Question

我在创建查询请求时遇到问题，该请求允许我从多个表中检索对象。

数据流的目标是在ContentProvider上进行请求调用'insert'或'update'，然后让我的视图从ContentProvider加载数据，而不是网络调用（用于离线持久缓存）。

我正在使用GSON进行json序列化和反序列化。

所以说从Web服务收到的Expense对象如下：

{
  "name"             : "Expense1",
  "amount"           : 10.10
  "date"             : "2014-03-23 12:32:22"
  "is_reimbursement" : false,
  "note"             : "This is a note :)",
  "spends"           : [
    {
      "user_id"          : 3,
      "amount_credited"  : 0,
      "amount_debited"   : 10.3
    }, {
      "user_id"          : 2,
      "amount_credited"  : 10.3,
      "amount_debited"   : 0
    }
  ],
  "debts"            : [
    {
      "amount"         : 10.3,
      "receiver_data" : {
        "confirmation"   : "wait",
        "user_id"        : 2
      },
      "giver_data" : {
        "confirmation"   : "wait",
        "user_id"        : 3
      }
    }
  ]
}

这是我对应的POJO字段：

    @SerializedName("is_reimbursement")
    private boolean IsReimbursement;

    @SerializedName("name")
    private String Name;

    @SerializedName("amount")
    private double Amount;

    @SerializedName("date")
    private Timestamp Date;

    @SerializedName("note")
    private String Note;

    @SerializedName("created_by_id")
    private int CreatedById;

    @SerializedName("spends")
    private List<ExpenseSpend> Spends;

    @SerializedName("debts")
    private List<ExpenseDebt> Debts;

    @SerializedName("pictures")
    private List<ExpensePicture> Pictures;

然后我有一个用于EXPENSES的SQL表，以及一个用于每个子项的表（Expense_Pictures的表，一个用于Expense_Debts，一个用于ExpenseSpend）。

要插入我的数据库，我在ContentProvider中创建了插入URI，并使用ContentProvider的getContentResolver().applyBatch(ContentProvider.AUTHORITY, ops);方法插入ExpenseObject，其中一个插入操作用于费用，然后一个用于每个子节点

这成功将上面复制的JSON对象插入到我的数据库的所有表中。

现在的问题是如何使用ContentProvider.query(...)检索同一个POJO？

要用不同的方式表达，如何向ContentProvider发出请求，返回数据库中的所有费用（POJO，有关系）？

现在，我的查询没有返回完整的POJO信息（它没有我的费用POJO的关系字段的信息）：

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {

    int requestType = _uriMatcher.match(uri);
    SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
    switch(requestType){
        case EXPENSES:
            queryBuilder.setTables(DatabaseHelper.TABLE_EXPENSE);
            queryBuilder.appendWhere(DatabaseHelper.KEY_ID + "=" + uri.getLastPathSegment());
            break;
        case EXPENSE_ID:
            queryBuilder.setTables(DatabaseHelper.TABLE_EXPENSE);
            queryBuilder.appendWhere(DatabaseHelper.KEY_ID + "=" + uri.getLastPathSegment());
            break;
        default:
            throw new IllegalArgumentException("Content provider error, could not match URI: " + uri);
    }

    SQLiteDatabase sqlDB = _db.getWritableDatabase();
    Cursor cursor = queryBuilder.query(sqlDB, projection, selection, selectionArgs, null, null, sortOrder);
    cursor.setNotificationUri(getContext().getContentResolver(), uri);
    return cursor;
}

数据库创建代码，供参考：

//EXPENSE Table create statement
private static final String CREATE_TABLE_EXPENSE = "CREATE TABLE "
        + TABLE_EXPENSE + "("
        + KEY_ID + " INTEGER PRIMARY KEY,"
        + KEY_IS_REIMBURSEMENT + " INTEGER,"
        + KEY_NAME + " TEXT,"
        + KEY_AMOUNT + " NUMERIC,"
        + KEY_DATE + " TEXT,"
        + KEY_NOTE + " TEXT,"
        + KEY_CREATED_BY_ID + " INTEGER,"
        + KEY_CREATED_AT + " TEXT,"
        + KEY_UPDATED_AT + " TEXT,"
        + KEY_DELETED_AT + " TEXT)";

//EXPENSE_DEBT Table create statement
private static final String CREATE_TABLE_EXPENSE_DEBT = "CREATE TABLE "
        + TABLE_EXPENSE_DEBT + "("
        + KEY_ID + " INTEGER PRIMARY KEY,"
        + KEY_EXPENSE_ID + " INTEGER,"
        + KEY_AMOUNT + " NUMERIC,"
        + KEY_GIVER_DATA_ID + " INTEGER,"
        + KEY_RECEIVER_DATA_ID + " INTEGER)";


//EXPENSE_DEBT_DATA Table create statement
private static final String CREATE_TABLE_EXPENSE_DEBT_DATA = "CREATE TABLE "
        + TABLE_EXPENSE_DEBT_DATA + "("
        + KEY_ID + " INTEGER PRIMARY KEY,"
        + KEY_USER_ID + " INTEGER,"
        + KEY_CONFIRMATION + " TEXT,"
        + KEY_CREATED_AT + " INTEGER,"
        + KEY_UPDATED_AT + " INTEGER)";

//EXPENSE_SPEND Table create statement
private static final String CREATE_TABLE_EXPENSE_SPEND = "CREATE TABLE "
        + TABLE_EXPENSE_SPEND + "("
        + KEY_ID + " INTEGER PRIMARY KEY,"
        + KEY_EXPENSE_ID + " INTEGER,"
        + KEY_USER_ID + " INTEGER,"
        + KEY_AMOUNT_CREDITED + " NUMERIC,"
        + KEY_AMOUNT_DEBITED + " NUMERIC)";

//EXPENSE_PICTURE Table create statement
private static final String CREATE_TABLE_EXPENSE_PICTURE = "CREATE TABLE "
        + TABLE_EXPENSE_PICTURE + "("
        + KEY_ID + " INTEGER PRIMARY KEY,"
        + KEY_EXPENSE_ID + " INTEGER,"
        + KEY_USER_ID + " INTEGER,"
        + KEY_DELETED_AT + " TEXT)";

一如既往，请不要犹豫，告诉我数据库创建代码是否有问题（如果我应该在这种情况下加入表格），或者另一种方法更适合我想要做的事情。

查询ContentProvider中的关系数据

0 个答案: