Question

我正在尝试从数据库中删除单个标记，但它似乎删除了整个数据库并完全清除了地图。我想删除一个标记。

这是我的LocationsDB课程：

public class LocationsDB extends SQLiteOpenHelper{
    private static String DBNAME = "locationmarkersqlite";
    private static int VERSION = 1;
    public static final String FIELD_ROW_ID = "_id";
    public static final String FIELD_LAT = "lat";
    public static final String FIELD_LNG = "lng";
    public static final String FIELD_ZOOM = "zom";
    public static final String FIELD_TITLE = "tle";
    public static final String FIELD_SNIPPET = "snip";
    public static final String FIELD_IMAGE = "blob";
    public static final String FIELD_FILEPATH = "filep";
    private static final String DATABASE_TABLE = "locations";

    private static SQLiteDatabase mDB;

    public LocationsDB(Context context) {
        super(context, DBNAME, null, VERSION);
        LocationsDB.mDB = getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "create table " + DATABASE_TABLE + " ( " +
                     FIELD_ROW_ID + " integer primary key autoincrement , " +
                     FIELD_LNG + " double , " +
                     FIELD_LAT + " double , " +
                     FIELD_ZOOM + " text , " +
                     FIELD_TITLE + " text , " +
                     FIELD_SNIPPET + " text , " +
                     FIELD_IMAGE + " blob , " +
                     FIELD_FILEPATH + " blob " +
                     " ) ";

        db.execSQL(sql);
    }

    public long insert(ContentValues contentValues){
        long rowID = mDB.insert(DATABASE_TABLE, null, contentValues);
        return rowID;
    }

    public int del(String[] selectionArgs){
        int cnt = mDB.delete(DATABASE_TABLE, FIELD_ROW_ID , selectionArgs);
        return cnt;
    }

    public Cursor getAllLocations(){
        return mDB.query(DATABASE_TABLE, new String[] 
            { FIELD_ROW_ID,  
              FIELD_LAT, 
              FIELD_LNG, 
              FIELD_ZOOM, 
              FIELD_TITLE, 
              FIELD_SNIPPET, 
              FIELD_IMAGE, 
              FIELD_FILEPATH}, 
              null, 
              null, 
              null, 
              null, 
              null, 
              null);
    }

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

    public static Cursor rawQuery(String string, Object object) {
        return null;
    }
}

我的LocationsContentProvider课程：

public class LocationsContentProvider extends ContentProvider{

    public static final String PROVIDER_NAME = "com.marker.markermap.locations";
    public static final Uri CONTENT_URI = Uri.parse("content://" + PROVIDER_NAME + "/locations" );
    private static final int LOCATIONS = 1;
    private static final UriMatcher uriMatcher ;

    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(PROVIDER_NAME, "locations", LOCATIONS);
    }

    LocationsDB mLocationsDB;

    @Override
    public boolean onCreate() {
        mLocationsDB = new LocationsDB(getContext());
        return true;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        long rowID = mLocationsDB.insert(values);
        Uri _uri=null;
        if(rowID>0){
            _uri = ContentUris.withAppendedId(CONTENT_URI, rowID);
        }else {
            try {
                throw new SQLException("Failed to insert : " + uri);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return _uri;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
        String[] selectionArgs) {
        return 0;
    }
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int cnt = 1;
        cnt = mLocationsDB.del(selectionArgs);
        return cnt;
    }
    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {

        if(uriMatcher.match(uri)==LOCATIONS){
            return mLocationsDB.getAllLocations();
        }
        return null;
    }

    @Override
    public String getType(Uri uri) {
        return null;
    }
}

在我的MainActivity课程中：

public void onClick(DialogInterface dialog,int id) {

    marker.remove();
    LocationDeleteTask deleteTask = new LocationDeleteTask();
    deleteTask.marker(marker.getTitle(), marker.getSnippet(), marker.getPosition(), marker.getId());
    deleteTask.execute();
        }
    });
    AlertDialog alertDialog = alertDialogBuilder.create();
    alertDialog.show();
    return;
  }
  ......
  @Override
  public void onLoaderReset(Loader<Cursor> arg0) {
  }
  class LocationInsertTask extends AsyncTask<ContentValues, Void, Void>{
      @Override
      protected Void doInBackground(ContentValues... contentValues) {
          getContentResolver().insert(LocationsContentProvider.CONTENT_URI, contentValues[0]);
          return null;
      }
  }

  private class LocationDeleteTask extends AsyncTask<Void, Void, Void>{

      @Override
      protected Void doInBackground(Void... params) {
         getContentResolver().delete(LocationsContentProvider.CONTENT_URI, null, null );
         return null;
          }

  public void marker(String title, String snippet, LatLng position, String id) {
      // TODO Auto-generated method stub

      }
  }
}

Answer 1

在您的MainActivity中，当您调用时，您将传入null作为selectionArgs：

getContentResolver().delete(LocationsContentProvider.CONTENT_URI, null, null );

此函数然后在LocationsContentProvider中调用delete：

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
    int cnt = 1;
    cnt = mLocationsDB.del(selectionArgs);
    return cnt;
}

其中selectionArgs为null。 LocationsContentProvider中的del（...）调用在LocationsDB中调用此函数：

public int del(String[] selectionArgs){
    int cnt = mDB.delete(DATABASE_TABLE, FIELD_ROW_ID , selectionArgs);
    return cnt;
}

SQLiteOpenHelper中的

并且selectionArgs仍然为null。

由于您将null作为selectionArgs传递给SQLiteOpenHelper中的SQLiteDatabase.delete（...）调用，因此整个表中的数据可能会被删除。

更新：在LocationsDB del（String [] selectionArgs）方法中，更改参数以包含要删除的行的行ID，而不是selectionArgs（在当前实现中无论如何都是null）。尝试类似：

public int del(String rowId){
    String whereClause = FIELD_ROW_ID + "=?";
    String[] whereArgs = new String[] { rowId };
    int cnt = mDB.delete(DATABASE_TABLE, whereClause, whereArgs);;
    return cnt;
}

从数据库android中删除一个标记（行）似乎不起作用

1 个答案: