Initial commit

.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea/caches
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+/.idea/navEditor.xml
+/.idea/assetWizardSettings.xml
+.DS_Store
+/build
+/captures
+.externalNativeBuild

app/.gitignore

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+/build

app/build.gradle

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+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 28
+    defaultConfig {
+        applicationId "academy.learnprogramming.calculator"
+        minSdkVersion 15
+        targetSdkVersion 28
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
+    testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+}

app/proguard-rules.pro

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+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

app/src/androidTest/java/academy/learnprogramming/calculator/ExampleInstrumentedTest.java

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+package academy.learnprogramming.calculator;
+
+import android.content.Context;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static org.junit.Assert.*;
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+@RunWith(AndroidJUnit4.class)
+public class ExampleInstrumentedTest {
+    @Test
+    public void useAppContext() {
+        // Context of the app under test.
+        Context appContext = InstrumentationRegistry.getTargetContext();
+
+        assertEquals("academy.learnprogramming.calculator", appContext.getPackageName());
+    }
+}

app/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="academy.learnprogramming.calculator">
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme">
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

app/src/main/java/academy/learnprogramming/calculator/MainActivity.java

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+package academy.learnprogramming.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 result;
+    private EditText newnumber;
+    private TextView displayOperation;
+
+    // Variabel to hold the operands and type of calculation
+    private Double operand1 = null;
+    private String pendingOperation = "=";
+
+    private static final String STATE_PENDING_OPERATION = "PendingOperation";
+    private static final String STATE_OPERAND1 = "Operand1";
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+
+        result = (EditText) findViewById(R.id.result);
+        newnumber = (EditText) findViewById(R.id.newNumber);
+        displayOperation = (TextView) findViewById(R.id.operation);
+
+        Button button0 = (Button) findViewById(R.id.button0);
+        Button button1 = (Button) findViewById(R.id.button1);
+        Button button2 = (Button) findViewById(R.id.button2);
+        Button button3 = (Button) findViewById(R.id.button3);
+        Button button4 = (Button) findViewById(R.id.button4);
+        Button button5 = (Button) findViewById(R.id.button5);
+        Button button6 = (Button) findViewById(R.id.button6);
+        Button button7 = (Button) findViewById(R.id.button7);
+        Button button8 = (Button) findViewById(R.id.button8);
+        Button button9 = (Button) findViewById(R.id.button9);
+
+        Button buttonDot = (Button) findViewById(R.id.buttonDot);
+        Button buttonEquals = (Button) findViewById(R.id.buttonEquals);
+        Button buttonDivide = (Button) findViewById(R.id.buttonDivide);
+        Button buttonMultiply = (Button) findViewById(R.id.buttonMultiply);
+        Button buttonMinus = (Button) findViewById(R.id.buttonMinus);
+        Button buttonPlus = (Button) findViewById(R.id.buttonPlus);
+        View.OnClickListener listener = new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                Button b = (Button) view;
+                newnumber.append(b.getText().toString());
+            }
+        };
+        button0.setOnClickListener(listener);
+        button1.setOnClickListener(listener);
+        button2.setOnClickListener(listener);
+        button3.setOnClickListener(listener);
+        button4.setOnClickListener(listener);
+        button5.setOnClickListener(listener);
+        button6.setOnClickListener(listener);
+        button7.setOnClickListener(listener);
+        button8.setOnClickListener(listener);
+        button9.setOnClickListener(listener);
+        buttonDot.setOnClickListener(listener);
+
+        View.OnClickListener opListener = new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                Button b = (Button) v;
+                String op = b.getText().toString();
+                String value = newnumber.getText().toString();
+                try {
+                    Double doubleValue = Double.valueOf(value);
+                    performOperation(doubleValue, op);
+                } catch (NumberFormatException e) {
+                    newnumber.setText("");
+                }
+                pendingOperation = op;
+                displayOperation.setText(pendingOperation);
+            }
+        };
+
+        buttonEquals.setOnClickListener(opListener);
+        buttonDivide.setOnClickListener(opListener);
+        buttonMultiply.setOnClickListener(opListener);
+        buttonMinus.setOnClickListener(opListener);
+        buttonPlus.setOnClickListener(opListener);
+
+        Button buttonNeg = (Button) findViewById(R.id.buttonNeg);
+
+        buttonNeg.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                String value = newnumber.getText().toString();
+                if (value.length() == 0){
+                    newnumber.setText("-");
+                } else {
+                    try {
+                        Double doubleValue = Double.valueOf(value);
+                        doubleValue *= -1;
+                        newnumber.setText(doubleValue.toString());
+                    } catch (NumberFormatException e){
+                        newnumber.setText("");
+                    }
+                }
+            }
+        });
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        outState.putString(STATE_PENDING_OPERATION, pendingOperation);
+        if (operand1 != null){
+            outState.putDouble(STATE_OPERAND1, operand1);
+        }
+        super.onSaveInstanceState(outState);
+    }
+
+    @Override
+    protected void onRestoreInstanceState(Bundle savedInstanceState) {
+        super.onRestoreInstanceState(savedInstanceState);
+        pendingOperation = savedInstanceState.getString(STATE_PENDING_OPERATION);
+        operand1 = savedInstanceState.getDouble(STATE_OPERAND1);
+        displayOperation.setText(pendingOperation);
+    }
+
+    private void performOperation(Double value, String operation) {
+        if (null == operand1) {
+            operand1 = value;
+        } else {
+            if (pendingOperation.equals("=")) {
+                pendingOperation = operation;
+            }
+            switch (pendingOperation) {
+                case "=":
+                    operand1 = value;
+                    break;
+                case "/":
+                    if (value == 0) {
+                        operand1 = 0.0;
+                    } else {
+                        operand1 /= value;
+                    }
+                    break;
+                case "*":
+                    operand1 *= value;
+                    break;
+                case "-":
+                    operand1 -= value;
+                    break;
+                case "+":
+                    operand1 += value;
+                    break;
+            }
+        }
+
+        result.setText(operand1.toString());
+        newnumber.setText("");
+    }
+}