我有一个应用程序,我试图在其中理解 AsyncStorage。我正在使用这个Amazing library这简化了实际AsyncStorage实现。
应用程序的流程是-
我设置初始状态
arr:[],
在 componentDidMount() 中,我调用
userTest()
并获得 promise 。我正在尝试在
中设置状态stateSetting()
我的观察-
在
stateSetting()
中,我不确定 setState 是否已设置(请参阅下面的日志)。render()
函数在 setState 之后不会执行。
[如果你想执行代码,它位于 Github ,克隆它来调试,或者拉请求,那就太好了]
代码-
'use strict';
var React = require('react-native');
var reactNativeStore = require('react-native-store');
var {
AsyncStorage,
PickerIOS,
Text,
AppRegistry,
View
} = React;
var reactNativeStore = require('react-native-store');
var RNStorage = require('./RNStorage');
var userArr =
[
{ name: 'j', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 3, location: { name: 'USA', coords: { lat: 123, lng: 123 } } },
{ name: 'a', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 4, location: { name: 'USA', coords: { lat: 123, lng: 123 } } },
{ name: 'v', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 1, location: { name: 'USA', coords: { lat: 123, lng: 123 } } },
{ name: 'a', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 2, location: { name: 'USA', coords: { lat: 123, lng: 123 } } },
{ name: 's', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 1, location: { name: 'EU', coords: { lat: 423, lng: 123 } } },
{ name: 'c', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 1, location: { name: 'EU', coords: { lat: 423, lng: 123 } } },
{ name: 'r', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 7, location: { name: 'EU', coords: { lat: 423, lng: 123 } } },
{ name: 'i', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 9, location: { name: 'Outer Space', coords: { lat: 999, lng: 999 } } },
{ name: 'p', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 4, location: { name: 'InterGalatic Space', coords: { lat: 9001, lng: 42 } } },
{ name: 't', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 999, location: { name: 'Outside', coords: { lat: -1, lng: 0 } } },
];
var differentArr =
[
{ name: 'j', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 1, location: { name: 'USA', coords: { lat: 101, lng: 101 } } },
{ name: 'a', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 2, location: { name: 'USA', coords: { lat: 101, lng: 101 } } },
{ name: 'v', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 3, location: { name: 'USA', coords: { lat: 101, lng: 101 } } },
{ name: 'a', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 4, location: { name: 'USA', coords: { lat: 101, lng: 101 } } },
{ name: 's', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 5, location: { name: 'EU', coords: { lat: 423, lng: 101 } } },
{ name: 'c', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 6, location: { name: 'EU', coords: { lat: 423, lng: 101 } } },
{ name: 'r', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 7, location: { name: 'EU', coords: { lat: 423, lng: 101 } } },
{ name: 'i', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 8, location: { name: 'Outer Space', coords: { lat: 999, lng: 999 } } },
{ name: 'p', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 9, location: { name: 'InterGalatic Space', coords: { lat: 9001, lng: 42 } } },
{ name: 't', img: 'https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png', price: 10, location: { name: 'Outside', coords: { lat: -1, lng: 0 } } },
];
var user = new RNStorage(userArr);
var diff = new RNStorage(differentArr);
async function userTest () {
console.info('=== start react-native-store USER test! ===')
await user.destroyModel();
await user.init();
await user.findTest();
await user.findByIdTest();
var returnVal = await user.updateTest();
console.log("returnVal = "+JSON.stringify(returnVal));
await user.updateByIdTest();
await user.removeTest();
await user.removeByIdTest();
console.info('=== react-native-store USER test complete! ===')
return returnVal;
}
async function diffTest () {
console.info('=== start react-native-store DIFF test! ===')
await diff.destroyModel();
await diff.init();
await diff.findTest();
await diff.findByIdTest();
var returnVal = await diff.updateTest();
console.log("returnVal = "+JSON.stringify(returnVal));
await diff.updateByIdTest();
await diff.removeTest();
await diff.removeByIdTest();
console.info('=== react-native-store DIFF test complete! ===')
}
//diffTest();
var AsyncStorageExample = React.createClass({
getInitialState: function () {
console.log("getInitialState");
return {
arr : [],
}
},
componentDidMount: function () {
console.log("componentDidMount");
var retval = userTest();
console.log("componentDidMount retval"+retval);
retval.then(function (argument) {
console.log("argument"+JSON.stringify(argument));
this.stateSetting(argument);
});
},
stateSetting: function(arrval) {
console.log("stateSetting");
this.setState({
arr : arrval,
});
console.log("value = "+this.state.arr);
},
render : function() {
console.log("render");
console.log("render - value of this.state.arr"+JSON.stringify(this.state.arr));
return (
<View>
{this.state.arr.map(arr =>
<Text key={arr.name}>
• {arr.name}
</Text>
)}
</View>
);
},
});
AppRegistry.registerComponent('AsyncStorageExample', () => AsyncStorageExample);
完整代码 - 关于 GITHUB
日志-
12-24 18:29:06.516 18964-7584/com.asyncstorageexample I/ReactNativeJS: Running application "AsyncStorageExample" with appParams: {"initialProps":{},"rootTag":1}. __DEV__ === true, development-level warning are ON, performance optimizations are OFF
12-24 18:29:06.541 18964-7584/com.asyncstorageexample I/ReactNativeJS: getInitialState
12-24 18:29:06.546 18964-7584/com.asyncstorageexample I/ReactNativeJS: render
12-24 18:29:06.546 18964-7584/com.asyncstorageexample I/ReactNativeJS: render - value of this.state.arr[]
12-24 18:29:06.551 18964-7584/com.asyncstorageexample I/ReactNativeJS: componentDidMount
12-24 18:29:06.556 18964-7584/com.asyncstorageexample I/ReactNativeJS: === start react-native-store USER test! ===
12-24 18:29:06.556 18964-7584/com.asyncstorageexample I/ReactNativeJS: componentDidMount retval[object Object]
12-24 18:29:06.606 18964-7584/com.asyncstorageexample I/ReactNativeJS: 0. init data
12-24 18:29:06.886 18964-7584/com.asyncstorageexample I/ReactNativeJS: 1. find method:
ALL ASYNCSTORAGE METHODS GET EXECUTED - CROPPING LOGS
12-24 18:29:07.176 18964-7584/com.asyncstorageexample I/ReactNativeJS: === react-native-store USER test complete! ===
12-24 18:29:07.176 18964-7584/com.asyncstorageexample I/ReactNativeJS: argument[{"name":"a","img":"https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png","price":0,"location":{"name":"USA","coords":{"lat":123,"lng":123}},"_id":2},{"name":"a","img":"https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png","price":0,"location":{"name":"USA","coords":{"lat":123,"lng":123}},"_id":4},{"name":"c","img":"https://cdn4.iconfinder.com/data/icons/48x48-free-object-icons/48/House.png","price":0,"location":{"name":"EU","coords":{"lat":423,"lng":123}},"_id":6}]
我做错了什么?请指导/帮助我。
最佳答案
问题在于范围
retval.then(function (argument) {
console.log("argument"+JSON.stringify(argument));
this.stateSetting(argument);
});
promise 中的 this
值不再是组件。您需要绑定(bind)该函数,或者使用闭包。
retval.then(function (argument) {
console.log("argument"+JSON.stringify(argument));
this.stateSetting(argument);
}.bind(this));
或者
var self = this;
retval.then(function (argument) {
console.log("argument"+JSON.stringify(argument));
self.stateSetting(argument);
});
关于javascript - native react : render function not being called after state change,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34453279/