Android SQLite数据库的添、删、查、改（简洁新手专用）

最新推荐文章于 2024-08-16 20:06:08 发布

原创最新推荐文章于 2024-08-16 20:06:08 发布 · 1.5k 阅读

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#Android

本文提供了一个Android应用中使用SQLite进行增删改查操作的完整示例。通过创建自定义的SQLiteOpenHelper子类，初始化数据库和表格，并实现了数据的插入、删除、更新及查询功能。

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前言
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正文

首先创建一个类MyOpenHelper，继承自SQLiteOpenHelper，用来打开或创建一个数据库

MyOpenHelper 

package com.SQLiteTest3;

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

publicclass MyOpenHelper extends SQLiteOpenHelper {
    String sql ="create table if not exists TestUsers"+
    "(id int primary key,name varchar,sex varchar)";

    public MyOpenHelper(Context context, String name, CursorFactory factory,
            int version) {
        super(context, name, factory, version);
        // TODO Auto-generated constructor stub
    }

    @Override
    publicvoid onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        db.execSQL(sql);

    }

    @Override
    publicvoid onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub

    }

}

然后是实现代码：

package com.SQLiteTest3;

import android.app.Activity;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.*;

publicclass SQLiteTest3 extends Activity {
    Button btnInsert;
    Button btnDelete;
    Button btnUpdate;
    Button btnSelect;
    EditText etName;
    EditText etSex;
    TextView tvShowContent;
    MyOpenHelper OpenHelper;
    SQLiteDatabase db =null;
    publicstaticfinal String DB_NAME ="DBTest";

    View.OnClickListener btnInsertListener =new View.OnClickListener() {
        
        @Override
        publicvoid onClick(View v) {
            // TODO Auto-generated method stub
            InsertTb();
        }
    };
    View.OnClickListener btnDeleteListener =new View.OnClickListener() {
        
        @Override
        publicvoid onClick(View v) {
            // TODO Auto-generated method stub
            DeleteTb();
        }
    };
    View.OnClickListener btnUpdateListener =new View.OnClickListener() {
        
        @Override
        publicvoid onClick(View v) {
            // TODO Auto-generated method stub
            UpdateTb();
        }
    };
    View.OnClickListener btnSelectListener =new View.OnClickListener() {
        
        @Override
        publicvoid onClick(View v) {
            // TODO Auto-generated method stub
            Select();
        }
    };
    /** Called when the activity is first created. */
    @Override
    publicvoid onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        OpenHelper =new MyOpenHelper(this, DB_NAME, null, 1);
        btnInsert = (Button) findViewById(R.id.main_btn_insert);
        btnDelete = (Button) findViewById(R.id.main_btn_delete);
        btnUpdate = (Button) findViewById(R.id.main_btn_update);
        btnSelect = (Button) findViewById(R.id.main_btn_select);
        tvShowContent = (TextView) findViewById(R.id.main_tv_showContent);
        etName = (EditText) findViewById(R.id.main_et_name);
        etSex = (EditText) findViewById(R.id.main_et_sex);
        btnInsert.setOnClickListener(btnInsertListener);
        btnDelete.setOnClickListener(btnDeleteListener);
        btnUpdate.setOnClickListener(btnUpdateListener);
        btnSelect.setOnClickListener(btnSelectListener);
    }

    publicvoid InsertTb(){
        int flag =-1;
        db = OpenHelper.getWritableDatabase();
        String strName = etName.getText().toString();
        String strSex = etSex.getText().toString();
        String sql ="insert into TestUsers (name,sex) values ('"+strName+"','"+strSex+"')";
        try {
            db.execSQL(sql);
            
        } catch (SQLException e) {
            Log.i("err", "insert failed");
            flag =0;
            Toast.makeText(SQLiteTest3.this, "插入失败！", Toast.LENGTH_SHORT).show();
        }
        db.close();
        if (flag ==-1){
            Toast.makeText(SQLiteTest3.this, "插入成功！", Toast.LENGTH_SHORT).show();
        }
       
    }
    publicvoid DeleteTb(){
        int flag =-1;
        db = OpenHelper.getWritableDatabase();
        String sql ="delete from TestUsers where id = 2";
        try {
            db.execSQL(sql);
        } catch (SQLException e) {
            Log.i("err", "delete failed");
            flag =0;
            Toast.makeText(SQLiteTest3.this, "删除失败！", Toast.LENGTH_SHORT).show();
        }
        db.close();
        if (flag ==-1){
            Toast.makeText(SQLiteTest3.this, "删除成功！", Toast.LENGTH_SHORT).show();
        }
    }
    publicvoid UpdateTb() {
        int flag =-1;
        db = OpenHelper.getWritableDatabase();
        String Name = etName.getText().toString();  
        String sql ="Update TestUsers set name = 'anhong',sex = 'men' where name = '"+Name+"'";
        try {
            db.execSQL(sql);
        } catch (SQLException e) {
            Log.i("err", "update failed");
            flag =0;
            Toast.makeText(SQLiteTest3.this, "更新失败！", Toast.LENGTH_SHORT).show();
        }
        db.close();
        if (flag ==-1){
            Toast.makeText(SQLiteTest3.this, "更新成功！", Toast.LENGTH_SHORT).show();
        }
    }
    publicvoid Select(){
        db = OpenHelper.getReadableDatabase();
        String sql ="select sex from TestUsers where name=?";    
        Cursor cursor = db.rawQuery(sql, new String[]
        { etName.getText().toString() });       //String sql = "select sex from TestUsers";      //Cursor cursor = db.rawQuery(sql, null);
        int count = cursor.getCount();
        String [] Sex =new String[count];
        int i =0;
        if (cursor.getCount() >0)
        {
            //  必须使用moveToFirst方法将记录指针移动到第1条记录的位置
/*    cursor.moveToFirst();  //取第一条记录
            String result = cursor.getString(cursor.getColumnIndex("sex"));
            tvShowContent.setText(result); */
            //取多条记录
int sexIndex = cursor.getColumnIndex("sex");
            for(cursor.moveToFirst();!(cursor.isAfterLast());cursor.moveToNext()){
                Sex[i] = cursor.getString(sexIndex);
                i++;
            }
        }
        for(int j =0; j < count; j++){
            tvShowContent.append("");
            tvShowContent.append(Sex[j]);
        }
    }



}

main.xml

main.xml 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<Button 
    android:text="@string/add" 
    android:id="@+id/main_btn_insert" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></Button>
<Button 
    android:text="@string/delete" 
    android:id="@+id/main_btn_delete" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></Button>
<Button 
    android:text="@string/select"
    android:id="@+id/main_btn_select" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></Button>    
<Button 
    android:text="@string/update" 
    android:id="@+id/main_btn_update" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></Button>    
<TextView 
    android:text="Name" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></TextView>    
<EditText  
    android:id="@+id/main_et_name" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"></EditText>
<TextView 
    android:text="Sex" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></TextView>
<EditText  
    android:id="@+id/main_et_sex" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"></EditText>
<TextView 
    android:id="@+id/main_tv_showContent" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"></TextView>

</LinearLayout>

主窗体运行截图