java - Android 计算器代码中的静态变量有问题吗？

Question

我正在编写一个 Android 计算器。我有我所有的代码，但是当使用计算器时，它总是打印“0.0”，这是我为total1和total2设置的原始值。所以，我的假设是这些方法没有看到这两个变量。所以我假设我必须将它们设置为静态变量，以便我的代码的其余部分可以使用它们并更改它们。我可能设置了错误的静态变量。但是将total1和total2设置为静态变量后，我仍然遇到同样的问题。我对程序无法正常工作的另一个猜测是我的 displayValue 变量。在我的 if 语句中，它表示未使用局部变量 displayValue 。我将不胜感激任何帮助。

package rechee.cool;

import android.app.Activity;

import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;




public class HelloAndroidActivity extends Activity {


/** Called when the activity is first created. */
public EditText display;
  String display1;
 double displayValue;

// I want to be able to use the following two variables everywhere in the code.
static double total1=0.0;
static double total2=0.0;


char theOperator;
public String buttonText;
public Button ButtonAdd, ButtonEqual, ButtonMultiply, ButtonDivide, ButtonMinus;







@Override
public  void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    display= (EditText) findViewById(R.id.editText1);




    if(display.length()!=0){
    String display1= display.getText().toString();
    // Says local variable displayValue has not been used. May be my problem?
    double displayValue= Double.parseDouble(display1);
}
}








    public void getOperator(String btnText){
        theOperator = btnText.charAt(0);



        total1+=displayValue;
        display.setText("");
    }







        public void onClick(View v) {
            switch(v.getId()){
                case R.id.bOne:

                    display.append("1");
                    break;
                case R.id.bTwo:

                    display.append("2");
                    break;
                case R.id.bThree:
                    display.append("3");
                    break;
                case R.id.bFour:
                    display.append("4");
                    break;
                case R.id.bFive:
                    display.append("5");
                    break;
                case R.id.bSix:
                    display.append("6");
                    break;

                case R.id.bSeven:
                    display.append("7");
                    break;
                case R.id.bEight:
                    display.append("8");
                    break;
                case R.id.bNine:
                    display.append("9");
                    break;
                case R.id.bZero:
                    display.append("0");
                    break;
                case R.id.bPoint:
                    display.append(".");
                    break;
                case R.id.bClear:
                    total2= 0.0;
                    display.setText("");
                    break;
                case R.id.bAdd:
                    buttonText="+";
                    ButtonAdd= (Button)findViewById(R.id.bAdd);

                    ButtonAdd.setText(buttonText);


                    getOperator(buttonText);
                    break;
                case R.id.bMinus:
                    buttonText="-";
                    ButtonMinus= (Button)findViewById(R.id.bMinus);
                    ButtonMinus.setText(buttonText);
                    getOperator(buttonText);
                    break;
                case R.id.bMultiply:
                    buttonText="*";
                    ButtonMultiply= (Button)findViewById(R.id.bMultiply);
                    ButtonMultiply.setText(buttonText);
                    getOperator(buttonText);
                    break;
                case R.id.bDivide:
                    buttonText="/";
                    ButtonDivide= (Button)findViewById(R.id.bDivide);
                    ButtonDivide.setText(buttonText);
                    getOperator(buttonText);
                    break;  
                case R.id.bEqual:


                    switch (theOperator){
                    case '+':
                    total2= total1 + displayValue;
                    break;
                    case '-':
                    total2= total1 - displayValue;
                    break;
                    case '*':
                    total2= total1 * displayValue;
                    break;
                    case '/':
                    total2= total1 / displayValue;
                    break;
                    }
                    display.setText(Double.toString(total2));
                    total1=0.0;
                    break;






                    }



                    }


}

Answer 1

您正在重新声明仅在 onCreate 范围内的本地变量。尝试一下

display1 = display.getText().toString();
//   v ^ these now refer to the members of class HelloAndroidActivity
displayValue = Double.parseDouble(display1);

建议阅读

• Variables^Oracle