android的資料儲存（3）(LitePal)
阿新 • • 發佈：2018-11-17
在上一章的SQLiteDatebase來操作資料庫好用嗎？不同的人有不同的答案，接下來你將接觸一個開源庫LitePal，它採用了物件關係對映的（ORM）的模式，並將我們平常用到的資料庫功能進行封裝，使用一行sql語句就可以完成各種建表和增刪改查的操作。
一、配置LitePal
1、要想使用開源庫LitePal就新增依賴庫，在配置檔案中新增如下的：
implementation 'org.litepal.android:core:1.4.1'
2、上面步驟就將LitePal成功引入專案中來了，接下來就是配置litepal.xml檔案，右擊app/src/main目錄-->new-->Directory,建立一個assets目錄，然後在assets目錄下面再建立一個litepal.xml檔案
<?xml version="1.0" encoding="utf-8" ?>
<litepal>
<dbname value="bookStoress"></dbname> //資料庫名
<version value="2"></version> //資料庫的版本號
<list>
<mapping class="com.example.asus.summary3.Pictrue"></mapping>
//用map對應對映模式（這裡需要寫類，讓繼承DataSupport，這裡一定是完整的類名，
<mapping class="com.example.asus.summary3.User"></mapping>
</list>
</litepal>
3、還需要配置一下AndroidManifest.xml檔案
在Application下面新增
android:name="org.litepal.LitePalApplication"
4、寫類，繼承DataSupport
5、建立資料庫，呼叫 LitePal.getDatabase()方法就建立了資料庫
6、在升級資料庫，以及需要修改表結構時，就沒必要像SQLiteDatabase那樣麻煩避免資料丟失。
LitePal就不存在這樣的問題，要升級資料庫只需要將版本號加1，要新增一張表，只需要在litepal.xml檔案中的<list>...</list>
中新增對應的map對映就可以了
7、新增資料
很簡單，只需要建立對應類的例項，呼叫一下save()方法就儲存了
例如：
Point p=new Point(2,10);
p.save() ;
8、更新資料
對於LitePal而言，物件是否已經儲存可以呼叫model.isSave()方法的結果來判斷，返回true就表示已經儲存，返回false就表示為】未儲存，
例如：
Book book=new Book("高數",20,"西華大學");
book.save(); //對book第一次儲存
book.setPrice(30); //修改書的價格
book.save(); //重新儲存
例如：
Book book=new Book();
book.setPrice(30);
book.setName("英語");
//將name="高數" author="李" 的書的價格改為30，name改為英語
book.updateAll("name=? and author=?","高數","李");
8、刪除資料，簡單
例如：
DataSupport.deleteAll(Book.class,"price>?","15"); //將資料庫中的全部資料中，書價格大於15的全部刪除掉
9、查詢
LitePal查詢返回的是一個List<Object>的集合
例如：
List<Book> books=DataSupport.findAll(Book.class); //查詢全部的資料
Book book=DateSupport.findFirst(Book.class)：//查詢第一個記錄
Book book=DataSupport.findLast(Book.class) //查詢最後一條記錄
除此之外，還可以通過連綴的方式查詢更多查詢方式
select()方法查詢哪幾列：
List<Book> books=DataSupport.select("name","price").find(Book.class);
where()指定查詢的約束條件：
List<Book> books=DtaSupport.where("price>?","30").find(Book.class);
order()方法指定結果的排序，
List<Book> books=DataSupport.order("price desc").find(Book.class)；
其中desc表式降序，asc表示升序
limit()方法指定偏移數量，比如只看表中的前3條資料，
List<Book> books=DataSupport.limit(3).find(Book.class);
offset()方法指定查詢結果的偏移量
List<Book> books=DtaSupport.limit(3).offset(1).find(Book.class);
幾個方法中和：
List<Book> books=DataSupport.select("name","price","page")
.where("page>?","40")
.order("page desc")
.limit(10)
.offset(10)
.find(Book.class);
查詢Book表中的第10條到20條的頁數大於20頁的條件的name,price,page這三項資料，按page降序
最後還可以，用原生的SQL語句
例：Cursor c=DataSupport.findSQL("select * from Book ");
例項：
1、litepal_activity.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="vertical">
<android.support.v4.view.ViewPager
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:id="@+id/pager">
<android.support.v4.view.PagerTabStrip
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="top"
android:id="@+id/pager_title">
</android.support.v4.view.PagerTabStrip>
</android.support.v4.view.ViewPager>
</LinearLayout>
2、litepal_fragment1.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:background="@drawable/b1"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp"
android:orientation="vertical">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/pictrue_messge"
android:hint="pictrue"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/add_pictrue"
android:layout_gravity="center"
android:text="新增圖"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp"
android:id="@+id/litepal_f1"
android:orientation="vertical">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/user_messge"
android:hint="user"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/add_user"
android:layout_gravity="center"
android:text="新增使用者"/>
</LinearLayout>
</LinearLayout>
3、litepal_fragment2.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="wrap_content"
android:id="@+id/litepal_f2"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/picture_recyclerview">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
4、litepal_fragment3.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="wrap_content"
android:id="@+id/litepal_f3"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/uer_recyclerview">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
5、pic_recyclerview_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="wrap_content">
<ImageView
android:layout_width="70dp"
android:layout_height="70dp"
android:layout_marginRight="10dp"
android:id="@+id/pic_item_picid"/>
<TextView
android:layout_width="match_parent"
android:layout_height="70dp"
android:textSize="25sp"
android:gravity="center_vertical"
android:id="@+id/pic_item_name"/>
</LinearLayout>
6、user_recyclerview_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="wrap_content">
<ImageView
android:layout_width="70dp"
android:layout_height="70dp"
android:layout_marginRight="10dp"
android:id="@+id/user_item_picid"/>
<TextView
android:layout_width="match_parent"
android:layout_height="70dp"
android:textSize="25sp"
android:gravity="center_vertical"
android:id="@+id/user_item_name"/>
</LinearLayout>
7、User.class
public class User extends DataSupport {
private String name;
private int u_picId;
private int id;
public User(String name, int u_picId, int id) {
this.name = name;
this.u_picId = u_picId;
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getU_picId() {
return u_picId;
}
public void setU_picId(int u_picId) {
this.u_picId = u_picId;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
8、Pictrue.class
public class Pictrue extends DataSupport{
private int id;
private int p_picId;
private String name;
public Pictrue(int id, int p_picId, String name) {
this.id = id;
this.p_picId = p_picId;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getP_picId() {
return p_picId;
}
public void setP_picId(int p_picId) {
this.p_picId = p_picId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
9、PictureRecyclerViewAdapter.class
public class PictureRecyclerViewAdapter extends RecyclerView.Adapter<PictureRecyclerViewAdapter.ViewHolder> {
private List<Pictrue> pictrueList;
public PictureRecyclerViewAdapter(List<Pictrue> pictrueList) {
this.pictrueList = pictrueList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view=LayoutInflater.from(parent.getContext()).inflate(R.layout.pic_recyclerview_item,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(final ViewHolder holder, final int position) {
Pictrue pictrue=pictrueList.get(position);
holder.pic_name.setText(pictrue.getName());
holder.pic_image.setImageResource(pictrue.getP_picId());
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(holder.itemView.getContext(),pictrueList.get(position).getName(),Toast.LENGTH_SHORT).show();
}
});
}
@Override
public int getItemCount() {
return pictrueList.size();
}
class ViewHolder extends RecyclerView.ViewHolder{
ImageView pic_image;
TextView pic_name;
public ViewHolder(View itemView) {
super(itemView);
pic_image=itemView.findViewById(R.id.pic_item_picid);
pic_name=itemView.findViewById(R.id.pic_item_name);
}
}
}
10、UserRecyclerViewAdapter.class
public class UserRecyclerViewAdapter extends RecyclerView.Adapter<UserRecyclerViewAdapter.ViewHolder> {
private List<User> userList;
public UserRecyclerViewAdapter(List<User> userList) {
this.userList = userList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.user_recyclerview_item,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(final ViewHolder holder, final int position) {
User user=userList.get(position);
holder.userName.setText(user.getName());
holder.userImage.setImageResource(user.getU_picId());
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(holder.itemView.getContext(),userList.get(position).getName(),Toast.LENGTH_SHORT).show();
}
});
}
@Override
public int getItemCount() {
return userList.size();
}
class ViewHolder extends RecyclerView.ViewHolder{
ImageView userImage;
TextView userName;
public ViewHolder(View itemView) {
super(itemView);
userImage=itemView.findViewById(R.id.user_item_picid);
userName=itemView.findViewById(R.id.user_item_name);
}
}
}
11、ListepalFragment1.class
public class ListepalFragment1 extends Fragment implements View.OnClickListener {
Context context;
EditText pic_messgae;
EditText user_message;
Button add_pic;
Button add_user;
int []pic_ids=new int[]{R.drawable.friend3,R.drawable.txxw,R.drawable.p8yx,R.drawable.part3_1,R.drawable.p6txkt};
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle bundle) {
View view=inflater.inflate(R.layout.litepal_fragment1,container,false);
this.context=container.getContext();
pic_messgae=view.findViewById(R.id.pictrue_messge);
user_message=view.findViewById(R.id.user_messge);
add_pic=view.findViewById(R.id.add_pictrue);
add_user=view.findViewById(R.id.add_user);
add_user.setOnClickListener(this);
add_pic.setOnClickListener(this);
return view;
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.add_pictrue:{
String picName=pic_messgae.getText().toString();
int i=(int)(Math.random()*pic_ids.length);
Pictrue pictrue=new Pictrue(0,pic_ids[i],picName);
pictrue.save();
pic_messgae.setText("");
LitepalFragment2 fragment2=((LitePalActivity)context).f2;
fragment2.init();
fragment2.adapter.notifyDataSetChanged();
break;
}
case R.id.add_user:{
String name=user_message.getText().toString();
int i=(int)(Math.random()*pic_ids.length);
User user=new User(name,pic_ids[i],0);
user.save();
user_message.setText("");
LitepalFragment3 fragment3=((LitePalActivity)context).f3;
fragment3.init();
fragment3.adapter.notifyDataSetChanged();
break;
}
}
}
}
12、LitepalFragment2.class
public class LitepalFragment2 extends Fragment {
List<Pictrue> pictrueList;
RecyclerView recyclerView;
PictureRecyclerViewAdapter adapter;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle bundle) {
View view=inflater.inflate(R.layout.litepal_fragment2,container,false);
init();
recyclerView=view.findViewById(R.id.picture_recyclerview);
LinearLayoutManager layoutManager=new LinearLayoutManager(getContext());
recyclerView.setLayoutManager(layoutManager);
adapter=new PictureRecyclerViewAdapter(pictrueList);
recyclerView.setAdapter(adapter);
return view;
}
public void init(){
pictrueList= DataSupport.findAll(Pictrue.class);
}
}
13、LitepalFragment3.class
public class LitepalFragment3 extends Fragment {
List<User> userList;
RecyclerView recyclerView;
UserRecyclerViewAdapter adapter;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle bundle) {
View view=inflater.inflate(R.layout.litepal_fragment3,container,false);
init();
recyclerView=view.findViewById(R.id.uer_recyclerview);
LinearLayoutManager layoutManager=new LinearLayoutManager(getContext());
recyclerView.setLayoutManager(layoutManager);
adapter=new UserRecyclerViewAdapter(userList);
recyclerView.setAdapter(adapter);
return view;
}
public void init(){
userList= DataSupport.findAll(User.class);
}
}
14、LitePalActivity.class
public class LitePalActivity extends FragmentActivity {
private List<String> pagertitle=new ArrayList<String>();
private List<Fragment> fragmentList=new ArrayList<Fragment>();
ViewPager pager;
PagerTabStrip pagerTabStrip;
MyViewPagerAdapter adapter;
ListepalFragment1 f1=new ListepalFragment1();
LitepalFragment2 f2=new LitepalFragment2();
LitepalFragment3 f3=new LitepalFragment3();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.litepal_activity);
init();
LitePal.getDatabase();
pager=findViewById(R.id.pager);
adapter=new MyViewPagerAdapter(getSupportFragmentManager(),pagertitle,fragmentList);
pager.setAdapter(adapter);
pagerTabStrip=findViewById(R.id.pager_title);
}
private void init(){
pagertitle.add("錄入");
pagertitle.add("圖片");
pagertitle.add("使用者");
fragmentList.add(f1);
fragmentList.add(f2);
fragmentList.add(f3);
for(int i=0;i<2;i++){
new Pictrue(0+1,R.drawable.rj,"p"+i).save();
new User("u"+i,R.drawable.txkt,0+1).save();
}
}
}
15、配置LitePal
在assets檔案下面的litepal.xml
<?xml version="1.0" encoding="utf-8" ?>
<litepal>
<dbname value="bookStoress"></dbname>
<version value="2"></version>
<list>
<mapping class="com.example.asus.summary3.Pictrue"></mapping>
<mapping class="com.example.asus.summary3.User"></mapping>
</list>
</litepal>
新增依賴庫：
implementation 'org.litepal.android:core:1.4.1'
在配置檔案：
android:name="org.litepal.LitePalApplication"