Question

我有一个小项目，可以创建一个计算学生GPA的应用程序。

到目前为止，我正在使用微调器让学生选择成绩。请注意，我只为一门课程创建了一个插槽，一旦运行正常，我将修改公式以计算所有课程。

一旦我单击了应该进行整理的按钮，就什么也没发生。

XML

    <?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.abdulelah.mygpa.GPA_51"
    tools:showIn="@layout/activity_gpa_51">

    <TextView
        android:id="@+id/Result5_1"
        android:layout_width="77dp"
        android:layout_height="28dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="TextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.501"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.443" />

    <Spinner
        android:id="@+id/spinner5_1"
        android:text="Spinner"
        android:layout_width="93dp"
        android:layout_height="28dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.029"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.036" />

    <EditText
        android:id="@+id/creditNum"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:inputType="number"
        app:layout_constraintBottom_toTopOf="@+id/Result5_1"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.232"
        app:layout_constraintStart_toEndOf="@+id/spinner5_1"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.021" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="48dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/Result5_1" />

</android.support.constraint.ConstraintLayout>

Java代码

package com.example.abdulelah.mygpa;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;

public class GPA_51 extends AppCompatActivity {

Spinner spinner;
double gradesValue;
double result;
EditText creditNum;
TextView result511;
Button ButtonResult;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_gpa_51);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    creditNum = (EditText)findViewById(R.id.creditNum);
    ButtonResult = (Button)findViewById(R.id.button1);
    result511 = (TextView)findViewById(R.id.Result5_1);




    spinner = (Spinner) findViewById(R.id.spinner5_1);
    final String[] grades = {"A+", "A", "B+", "B", "C+", "C", "D+", "D", "F"};

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, grades);
    spinner.setAdapter(adapter);

    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int i, long id) {
            parent.getItemAtPosition(i);

            if (grades.equals("A+"))
                gradesValue=4.00;
            else if (grades.equals("A"))
                gradesValue=3.75;
            else if (grades.equals("B+"))
                gradesValue=3.50;
            else if (grades.equals("B"))
                gradesValue=3.00;
            else if (grades.equals("C+"))
                gradesValue=2.50;
            else if (grades.equals("C"))
                gradesValue=2.00;
            else if (grades.equals("D+"))
                gradesValue=1.50;
            else if (grades.equals("D"))
                gradesValue=1.00;
            else if (grades.equals("F"))
                gradesValue=0;



        }

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

        }
    });




    ButtonResult.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String creditNumber1 = creditNum.getText().toString();
            int numberOfCredit = Integer.parseInt(creditNumber1);


            result = gradesValue * numberOfCredit;

            result511.setText(String.valueOf(result));
             }
    });


}

}

Answer 1

您应该通过这种方式检查

if(parent.getItemAtPosition(position).toString().equalsIgnoreCase("A+")){gradesValue=4.00;}

Answer 2

因为您正在比较错误的变量。 grades是一个字符串数组。

String selectedGrade = parent.getItemAtPosition(i);
//now use
if(selectedGrade.equals("A+")){
}...

在Android Studio中计算GPA

2 个答案: