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我有三个旋转器。第三个旋转器依赖于第二个旋转器，第二个旋转器依赖于第一个旋转器。微调器中的字段由外部 sqlite 数据库填充。现在的问题是，如果我有一个巨大的数据库，说有数千条记录，我是否必须为所有数千条记录编写条件，以便当我单击第一个微调器的第一个位置时，结果值应该显示在第二个微调器上等等在第三个微调器上。

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2 回答 2

2

//这是我的主要活动类

   public class MainActivity extends Activity implements OnItemSelectedListener{
   private CarHelper dbcarhelper=null;
   private Cursor ourCursor = null,cur=null,vercur=null;
   private CarAdapter car_adapter = null;
   public Spinner spinner,spinner2,spinner3,spinner4;
   public String a;


   @Override
   protected void onCreate(Bundle savedInstanceState)
   {
try
{

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    spinner = (Spinner)findViewById(R.id.spinner1);
    spinner2=(Spinner)findViewById(R.id.spinner2);
    spinner3= (Spinner)findViewById(R.id.spinner3);

    dbcarhelper = new CarHelper(this);
    dbcarhelper.createDatabase();
    dbcarhelper.openDataBase();

    ourCursor = dbcarhelper.getCursor();
    startManagingCursor(ourCursor);
    car_adapter = new CarAdapter(ourCursor);
    spinner.setAdapter(car_adapter);
    spinner.setOnItemSelectedListener(this);

    startManagingCursor(cur);
    spinner2.setOnItemSelectedListener(this);
    startManagingCursor(vercur);


}
catch(Exception e)
{
    Log.e("ERROR","ERROR IN CODE:" + e.toString());
    e.printStackTrace();
}
   }

   class CarAdapter extends CursorAdapter
   {

 CarAdapter(Cursor c ) {
    super(MainActivity.this, c);
 }

@Override
public void bindView(View row, Context ctxt, Cursor c) {
    CarHolder holder= (CarHolder)row.getTag();
    holder.populateFrom(c,dbcarhelper);

}

@Override
public View newView(Context ctxt, Cursor c, ViewGroup parent) {
    // TODO Auto-generated method stub
    LayoutInflater inflater = getLayoutInflater();
    View row = inflater.inflate(R.layout.row, parent, false);
    CarHolder holder= new CarHolder(row);
    row.setTag(holder);
    return (row);
}

}
   static class CarHolder {
       private TextView make = null, model= null, ver=null;
   CarHolder (View row)
   {
   make = (TextView)row.findViewById(R.id.carText);
   model = (TextView)row.findViewById(R.id.carText);
   ver = (TextView)row.findViewById(R.id.carText);
   }

   void populateFrom(Cursor c,CarHelper r)
   {
   make.setText(r.getName(c));
   model.setText(r.getName(c));
   ver.setText(r.getName(c));
   }


   }

   public void onItemSelected(AdapterView<?> parent, View arg1,int position,long        arg3) 
   {
       int id = parent.getId();
   switch(id)
   {
case R.id.spinner1:

int b = spinner.getSelectedItemPosition();
b++;
a = Integer.toString(b);

if(a!=null)
{
    dbcarhelper.m_pop(a);
}   

CarHelper ch = new CarHelper(getApplicationContext());

List<String> lables = ch.getAllLabels();
//ch.getAllLabels(str);

ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
    android.R.layout.simple_spinner_item, lables);

dataAdapter
    .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

spinner2.setAdapter(dataAdapter);

break;

case R.id.spinner2:
    int i = spinner.getSelectedItemPosition();
    i++;
    a = Integer.toString(i);

    if(a!=null)
    {
        dbcarhelper.v_pop(a);
    }   

    CarHelper c = new CarHelper(getApplicationContext());

    List<String> lable = c.getAllLabel();

    ArrayAdapter<String> dAdapter = new ArrayAdapter<String>(this,
        android.R.layout.simple_spinner_item, lable);

    dAdapter
        .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    spinner3.setAdapter(dAdapter);
    break;

}

   }

   @Override
   public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub

   }
于 2013-02-23T06:26:30.337 回答
1

//这是我的助手类

   public class CarHelper extends SQLiteOpenHelper{

private static final String DATABASE_PATH= "//data//data//com.example.dropdown//databases//";
private static final String DATABASE_NAME= "car_Database.sqlite";
private static final int SCHEMA_VERSION =1;
public static final String COLUMN_ID = "_id";
public static final String TABLE_NAME = "Make";
public static final String COLUMN_TITLE = "car_make";

public static final String TABLE_MODEL = "Model";
public static final String COLUMN_MODEL = "car_model";

public static final String TABLE_VER = "Version";
public static final String COLUMN_VER = "car_ver";


public SQLiteDatabase dbsqlite,db1;
private final Context myContext;

public CarHelper(Context context) {
    super(context, DATABASE_NAME, null, SCHEMA_VERSION);
    this.myContext = context;
    // TODO Auto-generated constructor stub
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub

}

public void createDatabase()
{
    createDB();
}

private void createDB()
{
    boolean dbExist = DBExists();
    if(!dbExist)
    {
        this.getReadableDatabase();
        copyDBFromResource();
    }
}

private boolean DBExists()
{
    SQLiteDatabase db = null;
    try
    {
        String databasePath = DATABASE_PATH + DATABASE_NAME;
        db = SQLiteDatabase.openDatabase(databasePath,null, SQLiteDatabase.OPEN_READWRITE);
        db.setLocale(Locale.getDefault());
        db.setLockingEnabled(true);
        db.setVersion(1);
    }
    catch(SQLiteException e)
    {
        Log.e("AqlHelper","database not found");
    }
    if(db!=null)
    {
        db.close();
    }
    return db!=null ? true : false;

}

private void copyDBFromResource()
{
    InputStream ip = null;
    OutputStream op = null;
    String dbFilePath = DATABASE_PATH + DATABASE_NAME;
    try
    {
        ip= myContext.getAssets().open(DATABASE_NAME);
        op = new FileOutputStream(dbFilePath);
        byte[] buffer = new byte[1024];
        int length;
        while((length = ip.read(buffer))>0)
        {
            op.write(buffer, 0, length);
        }
        op.flush();
        op.close();
        ip.close();
    }
    catch(IOException e)
    {
        throw new Error("Problemcopying database from Resource");
    }
}

public void openDataBase() throws SQLException
{
    String myPath = DATABASE_PATH + DATABASE_NAME;
    dbsqlite = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close()
{
    if(dbsqlite != null)
    {
        dbsqlite.close();
    }
    super.close();
}

public Cursor getCursor()
{
    SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
    queryBuilder.setTables(TABLE_NAME);
    String[] asColumnsToReturn = new String[] {COLUMN_ID,COLUMN_TITLE};
    Cursor mCursor = queryBuilder.query(dbsqlite, asColumnsToReturn, null, null, null, null, "car_make ASC");
    return mCursor;
}


public void m_pop(String st){
    String a = st;
    dbsqlite.execSQL("delete from temp");
    dbsqlite.execSQL("insert into temp(name) select car_model from Model where make_id="+a); 


}
public List<String> getAllLabels(){
    List<String> labels = new ArrayList<String>();
    String selectQuery = "select name from temp";
    dbsqlite = this.getReadableDatabase();
    Cursor cursor = dbsqlite.rawQuery(selectQuery, null);


    if (cursor.moveToFirst()) {
        do {
            labels.add(cursor.getString(cursor.getColumnIndex("name")));


        } while (cursor.moveToNext());
    }

    cursor.close();
    dbsqlite.close();

    return labels;
}





public void v_pop(String st){
    String a = st;
    dbsqlite.execSQL("delete from temp");
    dbsqlite.execSQL("insert into temp(name) select car_ver from Version where _id="+a); 


}
public List<String> getAllLabel(){
    List<String> label = new ArrayList<String>();

    String selectQuery = "select name from temp";
    dbsqlite = this.getReadableDatabase();
    Cursor cursor = dbsqlite.rawQuery(selectQuery, null);


    if (cursor.moveToFirst()) {
        do {
            label.add(cursor.getString(cursor.getColumnIndex("name")));


        } while (cursor.moveToNext());
    }

    cursor.close();
    dbsqlite.close();

    return label;
}



public String getName(Cursor c){
    return (c.getString(1));
}


   }
于 2013-02-23T06:31:36.127 回答