Androids中数据库的使用SQLite

（一）

知识点：

SQLite3支持的数据类型：NULL，INTEGER,REAL(浮点数字)，TEXT（字符串文本），BLOB（二进制对象），虽然他支持的类型只有五种，但实际上sqlite3也接受varchar（n），char（n）等数据类型

1.效果图：点击增加数据，显示增加完毕，点击查询数据，可以查看加进去的数据   。。。。

2.布局

（1）activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.administrator.hello.MainActivity"
    android:orientation="vertical">

    <TextView
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="数据库使用" />
         <Button
             android:id="@+id/btn_add"
             android:onClick="doClick"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:text="增加数据"/>
        <Button
             android:id="@+id/btn_query"
             android:onClick="doClick"
             android:layout_width="match_parent"
            android:layout_height="wrap_content"
             android:text="查询数据"/>
    <Button
        android:id="@+id/btn_update"
        android:onClick="doClick"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="修改数据"/>
    <Button
        android:id="@+id/btn_delete1"
        android:onClick="doClick"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="删除指定数据"/>
    <Button
        android:id="@+id/btn_delete2"
        android:onClick="doClick"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="删除全部数据"/>

        <ListView
             android:id="@+id/lv"
            android:layout_width="match_parent"
             android:layout_height="wrap_content"></ListView>
</LinearLayout>

(2)item.xml

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     >

     <TextView
         android:id="@+id/user_Id"
         android:layout_width="50dp"
         android:layout_height="wrap_content" />
     <TextView
         android:id="@+id/user_Name"
         android:layout_width="100dp"
         android:layout_height="wrap_content" />
     <TextView
         android:id="@+id/user_Age"
        android:layout_width="50dp"
         android:layout_height="wrap_content" />

 </LinearLayout>

3.UserDao.java

package com.example.administrator.hello.Dao;

/**
 * Created by Administrator on 2018/5/25.
 */

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import com.example.administrator.hello.DBUtil.MySQLiteHelper;
import com.example.administrator.hello.entity.User;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Administrator on 2018/5/24.
 */
public class UserDao {
    private MySQLiteHelper mySQLiteHelper;
    private SQLiteDatabase db;

    public UserDao(Context context) {
        mySQLiteHelper = new MySQLiteHelper(context);
        db = mySQLiteHelper.getReadableDatabase(); //获取数据库对象
    }

    public void insertUser() {
        //使用字符串拼接方式操作数据
        String sql = "insert into t_user(userName,userAge) values ('zhangsan',20)";
        db.execSQL(sql);
        //通过占位符的形式进行数据操作
        db.execSQL("insert into t_user(userName,userAge) values(?,?)", new Object[]{"lisi", 21});
        //使用系统自带的方法实现数据操作
        ContentValues values = new ContentValues();
        values.put("userName", "wangwu");
        values.put("userAge", 22);
        db.insert("t_user", null, values);

    }

    public List<User> query() {
        List<User> list = new ArrayList<>();
        Cursor cursor = db.rawQuery("select * from t_user", null);
        if (cursor != null) {
            while (cursor.moveToNext()) {
                int userId = cursor.getInt(cursor.getColumnIndex("userId"));
                String userName = cursor.getString(1);
                int userAge = cursor.getInt(2);
                User user = new User(userId, userName, userAge);
                list.add(user);

            }
        }
        cursor.close();
        return list;

    }

    public void  update(){
        db.execSQL("update t_user set userName=? where userId =?",new Object[]{"李四",2});
        ContentValues values = new ContentValues();
        values.put("userName","王五");
        db.update("t_user",values,"userId=?",new String[]{3+""});
    }
    public  void  update(String name,String id){
        db.execSQL("update t_user set userName='"+name+"' where userId="+id);
    }

    public  void  delete(){
        //
        db.execSQL("delete from t_user where userId ='1'");
        //
        db.execSQL("delete from t_user where userId=?",new Object[]{"2"});
        //
        db.delete("t_user","userId=?",new  String[]{"3"});
    }
    public  void  deleteAll(){
        db.execSQL("delete from t_user");
    }

}

4.MySQLiteHelper

package com.example.administrator.hello.DBUtil;

/**
 * Created by Administrator on 2018/5/25.
 */

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by Administrator on 2018/5/24.
 */
public class MySQLiteHelper extends SQLiteOpenHelper {
    private static final String NAME = "mydata.db";
    private static final int version = 1;

    public MySQLiteHelper(Context context) {

        super(context, NAME, null, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table t_user(userId integer primary key autoincrement,userName text not null,userAge integer not null)");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

5.User.java

 package com.example.app5.entity;

 /**
  * Created by Administrator on 2018/5/24.
  */
 public class User {
     private int userId;
     private String userName;
     private int useAge;

     public User(int userId, String userName, int useAge) {
         this.userId = userId;
         this.userName = userName;
         this.useAge = useAge;
     }

     public int getUserId() {
         return userId;
     }

     public void setUserId(int userId) {
         this.userId = userId;
     }

     public String getUserName() {
         return userName;
     }

     public void setUserName(String userName) {
         this.userName = userName;
     }

     public int getUseAge() {
         return useAge;
     }

     public void setUseAge(int useAge) {
         this.useAge = useAge;
     }
 }

6.MainActivity.java

package com.example.administrator.hello;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.ListViewCompat;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;

import com.example.administrator.hello.Dao.UserDao;
import com.example.administrator.hello.entity.User;

import java.util.List;

public class MainActivity extends AppCompatActivity {
    private UserDao userDao;
    private List<User> list;
    private MyAapter myAapter;
    private ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        userDao = new UserDao(MainActivity.this);
        listView = (ListView) findViewById(R.id.lv);
    }

    public void doClick(View view) {
        switch (view.getId()) {
            case R.id.btn_add:
                userDao.insertUser();
                Toast.makeText(MainActivity.this, "插入数据成功", Toast.LENGTH_SHORT).show();
                break;
            case R.id.btn_query:
                list = userDao.query();
                myAapter = new MyAapter(list, MainActivity.this);
                listView.setAdapter(myAapter);
                break;
            case  R.id.btn_update:
                String name="张三" ;
                String id ="1";
                userDao.update(name,id);
                userDao.update();
                Toast.makeText(MainActivity.this, "修改数据成功", Toast.LENGTH_SHORT).show();
                break;
            case  R.id.btn_delete1:
                userDao.delete();
                Toast.makeText(MainActivity.this, "删除指定数据成功", Toast.LENGTH_SHORT).show();
                break;
            case  R.id.btn_delete2:
                userDao.deleteAll();
                Toast.makeText(MainActivity.this, "删除全部数据成功", Toast.LENGTH_SHORT).show();
                break;

        }
    }
}

7.MyAapter

 package com.example.app5;

 import android.content.Context;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import android.widget.TextView;

 import com.example.app5.entity.User;

 import java.util.List;

 /**
  * Created by Administrator on 2018/5/24.
  */
 public class MyAapter extends BaseAdapter {
     private Context context;
     private List<User> list;

     public MyAapter(List<User> list, Context context) {
         this.list = list;
         this.context = context;
     }
     @Override
     public int getCount() {
         return list.size();
     }

     @Override
     public Object getItem(int position) {
         return list.get(position);
     }

     @Override
     public long getItemId(int position) {
         return position;
     }

     @Override
     public View getView(int position, View convertView, ViewGroup parent) {
         ViewH viewH;
         if (convertView==null){
             convertView= LayoutInflater.from(context).inflate(R.layout.item,null);
             viewH = new ViewH();
             viewH.tv_id=(TextView)convertView.findViewById(R.id.user_Id);
             viewH.tv_age=(TextView)convertView.findViewById(R.id.user_Age);
             viewH.tv_name=(TextView)convertView.findViewById(R.id.user_Name);
             convertView.setTag(viewH);
         }else {
             viewH=(ViewH)convertView.getTag();
         }
         viewH.tv_id.setText(list.get(position).getUserId()+"");
         viewH.tv_name.setText(list.get(position).getUserName()+"");
         viewH.tv_age.setText(list.get(position).getUseAge()+"");
         return convertView;
     }

     class  ViewH{
         private TextView tv_id;
         private TextView tv_age;
         private  TextView tv_name;
     }
 }