DTS二次开发文档二次开发：异步接口调用方式说明文档
DigitalTwinAPI的接口大部分都是异步的，所以在调用的时候需要进行特殊处理，否则可能因为调用错误而不能实现预期的效果。目前有三种异步接口的调用方式，DigitalTwinAPI同时支持这3种方式，需要注意的是：在一个函数体内，这3种方式不能混合使用，只能选择其中一种。
方式一：使用callback回调函数进行调用
这是最先支持的一种方式，代码逻辑简单，容易理解，但是当一个函数体内调用的异步接口比较多的时候，代码可读性变差，维护比较麻烦，在下面的例子里可以看到使用了多个嵌套函数，括号太多，比较混乱。
fdapi.tag.delete('tag1', function () {
fdapi.camera.get(function (cam) {
let o = new TagData('tag1');
o.coordinate = [cam.x, cam.y, 25.4];
o.imagePath = HostConfig.Path + '/samples/images/tag.png';
o.imageSize = [28, 28];
o.text = '北京银行';
o.showLine = true;
fdapi.tag.add(o, function () {
fdapi.tag.focus(o.id, 500, 0.2, function () {
log("Test Finished.");
}); //focus
}); //add
}) //get
}); //delete
方式二：使用then链的方式调用
这种方式通过连续的then调用来解决函数嵌套问题，可读性比回调的方式要好一些。
fdapi.tag.delete('tag1').then(() => fdapi.camera.get())
.then((cam) => {
let o = new TagData('tag1');
o.coordinate = [cam.x, cam.y, 25.4];
o.imagePath = HostConfig.Path + '/samples/images/tag.png';
o.imageSize = [28, 28];
o.text = '北京银行';
o.showLine = true;
fdapi.tag.add(o);
})
.then(() => fdapi.tag.focus('tag1', 500, 0.2))
.then(() => {
log("Test Finished.");
})
方式3：使用async/await的异步方式调用
这种方式其实是第2种方式的语法糖，但是可读性大大提高。
await fdapi.tag.delete('tag1')
let cam = await fdapi.camera.get();
let o = new TagData('tag1');
o.coordinate = [cam.x, cam.y, 25.4];
o.imagePath = HostConfig.Path + '/samples/images/tag.png';
o.imageSize = [28, 28];
o.text = '北京银行';
o.showLine = true;
await fdapi.tag.add(o);
await fdapi.tag.focus(o.id, 500, 0.2);
log("Test Finished.");
在int.html运行上面三种方式的代码，可以看到页面的输出都是一样的：
Request: CustomTag_Delete（下午1:40:10）
{"command":37,"ids":["tag1"],"timestamp":1616132410590,"callbackIndex":35,"__command":"CustomTag_Delete"}
Response: CustomTag_Delete（耗时：33ms）
请求时间：下午1:40:10 响应时间：下午1:40:10
{
"command": 37,
"timestamp": 1616132410590,
"callbackIndex": 35,
"result": 0,
"resultMessage": "OK",
"message": {
},
"ids": ["tag1"]
}
Request: Camera_GetCamera（下午1:40:10）
{"command":6,"timestamp":1616132410624,"callbackIndex":36,"__command":"Camera_GetCamera"}
Response: Camera_GetCamera（耗时：100ms）
请求时间：下午1:40:10 响应时间：下午1:40:10
{
"command": 6,
"timestamp": 1616132410624,
"callbackIndex": 36,
"result": 0,
"resultMessage": "OK",
"x": -57.773582,
"y": -3309.501221,
"z": 687.396240,
"pitch": -44.999958,
"yaw": -88.999962,
"roll": 0.000002,
"camera": [-57.773582, -3309.501221, 687.396240, -44.999958, -88.999962, 0.000002]
}
Request: Tag_Add（下午1:40:10）
{"command":36,"data":[{"id":"tag1","coordinate":[-57.773582,-3309.501221,25.4],"imagePath":"D:\\Pojects\\DigitalTwinCloud\\SDK/images/tag.png","imageSize":[28,28],"text":"北京银行","range":[1,100000],"showLine":true,"textColor":[0,0,0,1],"textBackgroundColor":[1,1,1,0.85],"textBorderColor":[0,0,0,0],"textRange":100000,"autoHidePopupWindow":true}],"timestamp":1616132410726,"callbackIndex":37,"__command":"Tag_Add"}
Response: Tag_Add（耗时：99ms）
请求时间：下午1:40:10 响应时间：下午1:40:10
{
"command": 36,
"timestamp": 1616132410726,
"callbackIndex": 37,
"result": 0,
"resultMessage": "OK",
"message": {
},
"ids": ["tag1"]
}
Request: CustomTag_Focus（下午1:40:10）
{"command":40,"ids":["tag1"],"distance":500,"flyTime":0.2,"timestamp":1616132410828,"callbackIndex":38,"__command":"CustomTag_Focus"}
Response: CustomTag_Focus（耗时：97ms）
请求时间：下午1:40:10 响应时间：下午1:40:10
{
"command": 40,
"timestamp": 1616132410828,
"callbackIndex": 38,
"result": 0,
"resultMessage": "OK"
}
Test Finished.
Response: Event
{
"eventtype": "CameraChanged",
"Pitch": -44.999958038330078,
"Yaw": -88.999961853027344,
"Position": [ -69.326980590820313, -3971.396484375, 687.396240234375 ]
}
OnEvent: CameraChanged
从上面的输出可以看到异步接口是按顺序执行的，每调用一次接口，都是收到服务器返回数据后才会往下继续执行下一次异步接口。
我们把代码做如下的修改，去掉所有的异步调用方式：
fdapi.tag.delete('tag1')
let cam = fdapi.camera.get();
let o = new TagData('tag1');
o.coordinate = [cam.x, cam.y, 25.4];
o.imagePath = HostConfig.Path + '/samples/images/tag.png';
o.imageSize = [28, 28];
o.text = '北京银行';
o.showLine = true;
fdapi.tag.add(o);
fdapi.tag.focus(o.id, 500, 0.2);
log("Test Finished.");
然后再执行，然后观察页面的输出：
Request: CustomTag_Delete（下午1:45:17）
{"command":37,"ids":["tag1"],"timestamp":1616132717350,"callbackIndex":39,"__command":"CustomTag_Delete"}
Request: Camera_GetCamera（下午1:45:17）
{"command":6,"timestamp":1616132717351,"callbackIndex":40,"__command":"Camera_GetCamera"}
Request: Tag_Add（下午1:45:17）
{"command":36,"data":[{"id":"tag1","coordinate":[null,null,25.4],"imagePath":"D:\\Pojects\\DigitalTwinCloud\\SDK/images/tag.png","imageSize":[28,28],"text":"北京银行","range":[1,100000],"showLine":true,"textColor":[0,0,0,1],"textBackgroundColor":[1,1,1,0.85],"textBorderColor":[0,0,0,0],"textRange":100000,"autoHidePopupWindow":true}],"timestamp":1616132717351,"callbackIndex":41,"__command":"Tag_Add"}
Request: CustomTag_Focus（下午1:45:17）
{"command":40,"ids":["tag1"],"distance":500,"flyTime":0.2,"timestamp":1616132717352,"callbackIndex":42,"__command":"CustomTag_Focus"}
Test Finished.
Response: Camera_GetCamera（耗时：73ms）
请求时间：下午1:45:17 响应时间：下午1:45:17
{
"command": 6,
"timestamp": 1616132717351,
"callbackIndex": 40,
"result": 0,
"resultMessage": "OK",
"x": -69.326981,
"y": -3971.396484,
"z": 687.396240,
"pitch": -44.999958,
"yaw": -88.999962,
"roll": 0.000002,
"camera": [-69.326981, -3971.396484, 687.396240, -44.999958, -88.999962, 0.000002]
}
Response: CustomTag_Delete（耗时：175ms）
请求时间：下午1:45:17 响应时间：下午1:45:17
{
"command": 37,
"timestamp": 1616132717350,
"callbackIndex": 39,
"result": 0,
"resultMessage": "OK",
"message": {
},
"ids": ["tag1"]
}
Response: Tag_Add（耗时：275ms）
请求时间：下午1:45:17 响应时间：下午1:45:17
{
"command": 36,
"timestamp": 1616132717351,
"callbackIndex": 41,
"result": 0,
"resultMessage": "OK",
"message": {
},
"ids": ["tag1"]
}
Response: Event
{
"eventtype": "CameraChanged",
"Pitch": -44.999958038330078,
"Yaw": -88.999961853027344,
"Position": [ -11.553402900695801, -661.8956298828125, 687.396240234375 ]
}
OnEvent: CameraChanged
Response: CustomTag_Focus（耗时：377ms）
请求时间：下午1:45:17 响应时间：下午1:45:17
{
"command": 40,
"timestamp": 1616132717352,
"callbackIndex": 42,
"result": 0,
"resultMessage": "OK"
}
从上面的输出可以看到，异步接口的Request、Response不再有序，而是混乱的， 另外从三维场景的变化也可以看到，并没有达到预期的效果。