如何在 ImageView 中将 OnTouchEvent 坐标转换/缩放到 Android 中的位图画布上

Question

我正在尝试将 OnTouchListener 设置为 ImageView，在该 ImageView 上进行大量自定义绘图。问题：我的 X 值已关闭，并且我经常将触摸记录到左侧太远。虽然 Y 值没问题，但我的算法的问题在哪里？

我使用的画布是 400 像素宽和 300 像素高。我没有对 ImageView 应用任何特殊的缩放，我只是依靠标准的 ImageView 行为，它会自行缩放以适应屏幕。小绿点应该出现在用户触摸屏幕的位置，但它们在我的 Nexus 5 上离左侧太远了。我的数学对于 Y 值是正确的，但在 X 值上是错误的，这是怎么回事？我要求 x 比例和 y 比例，所以即使 ImageView 正在改变纵横比，我也应该考虑到这一点，对吧？

public class FullscreenActivity extends AppCompatActivity {

    private ImageView drawingImageView;
    private Canvas canvas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        int mUIFlag = View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                | View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                | View.SYSTEM_UI_FLAG_LOW_PROFILE
                | View.SYSTEM_UI_FLAG_FULLSCREEN
                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
        getWindow().getDecorView().setSystemUiVisibility(mUIFlag);
        setContentView(R.layout.activity_fullscreen);

        drawingImageView = (ImageView) this.findViewById(R.id.game_map_fixed_id);
        Bitmap bitmap = Bitmap.createBitmap(Map.width, Map.height, Bitmap.Config.ARGB_8888);
        canvas = new Canvas(bitmap);
        drawingImageView.setImageBitmap(bitmap);
        drawingImageView.setOnTouchListener(mapOnTouchListener);
    }

    View.OnTouchListener mapOnTouchListener = new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {

            float[] bounds = new float[6];
            bounds = getBitmapPositionInsideImageView(drawingImageView);

            float x = event.getX() / bounds[4] - bounds[0];
            float y = event.getY() / bounds[5] - bounds[1];

            Paint paint = new Paint();
            paint.setStyle(Paint.Style.FILL_AND_STROKE);
            paint.setColor(Color.GREEN);
            canvas.drawCircle(x, y, 1, paint);
            return false;
        }
    };

    public static float[] getBitmapPositionInsideImageView(ImageView imageView) {
        float[] rect = new float[6];

        if (imageView == null || imageView.getDrawable() == null)
            return rect;

        // Get image dimensions
        // Get image matrix values and place them in an array
        float[] f = new float[9];
        imageView.getImageMatrix().getValues(f);

        // Extract the scale values using the constants (if aspect ratio maintained, scaleX == scaleY)
        final float scaleX = f[Matrix.MSCALE_X];
        final float scaleY = f[Matrix.MSCALE_Y];

        rect[4] = scaleX;
        rect[5] = scaleY;

        // Get the drawable (could also get the bitmap behind the drawable and getWidth/getHeight)
        final Drawable d = imageView.getDrawable();
        final int origW = d.getIntrinsicWidth();
        final int origH = d.getIntrinsicHeight();

        // Calculate the actual dimensions
        final int actW = Math.round(origW * scaleX);
        final int actH = Math.round(origH * scaleY);

        rect[2] = actW;
        rect[3] = actH;

        // Get image position
        // We assume that the image is centered into ImageView
        int imgViewW = imageView.getWidth();
        int imgViewH = imageView.getHeight();

        float left = (imgViewW - actW)/2;
        float top = (imgViewH - actH)/2;

        rect[0] = left;
        rect[1] = top;

        return rect;
    }
}

Answer 1

错误是在从getBitmapPositionInsideImageView接收到信息后计算点数。

        float x = event.getX() / bounds[4] - bounds[0];
        float y = event.getY() / bounds[5] - bounds[1];

应该是

        float x = (event.getX() - bounds[0]) / bounds[4];
        float y = (event.getY() - bounds[1]) / bounds[5];

我在垂直轴上没有任何问题的原因是图像在顶部或底部没有收到任何填充，这意味着 bounds[5] 始终为零，从而隐藏了该等式中的错误。