graph TD;
    A[开始] --> B[用户输入收入/支出]
    B --> C[数据保存至 Room 数据库]
    C --> D{是否要生成报告?}
    D -- 是 --> E[从数据库读取数据]
    E --> F[数据处理和统计]
    F --> G[显示图表]
    D -- 否 --> H[返回首页]
    G --> I[结束]
    H --> I
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// Entity 类
@Entity(tableName = "transactions")
public class Transaction {
    @PrimaryKey(autoGenerate = true)
    public int id;
    
    @ColumnInfo(name = "type")
    public String type;  // "income" 或 "expense"
    
    @ColumnInfo(name = "amount")
    public double amount;
    
    @ColumnInfo(name = "date")
    public Date date;
}

// DAO 接口
@Dao
public interface TransactionDao {
    @Insert
    void insert(Transaction transaction);
    
    @Query("SELECT * FROM transactions WHERE date BETWEEN :startDate AND :endDate")
    List<Transaction> getTransactionsByDateRange(Date startDate, Date endDate);
}

// Database 类
@Database(entities = {Transaction.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
    public abstract TransactionDao transactionDao();
}
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public void displayChart(List<Transaction> transactions) {
    BarChart barChart = findViewById(R.id.barChart);
    
    List<BarEntry> entries = new ArrayList<>();
    for (int i = 0; i < transactions.size(); i++) {
        entries.add(new BarEntry(i, transactions.get(i).amount));
    }
    
    BarDataSet dataSet = new BarDataSet(entries, "Transactions");
    BarData barData = new BarData(dataSet);
    barChart.setData(barData);
    barChart.invalidate(); // Refresh chart
}
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@RunWith(AndroidJUnit4.class)
public class DatabaseTest {
    private AppDatabase db;
    private TransactionDao transactionDao;

    @Before
    public void createDb() {
        Context context = ApplicationProvider.getApplicationContext();
        db = Room.inMemoryDatabaseBuilder(context, AppDatabase.class).build();
        transactionDao = db.transactionDao();
    }

    @After
    public void closeDb() {
        db.close();
    }

    @Test
    public void writeReadTest() {
        Transaction transaction = new Transaction();
        transaction.type = "income";
        transaction.amount = 100.0;
        transaction.date = new Date();
        transactionDao.insert(transaction);

        List<Transaction> transactions = transactionDao.getTransactionsByDateRange(new Date(0), new Date());
        assertEquals(transactions.get(0).amount, 100.0, 0);
    }
}
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