Question

我有这个代码来检测图像中的面部并在其周围绘制一个红色矩形，但我有一个运行时异常可以任何人修复它请我不知道该怎么做，我尝试了很多面部检测代码但是也没有工作

{
  public class MainActivity extends AppCompatActivity
   {
 Button btn = (Button) findViewById(R.id.button);
 ImageView myImageView = (ImageView) findViewById(R.id.imgview);

@Override
protected void onCreate(Bundle savedInstanceState)

{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);




    btn.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inMutable=true;
            Bitmap myBitmap = BitmapFactory.decodeResource(
                    getApplicationContext().getResources(),
                    R.drawable.test1,
                    options);

            Paint myRectPaint = new Paint();
            myRectPaint.setStrokeWidth(5);
            myRectPaint.setColor(Color.RED);
            myRectPaint.setStyle(Paint.Style.STROKE);

            Bitmap tempBitmap = Bitmap.createBitmap(myBitmap.getWidth(), myBitmap.getHeight(), Bitmap.Config.RGB_565);
            Canvas tempCanvas = new Canvas(tempBitmap);
            tempCanvas.drawBitmap(myBitmap, 0, 0, null);

            FaceDetector faceDetector = new
                    FaceDetector.Builder(getApplicationContext()).setTrackingEnabled(false)
                    .build();
            if(!faceDetector.isOperational()){
                new AlertDialog.Builder(v.getContext()).setMessage("Could not set up the face detector!").show();
                return;
            }
            Frame frame = new Frame.Builder().setBitmap(myBitmap).build();
            SparseArray<Face> faces = faceDetector.detect(frame);

            for(int i=0; i<faces.size(); i++) {
                Face thisFace = faces.valueAt(i);
                float x1 = thisFace.getPosition().x;
                float y1 = thisFace.getPosition().y;
                float x2 = x1 + thisFace.getWidth();
                float y2 = y1 + thisFace.getHeight();
                tempCanvas.drawRoundRect(new RectF(x1, y1, x2, y2), 2, 2, myRectPaint);
            }
            myImageView.setImageDrawable(new BitmapDrawable(getResources(),tempBitmap));

        }
    });


}

}

       here is the exception
   java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.hadeel.hadd/com.example.hadeel.hadd.MainActivity}: java.lang.NullPointerException

Answer 1

Button btn = (Button) findViewById(R.id.button); ImageView myImageView = (ImageView) findViewById(R.id.imgview);

你不应该对包含如上所述的android小部件的引用的变量进行初始化，因为活动的布局不会膨胀（方法onCreate将在创建此对象后运行）。您应该在方法findViewById

之后立即调用setContentView

我想在android中检测来自图像的脸

1 个答案: