如何在Android imageView中限制图像平移边界

Question

我有一个带有多点触控的imageView,大致基于本教程.其中一位评论者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动.

有没有人知道一个不那么混乱和实际功能的方法来限制图像拖动？

这是Android应用程序开发的一个非常重要的概念,没有得到充分解决....

我在考虑以下想法:

1)当zoom = 1.0F(即最小缩放)时setScaleType(scaleType.fitXY),并且只有在zoom> 1.0f时才启用拖动

2)当缩放> 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语句你只允许在图像边缘没有打开时拖动屏幕.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;