android 43 SQLite数据库

SQLite数据库很小，占用内存只有几百K,安卓和IOS都是用的SQLite数据库。

 

 页面：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btnInsertData"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="添加数据" />
    <Button
        android:id="@+id/btnDeleteData"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="删除数据" />
    <Button
        android:id="@+id/btnUpdateData"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="修改数据" />
    <Button
        android:id="@+id/btnQueryData"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查询数据" />
    
</LinearLayout>

 java

package com.sxt.day06_09;

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

import com.sxt.day06_09.entity.StudentBean;

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

public class MainActivity extends Activity {

    static final String DB_NAME="students.db";
    static final String TABLE_NAME="student";
    static final String ID="_id";//只能写下划线id
    static final String NAME="name";
    static final String SEX="sex";
    static final String BIRTHDAY="birthday";
    static final String HEIGHT="height";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        creatDataBase();//创建数据库
        setListener();
    }

    private void setListener() {
        setInsertClickListener();
        setDeleteClickListener();
        setQueryClickListener();
    }

    private void setQueryClickListener() {
        findViewById(R.id.btnQueryData).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = openOrCreateDatabase(DB_NAME, MODE_PRIVATE, null);
                String sql="select * from "+TABLE_NAME+" where "+NAME+" like ?";
                String sql1="select * from "+TABLE_NAME;
                Cursor c = db.rawQuery(sql, new String[]{"'%菲%'"});
                Cursor c = db.rawQuery(sql, null);//查询只能用rawQuery，返回游标就是查询结果集
                List<StudentBean> students=new ArrayList<StudentBean>();
                boolean flag = c.moveToFirst();
                while(c.moveToNext()){//遍历每一行
                    int id=c.getInt(c.getColumnIndex(ID));//获取一行的id列
                    String name=c.getString(c.getColumnIndex(NAME));
                    String sex=c.getString(c.getColumnIndex(SEX));
                    String birthday=c.getString(c.getColumnIndex(BIRTHDAY));
                    double height=c.getDouble(c.getColumnIndex(HEIGHT));
                    StudentBean bean=new StudentBean(id, name, sex, birthday, height);
                    students.add(bean);
                }
                for(StudentBean bean:students){
                    Log.i("main",bean.toString());
                }
                c.close();//释放资源
            }
        });
    }

    private void setDeleteClickListener() {
        findViewById(R.id.btnDeleteData).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = openOrCreateDatabase(DB_NAME, MODE_PRIVATE, null);
                String sql="delete from "+TABLE_NAME+" where "+NAME+" like '%菲%'";
                db.execSQL(sql);
            }
        });
    }

    private void setInsertClickListener() {
        findViewById(R.id.btnInsertData).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db=openOrCreateDatabase(DB_NAME, MODE_PRIVATE, null);
                insertData(db);
                //数据库路径为：data/data/com.ityw.exer15_1/databases/students.db
            }
        });
    }

    //创建数据库
    private void creatDataBase() {
        SQLiteDatabase db = openOrCreateDatabase(DB_NAME, MODE_PRIVATE, null);//创建数据库
        String sql="create table if not exists "+TABLE_NAME+"("
            +ID+" integer primary key autoincrement,"
            +NAME+" varchar(50),"
            +SEX+" varchar(2),"
            +BIRTHDAY+" datetext,"
            +HEIGHT+" real)";
        db.execSQL(sql);
    }

    private void insertData(SQLiteDatabase db) {
        String sql="insert into "+TABLE_NAME+"("+
            NAME+","+SEX+","+BIRTHDAY+","+HEIGHT+")values("+
            "'张飞','男','1990-5-5',1.99)";
        db.execSQL(sql);
        sql="insert into "+TABLE_NAME+"("+
                NAME+","+SEX+","+BIRTHDAY+","+HEIGHT+")values("+
                "'王菲','女','1990-8-5',1.69)";
        db.execSQL(sql);    
        sql="insert into "+TABLE_NAME+"("+
                NAME+","+SEX+","+BIRTHDAY+","+HEIGHT+")values("+
                "'刘亦菲','女','1991-8-5',1.71)";
        db.execSQL(sql);
    }

}