OpenLayers 3 实现划线，画点

//划线    
    this.drawLine = function (type) {
        //清除双击放大效果
        this.map.getInteractions().item(1).setActive(false);
        var draw = new ol.interaction.Draw({
            source: _vector.getSource(),
            type: (type == 'point' ? 'Point' : 'LineString'),
            style: new ol.style.Style({
                fill: new ol.style.Fill({
                    color: 'rgba(255, 255, 255, 0.2)'
                }),
                //划线的时候的图样
                stroke: new ol.style.Stroke({
                    color: 'rgba(0, 0, 0, 0.5)',
                    lineDash: [10, 10],
                     2
                }),
                image: new ol.style.Circle({
                    radius: 5,
                    stroke: new ol.style.Stroke({
                        color: 'rgba(0, 0, 0, 0.7)'
                    }),
                    fill: new ol.style.Fill({
                        color: 'rgba(255, 255, 255, 0.2)'
                    })
                })
            })
        });
        this.map.addInteraction(draw);
        //画好线的操作
        draw.on('drawend', function (evt) {
            this.map.removeInteraction(draw);            
        },this)

        
    }