android - 如何从 ANDROID 中的 sqlite 数据库中获取列数据？

Question

我是第一次在 Android 中使用 sqlite 数据库。我已经在 Sqlite 中创建了我的数据库并将其复制到 androids "data/data/App package/databases"。我能够复制和打开数据库。我在数据库中有四个表，我想要 “State_Master(Table)”中的“State_Name(Column)”。

但我无法从表中获取任何数据(州名)。

我在这里发布我的代码:

//DataBase Helper

public class DatabaseHelper extends SQLiteOpenHelper {

private String[] stateArray;
private Context context;
private String DB_PATH;
private static String DB_NAME = "myDatabase.sqlite";
public static SQLiteDatabase myDatabase;
public static final String STATE_NAME = "State_Name";

public LoveGodDB(Context context) throws Exception {
    super(context, DB_NAME, null, 1);
    this.context = context;
    DB_PATH = "/data/data/" + context.getApplicationContext().getPackageName() + "/databases/";
    boolean dbexist = checkdatabase();
    if (dbexist) {
        opendatabase();
    } else {
        createdatabase();
    }

}
@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(STATE_NAME);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
public void createdatabase() throws Exception {
    boolean dbexist = checkdatabase();
    if (dbexist) {
    } else {
        this.getReadableDatabase();
        try {
            copydatabase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}
private boolean checkdatabase() throws Exception {
    boolean checkdb = false;
    try {
        String myPath = DB_PATH + DB_NAME;
        File dbfile = new File(myPath);
        checkdb = dbfile.exists();
    } catch (SQLiteException sle) {
        throw sle;
    }
    return checkdb;
}
private void copydatabase() throws IOException {

    InputStream myinput = context.getApplicationContext().getAssets().open(DB_NAME);
    OutputStream myoutput = new FileOutputStream("/data/data/"+ context.getApplicationContext().getPackageName() +"/databases/myDataBase.sqlite");
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myinput.read(buffer)) > 0) {
        myoutput.write(buffer, 0, length);
    }

    myoutput.flush();
    myoutput.close();
    myinput.close();
}
public void opendatabase() throws SQLException {
    String mypath = DB_PATH + DB_NAME;
    LGDataBase = SQLiteDatabase.openDatabase(mypath, null,
            SQLiteDatabase.OPEN_READWRITE);

}
public synchronized void close() {
    if (LGDataBase != null) {
        LGDataBase.close();
    }
    super.close();
}
public Cursor fetchAllTopics() {

    return LGDataBase.query("State_Master", new String[] {STATE_NAME}, 
            null, 
            null, 
            null, 
            null, 
            null);
};


}

和我想在字符串数组中存储数据的 Activity :

public class MyStateGrid extends Activity{

private Button back;
private String[] stateNameArray ;
private GridView gridview = null;
private DatabaseHelper lgDB;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.errandboy_state);

    back = (Button) findViewById(R.id.back);
    gridview = (GridView) findViewById(R.id.gridview);
    gridview.setAdapter(new ImageAdapter(this));

    //stateNameArray = getResources().getStringArray(R.array.stateName);
    try {
        lgDB = new LoveGodDB(this);
        lgDB.opendatabase();
        Cursor c = lgDB.fetchAllTopics();
                    startManagingCursor(c); 
        stateNameArray = new String[]LoveGodDB.STATE_NAME};
    } catch (IOException e) {

    } catch (Exception e) {

    }finally{
        if(lgDB != null){
            lgDB.close();
        }
    }

    gridview.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            Intent stamp = new Intent(getParent(), xxxx.class);
            TabGroupActivity parentActivity = (TabGroupActivity)getParent();
            parentActivity.startChildActivity("Stamp", stamp);

        }
    });

    OnTouchListener backListener = new OnTouchListener() {
        public boolean  onTouch  (View  v, MotionEvent  event) {
            if (event.getAction()==MotionEvent.ACTION_UP){
                finish();
            }
            return false;
        }
    };

    back.setOnTouchListener(backListener);
}
public class ImageAdapter extends BaseAdapter {
    @SuppressWarnings("unused")
    private Context mContext;

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return stateImageArray.length;
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        LayoutInflater vi = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = vi.inflate(R.layout.galchild, null);
        ImageView stampImage;
        TextView stampName;
        stampImage = (ImageView) v.findViewById(R.id.ImageView01);
        stampName = (TextView) v.findViewById(R.id.stampName);
        stampImage.setScaleType(ImageView.ScaleType.FIT_XY);
        stampImage.setImageResource(R.drawable.stamps);
        stampName.setText(stateNameArray[position]);
        return v;
    }
}

有什么建议吗？

谢谢...

Answer 1

我不明白这一行:

stateNameArray = new String[]LoveGodDB.STATE_NAME

尝试将其更改为:

stateNameArray = new String[c.count()];

然后需要将Cursor中的状态名称放入String数组中:

int i = 0;
c.moveToFirst();
while (c.isAfterLast() == false) {
    statNameArray[i]  = c.getString(0);
    i++;
    c.moveToNext();
}

答案改编自:Iterate through rows from Sqlite-query