如何在Android App中的模拟器启动时填充SQLite数据库。

Question

我有一个包含4个字段的excel文件，我想在首次使用模拟器时使用它来填充数据库。以前，我曾经将数据库文件直接存储在手机上，但如果在创建时填充这些项目会更容易。如何从excel文件或文本文件中读取并在模拟器启动时填充数据库？

Answer 1

假设有一个电子表格，如： -

使用文件资源管理器将 CSV 文件 Book1.csv 保存到应用程序 < strong> asset 文件夹（如果需要，创建名为assets的文件夹），例如

即。 D:\Android_Applications\LoadDataFromExcel\app\src\main\assets

和DatabaseHelper（即SQLiteOpenHelper的子类）按照： -

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "mydb";
    public static final int DBVERSION = 1;
    public static final String MYDATA_TBL = "mydata";
    public static final String MYDATA_ID_COL = "_id";
    public static final String MYDATA_NAME_COL = "_name";
    public static final String MYDATA_AMOUNT_COL = "_amount";
    public static final String MYDATA_DATE_COL = "_date";
    public static final String MYDATA_DESCRIPTION_COL = "_description";

    private static final String TBLCREATESQL =
            "CREATE TABLE " + MYDATA_TBL +
                    "(" +
                    MYDATA_ID_COL + " INTEGER PRIMARY KEY," +
                    MYDATA_NAME_COL + " TEXT," +
                    MYDATA_AMOUNT_COL + " INTEGER," +
                    MYDATA_DATE_COL + " TEXT, " +
                    MYDATA_DESCRIPTION_COL + " TEXT" +
                    ")";

    private SQLiteDatabase mDB;


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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(TBLCREATESQL);
    }

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

    }

    public long insertRow(String name, int amount, String date, String description) {
        ContentValues cv = new ContentValues();
        cv.put(MYDATA_NAME_COL,name);
        cv.put(MYDATA_AMOUNT_COL,amount);
        cv.put(MYDATA_DATE_COL,date);
        cv.put(MYDATA_DESCRIPTION_COL,description);
        return mDB.insert(MYDATA_TBL,null,cv);
    }
}

然后你可以得到一些基于： -

public class MainActivity extends AppCompatActivity {

    DatabaseHelper dbh;

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

        dbh = new DatabaseHelper(this);
        loadExternalData();
    }


    private void loadExternalData() {

        InputStream importdata;
        BufferedReader br;
        String line;
        String[] splitdata;
        int linecount = 0;

        final String tag = "loadExternalData";
        try {
            importdata = this.getAssets().open("Book1.csv");
        } catch (IOException e) {
            Log.d(tag,"Error opening asset file");
            return;
        }
        br = new BufferedReader(new InputStreamReader(importdata));
        try {
            while ( (line = br.readLine()) != null) {
                // Skip column headings
                if (linecount++ > 0) {
                     splitdata = line.split(",");
                     dbh.insertRow(
                             splitdata[0],
                             new Integer(splitdata[1]),
                             splitdata[2],
                             splitdata[3]
                     );
                }
            }
        } catch (IOException e) {
            Log.d(tag,"IO Error reading data at line " + (linecount + 1));
            e.printStackTrace();
        }
    }
}

注意！这是非常基本的，而不是原则上的证明，例如，它不会处理数据中的逗号，并且每次运行时都会创建一组新的行

结果数据库： -

编辑 - 更改为仅添加一次行（但允许添加新数据）

1）向DatabaseHelper类添加新方法： -

public boolean ifRowExists(String name, int amount, String date, String description) {
    Cursor csr = mDB.query(MYDATA_TBL,null,
            MYDATA_NAME_COL + "=? AND " +
                    MYDATA_AMOUNT_COL + "=? AND " + 
                    MYDATA_DATE_COL + "=? AND " + 
                    MYDATA_DESCRIPTION_COL + "=?",
            new String[]{name,Integer.toString(amount), date, description},
            null,null,null
    );
    boolean rv = csr.getCount() > 0;
    csr.close();
    return rv;
}

2）修改调用类中的loadExternalData方法以检查是否存在要插入的行： -

private void loadExternalData() {

    InputStream importdata;
    BufferedReader br;
    String line;
    String[] splitdata;
    int linecount = 0;

    final String tag = "loadExternalData";
    try {
        importdata = this.getAssets().open("Book1.csv");
    } catch (IOException e) {
        Log.d(tag,"Error opening asset file");
        return;
    }
    br = new BufferedReader(new InputStreamReader(importdata));
    try {
        while ( (line = br.readLine()) != null) {
            // Skip column headings
            if (linecount++ > 0) {
                splitdata = line.split(",");
                if (!dbh.ifRowExists(splitdata[0], new Integer(splitdata[1]), splitdata[2], splitdata[3])) {
                    dbh.insertRow(
                            splitdata[0],
                            new Integer(splitdata[1]),
                            splitdata[2],
                            splitdata[3]
                    );
                }
            }
        }
    } catch (IOException e) {
        Log.d(tag,"IO Error reading data at line " + (linecount + 1));
        e.printStackTrace();
    }
}