每次按下按钮时导致我的应用程序崩溃的原因是什么？

Question

在我输入每门课程的学分和成绩后，然后按下计算 GPA 按钮，我的应用程序就崩溃了。我尝试过调试，发现所有逻辑都运行良好，直到为我的 textview 设置文本。然后它崩溃并且不显示按钮下方的 GPA。package com.example.gpa_tejadaa4_calculator;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class MainActivity extends AppCompatActivity {    private EditText ch1,ch2,ch3,ch4,ch5;    private EditText g1,g2,g3,g4,g5;    private Button gpa_calc;    private TextView result;    //private int credit_sum = 0;    //private int grade_sum = 0;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //Credit Hours        ch1 = (EditText)findViewById(R.id.C_H1);        ch2 = (EditText)findViewById(R.id.C_H2);        ch3 = (EditText)findViewById(R.id.C_H3);        ch4 = (EditText)findViewById(R.id.C_H4);        ch5 = (EditText)findViewById(R.id.C_H5);        //Grades        g1= (EditText)findViewById(R.id.L_G1);        g2= (EditText)findViewById(R.id.L_G2);        g3= (EditText)findViewById(R.id.L_G3);        g4= (EditText)findViewById(R.id.L_G4);        g5= (EditText)findViewById(R.id.L_G5);        //Button        gpa_calc = (Button) findViewById(R.id.button);        //Result        result = (TextView)findViewById(R.id.result);        gpa_calc.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                calculateGPA();            }        });    }    public void calculateGPA() {        double quality_points = 0;        double credit_sum = 0;        double gpa=0;        double chour1 = Double.valueOf(ch1.getText().toString());        double chour2 = Double.valueOf(ch2.getText().toString());        double chour3 = Double.valueOf(ch3.getText().toString());        double chour4 = Double.valueOf(ch4.getText().toString());

Answer 1

public class MainActivity extends AppCompatActivity {

    private EditText ch1,ch2,ch3,ch4,ch5;

    private EditText g1,g2,g3,g4,g5;

    private Button gpa_calc;

    private TextView result;

     Double final =0;

    //private int credit_sum = 0;

    //private int grade_sum = 0;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        //Credit Hours

        ch1 = (EditText)findViewById(R.id.C_H1);

        ch2 = (EditText)findViewById(R.id.C_H2);

        ch3 = (EditText)findViewById(R.id.C_H3);

        ch4 = (EditText)findViewById(R.id.C_H4);

        ch5 = (EditText)findViewById(R.id.C_H5);

        //Grades

        g1= (EditText)findViewById(R.id.L_G1);

        g2= (EditText)findViewById(R.id.L_G2);

        g3= (EditText)findViewById(R.id.L_G3);

        g4= (EditText)findViewById(R.id.L_G4);

        g5= (EditText)findViewById(R.id.L_G5);

        //Button

        gpa_calc = (Button) findViewById(R.id.button);

        //Result

        result = (TextView)findViewById(R.id.result);

        gpa_calc.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

               final= calculateGPA();

              result.setText(final.toString());

            }

        });

    }

    public double calculateGPA() {

        double quality_points = 0;

        double credit_sum = 0;

        double gpa=0;

        double chour1 = Double.valueOf(ch1.getText().toString());

        double chour2 = Double.valueOf(ch2.getText().toString());

        double chour3 = Double.valueOf(ch3.getText().toString());

        double chour4 = Double.valueOf(ch4.getText().toString());

        double chour5 = Double.valueOf(ch5.getText().toString());

        String l1 = String.valueOf(g1.getText());

        String l2 = String.valueOf(g2.getText());

        String l3 = String.valueOf(g3.getText());

        String l4 = String.valueOf(g4.getText());

        String l5 = String.valueOf(g5.getText());

        double[] creditArray = new double[]{chour1, chour2, chour3, chour4, chour5};

        String[] gradeArray = new String[]{l1,l2,l3,l4,l5};

        credit_sum = chour1+chour2+chour3+chour4+chour5;

        for(int i=0; i<gradeArray.length; i++){

            if (gradeArray[i].equals("A")){

                quality_points += (creditArray[i] * 4);

            }

            else if (gradeArray[i].equals("B")){

                quality_points += (creditArray[i] * 3);

            }

            else if (gradeArray[i].equals("C")){

                quality_points += (creditArray[i] * 2);

            }

            else if (gradeArray[i].equals("D")){

                quality_points += (creditArray[i] * 1);

            }

            else if (gradeArray[i].equals("F")){

                quality_points += (creditArray[i] * 0);

            }

        }

        gpa = (quality_points/credit_sum);

        String str = Double.toString(gpa);

       return gpa;

    }}

Answer 2

这可能与您的问题无关，但我修复了您的布局。当然，您仍然可以改进它。

<?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"

    tools:context=".MainActivity">

    <EditText

        android:id="@+id/L_G5"

        android:layout_width="113dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="24dp"

        android:layout_marginEnd="8dp"

        android:ems="10"

        android:hint="@string/Grade"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/C_H5"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toEndOf="@+id/C_H5"

        tools:targetApi="o" />

    <EditText

        android:id="@+id/L_G4"

        android:layout_width="113dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:layout_marginEnd="8dp"

        android:ems="10"

        android:hint="@string/Grade"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/C_H4"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toEndOf="@+id/C_H4"

        tools:targetApi="o" />

    <EditText

        android:id="@+id/C_H5"

        android:layout_width="114dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:ems="10"

        android:hint="@string/credit_hours"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/c5"

        app:layout_constraintStart_toEndOf="@+id/c5"

        tools:targetApi="o" />

    <TextView

        android:id="@+id/c5"

        android:layout_width="70dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="24dp"

        android:layout_marginTop="50dp"

        android:text="@string/course_5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/c4" />

    <TextView

        android:id="@+id/c3"

        android:layout_width="70dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="24dp"

        android:layout_marginTop="50dp"

        android:text="@string/course_3"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/c2" />

    <EditText

        android:id="@+id/C_H4"

        android:layout_width="110dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:layout_marginLeft="32dp"

        android:layout_marginTop="24dp"

        android:ems="10"

        android:hint="@string/credit_hours"

        android:inputType="textPersonName"

        app:layout_constraintStart_toEndOf="@+id/c4"

        app:layout_constraintTop_toBottomOf="@+id/C_H3"

        android:importantForAutofill="no" tools:targetApi="o" />

    <TextView

        android:id="@+id/c4"

        android:layout_width="70dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="24dp"

        android:layout_marginTop="50dp"

        android:text="@string/course_4"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/c3" />

    <EditText

        android:id="@+id/L_G3"

        android:layout_width="113dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:layout_marginEnd="8dp"

        android:ems="10"

        android:hint="@string/Grade"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/C_H3"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toEndOf="@+id/C_H3"

        tools:targetApi="o" />

    <EditText

        android:id="@+id/C_H3"

        android:layout_width="110dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:ems="10"

        android:hint="@string/credit_hours"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/c3"

        app:layout_constraintStart_toEndOf="@+id/c3"

        tools:targetApi="o" />

    <EditText

        android:id="@+id/L_G2"

        android:layout_width="112dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:layout_marginEnd="8dp"

        android:ems="10"

        android:hint="@string/Grade"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/C_H2"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toEndOf="@+id/C_H2"

        tools:targetApi="o" />

    <EditText

        android:id="@+id/C_H2"

        android:layout_width="110dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:ems="10"

        android:hint="@string/credit_hours"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/c2"

        app:layout_constraintStart_toEndOf="@+id/c2"

        tools:targetApi="o" />

    <TextView

        android:id="@+id/c2"

        android:layout_width="70dp"

        android:layout_height="21dp"

        android:layout_marginStart="24dp"

        android:layout_marginTop="50dp"

        android:text="@string/course_2"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/c1" />

    <TextView

        android:id="@+id/c1"

        android:layout_width="70dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="24dp"

        android:layout_marginTop="112dp"

        android:text="@string/course_1"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

    <EditText

        android:id="@+id/C_H1"

        android:layout_width="110dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:ems="10"

        android:hint="@string/credit_hours"

        android:importantForAutofill="no"

        android:inputType="numberDecimal"

        app:layout_constraintBaseline_toBaselineOf="@+id/c1"

        app:layout_constraintStart_toEndOf="@+id/c1"

        tools:targetApi="o" />

    <EditText

        android:id="@+id/L_G1"

        android:layout_width="110dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="32dp"

        android:layout_marginEnd="8dp"

        android:ems="10"

        android:hint="@string/Grade"

        android:importantForAutofill="no"

        android:inputType="textPersonName"

        app:layout_constraintBaseline_toBaselineOf="@+id/C_H1"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toEndOf="@+id/C_H1"

        tools:targetApi="o" />

    <Button

        android:id="@+id/button"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginStart="8dp"

        android:layout_marginLeft="8dp"

        android:layout_marginTop="78dp"

        android:layout_marginEnd="8dp"

        android:layout_marginRight="8dp"

        android:text="@string/compute_gpa"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.498"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/C_H5" />

    <TextView

        android:id="@+id/result"

        android:layout_width="66dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="170dp"

        android:layout_marginTop="46dp"

        android:layout_marginEnd="175dp"

        android:layout_marginBottom="119dp"

        android:textSize="18sp"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/button" />

</android.support.constraint.ConstraintLayout>