LitePal

一.什么是LitePal？

LitePal是一款做开源的Andoid数据库框架，它采用了对象关系映射(ORM) 的模式，并将我
们平时开发最常用到的一些数据库功能进行了封装，使得不用编写一行SQL 语句就可以完成各
种建表和增剧改查的操作。LitePal 的项目主页上也有详细的使用文档，地址是https://github.com/LitePalFramework/LitePalLitePal

二.配置LitePal

要使用LitePal 的第一步，就是编辑app/buildr.grade文件，在dependencies 闭包中添加
如下内容:

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
   compile 'org.litepal.android:core:1.6.1'
}

这样我们就把LitePal 成功引人到当前项目中了，接下来需要配置litepal.xml 文件。右击app/src/mai 目录-New-Directory,创建一个assets 目录，然后在assets 目录下再新建一个itpalxm 文件，接着编辑litepal.xml 文件中的内容如下：

<?xml version="1.0" encoding="utf-8"?>
<litepal>


    <dbname value="demo" />


    <version value="1" />

    <list>
        <mapping class="com.example.administrator.litepaltest1.Album"></mapping>
        <mapping class="com.example.administrator.litepaltest1.Song"></mapping>
    </list>



</litepal>

最后还要在AndroidManifest.xml中配置一下LitePalApplication代码如下：

  android:name="org.litepal.LitePalApplication"

之后新建类继承DataSupport：

package com.example.administrator.litepaltest1;

import org.litepal.annotation.Column;
import org.litepal.crud.DataSupport;

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

/**
 * Created by Administrator on 2018/4/2/002.
 */

public class Album extends DataSupport {
    @Column(unique = true, defaultValue = "unknown")
    private String name;

    private float price;

    private byte[] cover;

    private List<Song> songs = new ArrayList<Song>();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }

    public byte[] getCover() {
        return cover;
    }

    public void setCover(byte[] cover) {
        this.cover = cover;
    }

    public List<Song> getSongs() {
        return songs;
    }

    public void setSongs(List<Song> songs) {
        this.songs = songs;
    }
}

package com.example.administrator.litepaltest1;

import org.litepal.annotation.Column;
import org.litepal.crud.DataSupport;

/**
 * Created by Administrator on 2018/4/2/002.
 */

public class Song extends DataSupport {

    @Column(nullable = false)
    private String name;

    private int duration;

    @Column(ignore = true)
    private String uselessField;

    private Album album;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getDuration() {
        return duration;
    }

    public void setDuration(int duration) {
        this.duration = duration;
    }

    public String getUselessField() {
        return uselessField;
    }

    public void setUselessField(String uselessField) {
        this.uselessField = uselessField;
    }

    public Album getAlbum() {
        return album;
    }

    public void setAlbum(Album album) {
        this.album = album;
    }
}

之后在mainactivity中可以对两张表进行操作：

package com.example.administrator.litepaltest1;

import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import org.litepal.LitePal;
import org.litepal.crud.DataSupport;

import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
private EditText nameET;
private Button button;
private Button mofify;
private Button delete;
private Button qurry;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SQLiteDatabase db = LitePal.getDatabase();
        nameET=findViewById(R.id.name_et);
        button=findViewById(R.id.name_bt);
        mofify=findViewById(R.id.mofify);
        delete=findViewById(R.id.delete);
        qurry=findViewById(R.id.qurry);
        button.setOnClickListener(this);
        mofify.setOnClickListener(this);
        delete.setOnClickListener(this);
        qurry.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.name_bt:
                String name=nameET.getText().toString();
                float price=56.5f;
                Album album=new Album();
                album.setName(name);
                album.setPrice(price);
                album.save();
                break;


            case R.id.mofify:
                Album album1= DataSupport.find(Album.class,1);
                album1.setName("qwe");
                album1.save();
                break;

            case R.id.delete:
//                int row=DataSupport.delete(Album.class,1);
                int row=DataSupport.deleteAll(Album.class,"id>?","3");
                Toast.makeText(this, "你删除了"+row+"行", Toast.LENGTH_SHORT).show();
                break;
            case R.id.qurry:
//                List<Album> albumList=DataSupport.findAll(Album.class);
                List<Album> albumList=DataSupport.where("name like ? and id>?","q%","7").order("name").find(Album.class);
                for (Album a:
                        albumList
                     ) {
                    Log.e("Album",a.getName()+"***");

                }
                break;
        }
    }
}