我正在尝试使用Hammer.js使用我的PDF.js执行压缩缩放，但是，尽管进行了很多尝试，但它无法正常工作。我在移动设备上调试代码时没有出现任何错误，但我仍然无法进行放大和缩小。如果您知道出了什么问题请帮忙，我的代码如下所示：
HTML：
<body>
<script type="text/javascript" src="reportviewer/hammer.js"></script>
<script>
var MIN_SCALE = 1; // 1=scaling when first loaded
var MAX_SCALE = 64;
// HammerJS fires "pinch" and "pan" events that are cumulative in nature and not
// deltas. Therefore, we need to store the "last" values of scale, x and y so that we can
// adjust the UI accordingly. It isn't until the "pinchend" and "panend" events are received
// that we can set the "last" values.
// Our "raw" coordinates are not scaled. This allows us to only have to modify our stored
// coordinates when the UI is updated. It also simplifies our calculations as these
// coordinates are without respect to the current scale.
var imgWidth = null;
var imgHeight = null;
var viewportWidth = null;
var viewportHeight = null;
var scale = null;
var lastScale = null;
var container = null;
var img = null;
var x = 0;
var lastX = 0;
var y = 0;
var lastY = 0;
var pinchCenter = null;
// We need to disable the following event handlers so that the browser doesn't try to
// automatically handle our image drag gestures.
var disableImgEventHandlers = function () {
var events = ['onclick', 'onmousedown', 'onmousemove', 'onmouseout', 'onmouseover',
'onmouseup', 'ondblclick', 'onfocus', 'onblur'];
events.forEach(function (event) {
img[event] = function () {
return false;
};
});
};
// Traverse the DOM to calculate the absolute position of an element
var absolutePosition = function (el) {
var x = 0,
y = 0;
while (el !== null) {
x += el.offsetLeft;
y += el.offsetTop;
el = el.offsetParent;
}
return { x: x, y: y };
};
var restrictScale = function (scale) {
if (scale < MIN_SCALE) {
scale = MIN_SCALE;
} else if (scale > MAX_SCALE) {
scale = MAX_SCALE;
}
return scale;
};
var restrictRawPos = function (pos, viewportDim, imgDim) {
if (pos < viewportDim / scale - imgDim) { // too far left/up?
pos = viewportDim / scale - imgDim;
} else if (pos > 0) { // too far right/down?
pos = 0;
}
return pos;
};
var updateLastPos = function (deltaX, deltaY) {
lastX = x;
lastY = y;
};
var translate = function (deltaX, deltaY) {
// We restrict to the min of the viewport width/height or current width/height as the
// current width/height may be smaller than the viewport width/height
var newX = restrictRawPos(lastX + deltaX / scale,
Math.min(viewportWidth, curWidth), imgWidth);
x = newX;
img.style.marginLeft = Math.ceil(newX * scale) + 'px';
var newY = restrictRawPos(lastY + deltaY / scale,
Math.min(viewportHeight, curHeight), imgHeight);
y = newY;
img.style.marginTop = Math.ceil(newY * scale) + 'px';
};
var zoom = function (scaleBy) {
scale = restrictScale(lastScale * scaleBy);
curWidth = imgWidth * scale;
curHeight = imgHeight * scale;
img.style.width = Math.ceil(curWidth) + 'px';
img.style.height = Math.ceil(curHeight) + 'px';
// Adjust margins to make sure that we aren't out of bounds
translate(0, 0);
};
var rawCenter = function (e) {
var pos = absolutePosition(container);
// We need to account for the scroll position
var scrollLeft = window.pageXOffset ? window.pageXOffset : document.body.scrollLeft;
var scrollTop = window.pageYOffset ? window.pageYOffset : document.body.scrollTop;
var zoomX = -x + (e.center.x - pos.x + scrollLeft) / scale;
var zoomY = -y + (e.center.y - pos.y + scrollTop) / scale;
return { x: zoomX, y: zoomY };
};
var updateLastScale = function () {
lastScale = scale;
};
var zoomAround = function (scaleBy, rawZoomX, rawZoomY, doNotUpdateLast) {
// Zoom
zoom(scaleBy);
// New raw center of viewport
var rawCenterX = -x + Math.min(viewportWidth, curWidth) / 2 / scale;
var rawCenterY = -y + Math.min(viewportHeight, curHeight) / 2 / scale;
// Delta
var deltaX = (rawCenterX - rawZoomX) * scale;
var deltaY = (rawCenterY - rawZoomY) * scale;
// Translate back to zoom center
translate(deltaX, deltaY);
if (!doNotUpdateLast) {
updateLastScale();
updateLastPos();
}
};
var zoomCenter = function (scaleBy) {
// Center of viewport
var zoomX = -x + Math.min(viewportWidth, curWidth) / 2 / scale;
var zoomY = -y + Math.min(viewportHeight, curHeight) / 2 / scale;
zoomAround(scaleBy, zoomX, zoomY);
};
var zoomIn = function () {
zoomCenter(2);
};
var zoomOut = function () {
zoomCenter(1 / 2);
};
var onLoad = function () {
img = document.getElementById('pinchzoom');
container = img.parentElement;
disableImgEventHandlers();
imgWidth = img.width;
imgHeight = img.height;
viewportWidth = img.parentElement.offsetWidth;
scale = viewportWidth / imgWidth;
lastScale = scale;
viewportHeight = img.parentElement.offsetHeight;
curWidth = imgWidth * scale;
curHeight = imgHeight * scale;
var hammer = new Hammer(container, {
domEvents: true
});
hammer.get('pinch').set({
enable: true
});
hammer.on('pan', function (e) {
translate(e.deltaX, e.deltaY);
});
hammer.on('panend', function (e) {
updateLastPos();
});
hammer.on('pinch', function (e) {
// We only calculate the pinch center on the first pinch event as we want the center to
// stay consistent during the entire pinch
if (pinchCenter === null) {
pinchCenter = rawCenter(e);
var offsetX = pinchCenter.x * scale - (-x * scale + Math.min(viewportWidth, curWidth) / 2);
var offsetY = pinchCenter.y * scale - (-y * scale + Math.min(viewportHeight, curHeight) / 2);
pinchCenterOffset = { x: offsetX, y: offsetY };
}
// When the user pinch zooms, she/he expects the pinch center to remain in the same
// relative location of the screen. To achieve this, the raw zoom center is calculated by
// first storing the pinch center and the scaled offset to the current center of the
// image. The new scale is then used to calculate the zoom center. This has the effect of
// actually translating the zoom center on each pinch zoom event.
var newScale = restrictScale(scale * e.scale);
var zoomX = pinchCenter.x * newScale - pinchCenterOffset.x;
var zoomY = pinchCenter.y * newScale - pinchCenterOffset.y;
var zoomCenter = { x: zoomX / newScale, y: zoomY / newScale };
zoomAround(e.scale, zoomCenter.x, zoomCenter.y, true);
});
hammer.on('pinchend', function (e) {
updateLastScale();
updateLastPos();
pinchCenter = null;
});
hammer.on('doubletap', function (e) {
var c = rawCenter(e);
zoomAround(2, c.x, c.y);
});
};
</script>
</body>
视图：
<div data-options="dxView : { name: 'myViewer', title: 'My Viewer', disableCache: true } ">
<div data-options="dxContent : { targetPlaceholder: 'content' } " class="dx-content-background">
<div>
<iframe onload="onLoad()" data-bind="attr: { src: EmbedPDFLink }" class="viewReport"/>
</div>
</div>
不是对于hammer.js ...但你可以使用（不准备生产）SVG后端将东西渲染到DOM中，这样你就不需要自己处理重画画布了。基于https://github.com/mozilla/pdf.js/blob/master/examples/components/pageviewer.html：
var url = "https://cdn.mozilla.net/pdfjs/tracemonkey.pdf";
var PAGE_TO_VIEW = 1;
var SCALE = 1.0;
var container = document.getElementById('container');
// Load document
PDFJS.getDocument(url).then(function (doc) {
return doc.getPage(PAGE_TO_VIEW).then(function (pdfPage) {
// Add div with page view.
var pdfPageView = new PDFJS.PDFPageView({
container: container,
renderer: 'svg',
id: PAGE_TO_VIEW,
scale: SCALE,
defaultViewport: pdfPage.getViewport(SCALE),
// We can enable text/annotations layers, if needed
textLayerFactory: new PDFJS.DefaultTextLayerFactory(),
annotationLayerFactory: new PDFJS.DefaultAnnotationLayerFactory()
});
// Associates the actual page with the view, and drawing it
pdfPageView.setPdfPage(pdfPage);
return pdfPageView.draw();
});
});<link href="https://npmcdn.com/pdfjs-dist/web/pdf_viewer.css" rel="stylesheet"/>
<script src="https://npmcdn.com/pdfjs-dist/web/compatibility.js"></script>
<script src="https://npmcdn.com/pdfjs-dist/build/pdf.js"></script>
<script src="https://npmcdn.com/pdfjs-dist/web/pdf_viewer.js"></script>
<div id="container" class="pdfViewer singlePageView"></div>