SQLite 数据库查询和 AsyncTask
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【中文标题】SQLite 数据库查询和 AsyncTask【英文标题】：SQLite Database query and AsyncTask 【发布时间】：2017-03-22 14:38:33 【问题描述】：你好安卓专家！！！
我目前正在编写一个具有 SQLite 数据库和 MPcharts 的应用程序。这个想法是我创建了一个带有几个数据库表的 SQLite 数据库，并将数据从数据库中提取出来并创建 MP 图表。我在不同的应用程序中使用了类似的方法，效果很好。在这种情况下，查询稍微复杂一些，应用程序停止，我的图表上没有显示任何数据。在网上调查之后，我觉得 AsyncTask 可以帮助我解决这个问题。我不确定如何将 AsyncTask 应用于我的案例。基本上，将 Arraylist xDataMonthCategory() 和 Arraylist yDataPieChartCategoryMonth() 链接到 Piechart 并使用 AsyncTask 在后台运行 SQLite 查询。我测试了我的查询，我知道数据在那里。请帮我。非常感谢！！！
这是 MP Piechart Java 类：
import android.graphics.Color;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import com.github.mikephil.charting.charts.PieChart;
import com.github.mikephil.charting.components.Legend;
import com.github.mikephil.charting.data.Entry;
import com.github.mikephil.charting.data.PieData;
import com.github.mikephil.charting.data.PieDataSet;
import com.github.mikephil.charting.formatter.PercentFormatter;
import java.util.ArrayList;
public class MTDPieCharts extends AppCompatActivity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_mtdpie_charts);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
);
MTDPieChartCategory();
//MTDPieChartItems();
//MTD Category PieChart
public void MTDPieChartCategory()
DataBaseHelper databasehelper = new DataBaseHelper(MTDPieCharts.this);
PieChart MTDcategoryChart = new PieChart(this);
MTDcategoryChart = (PieChart) findViewById(R.id.MTDPieChartCategory);
//get yVals and datasets of MTD Category chart
ArrayList<Entry> yValsCategoryAMT = new ArrayList<Entry>();
for(int i = 0; i < databasehelper.yDataPieChartCategoryMonth().size(); i++)
yValsCategoryAMT.add(new Entry(databasehelper.yDataPieChartCategoryMonth().get(i), i));
//get xVals of MTD Category chart
ArrayList<String> xValsCategory = new ArrayList<String>();
for(int i = 0; i < databasehelper.xDataMonthCategory().size(); i++)
xValsCategory.add(databasehelper.xDataMonthCategory().get(i));
PieDataSet MTDCategorySet = new PieDataSet(yValsCategoryAMT, "");
//set yvals attribute
MTDCategorySet.setSliceSpace(3);
MTDCategorySet.setSelectionShift(5);
//add many colors
MTDCategorySet.setColors(new int[]R.color.BlueA100, R.color.Cyan500, R.color.colorAccent, R.color.DeepPurpleA200, R.color.BlueA100, R.color.Teal200, R.color.Pink200, R.color.Pink500, R.color.purple,this);
// configue pie chart
MTDcategoryChart.setUsePercentValues(true);
MTDcategoryChart.setRotationEnabled(true);
MTDcategoryChart.setRotationAngle(0);
MTDcategoryChart.setDescriptionPosition(350, 550);
MTDcategoryChart.setDrawHoleEnabled(true);
MTDcategoryChart.setHoleColor(Color.TRANSPARENT);
MTDcategoryChart.setHoleRadius(13);
MTDcategoryChart.setTransparentCircleRadius(18);
MTDcategoryChart.getLegend().setPosition(Legend.LegendPosition.RIGHT_OF_CHART);
//MTDcategoryChart.getLegend().setXEntrySpace(3);
// MTDcategoryChart.getLegend().setYEntrySpace(3);
MTDcategoryChart.getLegend().setTextColor(Color.BLUE);
MTDcategoryChart.setDescription("Category");
MTDcategoryChart.setDescriptionTextSize(13);
MTDcategoryChart.setDescriptionColor(Color.BLUE);
//get category chart data
PieData MTDCategoryPieData = new PieData(xValsCategory, MTDCategorySet);
MTDCategoryPieData.setValueFormatter(new PercentFormatter());
MTDCategoryPieData.setValueTextSize(11);
MTDCategoryPieData.setValueTextColor(Color.BLUE);
MTDcategoryChart.setData(MTDCategoryPieData);
//refresh data
MTDcategoryChart.invalidate();
数据库助手类：
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
//create category table
public static final String Create_Table_Category="create table if not exists "+
TableData.TableInfo.DataBase_Table_Category+ "(" +
TableData.TableInfo.COL_C1_CategoryID+" integer primary key autoincrement,"+
TableData.TableInfo.COL_C2_Description+" text not null);";
//create table spending
public static final String Create_Table_Spending="create table if not exists "+
TableData.TableInfo.DataBase_Table_Spending+" ("+TableData.TableInfo.COL_S1_SpendingID+" integer primary key autoincrement,"+
TableData.TableInfo.COL_S2_Spending_DT+" Datetime not null,"+
TableData.TableInfo.COL_S3_ItemID+" integer not null,"+
TableData.TableInfo.COL_S4_AMT+" Float not null," +
"FOREIGN key ("+TableData.TableInfo.COL_S3_ItemID+") REFERENCES " +TableData.TableInfo.DataBase_Table_Items+" ("+TableData.TableInfo.COL_I1_ItemID+") ON DELETE CASCADE);";
// create table Item
public static final String Create_Table_Items="Create table if not exists " +
TableData.TableInfo.DataBase_Table_Items+" ("+
TableData.TableInfo.COL_I1_ItemID+" integer primary key autoincrement,"+
TableData.TableInfo.COL_I2_Description+" Text not null,"+
TableData.TableInfo.COL_I3_CategoryID+" integer not null,"+
"FOREIGN key ("+TableData.TableInfo.COL_I3_CategoryID+") REFERENCES " +TableData.TableInfo.DataBase_Table_Category+ " ("+TableData.TableInfo.COL_C1_CategoryID+") ON DELETE CASCADE);";
// create table Users
public static final String Created_Table_Users="create table if not exists "+
TableData.TableInfo.DataBase_Table_Users+ " ("+ TableData.TableInfo.COL_U1_UserID+" integer primary key autoincrement ,"+
TableData.TableInfo.COL_U2_UserName+" text not null ,"+ TableData.TableInfo.COL_U3_Password+" Text not null, "+
TableData.TableInfo.COL_U4_Created_DT+" Datetime not null);";
public static final String Drop_table_Category="drop table if exists "+TableData.TableInfo.DataBase_Table_Category;
public static final String Drop_table_Items="drop table if exists "+TableData.TableInfo.DataBase_Table_Items;
public static final String Drop_table_Spending="drop table if exists "+TableData.TableInfo.DataBase_Table_Spending;
public static final String Drop_table_Users="drop table if exists "+ TableData.TableInfo.DataBase_Table_Users;
SQLiteDatabase db;
// declare variables
public static final String YearEndPieChartMonth="YearEndPieChartMonth";
public static final YearEndPieChartMonthValues= String "YearEndPieChartMonthValues";
public static final String MonthPieChartCategory="MonthPieChartCategory";
public static final String MonthPieCHartCategoryValues="MonthPieCHartCategoryValues";
public static final String MonthPieChartItems="MonthPieChartItems";
public static final String MonthPiechartItemsValues="MonthPiechartItemsValues";
public static final String YearEndPieChartCategory="YearEndPieChartCategory";
public static final String YearEndCategoryValues="YearEndCategoryValues";
public static final String YearEndPieChartItems="YearEndPieChartItems";
public static final String YearEndItemsValues="YearEndItemsValues";
public DataBaseHelper(Context context)
super(context, TableData.TableInfo.DataBase_Name, null, TableData.TableInfo.DataBase_version);
@Override
public void onCreate(SQLiteDatabase db)
//create Category table
db.execSQL(Create_Table_Category);
Log.d("Database operation:", "Category table created");
//insert data into Category table
String sql_category="INSERT INTO " + TableData.TableInfo.DataBase_Table_Category+" ("+ TableData.TableInfo.COL_C2_Description+" )
VALUES('Housing'),('Utilities'),('Household'),('Groceries'),('Living'),('Transportation'),('HealthCare'),('Personal'),('EatingOut'),('Entertainments'),('Children'),('DebtPayments'),('Savings')";
db.execSQL(sql_category);
Log.d("Category table:","Data inserted");
//create Items table
db.execSQL(Create_Table_Items);
Log.d("Datbase operation:", "Item table created ");
// insert data into Item table
String sql_Items="insert into "+ TableData.TableInfo.DataBase_Table_Items+ " ("+ TableData.TableInfo.COL_I2_Description+" ,"+ TableData.TableInfo.COL_I3_CategoryID+" ) values('Rent',1),('Mortgage',1),('StrataFees',1),('PropertyTaxes',1),('HouseInsurance',1),('Phone',2),('Cell',2),('CableTVInternet',2),('GAS',2),('Hybro',2), ('Security',2),('Electricity',2),('Water',2),('StorageLocker',3),('Decor',3),('Gardening',3),('Garbage',3),('MiscItems',3),('Food',4),('BabyNeeds',4),('Cleaning',4),('Toiletries',4),('Kitchenwares',4),('PersonalCare',5),('BankFees',5), ('DryCleaning',5),('PetCosts',5),('Fuel',6),('AutoInsurance',6),('Transit',6),('Parking',6),('Taxi',6),('MedicalPremiums',7),('LifeInsurance',7),('Medication',7),('EyeCare',7),('Dental',7),('WellnessCosts',7),('Tobacco',8),('Alcohol',8),('BooksCDs',8),('Donations',8),('Subscriptions',8),('Meals',9),('Snacks',9),('TakeOut',9),('CoffeeWater',9),('SportsEquipmentFees',10),('Movies',10),('Hobbies',10),('Gaming',10),('FitnessMemberships',10),('DayCare',11),('LessonsActivities',11),('Allowance',11),('SchoolSuppliesFees',11),('Babysitting',11),('Loans',12),('CreditCards',12),('Leases',12),('SupportPayments',12),('GovernmentDebts',12),('EmergencyFund',13),('RRSP',13),('RESPs',13),('TravelVacations',13),('CarRepairs',13),('CLothing',13), ('Gifts',13),('AssistingFamilyFriends',13)";
db.execSQL(sql_Items);
Log.d("Items","Data inserted");
//create spending table
db.execSQL(Create_Table_Spending);
Log.d("Database operation:", "Spending table created ");
db.execSQL(Created_Table_Users);
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
db.execSQL(Drop_table_Category);
db.execSQL(Drop_table_Items);
db.execSQL(Drop_table_Spending);
db.execSQL(Drop_table_Users);
onCreate(db);
public DataBaseHelper open() throws SQLException
db = this.getWritableDatabase();
return this;
public void close()
db.close();
public SQLiteDatabase getDatabaseInstance()
return db;
public String getTime()
SimpleDateFormat dateFormat=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date=new Date();
return dateFormat.format(date);
//current month pie chart category
public ArrayList<String> xDataMonthCategory()
ArrayList<String> xnewDataCategory=new ArrayList<String>();
SQLiteDatabase db=this.getReadableDatabase();
String sql="select distinct c."+ TableData.TableInfo.COL_C2_Description+" as MonthPieChartCategory from " + TableData.TableInfo.DataBase_Table_Spending+" s join "+ TableData.TableInfo.DataBase_Table_Items+" i on i."+ TableData.TableInfo.COL_I1_ItemID+"=s."+ TableData.TableInfo.COL_S3_ItemID+" join "+ TableData.TableInfo.DataBase_Table_Category+" c on c."+ TableData.TableInfo.COL_C1_CategoryID+"=i."+ TableData.TableInfo.COL_I3_CategoryID+" where strftime('%Y',"+ TableData.TableInfo.COL_S2_Spending_DT+")=strftime('%Y',date('now')) and strftime('%m',"+ TableData.TableInfo.COL_S2_Spending_DT+")=strftime('%m',date('now')) group by c."+ TableData.TableInfo.COL_C2_Description+" order by c."+ TableData.TableInfo.COL_C2_Description+" desc";
Cursor cursor=db.rawQuery(sql,null);
for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToLast())
xnewDataCategory.add(cursor.getString(cursor.getColumnIndex(MonthPieChartCategory)));
cursor.close();
return xnewDataCategory;
//current month pie chart category y values
public ArrayList<Float> yDataPieChartCategoryMonth()
ArrayList<Float> ynewDataPieCHartCategoryMonth=new ArrayList<Float>();
SQLiteDatabase db=this.getReadableDatabase();
String sql="select sum("+ TableData.TableInfo.COL_S4_AMT+") MonthPieCHartCategoryValues,c."+ TableData.TableInfo.COL_C2_Description+" Category from "+ TableData.TableInfo.DataBase_Table_Spending+" s join "+ TableData.TableInfo.DataBase_Table_Items+" i on i."+ TableData.TableInfo.COL_I1_ItemID+"=s."+ TableData.TableInfo.COL_S3_ItemID+ " join "+ TableData.TableInfo.DataBase_Table_Category+" c on c."+ TableData.TableInfo.COL_C1_CategoryID+"=i."+ TableData.TableInfo.COL_I3_CategoryID + " where strftime('%Y',"+ TableData.TableInfo.COL_S2_Spending_DT+")=strftime('%Y',Date('now')) and strftime('%m',"+ TableData.TableInfo.COL_S2_Spending_DT+")=strftime('%m',date('now')) group by c."+ TableData.TableInfo.COL_C2_Description+" order by Category desc";
Cursor cursor=db.rawQuery(sql,null);
for(cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToLast())
ynewDataPieCHartCategoryMonth.add(cursor.getFloat(cursor.getColumnIndex(MonthPieCHartCategoryValues)));
cursor.close();
return ynewDataPieCHartCategoryMonth;
【问题讨论】：
【参考方案1】：您必须使用光标加载器和内容提供程序。
https://developer.android.com/training/load-data-background/index.html
【讨论】：
好吧，您没有必须使用光标加载器和内容提供程序，但这并不是一个糟糕的方法。您确实必须在后台线程上进行数据库访问，而不是在 UI 线程上。有很多方法可以做到这一点。 你能给我一个提示吗？我正在尝试做....但还不能。我是新手。 我能做到这一点，但不知道下一步该去哪里。以上是关于SQLite 数据库查询和 AsyncTask的主要内容，如果未能解决你的问题，请参考以下文章
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