Android——Greendao封装进行

我不是女神ヾ 2022-06-04 02:26 358阅读 0赞

## 关于GreenDao ##

greenDao是一个将对象映射到SQLite数据库中的轻量且快速的ORM解决方案。  
关于greenDAO的概念可以看官网greenDAO

## greenDAO 优势 ##

1、一个精简的库  
2、性能最大化  
3、内存开销最小化  
4、易于使用的 APIs  
5、对 Android 进行高度优化

## GreenDao 3.0使用 ##

GreenDao 3.0采用注解的方式来定义实体类，通过gradle插件生成相应的代码。

**第一步** 在工程的Build Gridle中进行配置

dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2'//加入
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }

**第二步** 在Demo的Build Gridle中配置

apply plugin: 'com.android.application'
    apply plugin: 'org.greenrobot.greendao'//加入
    android {
        compileSdkVersion 26
        buildToolsVersion "26.0.2"
    
        defaultConfig {
            applicationId "com.bwie.com.myapplication"
            minSdkVersion 19
            targetSdkVersion 26
            versionCode 1
            versionName "1.0"
    
            testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

添加依赖

compile 'org.greenrobot:greendao:3.2.2'

**第三步 **自定义路径

greendao {
        schemaVersion 1
        daoPackage 'com.bwie.com.myapplication.gen'
        targetGenDir 'src/main/java'
    }

**第四步** 创建一个实体类

@Entity
    public class DataBean {
        @Id
        private long cid;
        private String createtime;
        private String icon;
        private int ishome;
        private String name;

}

**第五步 **MakeProject 自动编译 会在gen目录下生成三个文件

![Center][]![Center 1][]

下面上代码：

先进行网络请求：

**HttpUtils**`/** * Created by Wangrx on 2017/11/30. */ public class HttpUtils { private static volatile HttpUtils instance; private Handler handler = new Handler(); private HttpUtils(){ } public static HttpUtils getInstance(){ if (instance==null){ synchronized (HttpUtils.class){ if (null==instance){ instance = new HttpUtils(); } } } return instance; } public void get(String url, Map<String,String> map, final CallBack callBack, final Class cls, final String tag){ if (TextUtils.isEmpty(url)){ return; } StringBuffer sb = new StringBuffer(); sb.append(url); if (url.contains("?")){ if (url.indexOf("?")==url.length()-1){ }else { sb.append("&"); } }else { sb.append("?"); } for (Map.Entry<String,String> entry:map.entrySet()){ sb.append(entry.getKey()) .append("=") .append(entry.getValue()) .append("&"); } if (sb.indexOf("&")!=-1){ sb.deleteCharAt(sb.lastIndexOf("&")); } OkHttpClient client = new OkHttpClient(); Request request = new Request.Builder() .get() .url(sb.toString()) .build(); Call call = client.newCall(request); call.enqueue(new Callback() { @Override public void onFailure(Call call, final IOException e) { handler.post(new Runnable() { @Override public void run() { callBack.onFailed(tag,e); } }); } @Override public void onResponse(Call call, Response response) throws IOException { final String result = response.body().string(); //请求成功后做解析，通过自己的回调接口将数据返回去 handler.post(new Runnable() { @Override public void run() { Object o; if (TextUtils.isEmpty(result)){ o = null; }else { o = GsonUtils.getInstance().fromJson(result, cls); } callBack.onSuccess(tag,o); } }); } }); } }`

`/** * Created by Wangrx on 2017/11/30. */ public class GsonUtils { private static Gson instance; private GsonUtils(){ } public static Gson getInstance(){ if (instance==null){ instance = new Gson(); } return instance; } }`

GsonUtils`/** * Created by Wangrx on 2017/11/30. */ public class GsonUtils { private static Gson instance; private GsonUtils(){ } public static Gson getInstance(){ if (instance==null){ instance = new Gson(); } return instance; } }`

CallBack`/** * Created by Wangrx on 2017/11/30. */ public interface CallBack { void onSuccess(String tag,Object o); void onFailed(String tag,Exception e); }`

NewsPresenter`/** * Created by Wangrx on 2017/11/30. */ public class NewsPresenter { private NewsView inv; public void attachView(NewsView inv){ this.inv = inv; } public void getNews(String url){ Map<String, String> map = new HashMap<>(); // map.put("keywords",show); // map.put("page",page+""); HttpUtils.getInstance().get(url, map, new CallBack() { @Override public void onSuccess(String tag, Object o) { JavaBean bean = (JavaBean) o; if (bean != null){ List<DataBean> data = bean.getData(); inv.success(tag,data); } } @Override public void onFailed(String tag, Exception e) { inv.failed(tag,e); } }, JavaBean.class,"news"); } public void detachView(){ if (inv!=null){ inv = null; } } }`

NewsView`/** * Created by Wangrx on 2017/11/30. */ public interface NewsView { void success(String tag, List<DataBean> data); void failed(String tag,Exception e); }`

以上是对网络请求数据以MVP模式进行封装

下面是对GreenDao的封装

**BaseApplication****(本地的数据)**`/** * Created by Wangrx on 2017/11/30. */ public class BaseApplication extends Application{ private static BaseApplication instance; private List<DataBean> list; @Override public void onCreate() { super.onCreate(); instance=this; } public static BaseApplication getInstance(){ return instance; } public List<DataBean> getData(){ if (list==null){ list=new ArrayList<>(); } return list; } public void setData(List<DataBean> list){ this.list = list; } }`

DBUtils（数据库中的数据）`/** * Created by Wangrx on 2017/11/30. */ public class DBUtils { private static volatile DBUtils instance; private final DataBeanDao dao; public DBUtils(Context context) { DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(context, "databean.db", null); SQLiteDatabase database = helper.getWritableDatabase(); DaoMaster daoMaster = new DaoMaster(database); DaoSession daoSession = daoMaster.newSession(); dao = daoSession.getDataBeanDao(); } public static DBUtils getInstance(Context context){ if (instance==null){ synchronized (DBUtils.class){ if (null==instance){ instance = new DBUtils(context); } } } return instance; } public DataBeanDao getDao(){ return dao; } }`

MainActivity（先判断本地是否有数据，没有的话从数据库中取出数据，判断数据库是否有数据，数据库中有数据的话将数据查询出来赋给本地数据，数据库中也没有数据的话就从网络上获取数据，网络上获取到数据后将数据存入数据库中，同时也赋给本地数据，将本地的数据拿出显示出来**）**`public class MainActivity extends AppCompatActivity implements NewsView { @BindView(R.id.recy_vieww) RecyclerView recyVieww; private List<DataBean> datas; private MyAdapter adapter; private NewsPresenter presenter; private DataBeanDao dao; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ButterKnife.bind(this); dao = DBUtils.getInstance(this).getDao(); initView(); } public void initView() { //首先从内存中看有没有数据 datas = BaseApplication.getInstance().getData(); adapter = new MyAdapter(this, datas); LinearLayoutManager manager = new LinearLayoutManager(this); recyVieww.setLayoutManager(manager); recyVieww.setAdapter(adapter); if (datas == null || datas.size() == 0) { Log.i("zzz", "内存中无数据"); //从数据库中取 List<DataBean> dataFromDB = getDataFromDB(); //数据库中也是空 if (dataFromDB==null||dataFromDB.size()==0){ Log.i("zzz", "数据控中为空"); //从网络中取数据 getDataFromNet(); }else { Log.i("zzz", "数据库中不为空"); putDataToMemory(dataFromDB); } } adapter.setOnItemClickListener(new MyAdapter.OnItemClickListener() { @Override public void onClick(int position) { // DataBean dataBean = new DataBean(); // dataBean.setCid(position+1); // dao.delete(dataBean); // List<DataBean> dataFromDB = getDataFromDB(); // putDataToMemory(dataFromDB); } @Override public void onLongClick(int position) { } }); } //从网络中取数据 public void getDataFromNet(){ Log.i("zzz", "从网上获取"); presenter = new NewsPresenter(); presenter.attachView(this); presenter.getNews("https://www.zhaoapi.cn/product/getCatagory"); } @Override public void success(String tag, List<DataBean> data) { if (data!=null){ Log.i("zzz", "网络不为空"); //将网络请求的数据存到内存中和数据库中 putDataToMemory(data); //将数据添加到数据库中 for (DataBean dataBean : data){ dao.insertOrReplace(dataBean); } } } //将数据添加到内存中 public void putDataToMemory(List<DataBean> data){ Log.i("zzz", "向内存中存数据"); datas.clear(); datas.addAll(data); adapter.notifyDataSetChanged(); BaseApplication.getInstance().setData(datas); } //从数据库中取数据 public List<DataBean> getDataFromDB(){ Log.i("zzz", "从数据库中取"); //查询所有数据 List<DataBean> dataBeen = dao.loadAll(); if (dataBeen==null||dataBeen.size()==0){ Log.i("zzz", "null"); }else { Log.i("zzz", "getDataFromDB: "+dataBeen.size()); } return dataBeen; } @Override public void failed(String tag, Exception e) { } @Override protected void onDestroy() { super.onDestroy(); if (presenter != null) { presenter.detachView(); } } }`

MyAdapter`/** * Created by Wangrx on 2017/11/30. */ public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { private Context context; private List<DataBean> list; public MyAdapter(Context context, List<DataBean> list) { this.context = context; this.list = list; } private OnItemClickListener mOnItemClickListener; public interface OnItemClickListener{ void onClick( int position); void onLongClick( int position); } public void setOnItemClickListener(OnItemClickListener onItemClickListener ){ this. mOnItemClickListener=onItemClickListener; } @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = View.inflate(context, R.layout.item, null); ViewHolder holder = new ViewHolder(view); return holder; } @Override public void onBindViewHolder(ViewHolder holder, final int position) { holder.itemTitle.setText(list.get(position).getName()); holder.itemTime.setText(list.get(position).getCreatetime()); if( mOnItemClickListener!= null){ holder.itemView.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { mOnItemClickListener.onClick(position); } }); holder. itemView.setOnLongClickListener( new View.OnLongClickListener() { @Override public boolean onLongClick(View v) { mOnItemClickListener.onLongClick(position); return false; } }); } } @Override public int getItemCount() { return list.size(); } public class ViewHolder extends RecyclerView.ViewHolder { @BindView(R.id.item_title) TextView itemTitle; @BindView(R.id.item_time) TextView itemTime; public ViewHolder(View itemView) { super(itemView); ButterKnife.bind(this,itemView); } } }`

[Center]: https://img-blog.csdn.net/20171201200921823?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQveHk4MTk5/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
[Center 1]: /images/20220604/faae995d91e649ebb8eab8c0c5722709.png