Question

我有一个带有多点触控的imageView，大致基于this tutorial。其中一位评论者将一种将图像拖动限制在图像边界的半脏方法放在一起，这样图像边缘就不会被拖到边缘之外。这种方法有效，但不完全。它只限制两条边的拖拽。

有没有人知道用于限制图像拖动的不那么混乱和实际功能的方法？

这是一个非常重要的Android应用程序开发概念，但没有得到充分解决....

我在考虑以下想法：

1）当缩放= 1.0F（即最小缩放）时，setScaleType（scaleType.fitXY），并且仅在缩放＆gt;时启用拖动。 1.0F

2）当缩放＆gt; 1.0f，setScaleType（scaleType.MATRIX），然后你确定图像边界和屏幕尺寸，并且在某种程度上对我来说太聪明了，使用if语句只允许在图像边缘不在屏幕上时拖动。我不知道如何宣布，是的。

无论如何，为了完整性，这里是该链接的限制泛码。这似乎是stackoverflow上最受欢迎的建议，但我认为我们可以做得更好：

// limit pan
matrix.getValues(matrixValues);
float currentY = matrixValues[Matrix.MTRANS_Y];
float currentX = matrixValues[Matrix.MTRANS_X];
float currentScale = matrixValues[Matrix.MSCALE_X];
float currentHeight = height * currentScale;
float currentWidth = width * currentScale;
float dx = event.getX() - start.x;
float dy = event.getY() - start.y;
float newX = currentX+dx;
float newY = currentY+dy; 

RectF drawingRect = new RectF(newX, newY, newX+currentWidth, newY+currentHeight);
float diffUp = Math.min(viewRect.bottom-drawingRect.bottom, viewRect.top-drawingRect.top);
float diffDown = Math.max(viewRect.bottom-drawingRect.bottom, viewRect.top-drawingRect.top);
float diffLeft = Math.min(viewRect.left-drawingRect.left, viewRect.right-drawingRect.right);
float diffRight = Math.max(viewRect.left-drawingRect.left, viewRect.right-drawingRect.right);
if(diffUp > 0 ){
dy +=diffUp; 
}
if(diffDown < 0){
dy +=diffDown;
} 
if( diffLeft> 0){ 
dx += diffLeft;
}
if(diffRight < 0){
dx += diffRight;
}
matrix.postTranslate(dx, dy);

Answer 1

private void limitDrag(Matrix m, ImageView view) {


    float[] values = new float[9];
    m.getValues(values);
    float transX = values[Matrix.MTRANS_X];
    float transY = values[Matrix.MTRANS_Y];
    float scaleX = values[Matrix.MSCALE_X];
    float scaleY = values[Matrix.MSCALE_Y];

    Rect bounds = view.getDrawable().getBounds();
    int viewWidth = getResources().getDisplayMetrics().widthPixels;
    int viewHeight = getResources().getDisplayMetrics().heightPixels;



    if(viewHeight<=480)
    {

        _y_up=0;
    }
    if(viewHeight>480&&viewHeight<980)
    {

        _y_up=140;
    }

    int width = bounds.right - bounds.left;
    int height = bounds.bottom - bounds.top;
    int __width=width;
    int __height=height;
    width = viewWidth / 2;
    height = viewHeight / 2;


    //height = 200 ;
    float minX = (-width) ;//* scaleX;
    float minY = (-height) ;//* scaleY;


    if ((transX) > (viewWidth)) {

        //_x_left

        transX = viewWidth;
    } else if (transX < minX) {


        transX = minX;
    }


    if ((-transX) > (viewWidth)) {
             // _x_right
        transX = -(viewWidth);
    } else if (-transX < minX) {

        transX = -(minX+30);
    }



    if ((transY) > (viewHeight)) {
    //  _y_up
        transY =( viewHeight);


    } else if (transY < minY) {

        transY = (minY+_y_up);
    }

    if ((-transY) > (viewHeight)) {
    //  _y_down
        transY = -(viewHeight);

    } else if (-transY < minY) {

        transY = -(minY+170);
    }

    values[Matrix.MTRANS_X] = transX;
    values[Matrix.MTRANS_Y] = transY;
    m.setValues(values);
}

在view.setImageMatrix（matrix）上面调用它;

Answer 2

我意识到现在已经很老了，但试试吧。 imageWidth和imageHeight是未缩放的值。

private void limitDrag(Matrix m, ImageView view, int imageWidth, int imageHeight) {
    float[] values = new float[9];
    m.getValues(values);
    float[] orig = new float[] {0,0, imageWidth, imageHeight};
    float[] trans = new float[4];
    m.mapPoints(trans, orig);

    float transLeft = trans[0];
    float transTop = trans[1];
    float transRight = trans[2];
    float transBottom = trans[3];
    float transWidth = transRight - transLeft;
    float transHeight = transBottom - transTop;

    float xOffset = 0;
    if (transWidth > view.getWidth()) {
        if (transLeft > 0) {
            xOffset = -transLeft;
        } else if (transRight < view.getWidth()) {
            xOffset = view.getWidth() - transRight;
        }
    } else {
        if (transLeft < 0) {
            xOffset = -transLeft;
        } else if (transRight > view.getWidth()) {
            xOffset = -(transRight - view.getWidth());
        }
    }

    float yOffset = 0;
    if (transHeight > view.getHeight()) {
        if (transTop > 0) {
            yOffset = -transTop;
        } else if (transBottom < view.getHeight()) {
            yOffset = view.getHeight() - transBottom;
        }
    } else {
        if (transTop < 0) {
            yOffset = -transTop;
        } else if (transBottom > view.getHeight()) {
            yOffset = -(transBottom - view.getHeight());
        }
    }

    float transX = values[Matrix.MTRANS_X];
    float transY = values[Matrix.MTRANS_Y];

    values[Matrix.MTRANS_X] = transX + xOffset;
    values[Matrix.MTRANS_Y] = transY + yOffset;
    m.setValues(values);
}

如何在Android imageView中限制图像平移边界

2 个答案: