uniapp阻止用户返回页面

问题遇到的现象和发生背景

想要点击两次退出应用，超过一秒的返回两次不退出，为什么第二次取的计数是累加后的值而不是重设的0

问题相关代码，请勿粘贴截图
    data() {
        return {
            backButtonPress: 0,
        }
    },
    onBackPress(options) {
        console.log(this.backButtonPress);
        this.backButtonPress++;
        console.log(this.backButtonPress);
        if (this.backButtonPress > 1) {
            plus.runtime.quit();
        } else {
            plus.nativeUI.toast('再按一次退出应用');
        }
        setTimeout(function() {
            this.backButtonPress = 0;
            console.log(this.backButtonPress);
        }, 1000);
        return true;
    },
运行结果及报错内容

10:35:07.809 [Number] 0 at pages/index/index.vue:102
10:35:07.829 [Number] 1 at pages/index/index.vue:104
10:35:08.814 [Number] 0 at pages/index/index.vue:112
10:35:11.730 [Number] 1 at pages/index/index.vue:102
10:35:11.750 [Number] 2 at pages/index/index.vue:104

我的解答思路和尝试过的方法
我想要达到的结果

把function改成箭头函数试下


onBackPress(options) {
        console.log(this.backButtonPress);
        this.backButtonPress++;
        console.log(this.backButtonPress);
        if (this.backButtonPress > 1) {
            plus.runtime.quit();
        } else {
            plus.nativeUI.toast('再按一次退出应用');
        }
        setTimeout(()=> {
            this.backButtonPress = 0;
            console.log(this.backButtonPress);
        }, 1000);
        return true;
    },

img