Android Calculator App在运行时立即崩溃

Question

我正在为学校的课堂项目开发一个计算器应用程序，但是在幕后似乎有些错误不是基于语法的。我尝试运行我的应用程序崩溃。我一直无法找到我的错误，但在点击提交按钮后它总是崩溃。我还没有一个应用程序完全拒绝运行。

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.stins.calculator">

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name="com.example.stins.calculator.MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>

            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>
</application>

MainActivity.java

package com.example.stins.calculator;

import android.content.ClipData;
import android.content.ClipboardManager;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;

import com.example.stins.calculator.Calculator;
import com.example.stins.calculator.CalculatorImpl;
import com.example.stins.calculator.Config;
import com.example.stins.calculator.Constants;
import com.example.stins.calculator.Formatter;
import com.example.stins.calculator.R;
import com.example.stins.calculator.Utils;

import butterknife.BindView;
import butterknife.ButterKnife;
import butterknife.OnClick;
import butterknife.OnLongClick;
import me.grantland.widget.AutofitHelper;

public class MainActivity extends SimpleActivity implements Calculator {@BindView(R.id.result)
    TextView mResult;@BindView(R.id.formula)
    TextView mFormula;

    private static CalculatorImpl mCalc;

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

        CalculatorImpl calc = new CalculatorImpl(this);
        AutofitHelper.create(mResult);
        AutofitHelper.create(mFormula);
    }

    @OnClick(R.id.btn_plus)
    public void plusClicked() {
        mCalc.handleOperation(Constants.PLUS);
    }

    @OnClick(R.id.btn_minus)
    public void minusClicked() {
        mCalc.handleOperation(Constants.MINUS);
    }

    @OnClick(R.id.btn_multiply)
    public void multiplyClicked() {
        mCalc.handleOperation(Constants.MULTIPLY);
    }

    @OnClick(R.id.btn_divide)
    public void divideClicked() {
        mCalc.handleOperation(Constants.DIVIDE);
    }

    @OnClick(R.id.btn_modulo)
    public void moduloClicked() {
        mCalc.handleOperation(Constants.MODULO);
    }

    @OnClick(R.id.btn_power)
    public void powerClicked() {
        mCalc.handleOperation(Constants.POWER);
    }

    @OnClick(R.id.btn_root)
    public void rootClicked() {
        mCalc.handleOperation(Constants.ROOT);
    }

    @OnClick(R.id.btn_clear)
    public void clearClicked() {
        mCalc.handleClear();
    }

    @OnLongClick(R.id.btn_clear)
    public boolean clearLongClicked() {
        mCalc.handleReset();
        return true;
    }

    @OnClick(R.id.btn_equals)
    public void equalsClicked() {
        mCalc.handleEquals();
    }

    @OnClick({
        R.id.btn_decimal,
        R.id.btn_0,
        R.id.btn_1,
        R.id.btn_2,
        R.id.btn_3,
        R.id.btn_4,
        R.id.btn_5,
        R.id.btn_6,
        R.id.btn_7,
        R.id.btn_8,
        R.id.btn_9
    })
    public void numpadClick(View view) {
        numpadClicked(view.getId());
    }

    public void numpadClicked(int id) {
        mCalc.numpadClicked(id);
    }

    @Override
    public void setValue(String value) {
        mResult.setText(value);
    }

    // used only by Robolectric
    @Override
    public void setValueDouble(double d) {
        mCalc.setValue(Formatter.doubleToString(d));
        mCalc.setLastKey(Constants.DIGIT);
    }

    public void setFormula(String value) {
        mFormula.setText(value);
    }

    public CalculatorImpl getCalc() {
        return mCalc;
    }
}

CalcImpl.java

package com.example.stins.calculator;

public class CalculatorImpl {
    private String mDisplayedValue;
    private String mDisplayedFormula;
    private String mLastKey;
    private String mLastOperation;
    private Calculator mCallback;

    private boolean mIsFirstOperation;
    private boolean mResetValue;
    private double mBaseValue;
    private double mSecondValue;

    public CalculatorImpl(Calculator calculator) {
        mCallback = calculator;
        resetValues();
        setValue("0");
        setFormula("");
    }

    public CalculatorImpl(Calculator calculatorInterface, String value) {
        mCallback = calculatorInterface;
        resetValues();
        mDisplayedValue = value;
        setFormula("");
    }

    private void resetValueIfNeeded() {
        if (mResetValue) mDisplayedValue = "0";

        mResetValue = false;
    }

    private void resetValues() {
        mBaseValue = 0;
        mSecondValue = 0;
        mResetValue = false;
        mLastKey = "";
        mLastOperation = "";
        mDisplayedValue = "";
        mDisplayedFormula = "";
        mIsFirstOperation = true;
    }

    public void setValue(String value) {
        mCallback.setValue(value);
        mDisplayedValue = value;
    }

    private void setFormula(String value) {
        mCallback.setFormula(value);
        mDisplayedFormula = value;
    }

    private void updateFormula() {
        final String first = Formatter.doubleToString(mBaseValue);
        final String second = Formatter.doubleToString(mSecondValue);
        final String sign = getSign(mLastOperation);

        if (sign.equals("√")) {
            setFormula(sign + first);
        } else if (!sign.isEmpty()) {
            setFormula(first + sign + second);
        }
    }

    public void setLastKey(String mLastKey) {
        this.mLastKey = mLastKey;
    }

    public void addDigit(int number) {
        final String currentValue = getDisplayedNumber();
        final String newValue = formatString(currentValue + number);
        setValue(newValue);
    }

    private String formatString(String str) {
        // if the number contains a decimal, do not try removing the leading zero anymore, nor add group separator
        // it would prevent writing values like 1.02
        if (str.contains(".")) return str;

        final double doubleValue = Formatter.stringToDouble(str);
        return Formatter.doubleToString(doubleValue);
    }

    private void updateResult(double value) {
        setValue(Formatter.doubleToString(value));
        mBaseValue = value;
    }

    public String getDisplayedNumber() {
        return mDisplayedValue;
    }

    public double getDisplayedNumberAsDouble() {
        return Formatter.stringToDouble(getDisplayedNumber());
    }

    public String getDisplayedFormula() {
        return mDisplayedFormula;
    }

    public void handleResult() {
        mSecondValue = getDisplayedNumberAsDouble();
        calculateResult();
        mBaseValue = getDisplayedNumberAsDouble();
    }

    public void calculateResult() {
        if (!mIsFirstOperation) updateFormula();

        switch (mLastOperation) {
        case Constants.PLUS:
            updateResult(mBaseValue + mSecondValue);
            break;
        case Constants.MINUS:
            updateResult(mBaseValue - mSecondValue);
            break;
        case Constants.MULTIPLY:
            updateResult(mBaseValue * mSecondValue);
            break;
        case Constants.DIVIDE:
            divideNumbers();
            break;
        case Constants.MODULO:
            moduloNumbers();
            break;
        case Constants.POWER:
            powerNumbers();
            break;
        case Constants.ROOT:
            updateResult(Math.sqrt(mBaseValue));
            break;
        default:
            break;
        }
        mIsFirstOperation = false;
    }

    private void divideNumbers() {
        double resultValue = 0;
        if (mSecondValue != 0) resultValue = mBaseValue / mSecondValue;

        updateResult(resultValue);
    }

    private void moduloNumbers() {
        double resultValue = 0;
        if (mSecondValue != 0) resultValue = mBaseValue % mSecondValue;

        updateResult(resultValue);
    }

    private void powerNumbers() {
        double resultValue = Math.pow(mBaseValue, mSecondValue);
        if (Double.isInfinite(resultValue) || Double.isNaN(resultValue)) resultValue = 0;
        updateResult(resultValue);
    }

    public void handleOperation(String operation) {
        if (mLastKey.equals(Constants.DIGIT)) handleResult();

        mResetValue = true;
        mLastKey = operation;
        mLastOperation = operation;

        if (operation.equals(Constants.ROOT)) calculateResult();
    }

    public void handleClear() {
        final String oldValue = getDisplayedNumber();
        String newValue = "0";
        final int len = oldValue.length();
        int minLen = 1;
        if (oldValue.contains("-")) minLen++;

        if (len > minLen) newValue = oldValue.substring(0, len - 1);

        newValue = newValue.replaceAll("\\.$", "");
        newValue = formatString(newValue);
        setValue(newValue);
        mBaseValue = Formatter.stringToDouble(newValue);
    }

    public void handleReset() {
        resetValues();
        setValue("0");
        setFormula("");
    }

    public void handleEquals() {
        if (mLastKey.equals(Constants.EQUALS)) calculateResult();

        if (!mLastKey.equals(Constants.DIGIT)) return;

        mSecondValue = getDisplayedNumberAsDouble();
        calculateResult();
        mLastKey = Constants.EQUALS;
    }

    public void decimalClicked() {
        String value = getDisplayedNumber();
        if (!value.contains(".")) value += ".";
        setValue(value);
    }

    public void zeroClicked() {
        String value = getDisplayedNumber();
        if (!value.equals("0")) addDigit(0);
    }

    private String getSign(String lastOperation) {
        switch (lastOperation) {
        case Constants.PLUS:
            return "+";
        case Constants.MINUS:
            return "-";
        case Constants.MULTIPLY:
            return "*";
        case Constants.DIVIDE:
            return "/";
        case Constants.MODULO:
            return "%";
        case Constants.POWER:
            return "^";
        case Constants.ROOT:
            return "√";
        }
        return "";
    }

    public void numpadClicked(int id) {
        if (mLastKey.equals(Constants.EQUALS)) mLastOperation = Constants.EQUALS;
        mLastKey = Constants.DIGIT;
        resetValueIfNeeded();

        switch (id) {
        case R.id.btn_decimal:
            decimalClicked();
            break;
        case R.id.btn_0:
            zeroClicked();
            break;
        case R.id.btn_1:
            addDigit(1);
            break;
        case R.id.btn_2:
            addDigit(2);
            break;
        case R.id.btn_3:
            addDigit(3);
            break;
        case R.id.btn_4:
            addDigit(4);
            break;
        case R.id.btn_5:
            addDigit(5);
            break;
        case R.id.btn_6:
            addDigit(6);
            break;
        case R.id.btn_7:
            addDigit(7);
            break;
        case R.id.btn_8:
            addDigit(8);
            break;
        case R.id.btn_9:
            addDigit(9);
            break;
        default:
            break;
        }
    }
}

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id="@+id/calculator_holder"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.stins.calculator.MainActivity">

<TextView
    android:id="@+id/formula"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="2.1"
    android:fontFamily="sans-serif-light"
    android:gravity="right|bottom"
    android:maxLines="1"
    android:paddingLeft="@dimen/activity_margin"
    android:paddingRight="@dimen/activity_margin"
    android:textSize="@dimen/formula_text_size"/>

<TextView
    android:id="@+id/result"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="1.8"
    android:fontFamily="sans-serif-light"
    android:gravity="center_vertical|right"
    android:maxLines="1"
    android:paddingLeft="@dimen/activity_margin"
    android:paddingRight="@dimen/activity_margin"
    android:text="0"
    android:textSize="@dimen/display_text_size"/>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="2"
    android:orientation="horizontal">

    <Button
        android:id="@+id/btn_modulo"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="mod"
        android:textAllCaps="false"
        android:textSize="@dimen/mod_text_size"/>

    <Button
        android:id="@+id/btn_power"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="^"/>

    <Button
        android:id="@+id/btn_root"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="√"/>

    <Button
        android:id="@+id/btn_clear"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="C"/>

    <Button
        android:id="@+id/btn_reset"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="AC"
        android:visibility="gone"/>
</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="2"
    android:orientation="horizontal">

    <Button
        android:id="@+id/btn_7"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="7"/>

    <Button
        android:id="@+id/btn_8"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="8"/>

    <Button
        android:id="@+id/btn_9"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="9"/>

    <Button
        android:id="@+id/btn_divide"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="÷"/>
</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="2"
    android:orientation="horizontal">

    <Button
        android:id="@+id/btn_4"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="4"/>

    <Button
        android:id="@+id/btn_5"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="5"/>

    <Button
        android:id="@+id/btn_6"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="6"/>

    <Button
        android:id="@+id/btn_multiply"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="*"/>
</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="2"
    android:orientation="horizontal">

    <Button
        android:id="@+id/btn_1"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="1"/>

    <Button
        android:id="@+id/btn_2"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="2"/>

    <Button
        android:id="@+id/btn_3"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="3"/>

    <Button
        android:id="@+id/btn_minus"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="-"/>
</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="2"
    android:orientation="horizontal">

    <Button
        android:id="@+id/btn_0"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="0"/>

    <Button
        android:id="@+id/btn_decimal"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="."/>

    <Button
        android:id="@+id/btn_equals"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="="/>

    <Button
        android:id="@+id/btn_plus"
        style="@style/MyButton"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:text="+"/>
</LinearLayout>
</LinearLayout>

logcat的

02-11 14:27:36.485 5006-5006/com.example.stins.calculator E/AndroidRuntime:    
FATAL EXCEPTION: main
    Process: com.example.stins.calculator, PID: 5006
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.stins.calculator/com.example.stins.calculator.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.widget.TextView.getContext()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
    at android.app.ActivityThread.-wrap11(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.widget.TextView.getContext()' on a null object reference
    at me.grantland.widget.AutofitHelper.<init>(AutofitHelper.java:246)
    at me.grantland.widget.AutofitHelper.create(AutofitHelper.java:62)
    at me.grantland.widget.AutofitHelper.create(AutofitHelper.java:46)
    at com.example.stins.calculator.MainActivity.onCreate(MainActivity.java:40)
    at android.app.Activity.performCreate(Activity.java:6237)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
    at android.app.ActivityThread.-wrap11(ActivityThread.java) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:5417) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

如果可能，有人会知道如何提供帮助吗？

我也包含了我的logcat

Answer 1

检查以确保annotationProcessor中设置了butterknife build.gradle dependencies。您应该在annotationProcessor 'com.jakewharton:butterknife-compiler:8.5.1'下面有一行如下所示：

{{1}}。

添加运行build-＆gt; rebuild项目后。