Android 在按中点缩放 Canvas 后修复坐标

Question

我有自定义类从 View 扩展而来，我在其中绘制 Bitmap 并希望缩放并限制拖动它。我的任务是创建将在画廊中使用的 ImageView，以查看完整照片。现在我意识到缩放和拖动但是当我开始意识到它们的局限性时，注意到在 canvas.scale(mScale, mSñale, mid.x, mid.y) 图像位置发生变化但我的值 mX, mY 没有改变。为此，我开始使用我们的中点进行缩放，并手动更改 mX 和 mY。所以我在手动更改此值时遇到问题。

我的类(class):

public class ZoomImageView2 extends View {

private File imageFile;
private Bitmap bitmap;

private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;


private PointF start = new PointF();
private PointF mid = new PointF();
private float oldDist = 1f;
private float d = 0f;
private float newRot = 0f;
private float[] lastEvent = null;

private int mX = 0, mY = 0;
private float mScale = 1f;

private Rect clipBounds_canvas;

private Handler mainHadler;

public ZoomImageView2(Context context) {
    super(context);
    mainHadler = new Handler(Looper.getMainLooper());
}

public ZoomImageView2(Context context, AttributeSet attrs) {
    super(context, attrs);
    mainHadler = new Handler(Looper.getMainLooper());
}

public ZoomImageView2(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mainHadler = new Handler(Looper.getMainLooper());
}

@Override
protected void onDraw(Canvas canvas) {
    //super.onDraw(canvas);
    if (bitmap != null) {
        canvas.save();
        clipBounds_canvas = canvas.getClipBounds();
        Log.w("SCALING_ZOOMIMAGE2", mX + " " + mY + " " + mScale);
        canvas.scale(mScale, mScale);
        canvas.drawBitmap(bitmap, mX, mY, new Paint());
        canvas.restore();
    }
}

public void setImageFile(final File imageFile) {
    this.imageFile = imageFile;
    new Thread(new Runnable() {
        @Override
        public void run() {
            bitmap = BitmapHelper.getINSTANCE().getSampledBitmapFromFile(imageFile.getAbsolutePath(), getResources().getDisplayMetrics().widthPixels, getResources().getDisplayMetrics().widthPixels);
            new Handler(Looper.getMainLooper()).post(new Runnable() {
                @Override
                public void run() {
                    if (bitmap.getWidth() >= bitmap.getHeight()) {
                        mStableScale = (float) getResources().getDisplayMetrics().widthPixels / (float) bitmap.getWidth();
                    } else {
                        mStableScale = (float) getResources().getDisplayMetrics().heightPixels / (float) bitmap.getHeight();
                    }
                    mScale = mStableScale;
                    invalidate();
                }
            });
        }
    }).start();
}

int mOldX, mOldY;
float mOldScale = 1f;
float mStableScale;
float maxScale = 5f;


@Override
public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            start.set(event.getX(), event.getY());
            mode = DRAG;
            lastEvent = null;
            mOldX = mX;
            mOldY = mY;
            mOldScale = mScale;
            break;

        case MotionEvent.ACTION_POINTER_DOWN:

            oldDist = spacing(event);
            if (oldDist > 10f) {
                midPoint(mid, event);
                mode = ZOOM;
            }

            lastEvent = new float[4];
            lastEvent[0] = event.getX(0);
            lastEvent[1] = event.getX(1);
            lastEvent[2] = event.getY(0);
            lastEvent[3] = event.getY(1);
            break;

        case MotionEvent.ACTION_UP:
            if (mScale < mStableScale) {
                animateScaleTo(false);
            }
            if (mScale > maxScale) {
                animateScaleTo(true);
            }

        case MotionEvent.ACTION_POINTER_UP:

            mode = NONE;
            lastEvent = null;
            break;

        case MotionEvent.ACTION_MOVE:

            if (mode == DRAG) {
                mX = (int) ((event.getX() - start.x) / mScale + mOldX);
                mY = (int) ((event.getY() - start.y) / mScale + mOldY);

            } else if (mode == ZOOM) {
                float newDist = spacing(event);

                if (newDist > 10f) {
                    mScale = (newDist / oldDist) * mOldScale;
                    mX = (int)-(getResources().getDisplayMetrics().widthPixels/2 * (mScale -1) - mOldX*mScale);
                    mY = (int)-(getResources().getDisplayMetrics().heightPixels/2 * (mScale -1) - mOldY*mScale);
                    //TODO!
                }

                if (lastEvent != null && event.getPointerCount() == 3) {

                    //newRot = rotation(event);
                    //float r = newRot - d;
                    //float[] values = new float[9];
                    //matrix.getValues(values);
                    //float tx = values[2];
                    //float ty = values[5];
                    //float sx = values[0];
                    //float xc = (view.getWidth() / 2) * sx;
                    //float yc = (view.getHeight() / 2) * sx;
                    //matrix.postRotate(r, tx + xc, ty + yc);

                }
            }
            break;
    }
    invalidate();
    return true;
}

private void animateScaleTo(final boolean forMax) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                int waiting = 1;
                if (forMax) {
                    waiting = (int) (100 / ((mScale - maxScale) / 0.05));
                } else {
                    waiting = (int) (100 / ((mStableScale - mScale) / 0.05));
                }
                if (waiting == 0) waiting = 1;
                while (forMax ? mScale >= maxScale : mScale <= mStableScale) {
                    if (forMax) {
                        mScale -= 0.05;
                    } else {
                        mScale += 0.05;
                    }
                    mainHadler.post(new Runnable() {
                        @Override
                        public void run() {
                            invalidate();
                        }
                    });
                    Thread.sleep(waiting);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }).start();
}


private void animateTranslateX(final boolean forEnd) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                int waiting;
                if (forEnd) {
                    waiting = (int) (300f / (mX - (float) bitmap.getWidth() * mScale));
                } else {
                    waiting = (int) (300f / (float) (mX));
                }
                if (waiting == 0) waiting = 1;
                while (forEnd ? mX > ((float) bitmap.getWidth() * mScale) : mX > 0) {
                    mX -= 5;
                    mainHadler.post(new Runnable() {
                        @Override
                        public void run() {
                            invalidate();
                        }
                    });
                    Thread.sleep(waiting);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }).start();
}

private void animateTranslateY(final boolean forEnd) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                int waiting;
                if (forEnd) {
                    waiting = (int) (300 / (mY - (float) bitmap.getHeight() * mScale));
                } else {
                    waiting = (int) (300 / (float) (mY));
                }
                if (waiting == 0) waiting = 1;
                while (forEnd ? mY > ((float) bitmap.getHeight() * mScale) : mY > 0) {
                    mY -= 5;
                    mainHadler.post(new Runnable() {
                        @Override
                        public void run() {
                            invalidate();
                        }
                    });
                    Thread.sleep(waiting);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }).start();
}


private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return (float) Math.sqrt(x * x + y * y);
}

private void midPoint(PointF point, MotionEvent event) {
    point.set(getResources().getDisplayMetrics().widthPixels / 2, getResources().getDisplayMetrics().heightPixels / 2);
}

我有问题:

if (newDist > 10f) {
   mScale = (newDist / oldDist) * mOldScale;
    mX = (int)-(getResources().getDisplayMetrics().widthPixels/2 * (mScale -1) - mOldX*mScale);
     mY = (int)-(getResources().getDisplayMetrics().heightPixels/2 * (mScale -1) - mOldY*mScale);
      //TODO!
   }

这里我必须设置值。现在错了。

我花了很多时间来解决这个问题。非常感谢您的帮助!对不起英语不好

Answer 1

根据评论讨论，部分解决方案如下:修改如下:

mX = (int)-(getResources().getDisplayMetrics().widthPixels/2 * (mScale -1) - mOldX*mScale);
mY = (int)-(getResources().getDisplayMetrics().heightPixels/2 * (mScale -1) - mOldY*mScale);

到:

mX = (int)-(getResources().getDisplayMetrics().widthPixels/2  - mOldX*mScale);
mY = (int)-(getResources().getDisplayMetrics().heightPixels/2 - mOldY*mScale);

删除不必要的额外乘法步骤，这会导致将图像缩放到太大的尺寸。