使用自制内容提供程序时，有什么方法可以重写 ManagedQuery 方法以包含限制参数吗？

Question

我已经构建了自己的内容提供程序，并且遇到了一个需要执行查询并包含限制参数的实例。

对 ManagedQuery 的方法调用不包含此参数，因此我看不出有什么办法可以以某种方式重写 ManagedQuery 方法来实现此功能？

我在我的内容提供程序中创建了第二个查询方法，它接受一个附加参数，即限制参数，但我认为我无法使 ManagedQuery 方法调用我的内容提供程序的此自定义查询方法。

最好的方法是什么？

作为参考，这是我的内容提供者类...... com.isi.sa 包；

import java.text.DateFormat;
import java.util.Date;
import java.util.HashMap;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

import com.isi.sa.SATest.Questions;
import com.isi.sa.SATest.Scores;

public class SAContentProvider extends ContentProvider {
  private static final String TAG            = "SAProvider";
    private static final String DATABASE_NAME      = "sa.db";
    private static final int DATABASE_VERSION      = 1;
    private static final String QUESTIONS_TABLE_NAME  = "questions";
    private static final String SCORES_TABLE_NAME    = "scores";

    private static HashMap<String, String> sQuestionsProjectionMap;
    private static HashMap<String, String> sScoresProjectionMap;

    private static final int QUESTIONS = 1;
    private static final int QUESTION_ID = 2;
    private static final int SCORES = 3;
    private static final int SCORE_ID = 4;

    private DatabaseHelper mOpenHelper;
    private static final UriMatcher sUriMatcher;


  @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 QUESTIONS:
      qb.setTables(QUESTIONS_TABLE_NAME);
      qb.setProjectionMap(sQuestionsProjectionMap);
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Questions.DEFAULT_SORT_ORDER;
      break;

    case QUESTION_ID:
      qb.setTables(QUESTIONS_TABLE_NAME);
      qb.setProjectionMap(sQuestionsProjectionMap);
      qb.appendWhere(Questions._ID + "=" + uri.getPathSegments().get(1));
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Questions.DEFAULT_SORT_ORDER;
      break;

    case SCORES:
      qb.setTables(SCORES_TABLE_NAME);
      qb.setProjectionMap(sScoresProjectionMap);
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Scores.DEFAULT_SORT_ORDER;
      break;

    case SCORE_ID:
      qb.setTables(SCORES_TABLE_NAME);
      qb.setProjectionMap(sScoresProjectionMap);
      qb.appendWhere(Scores._ID + "=" + uri.getPathSegments().get(1));
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Scores.DEFAULT_SORT_ORDER;
      break;

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

        // Get the database and run the query
    SQLiteDatabase db = mOpenHelper.getReadableDatabase();
    Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, sortOrder);

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


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

    switch (sUriMatcher.match(uri)){
    case QUESTIONS:
      qb.setTables(QUESTIONS_TABLE_NAME);
      qb.setProjectionMap(sQuestionsProjectionMap);
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Questions.DEFAULT_SORT_ORDER;
      break;

    case QUESTION_ID:
      qb.setTables(QUESTIONS_TABLE_NAME);
      qb.setProjectionMap(sQuestionsProjectionMap);
      qb.appendWhere(Questions._ID + "=" + uri.getPathSegments().get(1));
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Questions.DEFAULT_SORT_ORDER;
      break;

    case SCORES:
      qb.setTables(SCORES_TABLE_NAME);
      qb.setProjectionMap(sScoresProjectionMap);
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Scores.DEFAULT_SORT_ORDER;
      break;

    case SCORE_ID:
      qb.setTables(SCORES_TABLE_NAME);
      qb.setProjectionMap(sScoresProjectionMap);
      qb.appendWhere(Scores._ID + "=" + uri.getPathSegments().get(1));
      if (TextUtils.isEmpty(sortOrder)) sortOrder = Scores.DEFAULT_SORT_ORDER;
      break;

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

        // Get the database and run the query
    SQLiteDatabase db = mOpenHelper.getReadableDatabase();
    Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, sortOrder, limit);

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


  @Override
  public Uri insert(Uri uri, ContentValues initialValues) {
        ContentValues values;
        SQLiteDatabase db;
        long rowId;

        if (sUriMatcher.match(uri) != QUESTIONS && sUriMatcher.match(uri) != SCORES) {
            throw new IllegalArgumentException("Unknown URI " + uri);
        }

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

    switch (sUriMatcher.match(uri)){
    case QUESTIONS:
          if (values.containsKey(Questions.QUESTION) == false) values.put(Questions.QUESTION, "");
        if (values.containsKey(Questions.QUESTION) == false) values.put(Questions.ANSWER, -1);
        if (values.containsKey(Questions.OPTION1) == false) values.put(Questions.OPTION1, "");
        if (values.containsKey(Questions.OPTION2) == false) values.put(Questions.OPTION2, "");
        if (values.containsKey(Questions.OPTION3) == false) values.put(Questions.OPTION3, "");
        if (values.containsKey(Questions.OPTION4) == false) values.put(Questions.OPTION4, "");
        if (values.containsKey(Questions.OPTION5) == false) values.put(Questions.OPTION5, "");
        if (values.containsKey(Questions.OPTION6) == false) values.put(Questions.OPTION6, "");
        if (values.containsKey(Questions.OPTION7) == false) values.put(Questions.OPTION7, "");
        if (values.containsKey(Questions.OPTION8) == false) values.put(Questions.OPTION8, "");
        if (values.containsKey(Questions.OPTION9) == false) values.put(Questions.OPTION9, "");
        if (values.containsKey(Questions.OPTION10) == false) values.put(Questions.OPTION10, "");

          if (values.get(Questions.QUESTION).toString().length() > 0 &&
            values.get(Questions.ANSWER).toString() != "-1" &&
            values.get(Questions.OPTION1).toString().length() > 0){
            db = mOpenHelper.getWritableDatabase();
            rowId = db.insert(QUESTIONS_TABLE_NAME, Questions.QUESTION, values);
            if (rowId > 0) {
                Uri noteUri = ContentUris.withAppendedId(Questions.CONTENT_URI, rowId);
                getContext().getContentResolver().notifyChange(noteUri, null);
                return noteUri;
            }
          }
          break;

    case SCORES:
        if (values.containsKey(Scores.SCORE) == false) values.put(Scores.SCORE, -1);
        if (values.containsKey(Scores.DATE_CREATED) == false) values.put(Scores.DATE_CREATED, DateFormat.getDateTimeInstance().format(new Date()));

          if (values.get(Scores.SCORE).toString() != "-1"){
            db = mOpenHelper.getWritableDatabase();
            rowId = db.insert(SCORES_TABLE_NAME, Scores.SCORE, values);
            if (rowId > 0) {
                Uri noteUri = ContentUris.withAppendedId(Questions.CONTENT_URI, rowId);
                getContext().getContentResolver().notifyChange(noteUri, null);
                return noteUri;
            }
      }
      break;
    }    

        throw new SQLException("Failed to insert row into " + uri);
  }


  @Override
  public int update(Uri uri, ContentValues values, String where, String[] whereArgs) {
    SQLiteDatabase db = mOpenHelper.getWritableDatabase();
    int count;

    switch(sUriMatcher.match(uri)){
    case QUESTIONS:
            count = db.update(QUESTIONS_TABLE_NAME, values, where, whereArgs);
            break;

    case QUESTION_ID:
            String questionId = uri.getPathSegments().get(1);
            count = db.update(QUESTIONS_TABLE_NAME, values, Questions._ID + "=" + questionId
                    + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);
      break;

    case SCORES:
            count = db.update(SCORES_TABLE_NAME, values, where, whereArgs);
      break;

    case SCORE_ID:
            String scoreId = uri.getPathSegments().get(1);
            count = db.update(SCORES_TABLE_NAME, values, Scores._ID + "=" + scoreId
                    + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);
      break;

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

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


  @Override
  public int delete(Uri uri, String where, String[] whereArgs) {
    SQLiteDatabase db = mOpenHelper.getWritableDatabase();
    int count;

    switch(sUriMatcher.match(uri)){
    case QUESTIONS:
            count = db.delete(QUESTIONS_TABLE_NAME, where, whereArgs);
            break;

    case QUESTION_ID:
            String questionId = uri.getPathSegments().get(1);
            count = db.delete(QUESTIONS_TABLE_NAME, Questions._ID + "=" + questionId
                    + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);
      break;

    case SCORES:
            count = db.delete(SCORES_TABLE_NAME, where, whereArgs);
      break;

    case SCORE_ID:
            String scoreId = uri.getPathSegments().get(1);
            count = db.delete(SCORES_TABLE_NAME, Scores._ID + "=" + scoreId
                    + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);
      break;

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

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


  @Override
  public String getType(Uri uri) {
        switch (sUriMatcher.match(uri)) {
        case QUESTIONS:
            return Questions.CONTENT_TYPE;
        case QUESTION_ID:
            return Questions.CONTENT_ITEM_TYPE;
        case SCORES:
            return Scores.CONTENT_TYPE;
        case SCORE_ID:
            return Scores.CONTENT_ITEM_TYPE;
        default:
            throw new IllegalArgumentException("Unknown URI " + uri);
        }
  }


    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 questions ("
              + "_id INTEGER PRIMARY KEY AUTOINCREMENT,"
              + "question TEXT,"
              + "answer INTEGER,"
              + "option1 TEXT,"
              + "option2 TEXT,"
              + "option3 TEXT,"
              + "option4 TEXT,"
              + "option5 TEXT,"
              + "option6 TEXT,"
              + "option7 TEXT,"
              + "option8 TEXT,"
              + "option9 TEXT,"
              + "option10 TEXT);");

            db.execSQL("CREATE TABLE scores ("
                + "_id INTEGER PRIMARY KEY AUTOINCREMENT,"
                + "score NUMERIC,"
                + "date_created TEXT);");
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
        }        
    }


    static {
        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        sUriMatcher.addURI(SATest.AUTHORITY, "questions", QUESTIONS);
        sUriMatcher.addURI(SATest.AUTHORITY, "questions/#", QUESTION_ID);
        sUriMatcher.addURI(SATest.AUTHORITY, "scores", SCORES);
        sUriMatcher.addURI(SATest.AUTHORITY, "scores/#", SCORE_ID);

        sQuestionsProjectionMap = new HashMap<String, String>();
        sQuestionsProjectionMap.put(Questions._ID, Questions._ID);
        sQuestionsProjectionMap.put(Questions.QUESTION, Questions.QUESTION);
        sQuestionsProjectionMap.put(Questions.ANSWER, Questions.ANSWER);
        sQuestionsProjectionMap.put(Questions.OPTION1, Questions.OPTION1);
        sQuestionsProjectionMap.put(Questions.OPTION2, Questions.OPTION2);
        sQuestionsProjectionMap.put(Questions.OPTION3, Questions.OPTION3);
        sQuestionsProjectionMap.put(Questions.OPTION4, Questions.OPTION4);
        sQuestionsProjectionMap.put(Questions.OPTION5, Questions.OPTION5);
        sQuestionsProjectionMap.put(Questions.OPTION6, Questions.OPTION6);
        sQuestionsProjectionMap.put(Questions.OPTION7, Questions.OPTION7);
        sQuestionsProjectionMap.put(Questions.OPTION8, Questions.OPTION8);
        sQuestionsProjectionMap.put(Questions.OPTION9, Questions.OPTION9);
        sQuestionsProjectionMap.put(Questions.OPTION10, Questions.OPTION10);

        sScoresProjectionMap = new HashMap<String, String>();
        sScoresProjectionMap.put(Scores._ID, Scores._ID);
        sScoresProjectionMap.put(Scores.SCORE, Scores.SCORE);
        sScoresProjectionMap.put(Scores.DATE_CREATED, Scores.DATE_CREATED);
    }
}

Answer 1

如果内容提供程序的使用者与内容提供程序本身位于同一应用程序中，则不要使用内容提供程序 - 直接访问数据库。 ContentProvider 专为进程间通信而设计，因此它会增加开销并限制您的 API。