如何在变量中使用等式和 if 语句？没用

Question

所以我正在打印我的变量 recommendedCalories 并且我给它一个标准输入 0 以查看是否正在打印任何东西，所以它打印 0。但是根据我从上一个屏幕获得的变量值，我应该得到一个不同的回答。我的方程式没有得到我想要的答案是怎么回事？

package com.example.optilife

import...

class WelcomeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_welcome)

        val userAge = intent.getIntExtra("EXTRA_AGE", 0)
        val userHeight = intent.getIntExtra("EXTRA_HEIGHT", 0)
        val userWeight = intent.getIntExtra("EXTRA_WEIGHT", 0)
        val userGender = intent.getStringExtra("EXTRA_GENDER")
        val userActivityLevel = intent.getStringExtra("EXTRA_ACTIVITYLEVEL")
        var userWeightGoal = intent.getStringExtra("EXTRA_WEIGHTGOAL")
        var userWeightGoalCalories = {
            userWeightGoal = if (userWeightGoal == "Weight loss") {
                "300"
            } else if (userWeightGoal == "Maintain weight") {
                "0"
            } else {
                "-300"
            }
        }

        var recommendedCalories = 0
        var recommendedCaloriesCalculator = {
            recommendedCalories = if (userGender == "Male") {
                (66 + 13.7userWeight + 5userHeight - 6.8userAge -                     
userWeightGoal.toString().toInt()).toString().toInt()
            } else {
                (655 + 9.6userWeight + 1.8userHeight - 4.7userAge -    
userWeightGoal.toString().toInt()).toString().toInt()
            }
    }

        findViewById<TextView>(R.id.tv_Test).apply {
            text = recommendedCalories.toString()
        }
    }
}

Answer 1

你在这里创建了一个函数

recommendedCaloriesCalculator()

：

var recommendedCaloriesCalculator = {
    recommendedCalories = ...
}

所以如果你没有明确调用

recommendedCaloriesCalculator()

，

recommendedCalories = ...

将永远不会被执行，因此

recommendedCalories

不会更新。

因此您可以在设置 TextView 之前调用

recommendedCaloriesCalculator()

。或者你可以简单地删除

var recommendedCaloriesCalculator = { ... }

并留下

recommendedCalories = ...

在那里：

package com.example.optilife

import...

class WelcomeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_welcome)

        val userAge = intent.getIntExtra("EXTRA_AGE", 0)
        val userHeight = intent.getIntExtra("EXTRA_HEIGHT", 0)
        val userWeight = intent.getIntExtra("EXTRA_WEIGHT", 0)
        val userGender = intent.getStringExtra("EXTRA_GENDER")
        val userActivityLevel = intent.getStringExtra("EXTRA_ACTIVITYLEVEL")
        var userWeightGoal = intent.getStringExtra("EXTRA_WEIGHTGOAL")
        var userWeightGoalCalories = {
            userWeightGoal = if (userWeightGoal == "Weight loss") {
                "300"
            } else if (userWeightGoal == "Maintain weight") {
                "0"
            } else {
                "-300"
            }
        }

        var recommendedCalories = 0
        // The simple solution is to remove recommendedCaloriesCalculator
        // BTW, do you miss * for the following equations?
        recommendedCalories = if (userGender == "Male") {
            (66 + 13.7userWeight + 5userHeight - 6.8userAge - userWeightGoal.toString().toInt()).toString().toInt()
        } else {
            (655 + 9.6userWeight + 1.8userHeight - 4.7userAge - userWeightGoal.toString().toInt()).toString().toInt()
        }

        findViewById<TextView>(R.id.tv_Test).apply {
            text = recommendedCalories.toString()
        }
    }
}