spatiallite空间数据库在Android平台的两种数据查询方式

spatialite在Android平台的学习资料非常少，它的数据查询方式主要有异步式和非异步式两种。

异步式

db = new jsqlite.Database();
File dbFile=new File(Environment.getExternalStorageDirectory().getPath()+"/test.sqlite");
db.open(dbFile.toString(), jsqlite.Constants.SQLITE_OPEN_READONLY);
String query = "SELECT name, peoples, AsText(Geometry) from Towns where peoples > 350000";
Callback cb = new Callback() {

@Override
public void columns(String[] coldata) {
Log.e(TAG, Arrays.toString(coldata));
}

@Override
public void types(String[] types) {
Log.e(TAG, "Types: " + Arrays.toString(types));
}

@Override
public boolean newrow(String[] rowdata) {
Log.e(TAG, rowdata[0]);
return false;
}
};

db.exec("select Distance(PointFromText('point(-77.35368 39.04106)', 4326), PointFromText('point(-77.35581 39.01725)', 4326));",
cb);
db.exec("SELECT AsGeoJSON(Geometry) from HighWays;",
cb);
db.exec("SELECT name from sqlite_sequence;",
cb);
db.exec("SELECT name, peoples, AsText(Geometry), GeometryType(Geometry), NumPoints(Geometry), SRID(Geometry), IsValid(Geometry) from Towns where peoples > 350000;",
cb);
db.exec("SELECT Distance( Transform(MakePoint(4.430174797, 51.01047063, 4326), 32631), Transform(MakePoint(4.43001276, 51.01041585, 4326),32631));",
cb);

db.close();

异步式查询是将查询的结果在回掉事件中输出，查询到一行输出一行。

非异步式

db = new jsqlite.Database();
File dbFile=new File(Environment.getExternalStorageDirectory().getPath()+"/test.sqlite");
db.open(dbFile.toString(), jsqlite.Constants.SQLITE_OPEN_READONLY);
String query = "SELECT name, peoples, AsText(Geometry) from Towns where peoples > 350000";
Stmt stmt = db.prepare(query);
stmt.step();
while (stmt.step()) {
String tableName = stmt.column_string(0);
String type = stmt.column_string(1);
String srid = stmt.column_string(2);
Log.e(TAG, tableName+type+srid);
}
stmt.close();
db.close();

非异步式则在主线程中一直判断是否有下一行，如果没有，则向后执行