我想手动拍摄照片，而不是使用现有的相机应用程序。所以我做了这个活动：
public class CameraActivity extends Activity {
private Camera mCamera;
private Preview mPreview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera);
// Create an instance of Camera
mCamera = Camera.open(0); if(mCamera !=null) Log.i("CameraActivity.onCreate()", "mCamera initialized");
// Create our Preview view and set it as the content of our activity.
mPreview = new Preview(this); if(mPreview !=null) Log.i("CameraActivity.onCreate()", "mPreview initialized");
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview); Log.i("CameraActivity.onCreate()", "mPreview added to FrameLayout");
mPreview.setCamera(mCamera); Log.i("CameraActivity.onCreate()", "mPreview.setCamera(mCamera)");
}
@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_camera, menu);
return true;
}
@Override
public void onPause() {
super.onPause();
mPreview.stopPreviewAndFreeCamera();
}
}
这是我想使用的 CameraPreview：
public class Preview extends ViewGroup implements SurfaceHolder.Callback {
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
private Camera mCamera;
List<Size> mSupportedPreviewSizes;
/**
* @param context
*/
public Preview(Context context) {
super(context);
mSurfaceView = new SurfaceView(context); Log.i("CameraPreview.constructor(...)", "mSurfaceView initialized");
if(mSurfaceView==null) {Log.i("CameraPreview.constructor(...)", "mSurfaceView is null");}
addView(mSurfaceView);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = mSurfaceView.getHolder(); Log.i("CameraPreview.constructor(...)", "mHolder setup");
if(mHolder==null) {Log.e("PreviewCamera", "mHolder is null");}
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
/**
* @param context
* @param attrs
*/
public Preview(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
}
/**
* @param context
* @param attrs
* @param defStyle
*/
public Preview(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
}
/* (non-Javadoc)
* @see android.view.ViewGroup#onLayout(boolean, int, int, int, int)
*/
@Override
protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) {
// TODO Auto-generated method stub
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(width, height);
requestLayout();
mCamera.setParameters(parameters);
/*
Important: Call startPreview() to start updating the preview surface. Preview must be
started before you can take a picture.
*/
mCamera.startPreview(); Log.i("CameraPreview.surfaceChanged(...)", "mCamera.startPreview()");
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null) {
/*
Call stopPreview() to stop updating the preview surface.
*/
mCamera.stopPreview(); Log.i("CameraPreview.surfaceDestroyed(...)", "mCamera.stopPreview()");
}
}
/**
* When this function returns, mCamera will be null.
*/
public void stopPreviewAndFreeCamera() {
if (mCamera != null) {
/*
Call stopPreview() to stop updating the preview surface.
*/
mCamera.stopPreview(); Log.i("CameraPreview.stopPreviewAndFreeCamera()", "mCamera.stopPreview()");
/*
Important: Call release() to release the camera for use by other applications.
Applications should release the camera immediately in onPause() (and re-open() it in
onResume()).
*/
mCamera.release(); Log.i("CameraPreview.stopPreviewAndFreeCamera()", "mCamera.release()");
mCamera = null;
}
}
/***
*
* @param camera
*/
public void setCamera(Camera camera) {
if (mCamera == camera) { Log.i("CameraPreview.setCamera()", "mCamera equals the Camera you want to set"); return; }
stopPreviewAndFreeCamera(); Log.i("CameraPreview.setCamera()", "stopPreviewAndFreeCamera()");
mCamera = camera; Log.i("CameraPreview.setCamera()", "setup new Camera");
if (mCamera != null) {
List<Size> localSizes = mCamera.getParameters().getSupportedPreviewSizes();
mSupportedPreviewSizes = localSizes;
requestLayout();
try {
mCamera.setPreviewDisplay(mHolder);
Log.i("CameraPreview.setCamera()", "mCamera.setPreviewDisplay(mHolder)");
} catch (IOException e) {
e.printStackTrace();
}
/*
Important: Call startPreview() to start updating the preview surface. Preview must
be started before you can take a picture.
*/
mCamera.startPreview(); Log.i("CameraPreview.setCamera()", "mCamera.startPreview()");
}
}
/***
*
* @param id
* @return
*/
public boolean safeCameraOpen(int id) {
boolean qOpened = false;
try {
releaseCameraAndPreview();
mCamera = Camera.open(id);
qOpened = (mCamera != null);
} catch (Exception e) {
// Log.e(R.string.app_name, "failed to open Camera");
e.printStackTrace();
}
return qOpened;
}
/**
*
*/
Camera.PictureCallback mPicCallback = new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
// TODO Auto-generated method stub
Log.d("lala", "pic is taken");
}
};
/**
*
*/
public void takePic() {
// mCamera.takePicture(null, mPicCallback, mPicCallback);
}
/**
*
*/
private void releaseCameraAndPreview() {
this.setCamera(null);
if (mCamera != null) {
mCamera.release();
mCamera = null;
}
}
}
这是CameraActivity的布局：
<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"
tools:context=".CameraActivity" >
<FrameLayout
android:id="@+id/camera_preview"
android:layout_width="0dip"
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>
但是当我启动 CameraActivity 时，我只看到一个空白的白色背景和 Capture-Button ？？？为什么我看不到相机屏幕？
编辑：Logcat：
12-16 13:09:39.941: I/CameraActivity.onCreate()(439): mCamera initialized
12-16 13:09:39.941: I/CameraPreview.constructor(...)(439): mSurfaceView initialized
12-16 13:09:39.941: I/CameraPreview.constructor(...)(439): mHolder setup
12-16 13:09:39.941: I/CameraActivity.onCreate()(439): mPreview initialized
12-16 13:09:39.952: I/CameraActivity.onCreate()(439): mPreview added to FrameLayout
12-16 13:09:39.952: I/CameraPreview.setCamera()(439): stopPreviewAndFreeCamera()
12-16 13:09:39.952: I/CameraPreview.setCamera()(439): setup new Camera
12-16 13:09:39.961: D/Camera(439): app passed NULL surface
12-16 13:09:39.961: I/CameraPreview.setCamera()(439): mCamera.setPreviewDisplay(mHolder)
12-16 13:09:39.971: I/CameraPreview.setCamera()(439): mCamera.startPreview()
12-16 13:09:39.971: I/CameraActivity.onCreate()(439): mPreview.setCamera(mCamera)
12-16 13:09:40.622: I/ActivityManager(60): Displayed com.example.popup/.CameraActivity: +810ms