使用SQLite数据库的动态微调工具

Question

我已经能够使用SimpleCursorAdapter成功地将两个微调工具链接到一个数据库。但是，我需要使第二个微调器选择依赖于第一个微调器选择。

下面是我链接数据的方式：

    public class epa_estimates_button extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.epa_estimates);
    final Cursor cYear;
    final Cursor cMake;
    final Spinner mMakeSpinner;
    final Spinner mModelSpinner;
    cYear = (Cursor) DataBaseHelper.getEPADataYear();
    this.startManagingCursor(cYear);

    SimpleCursorAdapter scaYear = new SimpleCursorAdapter(this, R.layout.spinner_layout,cYear,new String[] {DataBaseHelper.EPA_COLUMN_ONE},new int[]{R.id.text1});
    scaYear.setDropDownViewResource(R.layout.spinner_dropdown);
    mYearSpinner = (Spinner) findViewById(R.id.yearSpinner);
    mYearSpinner.setAdapter(scaYear);

    cMake = (Cursor) DataBaseHelper.getEPADataMake();
    this.startManagingCursor(cMake);

    SimpleCursorAdapter scaMake = new SimpleCursorAdapter(this, R.layout.spinner_layout,cMake,new String[] {DataBaseHelper.EPA_COLUMN_TWO},new int[]{R.id.text1});
    scaMake.setDropDownViewResource(R.layout.spinner_dropdown);
    mMakeSpinner = (Spinner) findViewById(R.id.makeSpinner);
    mMakeSpinner.setAdapter(scaMake);
}}

这是我的DataBaseHelper

    public class DataBaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/org.application.ocdmpg/databases/";
private static String DB_NAME = "ocd_mpg.mp3";
private final int DB_VERSION = 1;
private static SQLiteDatabase myDataBase; 
private final Context myContext;
private static final String EPA_TABLE_NAME = "epa_data";
private static final String EPA_COLUMN_ID = "_id";
public DataBaseHelper(Context context) {

    super(context, DB_NAME, null, 1);
    this.myContext = context;
}
    public static Cursor getEPADataYear() 
{
    return myDataBase.query(EPA_TABLE_NAME, //table name
            new String[] {EPA_COLUMN_ID, EPA_COLUMN_ONE}, //list of columns to return
            null, //filter declaring which rows to return; formatted as SQL WHERE clause
            null,
            EPA_COLUMN_ONE, //filter declaring how to group rows; formatted as SQL GROUP BY clause
            null, //filter declaring which row groups to include in cursor; formatted as SQL HAVING clause
            null); //how to order rows; formatted as SQL ORDER BY clause
}
public static Cursor getEPADataMake() 
{
    return myDataBase.query(EPA_TABLE_NAME, new String[] {
            EPA_COLUMN_ID,
            EPA_COLUMN_TWO,
            }, 
            null, 
            null, 
            EPA_COLUMN_TWO, 
            null, 
            null);
}}

我已经找到了setOnItemSelectedListener的代码，并尝试添加用于将数据链接到微调器的代码，但startManagingCursor方法和SimpleCursorAdapter构造函数给出了一个未定义的错误。我应该使用ArrayAdapter来填充我的微调器吗？或者有没有办法改正下面的代码？

        mYearSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
            // your code here
            cMake = (Cursor) DataBaseHelper.getEPADataMake();
            this.startManagingCursor(cMake);

            SimpleCursorAdapter scaMake = new SimpleCursorAdapter(this, R.layout.spinner_layout,cMake,new String[] {DataBaseHelper.EPA_COLUMN_TWO},new int[]{R.id.text1});
            scaMake.setDropDownViewResource(R.layout.spinner_dropdown);
            mMakeSpinner = (Spinner) findViewById(R.id.makeSpinner);
            mMakeSpinner.setAdapter(scaMake);
        }

        @Override
        public void onNothingSelected(AdapterView<?> parentView) {
            // your code here
        }

        });

Answer 1

根据您的编辑和评论更新了

您对this.startManagingCursor(cMake)的调用需要更改为startManagingCursor(cMake)或epa_estimates_button.this.startManagingCursor(cMake)，因为它是从内部类( OnItemSelectedListener)进行的。它不需要'this‘(前一种情况)就可以工作，因为，好吧，基本上，Java知道你指的是哪个this。它与类名一起工作，因为这清楚地表明了Java将自己弄清楚的东西。但是未限定的this意味着您引用的是内部类this，这是行不通的。

非常类似地，在您的onItemSelectedListener中，对startManagingCursor的调用需要重写为：

SimpleCursorAdapter scaMake = new SimpleCursorAdapter(epa_estimates_button.this,
    R.layout.spinner_layout,cMake,new String[] {DataBaseHelper.EPA_COLUMN_TWO},
    new int[]{R.id.text1});

(我认为您的数据库查询将需要工作--您似乎没有使用任何类型的WHERE子句将“make”结果限制在适当的年份。但如果你真的被这个问题卡住了，请将其作为另一个问题发布。)