Question

在我的Android应用程序中，我使用在EditTexts中输入的值并尝试将答案放入TextView来计算double值。我的代码是这样的：

double scoreDouble;
TextView score;
EditText gpa;
EditText sat;
EditText act;
Button calc;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    gpa = (EditText) findViewById(R.id.gpa);
    String gpaString = gpa.getText().toString();
    if(gpaString.equals("")){
        gpaString = "0";
    }
    final double gpaDouble = Double.parseDouble(gpaString);     
    sat = (EditText) findViewById(R.id.sat);
    String satString = sat.getText().toString();
    if(satString.equals("")){
        satString = "0";
    }
    final int satInt = Integer.parseInt(satString);     
    act = (EditText) findViewById(R.id.act);
    String actString = act.getText().toString();
    if(actString.equals("")){
        actString = "0";
    }
    final int actInt = Integer.parseInt(actString);     
    score = (TextView) findViewById(R.id.score);            
    calc = (Button) findViewById(R.id.calc);
    calc.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            if(actInt/36>satInt/2400){
                scoreDouble= (0.6*gpaDouble*25)+(0.4*(actInt/36)*100);
                String scoreString = Double.toString(scoreDouble);
                score.setText("Your score is "+scoreString);
            }else{
                scoreDouble = (0.6*gpaDouble*25)+(0.4*(satInt/2400)*100);
                String scoreString = Double.toString(scoreDouble);
                score.setText("Your score is "+scoreString);
            }


        }
    });
}

截至目前，当按下按钮时，TextView会显示：＆＃34;您的分数为0.0。＆＃34;我觉得这与我将EditTexts的默认值设置为0的事实有关。在我这样做之前，我收到一个错误，指出NumberFormatException：无效的double：＆＃34;＆＃34;。如果这是问题，我应该如何解决它。如果那不是问题，它是什么？

Answer 1

您将actInt和satInt定义为最终变量，并且它们将仅被赋值一次（当执行onCreate方法时）和初始值将为零，因为编辑文本不包含任何内容。

要解决此问题：

将actInt和actInt从局部变量移动到字段变量并删除final关键字。（我的意思是将这些变量定义为类中的私有变量）并在onclick方法中为变量赋值。

public class test extends Activity {

double scoreDouble;
TextView score;
EditText gpa;
EditText sat;
EditText act;
Button calc;

private int satInt;
private int actInt;

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

    gpa = (EditText) findViewById(R.id.gpa);

    sat = (EditText) findViewById(R.id.sat);

    act = (EditText) findViewById(R.id.act);

    score = (TextView) findViewById(R.id.score);
    calc = (Button) findViewById(R.id.calc);
    calc.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            String gpaString = gpa.getText().toString();
            if (gpaString.equals("")) {
                gpaString = "0";
            }
            double gpaDouble = Double.parseDouble(gpaString);

            String satString = sat.getText().toString();
            if (satString.equals("")) {
                satString = "0";
            }
            int satInt = Integer.parseInt(satString);

            String actString = act.getText().toString();
            if (actString.equals("")) {
                actString = "0";
            }
            int actInt = Integer.parseInt(actString);
            if (actInt / 36 > satInt / 2400) {
                scoreDouble = (0.6 * gpaDouble * 25)
                        + (0.4 * (actInt / 36) * 100);
                String scoreString = Double.toString(scoreDouble);
                score.setText("Your score is " + scoreString);
            } else {
                scoreDouble = (0.6 * gpaDouble * 25)
                        + (0.4 * (satInt / 2400) * 100);
                String scoreString = Double.toString(scoreDouble);
                score.setText("Your score is " + scoreString);
            }

        }
    });
}
}

Answer 2

您正在使用onCreate方法执行所有操作。因此，在应用程序开始时调用所有代码。此时，您的EditText为空，您的代码将转到这些部分：

 if(gpaString.equals("")){
        gpaString = "0";
 }

 if(actString.equals("")){
        actString = "0";
 }

 if (actString.equals("")) {
        actString = "0";
 }

这意味着您的值gpaDouble，actInt和satInt等于0.

然后，您正在执行以下操作：

scoreDouble = (0.6*gpaDouble*25)+(0.4*(satInt/36)*100);

和此：

scoreDouble = (0.6*gpaDouble*25)+(0.4*(satInt/2400)*100);

如果值为0，则scoreDouble值只能等于0.

要解决此问题，请获取EditText s＆＃39;您onClick的{{1}}方法中的文字。

将双值放入TextView

2 个答案: