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2 years ago
# combo一些不为人知的特性
## combo的trigger属性是可以设置为空的
去掉combo的默认弹出事件,手动控制showView,在某些场景中很有用.例如需要控制有些场景要弹出,有些场景不要弹出.
2 years ago
例如BI业务中有一个场景,叫做"开启权限继承后气泡提示"
![示例](../images/17.gif)
```demo
let combo;
let switchBtn;
BI.createWidget({
type: "bi.bubble_combo",
ref: (ref) => combo = ref,
el: {
type: "bi.switch",
ref: (ref) => switchBtn = ref,
handler: () => {
switchBtn.isSelected() ? combo.showView() : combo.hideView();
},
},
trigger: "",
popup: {
el: {
type: "bi.label",
text: "提示文字",
},
},
});
```
另一个场景,有些提示文本提示一次后不再提示,
2 years ago
```demo
let combo;
BI.createWidget({
type: "bi.vertical",
items: [
{
type: "bi.combo",
ref: ref => combo = ref,
trigger: "",
el: {
type: "bi.button",
text: "触发弹出",
handler: () => {
if (BI.Cache.getItem("confirmed")) {
combo.showView();
return;
}
BI.Msg.confirm("弹出是手动的,你知道吧", confirmed => {
if (confirmed) {
BI.Cache.setItem("confirmed", true);
combo.showView();
}
});
},
},
popup: {
el: {
type: "bi.label",
text: "popup",
},
},
},
],
});
```
## combo的popup是在弹出时候创建的,但是props却是在combo创建时候确定的
应对这种情况,常见的解决方案是`isDefaultInit: true`或者将popup属性改为函数
注意设置了`isDefaultInit: true`后会有响应的性能或体验损失
```demo
BI.createWidget({
type: "bi.vertical",
items: [
{
type: "bi.combo",
el: {
type: "bi.label",
text: BI.getDate(),
},
popup: {
el: {
type: "bi.label",
text: BI.getDate(),
},
},
}, {
type: "bi.combo",
el: {
type: "bi.label",
text: BI.getDate(),
},
isDefaultInit: true,
popup: {
el: {
type: "bi.label",
text: BI.getDate(),
},
},
}, {
type: "bi.combo",
el: {
type: "bi.label",
text: BI.getDate(),
},
popup: () => ({
el: {
type: "bi.label",
text: BI.getDate(),
},
}),
},
],
});
```
## combo的value传递和getValue很奇怪
在多数场景中,给bi.combo传递value属性,可以使下拉框在展开时候自动选中某一项.前提是popup的el组件支持value属性
如下的combo,value是不生效的.需要对bi.button_group传递value属性
同样的,如果在展开之前value可能发生改变,要注意value的同步
```demo
var Combo = BI.inherit(BI.Widget, {
render: function () {
return {
type: "bi.combo",
el: {
type: "bi.label",
},
ref: ref => this.combo = ref,
value: this.options.value,
popup: {
el: {
type: "bi.vertical",
items: [
{
type: "bi.button_group",
layouts: [
{
type: "bi.vertical",
},
],
items: [
{
type: "bi.single_select_radio_item",
text: "1",
value: 1,
}, {
type: "bi.single_select_radio_item",
text: "2",
value: 2,
},
],
},
],
},
},
};
},
getValue: function () {
return this.combo.getValue();
},
setValue: function (v) {
this.combo.setValue(v);
},
});
BI.shortcut("demo.combo", Combo);
```
## destroyWhenHide
当控制下拉框的状态比较复杂的时候,可以通过收起时候销毁再重新创建来简化
例如消息下拉框,内部两个独立的业务组件,一个展示消息列表,一个展示二维码.希望每次弹出都能重新加载消息.配置destroyWhenHide可以完全交友message_list
的生命周期去控制,避免了监听combo弹出事件,在命令式调用刷新逻辑.
```demo
BI.createWidget({
type: "bi.vertical",
items: [
{
type: "bi.combo",
ref: ref => combo = ref,
trigger: "",
el: {
type: "bi.button",
text: "触发弹出",
},
destroyWhenHide: true,
popup: {
el: {
type: "bi.vertical",
items: [
{
type: "message_list",
}, {
type: "qr_code",
},
],
},
},
listeners: [
{
eventName: BI.Combo.EVENT_AFTER_POPUPVIEW,
action: function () {
// do something
},
},
],
},
],
});
```
## hideWhenBlur
先说怎么屏蔽这个行为,再说为什么设计这个属性
1. 全局变量`BI.EVENT_BLUR`改为`false`
2. combo配置`hideWhenBlur: false`
为什么要添加这一个特性呢,实际上是因为iframe会隔离事件的缘故,下拉框弹出后,鼠标在iframe中操作并不会触发外部的`document.mousedown`
因此下拉框也就无法收起了.
以前是怎么处理呢,`trigger: "click-hover"`,即点击触发弹出,鼠标移除触发收起,但是体验差点意思
![](../images/2.png)