Android中的成功构建仍然在设备上崩溃

Question

我仍然是一个初学者，我已经尝试做一个应用程序，以减轻我在实验室的工作。只是一些基本的计算。我想做一个应用程序是兼容的大多数设备，以防止其有用的信息。尽管应用程序的构建似乎很成功，但一旦它在我的设备上启动，它就会立即崩溃。下面列出了所使用的文件。我尝试了Android给我的所有提示，但都没有结果。App还是崩溃了。

会非常感谢一些提示和建设性的软肋！

Main Activity.java

package com.e.concalc;

import androidx.appcompat.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 protein_sp;
private EditText salt_sp;
private EditText protein_st;
private EditText salt_st;
private EditText volume_sp;

private TextView tv_resultH2O;
private TextView tv_resultSalt;
private TextView tv_resultProtein;

private Button button1;

public MainActivity(TextView tv_resultH2O, TextView tv_resultSalt, TextView tv_resultProtein, Button button1) {
    this.tv_resultH2O = tv_resultH2O;
    this.tv_resultSalt = tv_resultSalt;
    this.tv_resultProtein = tv_resultProtein;
    this.button1 = button1;
}

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

    protein_sp = findViewById(R.id.edit1);
    protein_st = findViewById(R.id.edit2);
    salt_sp = findViewById(R.id.edit3);
    salt_st = findViewById(R.id.edit4);
    volume_sp = findViewById(R.id.edit5);



    button1.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            makeCalculations();
        }
    });
}


private void makeCalculations() {
    double p_sp = Double.valueOf(protein_sp.getText().toString());
    double p_st = Double.valueOf(protein_st.getText().toString());
    double s_sp = Double.valueOf(salt_sp.getText().toString());
    double s_st = Double.valueOf(salt_st.getText().toString());
    double v_sp = Double.valueOf(volume_sp.getText().toString());

    double resultH2O;
    double resultSalt;
    double resultProtein;

    resultProtein = p_sp * v_sp / p_st;
    resultSalt = s_sp * v_sp / s_st;
    resultH2O = v_sp - resultProtein - resultSalt;



    tv_resultH2O.setText(Double.toString(resultH2O));
    tv_resultSalt.setText(Double.toString(resultSalt));
    tv_resultProtein.setText(Double.toString(resultProtein));
    }
}

activity_main.xml -布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
android:orientation="vertical"
tools:context=".MainActivity">



<TextView
    android:id="@+id/text1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/Protein1"
    android:textSize="20sp"
    android:textStyle="bold"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintHorizontal_bias="0.133"
    app:layout_constraintVertical_bias="0.070" />

<TextView
    android:id="@+id/text2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/Protein2"
    android:textSize="20sp"
    android:textStyle="bold"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.77"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.070" />


<TextView
    android:id="@+id/text4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/Salt1"
    android:textSize="20sp"
    android:textStyle="bold"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="@+id/text2"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.21" />

<TextView
    android:id="@+id/text3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/Salt2"
    android:textSize="20sp"
    android:textStyle="bold"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="@+id/text1"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.21" />

<TextView
    android:id="@+id/text5"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/SampleVolume"
    android:textSize="20sp"
    android:textStyle="bold"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="@+id/text3"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.35" />


<EditText
    android:id="@+id/edit1"
    android:layout_width="100dp"
    android:layout_height="40dp"
    android:textSize="15sp"
    android:inputType="number"
    android:hint="@string/hint"
    app:layout_constraintStart_toStartOf="@+id/text1"
    app:layout_constraintTop_toBottomOf="@+id/text1"
    android:importantForAutofill="no" />

<EditText
    android:id="@id/edit2"
    android:layout_width="100dp"
    android:layout_height="40dp"
    android:textSize="15sp"
    android:inputType="number"
    android:hint="@string/hint"
    app:layout_constraintStart_toStartOf="@+id/text2"
    app:layout_constraintTop_toBottomOf="@+id/text2"
    android:importantForAutofill="no" />

<EditText
    android:id="@id/edit4"
    android:layout_width="100dp"
    android:layout_height="40dp"
    android:textSize="15sp"
    android:inputType="number"
    android:hint="@string/hint"
    app:layout_constraintStart_toStartOf="@+id/text4"
    app:layout_constraintTop_toBottomOf="@+id/text4"
    android:importantForAutofill="no" />

<EditText
    android:id="@id/edit3"
    android:layout_width="100dp"
    android:layout_height="40dp"
    android:textSize="15sp"
    android:inputType="number"
    android:hint="@string/hint"
    app:layout_constraintStart_toStartOf="@+id/text3"
    app:layout_constraintTop_toBottomOf="@+id/text3"
    android:importantForAutofill="no" />

<EditText
    android:id="@+id/edit5"
    android:layout_width="100dp"
    android:layout_height="40dp"
    android:textSize="15sp"
    android:inputType="number"
    android:hint="@string/hint"
    app:layout_constraintStart_toStartOf="@+id/text5"
    app:layout_constraintTop_toBottomOf="@+id/text5"
    android:importantForAutofill="no" />

<Button
    android:id="@+id/button1"
    android:layout_width="120dp"
    android:layout_height="40dp"
    android:layout_marginBottom="128dp"
    android:text="@string/button1"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.158"
    app:layout_constraintStart_toStartOf="parent" />


<Button
    android:id="@+id/button2"
    android:layout_width="120dp"
    android:layout_height="40dp"
    android:layout_marginStart="51dp"
    android:layout_marginLeft="51dp"
    android:text="@string/button2"
    app:layout_constraintBottom_toBottomOf="@+id/button1"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.745"
    app:layout_constraintStart_toEndOf="@+id/button1"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="@+id/button1" />


<TextView
    android:id="@+id/tv_resultH2O"
    android:layout_width="100dp"
    android:layout_height="50dp"
    android:layout_centerInParent="true"

    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintHorizontal_bias="0.1"
    app:layout_constraintVertical_bias="0.6"/>


<TextView
    android:id="@+id/tv_resultSalt"
    android:layout_width="100dp"
    android:layout_height="50dp"
    android:layout_centerInParent="true"
    android:textAppearance="?android:attr/textAppearanceLarge"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintVertical_bias="0.6"/>

<TextView
    android:id="@+id/tv_resultProtein"
    android:layout_width="100dp"
    android:layout_height="50dp"
    android:layout_centerInParent="true"
    android:textAppearance="?android:attr/textAppearanceLarge"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintHorizontal_bias="0.9"
    app:layout_constraintVertical_bias="0.6"/>
</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

你忘了findViewById button1.So in onCreate方法，在button1.setOnClickListener之前.增加这一行：

button1 = findViewById(R.id.button1);

Answer 2

删除您的自定义构造函数。

活动必须有一个非参数构造函数，Android用来创建类，当您定义任何重写时，就不再自动在Java中为您创建无参数构造函数.