在Android相机界面上添加一个虚线圆圈

Question

我正在开发一个脸部识别应用程序。我需要在相机界面上显示一个小圆圈以放置人物的脸部，以便用户可以比拍摄照片更好地训练应用程序以不同的比例。 我跟着"This link"，但我不知道如何在相机界面上做到这一点。所以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？在此先感谢..

编辑-2013-02-14
确定该代码正在工作。但我又遇到了2个问题。

1. 我可以画圆。但它总是不在同一个位置。当屏幕尺寸改变时，它的位置总是在变化。我尝试过使用getWidht（）和getHeight（）方法，但是我无法在屏幕中心画圆。你对此有什么想法吗？

2. 根据你的回答，我必须以编程方式创建所有视图。所以现在我需要添加一个捕捉按钮到我的界面。你能解释一下你的答案吗？

Answer 1

编辑：编辑在中心绘制圆圈，并添加上表面视图捕获图像按钮

代码。

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> 

不要忘了添加权限：

<uses-permission android:name="android.permission.CAMERA" /> 
<uses-feature android:name="android.hardware.camera" /> 

新许可补充说：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />