问在Android上将内容从file:///移动到内容:// (xapk/obb)后，Canvas.toDataURL()会导致soild黑色

EN

<meta http-equiv="Content-Security-Policy" 
    content="default-src 'self' 'unsafe-inline' 'unsafe-eval' 
      data: gap: content: cdvfile: ....google-URLS...; 
    img-src data: gap: file: content: cdvfile: ....google-URLS...; 
    style-src 'self' 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; 
    connect-src 'self' ....google-URLS..." />

<allow-navigation href="http://*/*" />
<access origin="*://*" />
<allow-intent href="content://*" />
<allow-intent href="content://*/*/*/*" />

html2canvas($("#layerA"), {onrendered:function(stageCanvas){
    var stageCtx = stageCanvas.getContext('2d');
    var tmpCanvas = document.createElement('canvas');
        tmpCanvas.width = stageCanvas.width;
        tmpCanvas.height = stageCanvas.height;
    var tmpCtx = stageCanvas.getContext('2d');
    var imgObj = new Image();
    imgObj.onload = function(){
        var destX = 0;
        var destY = 0;

        tmpCtx.drawImage(imgObj,
            sourceX, sourceY, sourceWidth, sourceHeight,
            0, 0, destWidth, destHeight);
        var data = tmpCtx.getImageData(sourceX, sourceY, sourceWidth, sourceHeight);

        stageCtx.clearRect(0, 0, stageCanvas.width, stageCanvas.height); //clear originalCanvas
        stageCanvas.width = sourceWidth;
        stageCanvas.height = sourceHeight;

        tmpCtx.putImageData(data,0,0);
        var datauri = null;
        try {
            datauri = stageCanvas.toDataURL('image/png');
        } catch(err) {
            alert(err);
        }

        // store the image and update UI
        $('#fav-img-'+maxFavUsed.toString()).attr('src', datauri);
        $("#fav-del-"+maxFavUsed.toString()).show();
        $('#fav-big').attr('src', datauri);

        if(typeof(Storage) !== "undefined") {
            localStorage.setItem('fav-img-'+maxFavUsed.toString(), datauri);
        }

        showFav(maxFavUsed);
        showUI();

        //clear memory!!!
        stageCtx.clearRect(0, 0,  sourceWidth, sourceHeight);//clear originalCanvas
        tmpCtx.clearRect(0, 0, sourceWidth, sourceHeight);//clear tmpCanvas
        data = null;
        datauri = null;
        tmpCanvas = null;
        stageCanvas = null;
        imgObj = null;
    };
    try {
        imgObj.src = tmpCanvas.toDataURL("image/png");
    } catch(err) {
        alert(err);
    }
}, width:canvasW, height:canvasH } );