My programming specifications

Indentation:

Use four spaces for indentation, not tabs.

Variable Naming:

Use meaningful variable names following the camelCase convention. Class member variables should start with a lowercase letter and can use prefixes to denote their type, e.g., strName. Constants should be in all uppercase letters with underscores separating words, e.g., MAX_VALUE.

Maximum Number of Characters per Line:

Each line of code should ideally not exceed 80-120 characters to improve readability. If it does, consider breaking the line.

Function and Class Naming:

Class names should start with an uppercase letter and use camelCase, e.g., MyClass. Method names should start with a lowercase letter and use camelCase, e.g., calculateTotal().

Blank Line Rule:

Leave blank lines between functions and class definitions to improve code readability.

Annotation Rules:

Use JavaDoc-style comments to document classes, methods, and members. Use line comments (//) or block comments (/* ... */) inside methods to explain the purpose or special cases of the code.

Space Before and After Operator:

Add spaces before and after binary operators, e.g., int sum = a + b;.

Other Rules:

Avoid using "magic numbers" (unnamed constants); use meaningful constants or enumeration types. Handle exceptions using try-catch blocks, ensuring that caught exceptions are appropriately handled or logged. Adhere to SOLID principles and design patterns in Java programming to improve code maintainability and extensibility.

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ScientificCaculator

The Link Your Class	https://bbs.csdn.net/forums/ssynkqtd-04
The Link of Requirement of This Assignment	https://bbs.csdn.net/topics/617378696
The Aim of This Assignment	Android Application - Calculator
MU STU ID and FZU STU ID	<21124825-832102119>
The Link of Code of this assignment of GitHub	https://github.com/CHENZHEN3078/ScientificCaculator

TOC

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PSP form

Personal Software Process Stages	Estimated Time（minutes）	Actual Time（minutes）
Planning
• Estimate	30	60
Development
• Analysis	10	10
• Design Spec	30	30
• Design Review	10	10
• Coding Standard	20	20
• Design	60	60
• Coding	400	600
• Code Review	60	90
• Test	60	60
Reporting
• Test Repor	60	60
• Size Measurement	20	10
• Postmortem & Process Improvement Plan	20	60
Sum	780	1090

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Design and implementation process

1. Basic functions Function 1: Basic operations and the correct order of operations Store the input string and the result in a back-end database Function 2: View the history Obtain historical calculation results from the back-end database
2. Extended function: Scientific calculator Better looking interface

Front end (caculator)

Main interface Continues the page design and configuration from the previous assignment Made some adjustments, added some buttons (index, factorial, parentheses, etc.), and text for reporting errors Jump button for history

History interface Refresh button for reading historical data Ten clickable texts, click on the text to obtain the formula on the text and save it in ANS, then return to the main interface

Scientific caculation Improve scientific computing functions Solved complex operations that were previously were not completed using inverse Polish notation Implement error reporting function

Accessing the backend URI for accessing content providers Call the backend to insert data after completing correct calculation on the main interface every time call the backend to query data after clicking the refresh button on the new page every time


Back end (sever)

Interacting with the front-end Using a database helper to implement insertion and query methods, providing data for the front-end

Database Create and manage databases Obtain a unique instance of the database helper

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Code description

Front-end code

The front-end calculation code and page are similar to before, with only some improvements made. Here, only the implementation code of the history interface is shown.

HistoryActivity.java

package com.example.caculator02;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import com.example.caculator02.entity.equation;

public class HistoryActivity extends AppCompatActivity implements View.OnClickListener {

    @SuppressLint("MissingInflatedId")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_history);
        findViewById(R.id.btn1).setOnClickListener(this);
        findViewById(R.id.text1).setOnClickListener(this);
        findViewById(R.id.text2).setOnClickListener(this);
        findViewById(R.id.text3).setOnClickListener(this);
        findViewById(R.id.text4).setOnClickListener(this);
        findViewById(R.id.text5).setOnClickListener(this);
        findViewById(R.id.text6).setOnClickListener(this);
        findViewById(R.id.text7).setOnClickListener(this);
        findViewById(R.id.text8).setOnClickListener(this);
        findViewById(R.id.text9).setOnClickListener(this);
        findViewById(R.id.text10).setOnClickListener(this);
    }

    private int num=0;
    public static String memory="";
    @SuppressLint("Range")
    @Override
    public void onClick(View v) {
        int id = v.getId();
        if (id == R.id.btn1) {
            Cursor cursor = getContentResolver().query(EquationInfoContent.CONTENT_URI, null, null, null, null);
            if (cursor != null) {
                while (cursor.moveToNext()) {
                    equation info = new equation();
                    //info.id = cursor.getInt(cursor.getColumnIndex(EquationInfoContent._ID));
                    info.str = cursor.getString(cursor.getColumnIndex(EquationInfoContent.EQUATION_STR));
                    info.ans = cursor.getDouble(cursor.getColumnIndex(EquationInfoContent.EQUATION_ANS));
                    Log.d("ning", info.toString());
                    TextView t;
                    if (num==0) t=(TextView)findViewById(R.id.text1);
                    else if (num==1)t=(TextView)findViewById(R.id.text2);
                    else if (num==2)t=(TextView)findViewById(R.id.text3);
                    else if (num==3)t=(TextView)findViewById(R.id.text4);
                    else if (num==4)t=(TextView)findViewById(R.id.text5);
                    else if (num==5)t=(TextView)findViewById(R.id.text6);
                    else if (num==6)t=(TextView)findViewById(R.id.text7);
                    else if (num==7)t=(TextView)findViewById(R.id.text8);
                    else if (num==8)t=(TextView)findViewById(R.id.text9);
                    else t=(TextView)findViewById(R.id.text10);
                    num++;
                    t.setText(info.toString());
                }
                num=0;
            }
        }else if (id== R.id.text1) {
            TextView a=(TextView)findViewById(R.id.text1);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text2) {
            TextView a=(TextView)findViewById(R.id.text2);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text3) {
            TextView a=(TextView)findViewById(R.id.text3);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text4) {
            TextView a=(TextView)findViewById(R.id.text4);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text5) {
            TextView a=(TextView)findViewById(R.id.text5);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text6) {
            TextView a=(TextView)findViewById(R.id.text6);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text7) {
            TextView a=(TextView)findViewById(R.id.text7);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text8) {
            TextView a=(TextView)findViewById(R.id.text8);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text9) {
            TextView a=(TextView)findViewById(R.id.text9);
            memory= (String) a.getText();
            finish();
        }else if (id== R.id.text10) {
            TextView a=(TextView)findViewById(R.id.text10);
            memory= (String) a.getText();
            finish();
        }
        }
    }

activity_history.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/bg3"
android:orientation="vertical"
android:padding="5dp">

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="#156200EE"
            android:gravity="center"
            android:text="@string/simple_calculator"
            android:textColor="#000000"
            android:textSize="25sp"
            android:textStyle="bold|italic" />

        <Button
            android:id="@+id/btn1"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:layout_columnWeight="1"
            android:background="@color/white"
            android:gravity="center"
            android:onClick="delete"
            android:text="Refresh"
            android:textColor="@color/black"
            android:textSize="20sp
" />


        <TextView
            android:id="@+id/text1"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:background="@color/white"
            android:clickable="true"
            android:gravity="center"
            android:text="equation1"
            android:textColor="@color/black"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text2"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation2"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text3"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation3"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text4"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation4"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text5"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation5"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text6"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation6"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text7"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation7"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />
        <TextView
            android:id="@+id/text8"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation8"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text9"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation9"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/text10"
            android:layout_width="match_parent"
            android:layout_height="@dimen/button_height"
            android:clickable="true"
            android:gravity="center"
            android:text="equation10"
            android:textColor="@color/black"
            android:background="@color/white"
            android:textSize="20dp" />

       <!-- <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true"
            android:layout_marginBottom="10dp"
            android:textColor="#FF0000"
            android:text="11111111111"
            android:textSize="20sp" />-->

    </LinearLayout>

</ScrollView>

</LinearLayout>

Back-end code

The backend is responsible for creating and managing databases, providing data for the front-end.

EquationDBHelper.java

package com.example.sever01.database;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class EquationDBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "equation.db";
    public static final String TABLE_NAME = "equation_info";
    private static final int DB_VERSION = 1;
    private static EquationDBHelper mHelper = null;

    private EquationDBHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    // 利用单例模式获取数据库帮助器的唯一实例
    public static EquationDBHelper getInstance(Context context) {
        if (mHelper == null) {
            mHelper = new EquationDBHelper(context);
        }
        return mHelper;
    }

    // 创建数据库，执行建表语句
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + " (" +
                "_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +
                " str VARCHAR NOT NULL," +
                " ans DOUBLE NOT NULL);";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }

}

EquationInfoProvider.java

package com.example.sever01.provider;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.util.Log;

import com.example.sever01.database.EquationDBHelper;

public class EquationInfoProvider extends ContentProvider {

    private EquationDBHelper dbHelper;
    private static final UriMatcher URI_MATCHER = new UriMatcher(UriMatcher.NO_MATCH);
    
    @Override
    public boolean onCreate() {
        Log.d("ning", "EquationInfoProvider onCreate");
        dbHelper = EquationDBHelper.getInstance(getContext());
        return true;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        //if (URI_MATCHER.match(uri) == EQUATIONS) {
        Log.d("chen", "EquationInfoProvider insert" + values);
        SQLiteDatabase db = dbHelper.getWritableDatabase();

        String deleteQuery = "DELETE FROM equation_info WHERE _id NOT IN (SELECT _id FROM equation_info ORDER BY _id DESC LIMIT 10)";
        db.execSQL(deleteQuery);

        long rowId = db.insert(EquationDBHelper.TABLE_NAME, null, values);
        if (rowId > 0) { // 判断插入是否执行成功
            Log.d("chen", "EquationInfoProvider insert " + values);
        }
        return uri;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        Log.d("chen", "EquationInfoProvider query");
        //if (URI_MATCHER.match(uri) == EQUATIONS) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        return db.query(EquationDBHelper.TABLE_NAME, projection, selection, selectionArgs, null, null, null);
        //}
        //return null;
    }


    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public String getType(Uri uri) {
        // TODO: Implement this to handle requests for the MIME type of the data
        // at the given URI.
        throw new UnsupportedOperationException("Not yet implemented");
    }


    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

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Result display

Screenshot

Main Page 

History Page  Partial error display Incorrect input  Divided by 0 

Screen recording

[video(video-znJiF44U-1697958892987)(type-csdn)(url-https://live.csdn.net/v/embed/337447)(image-https://video-community.csdnimg.cn/vod-84deb4/03d0a26070aa71ee9f7f0675b3ed0102/snapshots/755bf59f342849b7aa1360757e10415c-00004.jpg?auth_key=4851558613-0-0-b3504613efd759b2bdb83ca1d63f3989)(title-Basic function)] Calculators can perform scientific and complex calculations

[video(video-Lf3JNGGx-1697958900348)(type-csdn)(url-https://live.csdn.net/v/embed/337446)(image-https://video-community.csdnimg.cn/vod-84deb4/f0cced9070a971ee839b4531958d0102/snapshots/e90763ebd959431b84e2778128afb8e1-00004.jpg?auth_key=4851558575-0-0-419e4fbd8463f94ba328f794ad57e427)(title-Save)] After proper calculation, the calculation results and formulas will be saved to the database (only ten records will be kept), which can be viewed in the history interface.

[video(video-RNwxoz8E-1697958906637)(type-csdn)(url-https://live.csdn.net/v/embed/337445)(image-https://video-community.csdnimg.cn/vod-84deb4/c16af42070a971ee92cf5107e0c90102/snapshots/f6cfe7a7a582403a8abf25394cbafb24-00004.jpg?auth_key=4851558501-0-0-300b4894e18fdb304d870ca75b0d57b3)(title-Read)] After clicking on a history record in the history interface, it will return to the main interface. Clicking on ANS can calculate this history record again.

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Summarize

Remaining issues

1.The function of brackets is abnormal (I'm still checking). 2.Can meet scientific calculations, but can still be improved.

Learning summar

Due to a lack of understanding of front-end and back-end separation, both learning and practice took more time than expected, but the final result was quite satisfactory and fully implemented all functions. In practical operation, I complete some functions by querying, imitating, and combining (mainly referring to the shopping cart code of Android 基础教程) and has solved many code issues. Through this assignment, I have gained a deeper understanding of the method of separating the front and rear ends, and I believe I can become more proficient and smooth next time.

Thank you for browsing！