video播放后没办法自动全屏是怎么回事呢？

<video @ended="videoPause(item)" @play="videoPlay('video'+index)" @pause="videoPause(item)" :id="'video'+index"  style="width: 150upx;height: 150upx;margin-top: 20upx;" :src="item" v-if="item.indexOf('mp4')!=-1"></video>