状态更新后,渲染函数不会更新视图

constructor(props){
    super(props);
    this.renderConversations = this.renderConversations.bind(this);
    this.startConversation = this.startConversation.bind(this);
    this.state = {
      conversationArray: []
    }
} 

在函数中 startConversation

startConversation(conversationObject) {
    let currentResponse = conversationObject["responses"];
    let thisResponse = currentResponse[Math.floor(Math.random() * currentResponse.length)];

    this.state.conversationArray.push(thisResponse);
    this.renderConversations();

}

在函数中 renderConversations

renderConversations(){
    let conversationContent = this.state.conversationArray.map((conv, i) => {
      return <View key={i} style={[globalStyle.conversationContainer,globalStyle.shadow]}><Text style= {globalStyle.conversationText}>{ conv }</Text></View>                            
    })
    return conversationContent
}

{this.renderConversations()} . 现在 但是每次我更新状态变量时,组件都没有更新,我做错了什么?