trying to do is launch 3 activities simultaneously.These all need to be handled in onActivityResult(). But a user cannot access 3 activities simultaneously.
so modifying your flow.
it should be something like
start CameraActivity
In the onActivityResult() of your calling activity ,you call do crop and do what you want.
You need to revisit your workflow because:
you are not launching 3 activites.
you are triggerring events based on user interaction and hence the sequence of functions should not be controlled from your code.

Your tasks are executing in wrong order because they are called asynchronously. To execute them in the order you have specified make a synchronous call, which can be done using startActivityForResult(intent, requestCode);

Customize Camera View for Android using zbar

I am new in android development. My app should activate the camera to scan a QR code and decode it to a string. This works fine, but I have one more requirement: to present the camera view in a frame and with a logo in one of the corners. I did not find an appropriate API in zbar sdk to make the frame and attach the logo. This is my code:
ZBarScannerActivity.java:
package com.myCompany.android;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.os.Handler;
import android.text.TextUtils;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Toast;
import net.sourceforge.zbar.Config;
import net.sourceforge.zbar.Image;
import net.sourceforge.zbar.ImageScanner;
import net.sourceforge.zbar.Symbol;
import net.sourceforge.zbar.SymbolSet;
public class ZBarScannerActivity extends Activity implements Camera.PreviewCallback, ZBarConstants {
private static final String TAG = "ZBarScannerActivity";
private CameraPreview mPreview;
private Camera mCamera;
private ImageScanner mScanner;
private Handler mAutoFocusHandler;
private boolean mPreviewing = true;
static {
System.loadLibrary("iconv");
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Hide the window title.
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
mAutoFocusHandler = new Handler();
// Create and configure the ImageScanner;
setupScanner();
// Create a RelativeLayout container that will hold a SurfaceView,
// and set it as the content of our activity.
mPreview = new CameraPreview(this, this, autoFocusCB);
setContentView(mPreview);
}
public void setupScanner() {
mScanner = new ImageScanner();
mScanner.setConfig(0, Config.X_DENSITY, 3);
mScanner.setConfig(0, Config.Y_DENSITY, 3);
int[] symbols = getIntent().getIntArrayExtra(SCAN_MODES);
if (symbols != null) {
mScanner.setConfig(Symbol.NONE, Config.ENABLE, 0);
for (int symbol : symbols) {
mScanner.setConfig(symbol, Config.ENABLE, 1);
}
//test customization
}
}
#Override
protected void onResume() {
super.onResume();
// Open the default i.e. the first rear facing camera.
mCamera = Camera.open();
mPreviewing = true;
mPreview.setCamera(mCamera);
}
#Override
protected void onPause() {
super.onPause();
// Because the Camera object is a shared resource, it's very
// important to release it when the activity is paused.
if (mCamera != null) {
mPreview.setCamera(null);
mCamera.cancelAutoFocus();
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
mCamera.release();
mPreviewing = false;
mCamera = null;
}
}
public void onPreviewFrame(byte[] data, Camera camera) {
Camera.Parameters parameters = camera.getParameters();
Camera.Size size = parameters.getPreviewSize();
Image barcode = new Image(size.width, size.height, "Y800");
barcode.setData(data);
int result = mScanner.scanImage(barcode);
if (result != 0) {
mCamera.cancelAutoFocus();
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
mPreviewing = false;
SymbolSet syms = mScanner.getResults();
for (Symbol sym : syms) {
String symData = sym.getData();
if (!TextUtils.isEmpty(symData)) {
Intent dataIntent = new Intent();
dataIntent.putExtra(SCAN_RESULT, symData);
dataIntent.putExtra(SCAN_RESULT_TYPE, sym.getType());
setResult(Activity.RESULT_OK, dataIntent);
finish();
break;
}
}
}
}
private Runnable doAutoFocus = new Runnable() {
public void run() {
if(mCamera != null && mPreviewing) {
mCamera.autoFocus(autoFocusCB);
}
}
};
// Mimic continuous auto-focusing
Camera.AutoFocusCallback autoFocusCB = new Camera.AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {
mAutoFocusHandler.postDelayed(doAutoFocus, 1000);
}
};
public void launchQRScanner(View v) {
if (isCameraAvailable()) {
//Toast.makeText(this, "Analyzing Image", Toast.LENGTH_LONG).show();
Intent intent = new Intent(this, ZBarScannerActivity.class);
intent.putExtra(ZBarConstants.SCAN_MODES, new int[]{Symbol.QRCODE});
startActivityForResult(intent, ZBAR_QR_SCANNER_REQUEST);
} else {
Toast.makeText(this, "Camera Unavailable", Toast.LENGTH_SHORT).show();
}
}
public boolean isCameraAvailable() {
PackageManager pm = getPackageManager();
return pm.hasSystemFeature(PackageManager.FEATURE_CAMERA);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
//getMenuInflater().inflate(R.menu.activity_qrimport_token, menu);
return true;
}
/* #Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
switch (requestCode) {
case ZBAR_SCANNER_REQUEST:
Toast.makeText(this, data.getStringExtra(ZBarConstants.SCAN_RESULT), Toast.LENGTH_LONG).show();
break;
case ZBAR_QR_SCANNER_REQUEST:
playSound();
if (resultCode == RESULT_OK) {
Toast.makeText(this, data.getStringExtra(ZBarConstants.SCAN_RESULT), Toast.LENGTH_LONG).show();
Toast.makeText(this, "Scan Result = " + data.getStringExtra(ZBarConstants.SCAN_RESULT), Toast.LENGTH_SHORT).show();
// put whatever you want to do with the code here
//TextView tv = new TextView(this);
//tv.setText(data.getStringExtra(ZBarConstants.SCAN_RESULT));
Log.d("Data",""+data.getStringExtra(ZBarConstants.SCAN_RESULT));
//setContentView(tv);
}
break;
}
}*/
/*private void playSound()
{
MediaPlayer mp = MediaPlayer.create(getBaseContext(), R.raw.camera_shutter);
mp.start();
mp.setOnCompletionListener(new OnCompletionListener()
{
#Override
public void onCompletion(MediaPlayer mp)
{
mp.release();
}
});
}*/
}
CameraPreview.java:
package com.myCompany.android;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.Size;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup;
import java.io.IOException;
import java.util.List;
class CameraPreview extends ViewGroup implements SurfaceHolder.Callback {
private final String TAG = "CameraPreview";
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
PreviewCallback mPreviewCallback;
AutoFocusCallback mAutoFocusCallback;
CameraPreview(Context context, PreviewCallback previewCallback, AutoFocusCallback autoFocusCb) {
super(context);
mPreviewCallback = previewCallback;
mAutoFocusCallback = autoFocusCb;
mSurfaceView = new SurfaceView(context);
addView(mSurfaceView);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
requestLayout();
}
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null) {
mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
}
}
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if (changed && getChildCount() > 0) {
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null) {
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth) {
final int scaledChildWidth = previewWidth * height / previewHeight;
child.layout((width - scaledChildWidth) / 2, 0,
(width + scaledChildWidth) / 2, height);
} else {
final int scaledChildHeight = previewHeight * width / previewWidth;
child.layout(0, (height - scaledChildHeight) / 2,
width, (height + scaledChildHeight) / 2);
}
}
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell it where
// to draw.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null) {
mCamera.cancelAutoFocus();
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null) return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the requirement
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
if (holder.getSurface() == null){
// preview surface does not exist
return;
}
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.setPreviewCallback(mPreviewCallback);
mCamera.startPreview();
mCamera.autoFocus(mAutoFocusCallback);
}
}
How to customize the camera view for android? I saw some suggested solutions for iPhone, but zbar API for Android is totally different and much smaller. I would be appreciated to get any idea/hint...

To present a frame in cameraview, add an imageview in the framelayout(camerapreview) in main.xml .
<FrameLayout
android:id="#+id/cameraPreview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1" >
<ImageView
android:id="#+id/imageView1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:alpha="0.6"
android:src="#drawable/overlay" />
</FrameLayout>
Use this code to make the frame(imageview) visible. As the frame(imageview) is already present in the framelayout in main.xml we need to remove it first.
FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
ImageView iv=(ImageView) findViewById(R.id.imageView1);
preview.addView(mPreview);
preview.removeView(iv);
preview.addView(iv);
To scan the camerapreview only from your frame you need to use setCrop().Adjust the size of camerapreview according to the frame.
barcode.setData(data);
//this is in portrait mode
//barcode.setCrop(left,top,width,height).
barcode.setCrop(100,230,600,10);
This worked for me and hope it will solve your problem too. Please excuse me for my grammatical mistakes. Thank you.

I think it's easier then you thought:
In the example code provided by the ZBar guy there are those two lines in the onCreate() method:
FrameLayout preview = (FrameLayout) findViewById(R.id.cameraPreview);
preview.addView(mPreview);
which are responsible for adding the "preview view" to the camerPreview Layout.
Find the mentioned lines in your code, create a new ImageView and also add it to the preview-Layout like this:
ImageView v = new ImageView(this);
v.setImageResource(R.drawable.icon);
preview.addView(v);
Adjust the size and the position of your view v and you are done!

I faced the same problem. The solution is simply add the CameraPrevie in your xml inside a frameLayout, and just after that the image you want to put on top of is.
eg.:
<FrameLayout
android:id="#+id/captionFrame"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="20dp"
android:layout_marginTop="50dp" >
<FrameLayout
android:id="#+id/cameraPreview"
android:layout_width="300dp"
android:layout_height="200dp"
android:layout_gravity="center"
android:paddingLeft="-5dp" >
</FrameLayout>
<ImageView
android:id="#+id/watermark"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right|bottom"
android:src="#drawable/watermark" />
</FrameLayout>
and populate it from your activity:
Camera mCamera = getCameraInstance();
ImageScanner scanner = new ImageScanner();
scanner.setConfig(0, Config.X_DENSITY, 3);
scanner.setConfig(0, Config.Y_DENSITY, 3);
CameraPreview mPreview = new CameraPreview(this, mCamera, null, autoFocusCallB);
FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
preview.addView(mPreview);

Android SurfaceView conflict between CameraPreview and GoogleMaps API v2 View

My application has a set of tabs hosting FragmentActivity's. Some of these tabs contain a GoogleMaps Api v2 Support MapFragment and/or MapView and another single one is a QR scanner.
The problem I am facing is that if you are currently viewing a SupportMapFragment or MapView on one tab, and then switch to the Scanner tab, the SurfaceView is still taken over by the previous SupportMapFragment / MapView (unless of course the Fragment/View is removed prior to selecting the Scanner tab). This was not a problem until trying to incorporate GoogleMaps Api v2, over v1, due to the SurfaceView use.
I'm not entirely sure how to address this problem, I am thinking something along the lines of "clearing" the SurfaceView when the Scanner tab is selected and the CameraPreview is started? And achieve this using a canvas somehow?
But I do not have a lot of knowledge on the SurfaceView class.
Attached is my "CameraPreview" class which is used to handle the Android Camera on the Scanner tab. The GoogleMaps api v2 class is just the basic setup provided by Google, nothing special.
Thank you for your time and help.
class CameraPreview extends ViewGroup implements SurfaceHolder.Callback {
private final String TAG = "CameraPreview";
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
PreviewCallback mPreviewCallback;
AutoFocusCallback mAutoFocusCallback;
CameraPreview(Context context, PreviewCallback previewCallback, AutoFocusCallback autoFocusCb) {
super(context);
mPreviewCallback = previewCallback;
mAutoFocusCallback = autoFocusCb;
mSurfaceView = new SurfaceView(context);
addView(mSurfaceView);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
requestLayout();
}
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null) {
mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
}
}
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if (changed && getChildCount() > 0) {
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null) {
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth) {
final int scaledChildWidth = previewWidth * height / previewHeight;
child.layout(0, 0, width, height);
} else {
final int scaledChildHeight = previewHeight * width / previewWidth;
child.layout(0, 0, width,height);
}
}
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell it where
// to draw.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
mCamera.setDisplayOrientation(90);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null) {
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null) return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the requirement
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
if (holder.getSurface() == null){
// preview surface does not exist
return;
}
// Now that the size is known, set up the camera parameters and begin
// the preview.
if(mCamera!=null){
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.setPreviewCallback(mPreviewCallback);
mCamera.startPreview();
mCamera.autoFocus(mAutoFocusCallback);
}
}
}

From the sounds of the documentation you should only have a single surface view running at once.
I had a similar MapFragment with CameraPreview in front, and found that I needed the MapFragment to release its resources before the camera preview fragment would work.
It meant swapping the MapFragment for a CamreaPreviewFragment rather than just adding it over the top.

I met the same problem some days before, I need to show a camera preview view on top of the GoogleMap v2, the following is my solution, hope it helps you.
// construct a camera preview layout then show it, or remove it then hide
popCamera.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
if(cameraBar.getVisibility() == View.VISIBLE) {
cameraBar.removeAllViews();
cameraBar.setVisibility(View.INVISIBLE);
}else if(cameraBar.getVisibility() == View.INVISIBLE) {
// new camera surface view then add to preview area
if (cameraSurfaceView == null) {
cameraSurfaceView = new CameraSurfaceView(getApplicationContext());
// === the key point ===
**cameraSurfaceView.setZOrderOnTop(true);**
LinearLayout.LayoutParams param = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.MATCH_PARENT);
previewArea.addView(cameraSurfaceView, param);
}
cameraBar.removeAllViews();
cameraBar.addView(previewArea);
cameraBar.addView(snapArea);
cameraBar.setVisibility(View.VISIBLE);
}
}
});

how to put a picture to front of a camera preview

I would like to make an app that have 2 activities. The first one is a CameraPreview from api demos that have an options menu by default. I added to it a second button that starts the second activity, what is a ImageSwitcher. I want to give back the selected photo to front of the preview at a specified width and height.
This block is fine for get and appear a photo in a plain activity's onCreate method, but I don't know how to do this with a CameraPreview:
setContentView(R.layout.picturelay);
int theID = getIntent().getExtras().getInt("the_image_id");
ImageView i = (ImageView) findViewById(R.id.cameralay);
i.setImageResource(theID);
My starting activity:
public class CameraPreview extends Activity {
private
Preview mPreview;
Camera mCamera;
int numberOfCameras;
int cameraCurrentlyLocked;
String uzenet;
// The first rear facing camera
int defaultCameraId;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Hide the window title.
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
// Create a RelativeLayout container that will hold a SurfaceView,
// and set it as the content of our activity.
mPreview = new Preview(this);
setContentView(mPreview);
try {
int theID = getIntent().getExtras().getInt("the_image_id");
ImageView i = (ImageView) findViewById(R.id.cameralay);
i.setImageResource(theID);
} catch (Exception e){
Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG);
}
// Find the total number of cameras available
numberOfCameras = Camera.getNumberOfCameras();
// Find the ID of the default camera
CameraInfo cameraInfo = new CameraInfo();
for (int i = 0; i < numberOfCameras; i++) {
Camera.getCameraInfo(i, cameraInfo);
if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK) {
defaultCameraId = i;
}
}
}
#Override
protected void onResume() {
super.onResume();
// Open the default i.e. the first rear facing camera.
mCamera = Camera.open();
cameraCurrentlyLocked = defaultCameraId;
mPreview.setCamera(mCamera);
}
#Override
protected void onPause() {
super.onPause();
// Because the Camera object is a shared resource, it's very
// important to release it when the activity is paused.
if (mCamera != null) {
mPreview.setCamera(null);
mCamera.release();
mCamera = null;
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate our menu which can gather user input for switching camera
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.camera_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.switch_cam:
// check for availability of multiple cameras
if (numberOfCameras == 1) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(this.getString(R.string.camera_alert))
.setNeutralButton("Close", null);
AlertDialog alert = builder.create();
alert.show();
return true;
}
// OK, we have multiple cameras.
// Release this camera -> cameraCurrentlyLocked
if (mCamera != null) {
mCamera.stopPreview();
mPreview.setCamera(null);
mCamera.release();
mCamera = null;
}
// Acquire the next camera and request Preview to reconfigure
// parameters.
mCamera = Camera
.open((cameraCurrentlyLocked + 1) % numberOfCameras);
cameraCurrentlyLocked = (cameraCurrentlyLocked + 1)
% numberOfCameras;
mPreview.switchCamera(mCamera);
// Start the preview
mCamera.startPreview();
return true;
case R.id.get_picture:
Intent intent2 = new Intent(CameraPreview.this, ImageSwitcher1.class);
//startActivityForResult(intent, 0);
startActivity(intent2);
return true;
}
return super.onOptionsItemSelected(item);
}
}
class Preview extends ViewGroup implements SurfaceHolder.Callback {
private final String TAG = "Preview";
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
Preview(Context context) {
super(context);
mSurfaceView = new SurfaceView(context);
addView(mSurfaceView);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
requestLayout();
}
}
public void switchCamera(Camera camera) {
setCamera(camera);
try {
camera.setPreviewDisplay(mHolder);
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
camera.setParameters(parameters);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null) {
mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
}
}
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if (changed && getChildCount() > 0) {
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null) {
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth) {
final int scaledChildWidth = previewWidth * height / previewHeight;
child.layout((width - scaledChildWidth) / 2, 0,
(width + scaledChildWidth) / 2, height);
} else {
final int scaledChildHeight = previewHeight * width / previewWidth;
child.layout(0, (height - scaledChildHeight) / 2,
width, (height + scaledChildHeight) / 2);
}
}
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell it where
// to draw.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null) {
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null) return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the requirement
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.startPreview();
}
}
The second activity:
public class ImageSwitcher1 extends Activity implements
AdapterView.OnItemSelectedListener, ViewSwitcher.ViewFactory {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.image_switcher_1);
mSwitcher = (ImageSwitcher) findViewById(R.id.switcher);
mSwitcher.setFactory(this);
mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
android.R.anim.fade_in));
mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
android.R.anim.fade_out));
Gallery g = (Gallery) findViewById(R.id.gallery);
g.setAdapter(new ImageAdapter(this));
g.setOnItemSelectedListener(this);
g.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView parent, View v, int position, long id) {
Intent intent = new Intent(ImageSwitcher1.this, CameraPreview.class);
intent.putExtra("the_image_id", mImageIds[position]);
startActivity(intent);
finish();
}
});
}
public void onItemSelected(AdapterView parent, View v, int position, long id) {
mSwitcher.setImageResource(mImageIds[position]);
}
public void onNothingSelected(AdapterView parent) {
}
public View makeView() {
ImageView i = new ImageView(this);
i.setBackgroundColor(0xFF000000);
i.setScaleType(ImageView.ScaleType.FIT_CENTER);
i.setLayoutParams(new ImageSwitcher.LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
return i;
}
private ImageSwitcher mSwitcher;
public class ImageAdapter extends BaseAdapter {
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
return mThumbIds.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ImageView i = new ImageView(mContext);
i.setImageResource(mThumbIds[position]);
i.setAdjustViewBounds(true);
i.setLayoutParams(new Gallery.LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
i.setBackgroundResource(R.drawable.picture_frame);
return i;
}
private Context mContext;
}
private Integer[] mThumbIds = {
R.drawable.1, R.drawable.2,
R.drawable.3, R.drawable.4,
R.drawable.5, R.drawable.6,
R.drawable.7, R.drawable.8,
R.drawable.9
};
private Integer[] mImageIds = {
R.drawable.1, R.drawable.2,
R.drawable.3, R.drawable.4,
R.drawable.5, R.drawable.6,
R.drawable.7, R.drawable.8,
R.drawable.9
};
}
Thank You for your replies!

I had a solution with a different Preview activity. So I can see the selected image front of the camera preview. This is the used preview activity:
public class PreviewDemo extends Activity {
private SurfaceView preview=null;
private SurfaceHolder previewHolder=null;
private Camera camera=null;
private boolean inPreview=false;
private boolean cameraConfigured=false;
private Context context;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
preview=(SurfaceView)findViewById(R.id.preview);
previewHolder=preview.getHolder();
previewHolder.addCallback(surfaceCallback);
previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
try {
int theID = getIntent().getExtras().getInt("the_image_id");
ImageView i = (ImageView) findViewById(R.id.cameralay);
i.setImageResource(theID);
} catch (Exception e){
Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG);
}
}
#Override
public void onResume() {
super.onResume();
camera=Camera.open();
startPreview();
}
#Override
public void onPause() {
if (inPreview) {
camera.stopPreview();
}
camera.release();
camera=null;
inPreview=false;
super.onPause();
}
private Camera.Size getBestPreviewSize(int width, int height,
Camera.Parameters parameters) {
Camera.Size result=null;
for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
if (size.width<=width && size.height<=height) {
if (result==null) {
result=size;
}
else {
int resultArea=result.width*result.height;
int newArea=size.width*size.height;
if (newArea>resultArea) {
result=size;
}
}
}
}
return(result);
}
private void initPreview(int width, int height) {
if (camera!=null && previewHolder.getSurface()!=null) {
try {
camera.setPreviewDisplay(previewHolder);
}
catch (Throwable t) {
Log.e("PreviewDemo-surfaceCallback",
"Exception in setPreviewDisplay()", t);
Toast
.makeText(PreviewDemo.this, t.getMessage(), Toast.LENGTH_LONG)
.show();
}
if (!cameraConfigured) {
Camera.Parameters parameters=camera.getParameters();
Camera.Size size=getBestPreviewSize(width, height,
parameters);
if (size!=null) {
parameters.setPreviewSize(size.width, size.height);
camera.setParameters(parameters);
cameraConfigured=true;
}
}
}
}
private void startPreview() {
if (cameraConfigured && camera!=null) {
camera.startPreview();
inPreview=true;
}
}
SurfaceHolder.Callback surfaceCallback=new SurfaceHolder.Callback() {
public void surfaceCreated(SurfaceHolder holder) {
// no-op -- wait until surfaceChanged()
}
public void surfaceChanged(SurfaceHolder holder,
int format, int width,
int height) {
initPreview(width, height);
startPreview();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// no-op
}
};
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate our menu which can gather user input for switching camera
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.camera_menu2, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.take_photo:
//code of taking a photo will be here...
return true;
}
return super.onOptionsItemSelected(item);
}
}
And my layout file that contains the surface view and image view:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.view.SurfaceView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/preview"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.view.SurfaceView>
<ImageView
android:id="#+id/cameralay"
android:layout_width="150dp"
android:layout_height="150dp"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:contentDescription="#+id/app_name">
</ImageView>
</RelativeLayout>

Accessing front facing camera "green screen"?

I developed an android2.3 project ,copy the sample code "CameraPreview" from ApiDemos,and run it on my evo 4g mobile,the back camera was correct ,when switch to front facing camera ,the screen was "green screen",what's the problem?
CameraPreview
// ----------------------------------------------------------------------
import java.io.IOException;
import java.util.List;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.CameraInfo;
import android.hardware.Camera.Size;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
public class CameraPreview extends Activity
{
private Preview mPreview;
Camera mCamera;
int numberOfCameras;
int cameraCurrentlyLocked;
// The first rear facing camera
int defaultCameraId;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// Hide the window title.
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
// Create a RelativeLayout container that will hold a SurfaceView,
// and set it as the content of our activity.
mPreview = new Preview(this);
setContentView(mPreview);
// Find the total number of cameras available
numberOfCameras = Camera.getNumberOfCameras();
// Find the ID of the default camera
CameraInfo cameraInfo = new CameraInfo();
for (int i = 0; i < numberOfCameras; i++)
{
Camera.getCameraInfo(i, cameraInfo);
if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK)
{
defaultCameraId = i;
}
}
}
#Override
protected void onResume()
{
super.onResume();
// Open the default i.e. the first rear facing camera.
mCamera = Camera.open();
cameraCurrentlyLocked = defaultCameraId;
mPreview.setCamera(mCamera);
}
#Override
protected void onPause()
{
super.onPause();
// Because the Camera object is a shared resource, it's very
// important to release it when the activity is paused.
if (mCamera != null)
{
mPreview.setCamera(null);
mCamera.release();
mCamera = null;
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate our menu which can gather user input for switching camera
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.camera_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item)
{
// Handle item selection
switch (item.getItemId())
{
case R.id.switch_cam:
// check for availability of multiple cameras
if (numberOfCameras == 1)
{
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(this.getString(R.string.camera_alert)).setNeutralButton("Close", null);
AlertDialog alert = builder.create();
alert.show();
return true;
}
// OK, we have multiple cameras.
// Release this camera -> cameraCurrentlyLocked
if (mCamera != null)
{
mCamera.stopPreview();
mPreview.setCamera(null);
mCamera.release();
mCamera = null;
}
// Acquire the next camera and request Preview to reconfigure
// parameters.
mCamera = Camera.open((cameraCurrentlyLocked + 1)
% numberOfCameras);
cameraCurrentlyLocked = (cameraCurrentlyLocked + 1)
% numberOfCameras;
mPreview.switchCamera(mCamera);
// Start the preview
mCamera.startPreview();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
// ----------------------------------------------------------------------
/**
* A simple wrapper around a Camera and a SurfaceView that renders a centered
* preview of the Camera to the surface. We need to center the SurfaceView
* because not all devices have cameras that support preview sizes at the same
* aspect ratio as the device's display.
*/
class Preview extends ViewGroup implements SurfaceHolder.Callback
{
private final String TAG = "Preview";
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
Preview(Context context)
{
super(context);
mSurfaceView = new SurfaceView(context);
addView(mSurfaceView);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera)
{
mCamera = camera;
if (mCamera != null)
{
mSupportedPreviewSizes = mCamera.getParameters().getSupportedPreviewSizes();
requestLayout();
}
}
public void switchCamera(Camera camera)
{
setCamera(camera);
try
{
camera.setPreviewDisplay(mHolder);
}
catch (IOException exception)
{
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
camera.setParameters(parameters);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null)
{
mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
}
}
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b)
{
if (changed && getChildCount() > 0)
{
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null)
{
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth)
{
final int scaledChildWidth = previewWidth * height
/ previewHeight;
child.layout((width - scaledChildWidth) / 2, 0, (width + scaledChildWidth) / 2, height);
} else
{
final int scaledChildHeight = previewHeight * width
/ previewWidth;
child.layout(0, (height - scaledChildHeight) / 2, width, (height + scaledChildHeight) / 2);
}
}
}
public void surfaceCreated(SurfaceHolder holder)
{
// The Surface has been created, acquire the camera and tell it where
// to draw.
try
{
if (mCamera != null)
{
mCamera.setPreviewDisplay(holder);
}
} catch (IOException exception)
{
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder)
{
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null)
{
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h)
{
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null)
return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes)
{
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE)
continue;
if (Math.abs(size.height - targetHeight) < minDiff)
{
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the requirement
if (optimalSize == null)
{
minDiff = Double.MAX_VALUE;
for (Size size : sizes)
{
if (Math.abs(size.height - targetHeight) < minDiff)
{
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h)
{
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.startPreview();
}
}
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.kiterive.magicmirror"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="9" />
<!-- We will request access to the camera, saying we require a camera
of some sort but not one with autofocus capability. -->
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" android:required="false" />
<application android:icon="#drawable/icon" android:label="#string/app_name">
<activity android:name=".MagicMirrorActivity"
android:label="#string/app_name"
android:screenOrientation="landscape">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

The EVO 4G (as of this writing) runs Android 2.2, which lacks support for the 2.3 front-facing camera APIs. I'm rather surprised your code example runs without tripping an exception for the 2.3 API calls you are invoking.

Most likely it is a device issue, drivers or something else.
Try testing it on another device.
Also make sure the device is running Android 2.3 or higher, below that it isn't supported.