Android核心技术-day03-01-创建SQLite数据库

版权声明：心灵泽尘 https://blog.csdn.net/github_38313789/article/details/83756876

MyDBOpenHelper.java

package com.gaozewen.createdb;

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

public class MyDBOpenHelper extends SQLiteOpenHelper {

    // 上下文  数据库名称 使用默认的游标工厂 数据库的版本号
    // 版本号只能变大不能变小
    public MyDBOpenHelper(Context context) {
        super(context, "gzwdb", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        System.out.println("onCreate 数据库被创建了");
        db.execSQL("create table contactinfo (id integer primary key autoincrement,name char(20),phone varchar(20));");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        System.out.println("onUpgrade 数据库被更新了");
//        db.execSQL("alter table contactinfo add account varchar(20);");
    }
}

MainActivity.java

package com.gaozewen.createdb;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import com.gaozewen.createdb.dao.ContactInfoDao;

public class MainActivity extends AppCompatActivity {

    private EditText mEt_name;
    private EditText mEt_phone;
    private ContactInfoDao dao;

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

        MyDBOpenHelper helper = new MyDBOpenHelper(this);
        helper.getWritableDatabase(); // 创建一个数据库

        // 1. 找到所需控件
        mEt_name = (EditText) findViewById(R.id.et_name);
        mEt_phone = (EditText) findViewById(R.id.et_phone);
        dao = new ContactInfoDao(this);
    }

    public void add(View view) {
        String name = mEt_name.getText().toString().trim();
        String phone = mEt_phone.getText().toString().trim();
        if (TextUtils.isEmpty(name) || TextUtils.isEmpty(phone)) {
            Toast.makeText(this, "不能为空", Toast.LENGTH_SHORT).show();
        } else {
            dao.add(name, phone);
            Toast.makeText(this, "添加成功", Toast.LENGTH_SHORT).show();
        }
    }

    public void delete(View view) {
        String name = mEt_name.getText().toString().trim();
        if (TextUtils.isEmpty(name)) {
            Toast.makeText(this, "name不能为空", Toast.LENGTH_SHORT).show();
        } else {
            dao.delete(name);
            Toast.makeText(this, "删除成功", Toast.LENGTH_SHORT).show();
        }
    }

    public void update(View view) {
        String name = mEt_name.getText().toString().trim();
        String phone = mEt_phone.getText().toString().trim();
        if (TextUtils.isEmpty(name) || TextUtils.isEmpty(phone)) {
            Toast.makeText(this, "不能为空", Toast.LENGTH_SHORT).show();
        } else {
            dao.update(name, phone);
            Toast.makeText(this, "修改成功", Toast.LENGTH_SHORT).show();
        }
    }

    public void query(View view) {
        String name = mEt_name.getText().toString().trim();
        if (TextUtils.isEmpty(name)) {
            Toast.makeText(this, "name不能为空", Toast.LENGTH_SHORT).show();
        } else {
            String phone = dao.query(name);
            Toast.makeText(this, "联系人电话是：" + phone, Toast.LENGTH_SHORT).show();
        }
    }
}