我的 android 应用程序总是崩溃

Question

我想做一个科学计算器（Android app）但是出现了一些问题。我不知道 Java 但我理解代码，因为我知道 C++。我已将普通计算器的代码修改为科学计算器，但代码似乎不起作用。只有 +、-、*、/ 等基本功能有效，但我添加的功能如 Sin、Cos、Tan、Sqrt、Pow、Exp 等在我使用这些函数时似乎不起作用，应用程序崩溃了。这是我的源代码。

MainActivity.java

package com.example.anant.scientificcalculator;

import android.databinding.DataBindingUtil;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import static java.lang.Math.*;
import java.text.DecimalFormat;
import com.example.anant.scientificcalculator.databinding.MainActivityBinding;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

private MainActivityBinding binding;

private static final char FACT = '!';
private static final char POWER = '^';
private static final String SQRT = "SQRT";

private static final String SIN = "SIN";
private static final String COS = "COS";
private static final String TAN = "TAN";
private static final String LOG = "LOG";

private static final char LEFTC = '(';
private static final char RIGHTC = ')';
private static final String EXP = "EXP";
private static final String PIE = "PIE";

private static final char ADD = '+';
private static final char SUBTRACT = '-';
private static final char MULTIPlY = '*';
private static final char DIVIDE = '/';

private char CURRENT_ACTION;
private String ADVANCE_ACTION;

private double valueOne = Double.NaN;
private double valueTwo;
private double valueTemp;

private DecimalFormat decimalFormat;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    decimalFormat = new DecimalFormat("#.##########");

    binding = DataBindingUtil.setContentView(this, R.layout.main_activity);

    binding.buttonDot.setOnClickListener(new View.OnClickListener(){
        @Override
                public void onClick(View view){
                    binding.editText.setText(binding.editText.getText() + ".");
        }
    });

    binding.buttonZero.setOnClickListener(new View.OnClickListener(){
        @Override
            public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "0");
        }
    });

    binding.buttonOne.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "1");
        }
    });

    binding.buttonTwo.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "2");
        }
    });

    binding.buttonThree.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "3");
        }
    });

    binding.buttonFour.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "4");
        }
    });

    binding.buttonFive.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "5");
        }
    });

    binding.buttonSix.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "6");
        }
    });

    binding.buttonSeven.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "7");
        }
    });

    binding.buttonEight.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "8");
        }
    });

    binding.buttonNine.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "9");
        }
    });

    binding.buttonLeftC.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + "(");
        }
    });

    binding.buttonRightC.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            binding.editText.setText(binding.editText.getText() + ")");
        }
    });

    binding.buttonExp.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            computeCalculation();
            ADVANCE_ACTION = EXP;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "EXP");
            binding.editText.setText(null);
        }
    });

    binding.buttonPie.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){
            computeCalculation();
            ADVANCE_ACTION = PIE;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "PIE");
            binding.editText.setText(null);
        }
    });

    binding.buttonAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            CURRENT_ACTION = ADD;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "+");
            binding.editText.setText(null);
        }
    });

    binding.buttonSubtract.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            CURRENT_ACTION = SUBTRACT;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "-");
            binding.editText.setText(null);
        }
    });

    binding.buttonMultiply.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            CURRENT_ACTION = MULTIPlY;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "*");
            binding.editText.setText(null);
        }
    });

    binding.buttonDivide.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            CURRENT_ACTION = DIVIDE;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "/");
            binding.editText.setText(null);
        }
    });

    binding.buttonFact.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            CURRENT_ACTION = FACT;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "!");
            binding.editText.setText(null);
        }
    });

    binding.buttonPow.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            CURRENT_ACTION = POWER;
            binding.infoTextView.setText(decimalFormat.format(valueOne) + "^");
            binding.editText.setText(null);
        }
    });

    binding.buttonSqrt.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            ADVANCE_ACTION = SQRT;
            binding.infoTextView.setText("SQRT(" + decimalFormat.format(valueOne) + ")");
            binding.editText.setText(null);
        }
    });

    binding.buttonSine.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            ADVANCE_ACTION = SIN;
            binding.infoTextView.setText("SIN(" + decimalFormat.format(valueOne) + ")");
            binding.editText.setText(null);
        }
    });

    binding.buttonCosine.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            ADVANCE_ACTION = COS;
            binding.infoTextView.setText("COS(" + decimalFormat.format(valueOne) + ")");
            binding.editText.setText(null);
        }
    });

    binding.buttonTangent.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            ADVANCE_ACTION = TAN;
            binding.infoTextView.setText("TAN(" + decimalFormat.format(valueOne) + ")");
            binding.editText.setText(null);
        }
    });

    binding.buttonLog.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            ADVANCE_ACTION = LOG;
            binding.infoTextView.setText("LOG(" + decimalFormat.format(valueOne) + ")");
            binding.editText.setText(null);
        }
    });

    binding.buttonEqual.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            computeCalculation();
            binding.infoTextView.setText(binding.infoTextView.getText().toString() +
                    decimalFormat.format(valueTwo) + " = " + decimalFormat.format(valueOne));
            valueOne = Double.NaN;
            CURRENT_ACTION = '0';
        }
    });

    binding.buttonClear.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(binding.editText.getText().length() > 0) {
                CharSequence currentText = binding.editText.getText();
                binding.editText.setText(currentText.subSequence(0, currentText.length()-1));
            }
            else {
                valueOne = Double.NaN;
                valueTwo = Double.NaN;
                binding.editText.setText("");
                binding.infoTextView.setText("");
            }
        }
    });

}

private void computeCalculation() {
    if(!Double.isNaN(valueOne)) {
        valueTwo = Double.parseDouble(binding.editText.getText().toString());
        binding.editText.setText(null);

        if(CURRENT_ACTION == ADD)
            valueOne = this.valueOne + valueTwo;
        else if(CURRENT_ACTION == SUBTRACT)
            valueOne = this.valueOne - valueTwo;
        else if(CURRENT_ACTION == MULTIPlY)
            valueOne = this.valueOne * valueTwo;
        else if(CURRENT_ACTION == DIVIDE)
            valueOne = this.valueOne / valueTwo;
        else if(CURRENT_ACTION == FACT)
        {
            valueTemp = this.valueOne;
            int i,valueThree=1;

            for(i=(int) valueTemp;i>0;i--) //type conversion
            {
                valueThree *= i;
            }
            valueOne = valueThree;
        }
        else if(CURRENT_ACTION == POWER) {
            valueTemp = this.valueOne;
            valueTemp = Math.pow(valueOne, valueTwo);
            valueOne = valueTemp;
        }
        else if(ADVANCE_ACTION == SQRT) {
            valueTemp = this.valueOne;
            valueOne = Math.sqrt(valueTemp);
        }
        else if(ADVANCE_ACTION == SIN) {
            valueTemp = this.valueOne;
            valueOne = Math.sin(valueTemp);
        }
        else if(ADVANCE_ACTION == COS) {
            valueTemp = this.valueOne;
            valueOne = Math.cos(valueTemp);
        }
        else if(ADVANCE_ACTION == TAN) {
            valueTemp = this.valueOne;
            valueOne = Math.tan(valueTemp);
        }
        else if(ADVANCE_ACTION == LOG) {
            valueTemp = this.valueOne;
            valueOne = Math.log(valueTemp);
        }
        else if(ADVANCE_ACTION == PIE) {
            valueTemp = this.valueOne;
            valueTemp = Math.PI;
            valueOne = valueTemp;
        }
        else if(ADVANCE_ACTION == EXP) {
            valueTemp = this.valueOne;
            valueTemp = Math.E;
            valueOne = valueTemp;
        }
    }
    else {
        try {
            valueOne = Double.parseDouble(binding.editText.getText().toString());
        }
        catch (Exception e){}
    }
}
}

谁能告诉我为什么我的应用总是崩溃？

main_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<layout>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_activity"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.anant.scientificcalculator.MainActivity">


<TextView
    android:id="@+id/infoTextView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="30dp"
    android:textSize="30sp" />

<EditText
    android:id="@+id/editText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/infoTextView"
    android:enabled="false"
    android:gravity="bottom"
    android:hint="0"
    android:inputType="numberDecimal"
    android:lines="2"
    android:maxLines="2"
    android:textAlignment="textEnd"
    android:textColor="@android:color/black"
    android:textSize="40sp" />

<Button
    android:id="@+id/buttonFact"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/editText"
    android:text="@string/buttonFact"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonPow"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/editText"
    android:layout_toRightOf="@id/buttonFact"
    android:text="@string/buttonPow"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonSqrt"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/editText"
    android:layout_toRightOf="@id/buttonPow"
    android:text="@string/buttonSqrt"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonClear"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@id/buttonSqrt"
    android:layout_below="@id/editText"
    android:text="@string/buttonClear"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonSine"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonFact"
    android:text="@string/buttonSine"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonCosine"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonPow"
    android:layout_toRightOf="@id/buttonSine"
    android:text="@string/buttonCosine"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonTangent"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonSqrt"
    android:layout_toRightOf="@id/buttonCosine"
    android:text="@string/buttonTangent"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonLog"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonClear"
    android:layout_toRightOf="@id/buttonTangent"
    android:text="@string/buttonLog"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonLeftC"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonSine"
    android:text="@string/buttonLeftC"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonRightC"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonCosine"
    android:layout_toRightOf="@id/buttonLeftC"
    android:text="@string/buttonRightC"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonExp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonTangent"
    android:layout_toRightOf="@id/buttonRightC"
    android:text="@string/buttonExp"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonPie"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonLog"
    android:layout_toRightOf="@id/buttonExp"
    android:text="@string/buttonPie"
    android:textSize="20sp" />


<Button
    android:id="@+id/buttonSeven"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonLeftC"
    android:text="@string/buttonSeven"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonEight"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonRightC"
    android:layout_toRightOf="@id/buttonSeven"
    android:text="@string/buttonEight"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonNine"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonExp"
    android:layout_toRightOf="@id/buttonEight"
    android:text="@string/buttonNine"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonFour"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonSeven"
    android:text="@string/buttonFour"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonFive"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonEight"
    android:layout_toRightOf="@id/buttonFour"
    android:text="@string/buttonFive"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonSix"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonNine"
    android:layout_toRightOf="@id/buttonFive"
    android:text="@string/buttonSix"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonOne"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonFour"
    android:text="@string/buttonOne"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonTwo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonFive"
    android:layout_toRightOf="@id/buttonOne"
    android:text="@string/buttonTwo"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonThree"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonSix"
    android:layout_toRightOf="@id/buttonTwo"
    android:text="@string/buttonThree"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonDot"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonOne"
    android:text="@string/buttonDot"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonZero"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/buttonTwo"
    android:layout_toRightOf="@id/buttonDot"
    android:text="@string/buttonZero"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonEqual"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignRight="@id/buttonNine"
    android:layout_below="@id/buttonThree"
    android:text="@string/buttonEqual"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonDivide"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@id/buttonNine"
    android:layout_toRightOf="@id/buttonNine"
    android:text="@string/buttonDIvide"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonMultiply"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@id/buttonSix"
    android:layout_toRightOf="@id/buttonSix"
    android:text="@string/buttonMultiply"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonSubtract"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@id/buttonThree"
    android:layout_toRightOf="@id/buttonThree"
    android:text="@string/buttonSubtract"
    android:textSize="20sp" />

<Button
    android:id="@+id/buttonAdd"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignTop="@id/buttonEqual"
    android:layout_toRightOf="@id/buttonEqual"
    android:text="@string/buttonAdd"
    android:textSize="20sp" />

</RelativeLayout>
</layout>

Answer 1

您需要这样的东西来解决您的问题..

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
     setContentView(R.layout.main_activity); 
  }

Answer 2

我设法运行你的代码稍作修改。

问题似乎出在这里：

private void computeCalculation() {
        if(!Double.isNaN(valueOne)) {
            valueTwo = Double.parseDouble(binding.editText.getText().toString());
            binding.editText.setText(null);

如果您在崩溃后查看 Android 监视器下方，您将看到如下内容：

    04-10 13:01:01.531 20742-20742/com.johnurrutia.so_43315233 E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                 Process: com.johnurrutia.so_43315233, PID: 20742
                                                                                 java.lang.NumberFormatException: Invalid double: ""
                                                                                     at java.lang.StringToReal.invalidReal(StringToReal.java:63)
                                                                                     at java.lang.StringToReal.parseDouble(StringToReal.java:267)
                                                                                     at java.lang.Double.parseDouble(Double.java:301)
                                                                                     at com.johnurrutia.so_43315233.MainActivity.computeCalculation(MainActivity.java:303)
                                                                                     at com.johnurrutia.so_43315233.MainActivity.access0(MainActivity.java:11)
...

它告诉你有一个致命的例外，因为一个有效的双倍。您可以在第 303 行跟踪到 MainActivity.java（您很可能会有不同的行）。

使用该行上的调试器，您可以检查并查看发生了什么。

我认为您正在尝试将空字符串转换为双精度字符串。

我对运行您的代码所做的更改如下。

1）布局文件中： a) 更改了名称为 android space 的布局标签。 b) 添加了一个空的占位符（不确定是否有必要）

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>

    </data>
    <RelativeLayout
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/main_activity"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.johnurrutia.so_43315233.MainActivity">

...
</layout>

c) 在 EditText 中有一个 "endText" 的对齐方式，它似乎与选定的重力不兼容，所以我只是将其删除。

d) 由于您还没有发布它，请确保您在 res/values/string.xml 文件中设置了所有 @string/stringname。

2) 当您使用数据绑定时，请检查您的 Gradle 应用模块文件。你必须拥有：

android {

    ...

    dataBinding {
        enabled = true
    }
}

3) 之后查看您的文件并确认您没有看到任何红色内容。

4) 点击构建->清理项目。然后运行.

我的 android 应用程序总是崩溃

My android app keeps on crashing

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android

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