java - 如何更改来自不同类的变量？

Question

在深入研究之前，我是 Android 的新手，上个月才开始学习 Java。我在尝试开发我的第一个简单应用程序时遇到了障碍。由于在线随机教程，大部分障碍都被跨越了。我的代码很乱。任何提示表示赞赏。

上面的问题很宽泛，但这就是我想做的:它本质上是一个血液酒精含量计算器/饮料跟踪器。基本布局:http://i.imgur.com/JGuh7.jpg

底部的按钮只是普通按钮，不是 ImageButtons(有问题)下面是其中的一些示例代码:

<Button android:id="@+id/Button01"
                    android:layout_width="wrap_content"
                    android:layout_marginRight="5dp"
                    android:background="@drawable/addbeer"/>

按钮和TextView都在main.xml中。

我在名为 Global.java 的类中定义了变量:

package com.dantoth.drinkingbuddy;

导入android.app.Activity；

公共(public)类全局扩展 Activity {

public static double StandardDrinks = 0;
public static double BeerOunces = 12;
public static double BeerPercentAlcohol = .05;
public static double BeerDrink = BeerOunces * BeerPercentAlcohol;
public static double BeerDrinkFinal = BeerDrink * 1.6666666;
public static double ShotOunces = 1.5;
public static double ShotPercentAlcohol = .4;
public static double ShotDrink = ShotOunces * ShotPercentAlcohol;
public static double ShotDrinkFinal = ShotDrink * 1.6666666;
public static double WineOunces = 5;
public static double WinePercentAlcohol = .12;
public static double WineDrink = WineOunces * WinePercentAlcohol;
public static double WineDrinkFinal = WineDrink * 1.6666666;
public static double OtherOunces;
public static double OtherPercentAlcohol;
public static double OtherDrink = OtherOunces * (OtherPercentAlcohol * .01);
public static double OtherDrinkFinal = OtherDrink * 1.6666666;
public static double GenderConstant = 7.5; //9 for female
public static double Weight = 180;
public static double TimeDrinking = 60;
public static double Hours = TimeDrinking / 60;
public static double Bac = ((StandardDrinks / 2) * (GenderConstant / Weight)) - (0.017 * Hours);

最后一个变量是重要的部分。它根据所涉及的因素计算您的 BAC。

当我按下添加啤酒按钮 (Button01) 时，我让它向 StandardDrinks 添加 1，模拟喝一瓶啤酒。 Bac 公式中的其他变量在 Global.java 中分配了值。

让啤酒按钮起作用的代码在我的常规类(class) drinkingbuddy.java 中:

public class DrinkingBuddy extends Activity {
/** Called when the activity is first created. */


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    Button button = (Button) findViewById(R.id.Button01);
    button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Global.StandardDrinks = Global.StandardDrinks + Global.BeerDrinkFinal;
            Toast.makeText(DrinkingBuddy.this, "Mmmm... Beer", Toast.LENGTH_SHORT).show();

        }
        });

根据我的看法，StandardDrinks 现在的值应该为 1。但是，当我单击计算 BAC 按钮 (Button05) 时，它仅输出变量 Bac，就好像 StandardDrinks 仍设置为 0 一样。这是计算的代码BAC 按钮 (Button05):

按钮 button4 = (Button) findViewById(R.id.Button05); button4.setOnClickListener(new OnClickListener() { @覆盖 public void onClick(View v) {

            TextView texty;

            texty = (TextView) findViewById(R.id.texty1);

            texty.setText("Your BAC is " + Global.Bac );

        }
        });

它向 TextView 输出以下内容:“您的 BAC 是 -0.017”。如果 StandardDrinks 仍为 0，则这是 Bac 值，因此很明显类之间的通信存在一些问题。谁能帮帮我？？

公式的其他元素(体重、饮酒时间和酒精百分比等)是变量，因为我最终将允许用户在设置中更改这些值。

我听说过全局变量不是好的编程风格，但这是我最接近它的工作方式。非常欢迎任何其他方式!

Answer 1

您的程序中存在一些逻辑错误。

public static double Bac = ((StandardDrinks / 2) * (GenderConstant / Weight)) - (0.017 * Hours);

此变量 Bac 将使用公式的值进行初始化。除非您明确这样做，否则用于计算 BAC 的公式中使用的变量的进一步变化不会反射(reflect)回它。我建议有一个函数来更新 BAC，如下所示

您可以在一个 Activity 中完成上述所有操作。

       public class DrinkingBuddy extends Activity {
/** Called when the activity is first created. */

 double StandardDrinks = 0;
 double BeerOunces = 12;
double BeerPercentAlcohol = .05;
 double BeerDrink = BeerOunces * BeerPercentAlcohol;
 double BeerDrinkFinal = BeerDrink * 1.6666666;
 double ShotOunces = 1.5;
 double ShotPercentAlcohol = .4;
 double ShotDrink = ShotOunces * ShotPercentAlcohol;
 double ShotDrinkFinal = ShotDrink * 1.6666666;
 double WineOunces = 5;
 double WinePercentAlcohol = .12;
double WineDrink = WineOunces * WinePercentAlcohol;
double WineDrinkFinal = WineDrink * 1.6666666;
 double OtherOunces;
 double OtherPercentAlcohol;
 double OtherDrink = OtherOunces * (OtherPercentAlcohol * .01);
 double OtherDrinkFinal = OtherDrink * 1.6666666;
 double GenderConstant = 7.5; //9 for female
 double Weight = 180;
 double TimeDrinking = 60;
 double Hours = TimeDrinking / 60;
 double Bac;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    Button button = (Button) findViewById(R.id.Button01);
    button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            StandardDrinks = StandardDrinks + BeerDrinkFinal;
            Toast.makeText(DrinkingBuddy.this, "Mmmm... Beer", Toast.LENGTH_SHORT).show();

        }
        });

Button button4 = (Button) findViewById(R.id.Button05); 
button4.setOnClickListener(new OnClickListener() 
{ 
@Override 
public void onClick(View v) {

            TextView texty;
            Bac = ((StandardDrinks / 2) * (GenderConstant / Weight)) - (0.017 * Hours);
            texty = (TextView) findViewById(R.id.texty1);
            texty.setText("Your BAC is " + Bac );

        }
        });

MY CODE IS VERY MESSY.

确实很乱。我很难删除所有不必要的公共(public)和静态声明。这document可能有助于在编写 Java 代码时遵循约定。

根据该文档引用

Variables should be initialized where they are declared and they should be declared in the smallest scope possible.

希望它对正确的方向有所帮助。