如何在不同设备上缩放自定义视图

Question

我有以下代码用于在用户屏幕上显示图像，并在脸部周围绘制一个矩形：

public class AndroidFaceDetector extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // setContentView(R.layout.main);
        setContentView(new myView(this));
    }

    private class myView extends View {

        private int imageWidth, imageHeight;
        private int numberOfFace = 5;
        private FaceDetector myFaceDetect;
        private FaceDetector.Face[] myFace;
        float myEyesDistance;
        int numberOfFaceDetected;

        Bitmap myBitmap;

        public myView(Context context) {
            super(context);
            // TODO Auto-generated constructor stub

            BitmapFactory.Options BitmapFactoryOptionsbfo = new BitmapFactory.Options();
            BitmapFactoryOptionsbfo.inPreferredConfig = Bitmap.Config.RGB_565;

            myBitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getAbsolutePath()+"/face.jpg", BitmapFactoryOptionsbfo);

            imageWidth = myBitmap.getWidth();
            imageHeight = myBitmap.getHeight();
            myFace = new FaceDetector.Face[numberOfFace];
            myFaceDetect = new FaceDetector(imageWidth, imageHeight,
                    numberOfFace);
            numberOfFaceDetected = myFaceDetect.findFaces(myBitmap, myFace);

        }

        @Override
        protected void onDraw(Canvas canvas) {
            // TODO Auto-generated method stub

            canvas.drawBitmap(myBitmap, 0, 0, null);

            Paint myPaint = new Paint();
            myPaint.setColor(Color.GREEN);
            myPaint.setStyle(Paint.Style.STROKE);
            myPaint.setStrokeWidth(3);

            for (int i = 0; i < numberOfFaceDetected; i++) {
                Face face = myFace[i];
                PointF myMidPoint = new PointF();
                face.getMidPoint(myMidPoint);
                myEyesDistance = face.eyesDistance();
                canvas.drawRect((int) (myMidPoint.x - myEyesDistance),
                        (int) (myMidPoint.y - myEyesDistance),
                        (int) (myMidPoint.x + myEyesDistance),
                        (int) (myMidPoint.y + myEyesDistance), myPaint);
            }
        }
    }
}

它在我的索尼爱立信x8上显示以下内容：

这是索尼xperia上的显示器：

有谁知道如何缩放图像以使其适合任何设备的屏幕？ 谢谢 ！

更新我已经尝试了以下方法，但是不起作用：

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    DisplayMetrics metrics=new DisplayMetrics();

    getWindowManager().getDefaultDisplay().getMetrics(metrics);
    height=metrics.heightPixels/metrics.xdpi;
    width=metrics.widthPixels/metrics.ydpi;
    // setContentView(R.layout.main);
    setContentView(new myView(this));
}

@Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub

        canvas.drawBitmap(myBitmap, 0, 0, null);

        Paint myPaint = new Paint();
        myPaint.setColor(Color.GREEN);
        myPaint.setStyle(Paint.Style.STROKE);
        myPaint.setStrokeWidth(3);

        for (int i = 0; i < numberOfFaceDetected; i++) {
            Face face = myFace[i];
            PointF myMidPoint = new PointF();
            face.getMidPoint(myMidPoint);
            myEyesDistance = face.eyesDistance();
            canvas.drawRect((int) (myMidPoint.x - myEyesDistance),
                    (int) (myMidPoint.y - myEyesDistance),
                    (int) (myMidPoint.x + myEyesDistance),
                    (int) (myMidPoint.y + myEyesDistance), myPaint);
        }


        canvas.scale(width, height);
    }
}

Answer 1

缩放画布，然后再绘制。

http://developer.android.com/reference/android/graphics/Canvas.html#scale(float,%20float）

编辑：或如Gabe所述生成新的位图。 在支持使用画布方法进行硬件加速缩放的现代设备上，运行时的成本非常低廉，但是将较大的位图保留在内存中将比保留较小的版本消耗更多的内存。 如果由于某些其他原因已经需要将完整分辨率版本保留在内存中，则在较新的设备上绘制时缩放它会更有效。 如果您再也不需要全分辨率版本，则在源图像较大的情况下，创建缩放的位图并丢弃原始图像将占用较少的内存。

Answer 2

DisplayMetrics metrics=new DisplayMetrics();

getWindowManager().getDefaultDisplay().getMetrics(metrics);
float height=metrics.heightPixels/metrics.xdpi;
float width=metrics.widthPixels/metrics.ydpi;
canvas.drawRect(0, 0, width, height, paint);

Answer 3

绘制位图时，请使用Bitmap.createScaledBitmap将位图缩放到视图的宽度和高度。 然后它将适合。 确保使位图上的所有点保持一致-使用原始位图或缩放位图中的位置，不要混合匹配，否则结果会很奇怪。