我正在开发一个人脸识别应用程序。我需要在我的相机界面上显示一个小虚线圆圈来放置人的脸，以便用户可以训练应用程序而不是使用不同比例的照片。我关注了“此链接”，但我不知道如何在相机界面上进行操作。那么任何人都可以上传一个示例项目或给我一些东西来继续我的项目吗？提前致谢..
Edit-2013-02-14
好的，代码正在运行。但我又遇到了两个问题。
我可以画圆。但它总是不在同一个位置。当屏幕尺寸发生变化时，它的位置总是在变化。我尝试使用 getWidht() 和 getHeight() 方法，但无法在屏幕中心绘制圆圈。您对此有任何想法吗？
根据您的回答，我必须以编程方式创建所有视图。所以现在我需要在我的界面中添加一个捕获按钮。你能用你的答案解释一下吗？
编辑 ：
编辑代码以在中心绘制圆圈并在表面视图上添加捕获图像按钮。
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.DashPathEffect;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Point;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Display;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.Window;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;
public class TestActivity extends Activity {
/** Called when the activity is first created. */
Camera mCamera = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.camera_layout);
mCamera = getCameraInstance();
Preview mPreview = new Preview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int screenCenterX = (size.x /2);
int screenCenterY = (size.y/2) ;
DrawOnTop mDraw = new DrawOnTop(this,screenCenterX,screenCenterY);
addContentView(mDraw, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
//Adding listener
Button captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
mCamera.takePicture(null, null, mPicture);
}
});
}
/**
* Helper method to access the camera returns null if
* it cannot get the camera or does not exist
* @return
*/
private Camera getCameraInstance() {
Camera camera = null;
try {
camera = Camera.open();
} catch (Exception e) {
// cannot get camera or does not exist
}
return camera;
}
PictureCallback mPicture = new PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
File pictureFile = getOutputMediaFile();
if (pictureFile == null){
return;
}
try {
FileOutputStream fos = new FileOutputStream(pictureFile);
fos.write(data);
fos.close();
Toast.makeText(TestActivity.this, "Photo saved to folder \"Pictures\\MyCameraApp\"", Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
}
};
private static File getOutputMediaFile(){
File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES), "MyCameraApp");
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;
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"IMG_"+ timeStamp + ".jpg");
return mediaFile;
}
}
class DrawOnTop extends View {
int screenCenterX = 0;
int screenCenterY = 0;
final int radius = 50;
public DrawOnTop(Context context, int screenCenterX, int screenCenterY) {
super(context);
this.screenCenterX = screenCenterX;
this.screenCenterY = screenCenterY;
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
Paint p = new Paint();
p.setColor(Color.RED);
DashPathEffect dashPath = new DashPathEffect(new float[]{5,5}, (float)1.0);
p.setPathEffect(dashPath);
p.setStyle(Style.STROKE);
canvas.drawCircle(screenCenterX, screenCenterY, radius, p);
invalidate();
super.onDraw(canvas);
}
}
//----------------------------------------------------------------------
class Preview extends SurfaceView implements SurfaceHolder.Callback {
SurfaceHolder mHolder;
Camera mCamera;
Preview(Context context, Camera camera) {
super(context);
// Install a SurfaceHolder.Callback so we get notified when
this.mCamera = camera;
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
//this is a deprecated method, is not required after 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell
// to draw.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the
// Because the CameraDevice object is not a shared resource,
// important to release it when the activity is paused.
mCamera.stopPreview();
mCamera.release();
mCamera = null;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// Now that the size is known, set up the camera parameters
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
List<Camera.Size> previewSizes = parameters.getSupportedPreviewSizes();
// You need to choose the most appropriate previewSize for your app
Camera.Size previewSize = previewSizes.get(0);
parameters.setPreviewSize(previewSize.width, previewSize.height);
mCamera.setParameters(parameters);
mCamera.startPreview();
}
}
camera_layout.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<FrameLayout
android:id="@+id/camera_preview"
android:layout_width="fill_parent"
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>
不要忘记添加权限：
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
新增权限：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />