如何在变量中使用方程式和if语句？它不起作用-解网

问：

所以我打印了我的变量 recommendedCalories，我给它一个标准输入 0 来查看是否正在打印任何内容，因此它打印了 0。但是，对于我从上一个屏幕中获得的变量值，我应该得到不同的答案。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()
        }
    }
}

Android Kotlin IF-语句变量公式

答：

0赞 Enowneb 3/16/2023 #1

您已在此处创建了一个函数：recommendedCaloriesCalculator()

var recommendedCaloriesCalculator = {
    recommendedCalories = ...
}

因此，如果您不显式调用，将永远不会被执行，因此不会更新。recommendedCaloriesCalculator()recommendedCalories = ...recommendedCalories

因此，您可以：

在设置 TextView 之前调用recommendedCaloriesCalculator()
只需移除并留在那里var recommendedCaloriesCalculator = { ... }recommendedCalories = ...

选项 1：

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
        // BTW, are you missing * for the following equations?
        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()
            }
        }
        // Call the function here to update recommendedCalories
        recommendedCaloriesCalculator()
        findViewById<TextView>(R.id.tv_Test).apply {
            text = recommendedCalories.toString()
        }
    }
}

选项 2：

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 simplest solution is to remove recommendedCaloriesCalculator
        // BTW, are you missing * 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()
        }
    }
}

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