android-studio SQL数据库

最新推荐文章于 2025-04-29 10:18:06 发布

原创最新推荐文章于 2025-04-29 10:18:06 发布 · 728 阅读

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这篇博客介绍了如何在Android Studio中使用SQLite数据库，包括创建数据库辅助类MyHelper，定义数据访问对象AccountDao，以及Account实体类的设计。通过MainActivity.java中的示例展示了数据库的增删查改操作。

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activity-main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_marginTop="8dp"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/addLL"
        android:orientation="horizontal"
        >
        <EditText
            android:id="@+id/nameET"
            android:layout_weight="1"
            android:hint="商品名称"
            android:inputType="textPersonName"
            android:layout_width="0dp"
            android:layout_height="wrap_content" />
        <EditText
            android:id="@+id/balanceET"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="商品金额"
            android:inputType="number"
            />
        <ImageView
            android:onClick="add"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/addIV"
            android:src="@android:mipmap/sym_def_app_icon"
            />
    </LinearLayout>
    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/accountLV"
        ></ListView>
</LinearLayout>

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"
    android:orientation="horizontal"
    android:padding="10dp"
    >
    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:id="@+id/idTV"
        android:text="13"
        android:textColor="#000000"
        android:textSize="20sp"
        />
    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:id="@+id/nameTV"
        android:singleLine="true"
        android:text="PQ"
        android:textSize="20sp"
        android:textColor="#000000"
        />
    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:id="@+id/balanceTV"
        android:singleLine="true"
        android:text="12345"
        android:textSize="20sp"
        android:textColor="#000000"
        />
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/upIV"
            android:layout_marginBottom="2dp"
            android:src="@android:drawable/ic_input_add"
            />
        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/downIV"
            android:layout_marginBottom="2dp"
            android:src="@android:drawable/button_onoff_indicator_on"
            />
    </LinearLayout>
    <ImageView
        android:id="@+id/deleteIV"
        android:layout_width="25dp"
        android:layout_height="25dp"
        android:src="@android:drawable/ic_menu_delete"
        />
</LinearLayout>

MainActivity.java

package com.example.sqlite;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;
import java.util.Locale;

public class MainActivity extends AppCompatActivity {

    private List<Account> list;
    private AccountDao dao;
    private EditText nameET;
    private EditText balanceET;
    private MyAdapter adapter;
    private ListView accountLV;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initView();
        dao=new AccountDao(this);
        list=dao.queryAll();
        adapter=new MyAdapter();
        accountLV.setAdapter(adapter);
    }

    private void initView() {
        accountLV=(ListView)findViewById(R.id.accountLV);
        nameET=(EditText)findViewById(R.id.nameET);
        balanceET=(EditText)findViewById(R.id.balanceET);
        accountLV.setOnItemClickListener(new MyOnItemClickListener());
    }
    public void add(){
        String name=nameET.getText().toString().trim();
        String balance=balanceET.getText().toString().trim();

        Account a=new Account(name,balance.equals("")?0:Integer.parseInt(balance));
        dao.insert(a);
        list.add(a);
        adapter.notifyDataSetChanged();
        accountLV.setSelection(accountLV.getCount()-1);
        nameET.setText("");
        balanceET.setText("");
    }
    private class MyAdapter extends BaseAdapter{
        public int getCount(){
            return  list.size();
        }
        public Object getItem(int position){
            return list.get(position);
        }
        public  long getItemId(int position){
            return position;
        }

        @Override
        public View getView(int position, View converview, ViewGroup partent) {
           View item=converview!=null?converview:View.inflate(getApplicationContext(),R.layout.item,null);
            TextView idTV=(TextView)findViewById(R.id.idTV);
            TextView nameTV=(TextView)findViewById(R.id.nameTV);
            TextView balanceTV=(TextView)findViewById(R.id.balanceTV);

            final Account a=list.get(position);
            idTV.setText(a.getId()+"");
            nameTV.setText(a.getName());
            balanceTV.setText(a.getBalance()+"");
            ImageView upIV=(ImageView)findViewById(R.id.upIV);
            ImageView downIV=(ImageView)findViewById(R.id.downIV);
            ImageView deleteIV=(ImageView)findViewById(R.id.deleteIV);

            upIV.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    a.setBalance(a.getBalance()+1);
                    notifyDataSetChanged();
                    dao.update(a);
                }
            });
            downIV.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    a.setBalance(a.getBalance()-1);
                    notifyDataSetChanged();
                    dao.update(a);
                }
            });
            deleteIV.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    android.content.DialogInterface.OnClickListener listener=new android.content.DialogInterface.OnClickListener(){
                        public void onClick(DialogInterface dialogInterface,int which){
                            list.remove(a);
                            dao.delete(a.getId());
                            notifyDataSetChanged();
                        }
                    };
                    AlertDialog.Builder builder=new AlertDialog.Builder(MainActivity.this);
                    builder.setTitle("确定要删除吗？");
                    builder.setPositiveButton("确定",listener);
                    builder.setPositiveButton("取消",null);
                    builder.show();
                }
            });
            return item;
        }
    }

    private class MyOnItemClickListener implements android.widget.AdapterView.OnItemClickListener {
        public void onItemClick(AdapterView<?>parent,View view,int position,long id){
            Account a=(Account)parent.getItemAtPosition(position);
            Toast.makeText(getApplicationContext(),a.toString(),Toast.LENGTH_SHORT).show();
        }
    }
}

MyHelper.java

package com.example.sqlite;

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

public class MyHelper extends SQLiteOpenHelper {
   public MyHelper(Context context){
        super(context,"itcasr.db",null,2);
   }
   public  void onCreate(SQLiteDatabase db){
       System.out.println("onCreate");
       db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),balance INTEGER )");
   }
   public  void  onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){
       System.out.println("onUpgrade");
   }
}

AccountDao.java

package com.example.sqlite;

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

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

public class AccountDao {
    private MyHelper helper;
    public AccountDao(Context context){
        helper=new MyHelper(context);
    }
    public void insert(Account account){
        SQLiteDatabase db=helper.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",account.getName());
        values.put("balance",account.getBalance());
        long id=db.insert("account",null,values);
        account.setId(id);
        db.close();
    }
    public int delete(long id){
        SQLiteDatabase db=helper.getWritableDatabase();
        int count=db.delete("account","_id=?",new String[]{id+""});
        db.close();
        return count;
    }
    public int update(Account account){
        SQLiteDatabase db=helper.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",account.getName());
        values.put("account",account.getBalance());
        int count=db.update("account",values,"_id=?",new String[]{account.getId()+""});
        db.close();
        return count;
    }
    public List<Account>queryAll(){
        SQLiteDatabase db=helper.getWritableDatabase();
        Cursor c=db.query("account",null,null,null,null,null,"balance DESC");
        List<Account> list=new ArrayList<Account>();
        while (c.moveToNext()){
            long id=c.getLong(c.getColumnIndex("_id"));
            String name=c.getString(1);
            int balance=c.getInt(2);
            list.add(new Account(id,name,balance));
        }
        c.close();
        db.close();
        return list;
    }
}

Account.java

package com.example.sqlite;

public class Account {
    private Long id;
    private String name;
    private Integer balance;
    public Long getId(){
        return id;
    }
    public void setId(Long id){
        this.id=id;
    }
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name=name;
    }
    public Integer getBalance(){
        return balance;
    }
    public void setBalance(Integer balance){
        this.balance=balance;
    }
    public Account(Long id,String name,Integer balance){
        super();
        this.id=id;
        this.name=name;
        this.balance=balance;
    }
    public Account(String name,Integer balance){
        super();
       this.name=name;
       this.balance=balance;
    }
    public Account(){
        super();
    }
    public String toString(){
        return "[序号："+id+",商品名称："+name+",商品金额："+balance+"]";
    }
}