CGPA计算器

Question

您好，我正在开发一个 Android 应用程序，它将帮助学生计算那里的大学 CGPA。该应用程序已完成 95%，但我有一个小错误，我注意到可以修复它。

错误是当我在微调器中输入所有值并在我启动我的应用程序时第一次按下 "CALCULATE" 按钮时它不会产生正确的结果并显示 "NaN" 错误.

根据我的研究，当输入为“0/0”时出现 "NaN" 错误是正常的，但真正的问题是即使我没有提供输入 0/0，它仍然会出现 NaN 错误第一次。当我更改微调器上的输入值并再次按 "CALCULATE" 时，它工作正常。

public class MainActivity extends AppCompatActivity {
    Spinner spinner,spinner2,spinner3,spinner4,spinner5,spinner6,spinner7,spinner8,spinner9,spinner10,spinner11,spinner12;
    TextView result;
    Button button1,button2;
    int a1=10,a2=10,a3=10,a4=10,a5=10,a6=10;
    int b1=0,b2=0,b3=0,b4=0,b5=0,b6=0;

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

        button1=(Button)findViewById(R.id.btn1);
        button2=(Button)findViewById(R.id.btn2);
        result=(TextView)findViewById(R.id.r1);

        spinner=(Spinner)findViewById(R.id.s1);
        spinner2=(Spinner)findViewById(R.id.s2);
        spinner3=(Spinner)findViewById(R.id.s3);
        spinner4=(Spinner)findViewById(R.id.s4);
        spinner5=(Spinner)findViewById(R.id.s5);
        spinner6=(Spinner)findViewById(R.id.s6);
        spinner7=(Spinner)findViewById(R.id.s7);
        spinner8=(Spinner)findViewById(R.id.s8);
        spinner9=(Spinner)findViewById(R.id.s9);
        spinner10=(Spinner)findViewById(R.id.s10);
        spinner11=(Spinner)findViewById(R.id.s11);
        spinner12=(Spinner)findViewById(R.id.s12);




        String[] crdt={"0","1","2","3","4","5"};
        String[] grade={"O","A+","A","B+","B","C","P","F"};
        ArrayAdapter<String> adapter1=new ArrayAdapter<String>(this,android.R.layout.simple_spinner_dropdown_item,crdt);
        spinner.setAdapter(adapter1);
        spinner3.setAdapter(adapter1);
        spinner5.setAdapter(adapter1);
        spinner7.setAdapter(adapter1);
        spinner9.setAdapter(adapter1);
        spinner11.setAdapter(adapter1);

        ArrayAdapter<String> adapter2=new ArrayAdapter<String>(this,android.R.layout.simple_spinner_dropdown_item,grade);
        spinner2.setAdapter(adapter2);
        spinner4.setAdapter(adapter2);
        spinner6.setAdapter(adapter2);
        spinner8.setAdapter(adapter2);
        spinner10.setAdapter(adapter2);
        spinner12.setAdapter(adapter2);

        result.setVisibility(View.GONE);


        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {


                result.setVisibility(View.VISIBLE);




                spinner2.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        switch (i)
                        {
                            case 0:a1=10; break;
                            case 1: a1=9;break;
                            case 2:a1=8;break;
                            case 3:a1=7;break;
                            case 4:a1=6;break;
                            case 5:a1=5;break;
                            case 6:a1=4;break;
                            case 7:a1=0;break;


                        }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> adapterView) {


                    }
                });
                spinner4.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        switch (i)
                        {
                            case 0:a2=10; break;
                            case 1: a2=9;break;
                            case 2:a2=8;break;
                            case 3:a2=7;break;
                            case 4:a2=6;break;
                            case 5:a2=5;break;
                            case 6:a2=4;break;
                            case 7:a2=0;break;


                        }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> adapterView) {


                    }
                }); spinner6.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        switch (i)
                        {
                            case 0:a3=10; break;
                            case 1: a3=9;break;
                            case 2:a3=8;break;
                            case 3:a3=7;break;
                            case 4:a3=6;break;
                            case 5:a3=5;break;
                            case 6:a3=4;break;
                            case 7:a3=0;break;


                        }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> adapterView) {


                    }
                }); spinner8.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        switch (i)
                        {
                            case 0: a4=10;break;
                            case 1: a4=9;break;
                            case 2:a4=8;break;
                            case 3:a4=7;break;
                            case 4:a4=6;break;
                            case 5:a4=5;break;
                            case 6:a4=4;break;
                            case 7:a4=0;break;


                        }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> adapterView) {


                    }
                }); spinner10.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        switch (i)
                        {
                            case 0:a5=10; break;
                            case 1: a5=9;break;
                            case 2:a5=8;break;
                            case 3:a5=7;break;
                            case 4:a5=6;break;
                            case 5:a5=5;break;
                            case 6:a5=4;break;
                            case 7:a5=0;break;


                        }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> adapterView) {


                    }
                }); spinner12.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                        switch (i)
                        {
                            case 0:a6=10; break;
                            case 1: a6=9;break;
                            case 2:a6=8;break;
                            case 3:a6=7;break;
                            case 4:a6=6;break;
                            case 5:a6=5;break;
                            case 6:a6=4;break;
                            case 7:a6=0;break;


                        }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> adapterView) {


                    }
                });







            spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    switch (i)
                    {
                        case 0:b1=0; break;
                        case 1:b1=1;break;
                        case 2:b1=2;break;
                        case 3:b1=3;break;
                        case 4:b1=4;break;
                        case 5:b1=5;break;


                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {


                }
            });spinner3.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    switch (i)
                    {
                        case 0:b2=0; break;
                        case 1:b2=1;break;
                        case 2:b2=2;break;
                        case 3:b2=3;break;
                        case 4:b2=4;break;
                        case 5:b2=5;break;


                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {


                }
            });spinner5.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    switch (i)
                    {
                        case 0:b3=0; break;
                        case 1:b3=1;break;
                        case 2:b3=2;break;
                        case 3:b3=3;break;
                        case 4:b3=4;break;
                        case 5:b3=5;break;


                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {


                }
            });spinner7.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    switch (i)
                    {
                        case 0:b4=0; break;
                        case 1:b4=1;break;
                        case 2:b4=2;break;
                        case 3:b4=3;break;
                        case 4:b4=4;break;
                        case 5:b4=5;break;


                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {


                }
            });spinner9.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    switch (i)
                    {
                        case 0:b5=0; break;
                        case 1:b5=1;break;
                        case 2:b5=2;break;
                        case 3:b5=3;break;
                        case 4:b5=4;break;
                        case 5:b5=5;break;


                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {


                }
            });spinner11.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    switch (i)
                    {
                        case 0:b6=0; break;
                        case 1:b6=1;break;
                        case 2:b6=2;break;
                        case 3:b6=3;break;
                        case 4:b6=4;break;
                        case 5:b6=5;break;



                    }
                }

                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {


                }
            });


            double p=(a1*b1+a2*b2+a3*b3+a4*b4+a5*b5+a6*b6);
            double q=(b1+b2+b3+b4+b5+b6);


            if(p==0 && q==0)
            {
                result.setText("Result is: 0.0");
            }
            else {
                double r = (p / q);


                result.setText("Result is:" + r);
            }


        }
    });
    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            spinner.setSelection(0);
            spinner2.setSelection(0);
            spinner3.setSelection(0);
            spinner4.setSelection(0);
            spinner5.setSelection(0);
            spinner6.setSelection(0);
            spinner7.setSelection(0);
            spinner8.setSelection(0);
            spinner9.setSelection(0);
            spinner10.setSelection(0);
            spinner11.setSelection(0);
            spinner12.setSelection(0);
            result.setText("Result is: 0.0");


        }
    });

Answer 1

问题应该是你除以 0 (and you can't)。

这些行没有对第二个成员进行 0 检查

        if(p==0 && q==0)
        {
            result.setText("Result is: 0.0");
        }
        else {
            double r = (p / q); //here, q might be 0


            result.setText("Result is:" + r);
        }

所以，首先决定如果 q 为 0 该怎么办，然后做这样的事情：

if(p==0 && q==0)
{
    result.setText("Result is: 0.0");
}
 else {
    double r = 0.0;
    if(q == 0){
        r = p; // or whatever you want
    } else{
        r = p / q;
    }
    result.setText("Result is:" + r);
}
...

如果我对问题的理解有误，请告诉我！

希望对您有所帮助

Answer 2

我看不出这道题有什么错误。这个问题很好理解。我猜问题出在你的代码上（一个简单的代码）。如果你能移动所有

spinner.setItemSelectedListener({
//your codes
{
//switch case and all
}
});

在 button1 操作之前，它应该有效。

CGPA计算器

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