docs(Picker): update document

src/picker/README.md

@@ -159,7 +159,7 @@ export default {
 };
 ```
 
-### Multi columns
+### Set Column Values
 
 ```html
 <van-picker :columns="columns" @change="onChange" />
@@ -175,15 +175,8 @@ export default {
   data() {
     return {
       columns: [
-        {
+        { values: Object.keys(states) },
-          values: Object.keys(states),
+        { values: states.Group1 }
-          className: 'column1'
-        },
-        {
-          values: states.Group1,
-          className: 'column2',
-          defaultIndex: 2
-        }
       ]
     };
   },
@@ -200,7 +193,24 @@ export default {
 When Picker columns data is acquired asynchronously, use `loading` prop to show loading prompt
 
 ```html
-<van-picker :columns="columns" loading />
+<van-picker :columns="columns" :loading="loading" />
+```
+
+```js
+export default {
+  data() {
+    return {
+      columns: [],
+      loading: true
+    };
+  },
+  created() {
+    setTimeout(() => {
+      this.loading = false;
+      this.columns = ['Option'];
+    }, 1000);
+  }
+};
 ```
 
 ### With Popup

src/picker/README.zh-CN.md

@@ -169,7 +169,9 @@ export default {
 };
 ```
 
-### 多列联动
+### 动态设置选项
+
+通过 Picker 上的实例方法可以更灵活地控制选择器，比如使用`setColumnValues`方法实现多列联动
 
 ```html
 <van-picker :columns="columns" @change="onChange" />
@@ -184,14 +186,10 @@ const citys = {
 export default {
   data() {
     return {
-      columns: [{
+      columns: [
-        values: Object.keys(citys),
+        { values: Object.keys(citys) },
-        className: 'column1'
+        { values: citys['浙江'] }
-      }, {
+      ]
-        values: citys['浙江'],
-        className: 'column2',
-        defaultIndex: 2
-      }]
     };
   },
   methods: {
@@ -207,7 +205,24 @@ export default {
 若选择器数据是异步获取的，可以通过 `loading` 属性显示加载提示
 
 ```html
-<van-picker :columns="columns" loading />
+<van-picker :columns="columns" :loading="loading" />
+```
+
+```js
+export default {
+  data() {
+    return {
+      columns: [],
+      loading: true
+    };
+  },
+  created() {
+    setTimeout(() => {
+      this.loading = false;
+      this.columns = ['选项'];
+    }, 1000);
+  }
+};
 ```
 
 ### 搭配弹出层使用

src/picker/demo/index.vue

@@ -46,7 +46,7 @@
       <van-picker :columns="$t('disabledColumns')" />
     </demo-block>
 
-    <demo-block :title="$t('title4')">
+    <demo-block :title="$t('setColumnValues')">
       <van-picker :columns="columns" @change="onChange2" />
     </demo-block>
 
@@ -82,7 +82,6 @@ export default {
   i18n: {
     'zh-CN': {
       city: '城市',
-      title4: '多列联动',
       cascade: '级联选择',
       withPopup: '搭配弹出层使用',
       chooseCity: '选择城市',
@@ -92,6 +91,7 @@ export default {
       disableOption: '禁用选项',
       cascadeColumns: cascadeColumns['zh-CN'],
       multipleColumns: '多列选择',
+      setColumnValues: '动态设置选项',
       textColumns: ['杭州', '宁波', '温州', '嘉兴', '湖州'],
       disabledColumns: [
         { text: '杭州', disabled: true },
@@ -106,7 +106,6 @@ export default {
     },
     'en-US': {
       city: 'City',
-      title4: 'Multi Columns',
       cascade: 'Cascade',
       withPopup: 'With Popup',
       chooseCity: 'Choose City',
@@ -116,6 +115,7 @@ export default {
       disableOption: 'Disable Option',
       cascadeColumns: cascadeColumns['en-US'],
       multipleColumns: 'Multiple Columns',
+      setColumnValues: 'Set Column Values',
       textColumns: ['Delaware', 'Florida', 'Georqia', 'Indiana', 'Maine'],
       disabledColumns: [
         { text: 'Delaware', disabled: true },