单击按钮后，如何在SQL数据库的两个表之间切换？

Question

我有一个字典应用程序，它从SQL数据库获取数据。 该数据库有一个“ First table”表，其中包含3列ID，单词，含义（单词法语，英语）

我插入了具有相同列的新表“第二表”，但这一次与我的意思相反（英语中的单词表示法语） 我想插入一个按钮以在搜索方法“使用法语单词进行搜索和使用英语单词进行搜索的按钮”之间切换 当用户单击按钮“ FR> ENG”时，我想从第一个表中获取数据（法语中的单词是英语），单击时则相反 按钮“ ENG> FR”，使用我之前添加的第二个表格（英语中的单词表示法语）

DataBaseHelper.java

public class DataBaseHelper extends SQLiteOpenHelper {
    public static String DB_PATH;
    public final Context context;
    public SQLiteDatabase database;
    public static String DB_NAME = "Database";
    public SQLiteDatabase getDb() {
        return this.database;
    }


    public DataBaseHelper(Context context) {
        super(context, DB_NAME, null, 1);

        this.context = context;
        DB_PATH = String.format("//data//data//%s//databases//", new Object[]{context.getPackageName()});
        openDataBase();
    }
    public void createDataBase() {
        if (checkDataBase()) {
            Log.i(getClass().toString(), "Database already exists");
            return;
        }
        getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e(getClass().toString(), "Copying error");
            throw new Error("Error copying database!");
        }
    }

    private boolean checkDataBase() {
        SQLiteDatabase checkDb = null;
        try {
            checkDb = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, 0);
        } catch (SQLException e) {
            Log.e(getClass().toString(), "Error while checking db");
        }
        if (checkDb != null) {
            checkDb.close();
        }
        if (checkDb != null) {
            return true;
        }
        return false;
    }

    private void copyDataBase() throws IOException {
        InputStream externalDbStream = this.context.getAssets().open(DB_NAME);
        OutputStream localDbStream = new FileOutputStream(DB_PATH + DB_NAME);
        byte[] buffer = new byte[1024];
        while (true) {
            int bytesRead = externalDbStream.read(buffer);
            if (bytesRead > 0) {
                localDbStream.write(buffer, 0, bytesRead);
            } else {
                localDbStream.close();
                externalDbStream.close();
                return;
            }
        }
    }

    public SQLiteDatabase openDataBase() throws SQLException {
        String path = DB_PATH + DB_NAME;
        if (this.database == null) {
            createDataBase();
            this.database = SQLiteDatabase.openDatabase(path, null, 0);
        }
        return this.database;
    }

    public synchronized void close() {
        if (this.database != null) {
            this.database.close();
        }
        super.close();
    }

    public void onCreate(SQLiteDatabase db) {
    }

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

DataManager.java

import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Base64;

import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

public class DataManager {
    DataBaseHelper myDbHelper;
    SQLiteDatabase db;

    public DataManager(Context context) {
        myDbHelper = new DataBaseHelper(context);
        myDbHelper.createDataBase();
        try {
            myDbHelper.openDataBase();
        } catch (SQLException sqle) {
            sqle.printStackTrace();
        }
        db = myDbHelper.getReadableDatabase();
    }

    //Get All Data
    public List<Word> getAllData() {
        Cursor cur = db.rawQuery("select * from table_fr_eng LIMIT 5000;", null);
        List<Word> item_data = new ArrayList<Word>();
        if (cur.getCount() != 1) {
            if (cur.moveToFirst()) {
                do {
                    Word obj = new Word();
                    obj.id = cur.getString(cur.getColumnIndex("Id"));
                    obj.word = cur.getString(cur.getColumnIndex("Word"));
                    obj.is_fav = cur.getString(cur.getColumnIndex("is_favourite"));
                    if (obj.is_fav!=null) {
                    } else {
                        obj.is_fav="0";
                    }
                    obj.meaning = cur.getString(cur.getColumnIndex("Meaning"));
                    item_data.add(obj);
                } while (cur.moveToNext());
            }
        }
        return item_data;
    }

    //Get Search Data
    public List<Word> getAllSearchData(String search) {
        Cursor cur = db.rawQuery("SELECT * FROM table_fr_eng WHERE Word LIKE '" + search + "%' LIMIT 30", null);
        List<Word> item_data = new ArrayList<Word>();
        if (cur.getCount() != 0) {
            if (cur.moveToFirst()) {
                do {
                    Word obj = new Word();
                    obj.id = cur.getString(cur.getColumnIndex("Id"));
                    obj.word = cur.getString(cur.getColumnIndex("Word"));
                    obj.is_fav = cur.getString(cur.getColumnIndex("is_favourite"));
                    if (obj.is_fav!=null) {
                    } else {
                        obj.is_fav="0";
                    }
                    obj.meaning = cur.getString(cur.getColumnIndex("Meaning"));
                    item_data.add(obj);
                } while (cur.moveToNext());
            }
        }
        return item_data;
    }

    //Add Word And Meaning 
    public Boolean InsertWord(String strWord, String strMeaning) {
        String insertQuery = "INSERT INTO table_fr_eng(Word,Meaning) values('" + strWord + "','"
                + strMeaning + "')";
        db.execSQL(insertQuery);
        db.close();
        return true;
    }

    //Get Day of The Word
    public Word DayOfWord() {
        Cursor cur = db.rawQuery("SELECT * FROM table_fr_eng ORDER BY RANDOM() LIMIT 1 ;",null);
        Word objWord = new Word();
        if (cur.getCount() != 0) {
            if (cur.moveToFirst()) {
                do {
                    objWord.word = cur.getString(cur.getColumnIndex("Word"));
                    objWord.meaning = cur.getString(cur.getColumnIndex("Meaning"));
                } while (cur.moveToNext());
            }
        }
        return objWord;
    }

    //Add Favourite Word
    public void FavouriteWord(String id) {
        String updateQuery = "UPDATE table_fr_eng SET is_favourite='"+1+"' WHERE Id=" +id;
        SQLiteDatabase db = this.myDbHelper.getWritableDatabase();
        db.execSQL(updateQuery);
        db.close();
    }
    //Add UnFavourite Word
    public void UnFavouriteWord(String id) {
        String updateQuery = "UPDATE table_fr_eng SET is_favourite='' WHERE Id=" +id;
        SQLiteDatabase db = this.myDbHelper.getWritableDatabase();
        db.execSQL(updateQuery);
        db.close();
    }
    //Get All Favourite Word
    public List<Word> getAllFavouriteData() {
        Cursor cur = db.rawQuery("select * from table_fr_eng where is_favourite=1;",null);
        List<Word> item_data = new ArrayList<Word>();
        if (cur.getCount() != 0) {
            if (cur.moveToFirst()) {
                do {
                    Word obj = new Word();
                    obj.id = cur.getString(cur.getColumnIndex("Id"));
                    obj.word = cur.getString(cur.getColumnIndex("Word"));
                    if (obj.is_fav!=null) {
                    } else {
                        obj.is_fav="1";
                    }
                    obj.meaning = cur.getString(cur.getColumnIndex("Meaning"));
                    item_data.add(obj);
                } while (cur.moveToNext());
            }
        }
        return item_data;
    }
    //Add History 
    public void InsertHistoryWord(String word, String meaning) {
        String insertQuery = "INSERT INTO tblHistory(word,meaning) values('" + word + "','"
                + Base64.encodeToString(meaning.getBytes(), Base64.DEFAULT) + "')";
        db.execSQL(insertQuery);
        db.close();
    }

    //Get All History Word
    public List<Word> getAllHistoryData() {
        Cursor cur = db.rawQuery("select * from tblHistory;", null);
        List<Word> item_data = new ArrayList<Word>();
        if (cur.getCount() != 0) {
            if (cur.moveToFirst()) {
                do {
                    Word obj = new Word();
                    obj.id = cur.getString(cur.getColumnIndex("Id"));
                    obj.word = cur.getString(cur.getColumnIndex("word"));
                    obj.meaning = cur.getString(cur.getColumnIndex("meaning"));
                    byte[] data1 = Base64.decode(obj.meaning, Base64.DEFAULT);
                    try {
                        obj.meaning = new String(data1, "UTF-8");
                    } catch (UnsupportedEncodingException e) {
                        e.printStackTrace();
                    }
                    item_data.add(obj);
                } while (cur.moveToNext());
            }
        }
        return item_data;
    }

    //Delete History 
    public List<Word> getDeleteHistoryData() {
        List<Word> item_data = new ArrayList<Word>();
        String deleteQuery = "delete from tblHistory";
        db.execSQL(deleteQuery);
        db.close();
        return item_data;
    }

    //Get Quiz Word and Meaning
    public List<Word> Quiz() {
        Cursor cur = db.rawQuery("SELECT * FROM table_fr_eng ORDER BY RANDOM() LIMIT 4 ;",null);
        List<Word> item_data = new ArrayList<Word>();
        if (cur.getCount() != 0) {
            if (cur.moveToFirst()) {
                do {
                    Word obj = new Word();
                    obj.id = cur.getString(cur.getColumnIndex("Id"));
                    obj.word = cur.getString(cur.getColumnIndex("Word"));
                    obj.meaning = cur.getString(cur.getColumnIndex("Meaning"));
                    item_data.add(obj);
                } while (cur.moveToNext());
            }
        }
        return item_data;
    }

    //Delete Favourite Word
    public List<Word> getDeleteFavouriteData() {
        List<Word> item_data = new ArrayList<Word>();
        String deleteQuery = "delete from table_fr_eng where is_favourite";
        db.execSQL(deleteQuery);
        db.close();
        return item_data;
    }

}

Answer 1

以下是一个有效的示例，它将根据单击的按钮给出输入到编辑文本中的单词的含义。

例如如果输入是，并且单击 Eng-> Fr 按钮，则会显示 单词Yes表示法语中的Oui。 。如果单击 Fr-> Eng 按钮，则会显示 单词是，表示我不懂英语。 （即没有在法语中为yes的意思。

反过来输入 Oui 会说 单词Oui意思是英语 或 Oui意味着我不知道法语。

MyDatabaseHelper.java

这是SQLiteOpenHelper的子类，是在Android中访问SQLiteDatabase的一种典型方法：-

public class MyDBHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "translator";
    public static final int DBVERSION = 1;

    public static final String TBL_ENGFR = "engfr";
    public static final String TBL_FRENG = "freng";

    public static final String COL_ID = BaseColumns._ID;
    public static final String COL_WORD = "word";
    public static final String COl_MEANING = "meaning";

    public static final int TRANSLATOR_TYPE_ENGLISH_TO_FRENCH = 0;
    public static final int TRANSLATOR_TYPE_FRENCH_TO_ENGLISH = 1;


    SQLiteDatabase mDB;

    public MyDBHelper(Context context) {
        super(context, DBNAME, null, DBVERSION);
        mDB = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(crt_table_sql(getTableToUse(TRANSLATOR_TYPE_ENGLISH_TO_FRENCH)));
        db.execSQL(crt_table_sql(getTableToUse(TRANSLATOR_TYPE_FRENCH_TO_ENGLISH)));
    }

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

    public String getMeaningOfWord(String word, int type) {
        String rv = "";
        String whereclause = COL_WORD + "=?";
        String[] whereargs = new String[]{word};
        Cursor csr = mDB.query(getTableToUse(type),null,whereclause,whereargs,null,null,null);
        if (csr.moveToFirst()) {
            rv = csr.getString(csr.getColumnIndex(COl_MEANING));
        }
        csr.close();
        return rv;
    }

    public long addWord(String word, String meaning,int type) {
        ContentValues cv = new ContentValues();
        cv.put(COL_WORD,word);
        cv.put(COl_MEANING,meaning);
        return mDB.insert(getTableToUse(type),null,cv);
    }

    private String crt_table_sql(String table) {
        return "CREATE TABLE IF NOT EXISTS " + table + "(" +
                COL_ID + " INTEGER PRIMARY KEY, " +
                COL_WORD + " TEXT, " +
                COl_MEANING + " TEXT" +
                ")";
    }

    private String getTableToUse(int type) {
        String rv = "";
        switch (type) {
            case    TRANSLATOR_TYPE_ENGLISH_TO_FRENCH:
                rv = TBL_ENGFR;
                break;
            case TRANSLATOR_TYPE_FRENCH_TO_ENGLISH:
                rv = TBL_FRENG;
                break;
        }
        return rv;
    }
}

在所有情况下，基础表都是根据定义帮助程序的两个常量所表示的int值（0（英语至法语）或1（法语至英语））确定的。

主要活动中的按钮还使用常量来确定含义的语言。

MainActivity.java

此活动包含3个UI元素，一个用于输入单词的编辑文本和两个按钮。单击一个将使用相应的表格来确定单词的含义。

public class MainActivity extends AppCompatActivity {
    EditText mWordToGetMeaningOf;
    Button mENG_TO_FR, mFR_TO_ENG;
    Context mContext;
    String mCurrentmeaning;
    MyDBHelper mDBhlpr;


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

        mWordToGetMeaningOf = this.findViewById(R.id.word_to_get_meaning_of);
        mENG_TO_FR = this.findViewById(R.id.eng_to_fr);
        mFR_TO_ENG = this.findViewById(R.id.fr_to_eng);
        mDBhlpr = new MyDBHelper(this);
        addSomeData();

        mENG_TO_FR.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCurrentmeaning = mDBhlpr.getMeaningOfWord(mWordToGetMeaningOf.getText().toString(),MyDBHelper.TRANSLATOR_TYPE_ENGLISH_TO_FRENCH);
                displayMeaning(MyDBHelper.TRANSLATOR_TYPE_ENGLISH_TO_FRENCH);
            }
        });
        mFR_TO_ENG.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCurrentmeaning = mDBhlpr.getMeaningOfWord(mWordToGetMeaningOf.getText().toString(),MyDBHelper.TRANSLATOR_TYPE_FRENCH_TO_ENGLISH);
                displayMeaning(MyDBHelper.TRANSLATOR_TYPE_FRENCH_TO_ENGLISH);
            }
        });
    }

    /**
     * Toasts the meaning of the word (also writes the same message to the log)
     * @param type
     */
    private void displayMeaning(int type) {
        String meaning_type = "";
        switch (type) {
            case MyDBHelper.TRANSLATOR_TYPE_ENGLISH_TO_FRENCH:
                meaning_type = "French";
                break;
            case MyDBHelper.TRANSLATOR_TYPE_FRENCH_TO_ENGLISH:
                meaning_type = "English";
                break;
        }
        if (mCurrentmeaning.length() < 1) {
            mCurrentmeaning = " I don't know ";
        }
        String message = "The Word " +
                mWordToGetMeaningOf.getText().toString() +
                " means " + mCurrentmeaning +
                " in " + meaning_type + ".";
        Toast.makeText(mContext, message, Toast.LENGTH_SHORT).show();
        Log.d("MEANING",message);
    }

    /**
     * Add some testing data
     */
    private void addSomeData() {
        mDBhlpr.addWord("Yes","Oui",MyDBHelper.TRANSLATOR_TYPE_ENGLISH_TO_FRENCH);
        mDBhlpr.addWord("Oui","Yes",MyDBHelper.TRANSLATOR_TYPE_FRENCH_TO_ENGLISH);
    }
}