Question

我是Android应用程序的新手 - 我想知道，如果我们必须创建一个应用程序，例如：使用GPS和相机API识别星星。

我们如何以及在哪里存储所有数据库？我认为如果我们将它们存储在手机上它会太小，抱歉这可能听起来很愚蠢，但我是关于构建移动开发的新手。

有什么想法吗？而就Camera API而言 - 我在哪里可以找到这些信息，这样如果我将我的相机指向天空中的特定星形，例如星号x称为y。我知道我们必须使用GPS坐标和相机API吗？确定这些，以便我们获得准确的信息。

有人可以帮我解决这些问题，或者我可以从哪里获得有关这些信息的信息吗？

非常感谢， theBorneo

Answer 1

Data Storage上有一个非常好的指南。我想你可以找到你想要的答案。

Answer 2

回答问题的第一部分，在Android中，我们通常使用SQLite，互联网上有很多例子，例如this一个。我并不特别喜欢在线的大多数例子，但基本的一个基本是：

   public class DataBaseHelper extends SQLiteOpenHelper {

    private static String DB_PATH = "/data/data/com.your.application/databases/";

    private static String DB_NAME = "android.db";

    private SQLiteDatabase myDataBase;

    private final Context myContext;

    /**
     * Constructor Takes and keeps a reference of the passed context in order to
     * access to the application assets and resources.
     * 
     * @param context
     */
    public DataBaseHelper(Context context) {

        super(context, DB_NAME, null, 1);
        this.myContext = context;
    }

    /**
     * Creates a empty database on the system and rewrites it with your own
     * database.
     */
    public void createDataBase() throws IOException {

        boolean dbExist = checkDataBase();

        if (dbExist) {
            // do nothing - database already exist
            Log.v("Database","Database Exists");
        } else {
            Log.v("Database","Data base needs creating");
            // By calling this method and empty database will be created into
            // the default system path
            // of your application so we are gonna be able to overwrite that
            // database with our database.
            this.getReadableDatabase();

            try {

                Log.v("Database","CopyDataBase");
                copyDataBase();

            } catch (IOException e) {

                throw new Error("Error Copying Database");

            }
        }

    }

    /**
     * Check if the database already exist to avoid re-copying the file each
     * time you open the application.
     * 
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase() {

        SQLiteDatabase checkDB = null;

        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READWRITE);

        } catch (SQLiteException e) {

            // database does't exist yet.

        }

        if (checkDB != null) {

            checkDB.close();

        }

        return checkDB != null ? true : false;
    }

    /**
     * Copies your database from your local assets-folder to the just created
     * empty database in the system folder, from where it can be accessed and
     * handled. This is done by transfering bytestream.
     */
    private void copyDataBase() throws IOException {

        // Open your local db as the input stream
        InputStream myInput = myContext.getAssets().open(DB_NAME);

        // Path to the just created empty db
        String outFileName = DB_PATH + DB_NAME;

        // Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        // transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }

        // Close the streams
        myOutput.flush();
        myOutput.close();
        myInput.close();

        Log.v("Log","Database copied sucsessfully");
    }

    public void openDataBase() throws SQLException {

        // Open the database
        String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READWRITE);

        Log.v("Logger","Database Opened");

    }

    @Override
    public synchronized void close() {

        if (myDataBase != null)
            myDataBase.close();

        super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

    public Cursor get() {
        return myDataBase.query("AwayMessages", null, null, null, null, null,null);
    }

    public SQLiteDatabase returnDatabase() {
        return myDataBase;
    }

}

假设在应用程序启动之前提前准备SQLite数据库，并保存在资产文件夹中

对于GPS，请尝试here

然后，要启动相机并将照片重新打印到您的应用程序中，请查看this question

在手机上存储数据？

2 个答案: