java - 有没有办法在Android应用程序关闭时删除所有Sqlite数据？

Question

我需要在应用程序关闭时删除所有 Sqlite 数据。

有什么办法可以做到这一点吗？

我使用一个名为 HostProvider 的类来启动数据数据库。

这是HostProvider.java的代码

public class HostProvider extends ContentProvider {

private static final String TAG = "HostProvider";

public static final String AUTHORITY = "org.xbmc.android.provider.remote";

private static final int DATABASE_VERSION = 4;
private static final String DATABASE_NAME = "xbmc_hosts.db";
private static final String HOSTS_TABLE_NAME = "hosts";

private static HashMap<String, String> sHostsProjectionMap;

private static final int HOSTS = 1;
private static final int HOST_ID = 2;

private static final UriMatcher sUriMatcher;

/**
 * This class helps open, create, and upgrade the database file.
 */
private static class DatabaseHelper extends SQLiteOpenHelper {

    DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + HOSTS_TABLE_NAME + " (" 
                + Hosts._ID + " INTEGER PRIMARY KEY," 
                + Hosts.NAME + " TEXT," 
                + Hosts.ADDR + " TEXT,"
                + Hosts.PORT + " INTEGER," 
                + Hosts.USER + " TEXT," 
                + Hosts.PASS + " TEXT," 
                + Hosts.ESPORT + " INTEGER," 
                + Hosts.TIMEOUT + " INTEGER," 
                + Hosts.WIFI_ONLY + " INTEGER,"
                + Hosts.ACCESS_POINT + " TEXT,"
                + Hosts.MAC_ADDR + " TEXT,"
                + Hosts.WOL_PORT + " INTEGER,"
                + Hosts.WOL_WAIT + " INTEGER"
                + ");");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String altertable;
        switch (oldVersion) {
        case 2:
            Log.d(TAG, "Upgrading database from version 2 to 3");
            altertable = "ALTER TABLE " + HOSTS_TABLE_NAME + " ADD COLUMN " + Hosts.WIFI_ONLY 
            + " INTEGER DEFAULT 0;";
            db.execSQL(altertable);
            Log.d(TAG, "executed: " + altertable);
            altertable = "ALTER TABLE " + HOSTS_TABLE_NAME + " ADD COLUMN " + Hosts.ACCESS_POINT 
            + " TEXT;";
            db.execSQL(altertable);
            Log.d(TAG, "executed: " + altertable);
            altertable = "ALTER TABLE " + HOSTS_TABLE_NAME + " ADD COLUMN " + Hosts.MAC_ADDR 
            + " TEXT;";
            db.execSQL(altertable);
            Log.d(TAG, "executed: " + altertable);
        case 3:
            Log.d(TAG, "Upgrading database from version 3 to 4");
             altertable = "ALTER TABLE " + HOSTS_TABLE_NAME + " ADD COLUMN " + Hosts.WOL_PORT
            + " INTEGER;";
             db.execSQL(altertable);
             Log.d(TAG, "executed: " + altertable);
             altertable = "ALTER TABLE " + HOSTS_TABLE_NAME + " ADD COLUMN " + Hosts.WOL_WAIT
             + " INTEGER;";
             db.execSQL(altertable);
             Log.d(TAG, "executed: " + altertable);

            //WARNING!!! ADD A break; BEFORE THE DEFAULT BLOCK OF THE DATABASE WILL BE DROPPED!!! 
             break;
        default: 
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS " + HOSTS_TABLE_NAME);
            onCreate(db);

        }
    }
}

private DatabaseHelper mOpenHelper;

@Override
public boolean onCreate() {
    mOpenHelper = new DatabaseHelper(getContext());
    return true;
}


@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
    SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

    switch (sUriMatcher.match(uri)) {
    case HOSTS:
        qb.setTables(HOSTS_TABLE_NAME);
        qb.setProjectionMap(sHostsProjectionMap);
        break;

    case HOST_ID:
        qb.setTables(HOSTS_TABLE_NAME);
        qb.setProjectionMap(sHostsProjectionMap);
        qb.appendWhere(Hosts._ID + "=" + uri.getPathSegments().get(1));
        break;

    default:
        throw new IllegalArgumentException("Unknown URI " + uri);
    }

    // If no sort order is specified use the default
    String orderBy;
    if (TextUtils.isEmpty(sortOrder)) {
        orderBy = Hosts.DEFAULT_SORT_ORDER;
    } else {
        orderBy = sortOrder;
    }

    // Get the database and run the query
    SQLiteDatabase db = mOpenHelper.getReadableDatabase();
    Log.d(TAG, "SQLite database version: " + db.getVersion());
    Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);

    // Tell the cursor what uri to watch, so it knows when its source data
    // changes
    c.setNotificationUri(getContext().getContentResolver(), uri);
    return c;
}

@Override
public String getType(Uri uri) {
    switch (sUriMatcher.match(uri)) {
    case HOSTS:
        return Hosts.CONTENT_TYPE;

    case HOST_ID:
        return Hosts.CONTENT_ITEM_TYPE;

    default:
        throw new IllegalArgumentException("Unknown URI " + uri);
    }
}

@Override
public Uri insert(Uri uri, ContentValues initialValues) {
    // Validate the requested uri
    if (sUriMatcher.match(uri) != HOSTS) {
        throw new IllegalArgumentException("Unknown URI " + uri);
    }

    ContentValues values;
    if (initialValues != null) {
        values = new ContentValues(initialValues);
    } else {
        values = new ContentValues();
    }

    if (values.containsKey(Hosts.NAME) == false) {
        Resources r = Resources.getSystem();
        values.put(Hosts.NAME, r.getString(android.R.string.untitled));
    }

    if (values.containsKey(Hosts.ADDR) == false) {
        values.put(Hosts.ADDR, "");
    }
    if (values.containsKey(Hosts.PORT) == false) {
        values.put(Hosts.PORT, 0);
    }
    if (values.containsKey(Hosts.USER) == false) {
        values.put(Hosts.USER, "");
    }
    if (values.containsKey(Hosts.PASS) == false) {
        values.put(Hosts.PASS, "");
    }
    if (values.containsKey(Hosts.ESPORT) == false) {
        values.put(Hosts.ESPORT, 0);
    }
    if (values.containsKey(Hosts.TIMEOUT) == false) {
        values.put(Hosts.TIMEOUT, -1);
    }
    if (values.containsKey(Hosts.WIFI_ONLY) == false) {
        values.put(Hosts.WIFI_ONLY, 0);
    }
    if (values.containsKey(Hosts.ACCESS_POINT) == false) {
        values.put(Hosts.ACCESS_POINT, "");
    }
    if (values.containsKey(Hosts.MAC_ADDR) == false) {
        values.put(Hosts.MAC_ADDR, "");
    }
    if (values.containsKey(Hosts.WOL_PORT) == false) {
        values.put(Hosts.WOL_PORT, 0);
    }
    if (values.containsKey(Hosts.WOL_WAIT) == false) {
        values.put(Hosts.WOL_WAIT, 0);
    }

    SQLiteDatabase db = mOpenHelper.getWritableDatabase();
    long rowId = db.insert(HOSTS_TABLE_NAME, Hosts.ADDR, values);
    if (rowId > 0) {
        Uri noteUri = ContentUris.withAppendedId(Hosts.CONTENT_URI, rowId);
        getContext().getContentResolver().notifyChange(noteUri, null);
        return noteUri;
    }
    throw new SQLException("Failed to insert row into " + uri);
}

@Override
public int delete(Uri uri, String where, String[] whereArgs) {
    SQLiteDatabase db = mOpenHelper.getWritableDatabase();
    int count;
    switch (sUriMatcher.match(uri)) {
    case HOSTS:
        count = db.delete(HOSTS_TABLE_NAME, where, whereArgs);
        break;

    case HOST_ID:
        String hostId = uri.getPathSegments().get(1);
        count = db.delete(HOSTS_TABLE_NAME, Hosts._ID + "=" + hostId + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);
        break;

    default:
        throw new IllegalArgumentException("Unknown URI " + uri);
    }

    getContext().getContentResolver().notifyChange(uri, null);
    return count;
}

@Override
public int update(Uri uri, ContentValues values, String where, String[] whereArgs) {
    SQLiteDatabase db = mOpenHelper.getWritableDatabase();
    int count;
    switch (sUriMatcher.match(uri)) {
    case HOSTS:
        count = db.update(HOSTS_TABLE_NAME, values, where, whereArgs);
        break;

    case HOST_ID:
        String hostId = uri.getPathSegments().get(1);
        count = db.update(HOSTS_TABLE_NAME, values, Hosts._ID + "=" + hostId + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);
        break;

    default:
        throw new IllegalArgumentException("Unknown URI " + uri);
    }

    getContext().getContentResolver().notifyChange(uri, null);
    return count;
}

static {
    sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    sUriMatcher.addURI(AUTHORITY, "hosts", HOSTS);
    sUriMatcher.addURI(AUTHORITY, "hosts/#", HOST_ID);

    sHostsProjectionMap = new HashMap<String, String>();
    sHostsProjectionMap.put(Hosts._ID, Hosts._ID);
    sHostsProjectionMap.put(Hosts.NAME, Hosts.NAME);
    sHostsProjectionMap.put(Hosts.ADDR, Hosts.ADDR);
    sHostsProjectionMap.put(Hosts.PORT, Hosts.PORT);
    sHostsProjectionMap.put(Hosts.USER, Hosts.USER);
    sHostsProjectionMap.put(Hosts.PASS, Hosts.PASS);
    sHostsProjectionMap.put(Hosts.ESPORT, Hosts.ESPORT);
    sHostsProjectionMap.put(Hosts.TIMEOUT, Hosts.TIMEOUT);
    sHostsProjectionMap.put(Hosts.WIFI_ONLY, Hosts.WIFI_ONLY);
    sHostsProjectionMap.put(Hosts.ACCESS_POINT, Hosts.ACCESS_POINT);
    sHostsProjectionMap.put(Hosts.MAC_ADDR, Hosts.MAC_ADDR);
    sHostsProjectionMap.put(Hosts.WOL_PORT, Hosts.WOL_PORT);
    sHostsProjectionMap.put(Hosts.WOL_WAIT, Hosts.WOL_WAIT);
}

/**
 * Notes table
 */
public static final class Hosts implements BaseColumns {

    // This class cannot be instantiated
    private Hosts() {
    }

    /**
     * The name of the host (as in label/title)
     * <P>
     * Type: TEXT
     * </P>
     */
    public static final String NAME = "name";

    /**
     * The address or IP of the host
     * <P>
     * Type: TEXT
     * </P>
     */
    public static final String ADDR = "address";

    /**
     * The note itself
     * <P>
     * Type: INTEGER
     * </P>
     */
    public static final String PORT = "http_port";

    /**
     * The user name if HTTP Auth is used
     * <P>
     * Type: TEXT
     * </P>
     */
    public static final String USER = "user";

    /**
     * The password if HTTP Auth is used
     * <P>
     * Type: TEXT
     * </P>
     */
    public static final String PASS = "pass";

    /**
     * The event server port
     * <P>
     * Type: INTEGER
     * </P>
     */
    public static final String ESPORT = "esport";

    /**
     * The socket read timeout in milliseconds
     * <P>
     * Type: INTEGER
     * </P>
     */
    public static final String TIMEOUT = "timeout";

    /**
     * If this connection is for wireless lan only
     * <P>
     * Type: BOOLEAN
     * </P>
     */
    public static final String WIFI_ONLY = "wifi_only";

    /**
     * If WIFI_ONLY is set this may or may not include an access point name
     * <P>
     * Type: TEXT
     * </P>
     */
    public static final String ACCESS_POINT = "access_point";

    /**
     * The MAC address of this host
     * <P>
     * Type: TEXT
     * </P>
     */
    public static final String MAC_ADDR = "mac_addr";

    /**
     * The time in seconds to wait after sending WOL paket
     * <P>
     * Type: INTEGER
     * </P>
     */
    public static final String WOL_WAIT = "wol_wait";

    /**
     * The port the WOL packet should be send to
     * <P>
     * Type: INTEGER
     * </P>
     */
    public static final String WOL_PORT = "wol_port";

    /**
     * The content:// style URL for this table
     */
    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + HOSTS_TABLE_NAME);

    /**
     * The MIME type of {@link #CONTENT_URI} providing a directory of notes.
     */
    public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.xbmc.host";

    /**
     * The MIME type of a {@link #CONTENT_URI} sub-directory of a single
     * note.
     */
    public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.xbmc.host";

    /**
     * The default sort order for this table
     */
    public static final String DEFAULT_SORT_ORDER = NAME + " ASC";

    }
}

在 Manifest.xml 中我添加了以下代码:

<provider
        android:name="org.xbmc.android.remote.business.provider.HostProvider"
        android:authorities="org.xbmc.android.provider.remote" />

当应用程序加载时，该类将被调用。为了使用此类，我需要在应用程序关闭时删除所有 SQLite 数据。

我该怎么做？或者还有其他方法可以做到这一点吗？

Answer 1

当您使用文件名:memory:时，数据库永远不会被放入文件中，并且连接时所有数据都会丢失(SQLiteDatabase对象)已关闭。

请注意，SQLiteOpenHelper 的自动创建/升级处理是为永久数据库设计的；您应该手动使用SQLiteDatabase。