号码选择器计算

Question

我已经创建了 3 个不同的数字选择器，我正在使用选择的 3 个不同的数字进行计算，但不知道为什么它不会在 totalP textView 中显示总和。这2行是错的吗？ "sum =(a*4)+(b*4)+(c*9); "和 "totalP.setText(sum+" cal");"

    public TextView carb;
    public TextView protein;
    public TextView fat;
    public TextView totalP;
    int carbNum,proteinNum,fatNum,cpv,ppv,fpv;
    int sum,a,b,c;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_adjust_macronutrients);

        Bundle extras = getIntent().getExtras();

        carb = (TextView) findViewById(R.id.carbsNum);
        carbNum = extras.getInt("Carb");
        carb.setText(carbNum+" g");

        protein = (TextView) findViewById(R.id.proteinNum);
        proteinNum = extras.getInt("Protein");
        protein.setText(proteinNum+" g");

        fat = (TextView) findViewById(R.id.fatNum);
        fatNum = extras.getInt("Fat");
        fat.setText(fatNum+" g");

        cpv=extras.getInt("carbP");
        ppv=extras.getInt("proteinP");
        fpv=extras.getInt("fatP");

        totalP=(TextView) findViewById(R.id.totalPercentage);

        final NumberPicker np1 = (NumberPicker) findViewById(R.id.carbPercentage);
        final NumberPicker np2 = (NumberPicker) findViewById(R.id.proteinPercentage);
        final NumberPicker np3 = (NumberPicker) findViewById(R.id.fatPercentage);

        np1.setMaxValue(1000);
        np1.setMinValue(0);
        np1.setValue(carbNum);
        np1.setWrapSelectorWheel(true);
        np1.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
            @Override
            public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
                a =np1.getValue();;
                carb.setText(a + " g");
            }
        });
        np2.setMaxValue(1000);
        np2.setMinValue(0);
        np2.setValue(proteinNum);
        np2.setWrapSelectorWheel(true);
        np2.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
            @Override
            public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
                b = np2.getValue();
                protein.setText(b + " g");

            }
        });
        np3.setMaxValue(1000);
        np3.setMinValue(0);
        np3.setValue(fatNum);
        np3.setWrapSelectorWheel(true);
        np3.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
            @Override
            public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
                c = np3.getValue();
                fat.setText(c + " g");
            }
        });

        sum =(a*4)+(b*4)+(c*9);
        // this line cant work, is because the a,b,c ??
        totalP.setText(sum+" cal");  
        // this line cant work  ??
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

    }
}

Answer 1

把这两行放在所有改变监听器中，它会起作用， 在 oncreate 函数中，a,b,c 在 setOnValueChangedListener 执行之前没有任何价值，这就是为什么那 2 行不起作用