[new feature] Picker: add loading prop (#619)

packages/picker/PickerColumn.vue

@@ -37,14 +37,11 @@ export default create({
     valueKey: String,
     className: String,
     itemHeight: Number,
+    visibleItemCount: Number,
     options: {
       type: Array,
       default: () => []
     },
-    visibleItemCount: {
-      type: Number,
-      default: 5
-    },
     defaultIndex: {
       type: Number,
       default: 0

packages/picker/index.vue

@@ -7,7 +7,10 @@
         <div class="van-picker__confirm" @click="emit('confirm')">{{ confirmButtonText || $t('confirm') }}</div>
       </slot>
     </div>
-    <div class="van-picker__columns" @touchmove.prevent>
+    <div v-if="loading" class="van-picker__loading">
+      <loading type="circular" />
+    </div>
+    <div class="van-picker__columns" :style="columnsStyle" @touchmove.prevent>
       <picker-column
         v-for="(item, index) in currentColumns"
         :key="index"
@@ -38,10 +41,14 @@ export default create({
 
   props: {
     title: String,
+    loading: Boolean,
     showToolbar: Boolean,
     confirmButtonText: String,
     cancelButtonText: String,
-    visibleItemCount: Number,
+    visibleItemCount: {
+      type: Number,
+      default: 5
+    },
     valueKey: {
       type: String,
       default: 'text'
@@ -78,6 +85,12 @@ export default create({
       return {
         height: this.itemHeight + 'px'
       };
+    },
+
+    columnsStyle() {
+      return {
+        height: this.itemHeight * this.visibleItemCount + 'px'
+      };
     }
   },