Android中sqlite之从网上获取数据更新UI

在这里，本人主要想做一个
1、首先从网上获取数据
2、将获取的数据存储到本地
3、地图上显示屏幕范围内的marker。
4、当地图状态改变时，要查询本地数据库，并更新地图。

BaiduMap有个setOnMapStatusChangeListener监听类，该类监听BaiduMap的状态，共有三个方法——onMapStatusChangeStart(),onMapStatusChangeFinish(),onMapStatusChange()。

void onMapStatusChangeStart(MapStatus status)手势操作地图，设置地图状态等操作导致地图状态开始改变。参数:status - 地图状态改变开始时的地图状态void onMapStatusChange(MapStatus status)地图状态变化中参数:status - 当前地图状态void onMapStatusChangeFinish(MapStatus status)地图状态改变结束参数:status - 地图状态改变结束后的地图状态

若BaiduMap状态改变，就会调用相应的函数。

其实这里有个笨方法，那就是每次地图状态改变，就从服务器获取数据，然后更新到地图上，但这样每次都要联网从服务器端获取数据，而且每次都要调用子线程，非常耗时间和内存，所以，本人想直接一次从服务器端获取数据，然后存在本地，每次地图状态改变时直接从本地获取数据然后更新到地图上，这样就会节约时间与内存。

但，子线程中从网络上获取的数据，怎么传给主线程呢？其实异步线程中有个方法很好实现这点。我们先来简单介绍一下异步线程的用法。

AsyncTask定义了三种泛型类型 Params，Progress和Result。Params 启动任务执行的输入参数，比如HTTP请求的URL。Progress 后台任务执行的百分比。Result 后台执行任务最终返回的结果，比如String。AsyncTask定义了几个方法1、doInBackground(Params…) 后台执行，比较耗时的操作都可以放在这里。注意这里不能直接操作UI。此方法在后台线程执行，完成任务的主要工作，通常需要较长的时间。在执行过程中可以调用publicProgress(Progress…)来更新任务的进度。2、onPostExecute(Result)  相当于Handler 处理UI的方式，在这里面可以使用在doInBackground 得到的结果处理操作UI。 此方法在主线程执行，任务执行的结果作为此方法的参数返回，本例中关键是这个方法。3、有必要的话你还得重写以下这三个方法，但不是必须的：onProgressUpdate(Progress…)   可以使用进度条增加用户体验度。 此方法在主线程执             行，用于显示任务执行的进度。onPreExecute()        这里是最终用户调用Excute时的接口，当任务执行之前开始调用此方法，可以在这里显示进度对话框。onCancelled()            用户调用取消时，要做的操作4、使用AsyncTask类，以下是几条必须遵守的准则：Task的实例必须在UI thread中创建；execute方法必须在UI thread中调用；不要手动的调用onPreExecute(), onPostExecute(Result)，doInBackground(Params...), onProgressUpdate(Progress...)这几个方法；该task只能被执行一次，否则多次调用时将会出现异常；

接下来，我们看看我想写的效果吧：

package com.yds.newpowerbike.fragment;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.app.Fragment;import android.content.SharedPreferences;import android.os.AsyncTask;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.baidu.location.BDLocation;import com.baidu.location.BDLocationListener;import com.baidu.location.LocationClient;import com.baidu.location.LocationClientOption;import com.baidu.mapapi.SDKInitializer;import com.baidu.mapapi.map.BaiduMap;import com.baidu.mapapi.map.BaiduMap.OnMapStatusChangeListener;import com.baidu.mapapi.map.BitmapDescriptor;import com.baidu.mapapi.map.BitmapDescriptorFactory;import com.baidu.mapapi.map.CircleOptions;import com.baidu.mapapi.map.MapStatus;import com.baidu.mapapi.map.MapStatusUpdate;import com.baidu.mapapi.map.MapStatusUpdateFactory;import com.baidu.mapapi.map.MapView;import com.baidu.mapapi.map.Marker;import com.baidu.mapapi.map.MarkerOptions;import com.baidu.mapapi.map.MyLocationData;import com.baidu.mapapi.map.OverlayOptions;import com.baidu.mapapi.map.Stroke;import com.baidu.mapapi.model.LatLng;import com.baidu.mapapi.utils.DistanceUtil;import com.yds.newpowerbike.R;import com.yds.newpowerbike.bean.PolePoint;import com.yds.newpowerbike.db.DBManager;import com.yds.newpowerbike.net.ConnectServerIml;import com.yds.newpowerbike.net.ShareData;import com.yds.newpowerbike.util.JsonParse;public class HomeFragment extends Fragment {    private Activity activity;    private MapView mMapView;    public MyLocationListener myListener = new MyLocationListener();     private DBManager mgr;    BaiduMap mBaiduMap;    LocationClient mLocClient;    boolean isFirstLoc = true;    boolean isLocationClientStop = false;    ConnectServerIml iml;    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,            Bundle savedInstanceState) {        // TODO Auto-generated method stub        super.onCreateView(inflater, container, savedInstanceState);        this.activity = getActivity();        SDKInitializer.initialize(activity.getApplicationContext());        return inflater.inflate(R.layout.fragment_home, container,false);    }    @Override    public void onActivityCreated(Bundle savedInstanceState) {        // TODO Auto-generated method stub        super.onActivityCreated(savedInstanceState);        mMapView = (MapView) activity.findViewById(R.id.mapview);        mBaiduMap = mMapView.getMap();        mBaiduMap.setMyLocationEnabled(true);        //数据库操作——实例化DBManager        mgr = new DBManager(activity);        mLocClient = new LocationClient(activity);        mLocClient.registerLocationListener(myListener);        LocationClientOption option = new LocationClientOption();        option.setOpenGps(true);        option.setCoorType("bd09ll");//bd09LL        option.setScanSpan(1000);        mLocClient.setLocOption(option);        mLocClient.start();        asyncTask task = new asyncTask();        task.execute();    }    class asyncTask extends AsyncTask<LatLng, Integer, DBManager>{        @Override        protected DBManager doInBackground(LatLng... params) {            // TODO Auto-generated method stub            //充电桩服务器查询            iml = new ConnectServerIml();            String url = ShareData.CHARGE_SEARCH;            String result = iml.ConcernByClientGet(url);            //json数据解析            ArrayList<PolePoint> list = JsonParse.search(result);            //数据库操作——插入数据            mgr.add(list);            return mgr;        }        @Override        protected void onPostExecute(final DBManager mgr) {            // TODO Auto-generated method stub            super.onPostExecute(mgr);            final List<PolePoint>list = mgr.query();            mBaiduMap.setOnMapStatusChangeListener(new OnMapStatusChangeListener() {                //地图状态改变前                Marker marker;                int length = list.size();                @Override                public void onMapStatusChangeStart(MapStatus status) {                    // TODO Auto-generated method stub                }                //地图状态改变后                @Override                public void onMapStatusChangeFinish(MapStatus status) {                    // TODO Auto-generated method stub                    LatLng mCenter = status.target;                    //数据库操作——数据查询                    for (int i = 0; i < length; i++) {                        String pt = list.get(i).PoleFix;                        double lat = iml.getLat(pt);                        double lng = iml.getLng(pt);                        //marker的经纬度                        LatLng pt_ll = new LatLng(lat, lng);                        //获得marker与圆中心点之间的距离。                        double distance = DistanceUtil.getDistance(pt_ll, mCenter);                        //圆的半径是8000，这里为美观取7600，距离小于7600的显示                        if(distance<7600){                            BitmapDescriptor bitmap = BitmapDescriptorFactory.fromResource(R.drawable.icon_gcoding);                            OverlayOptions options = new MarkerOptions()                            .position(pt_ll)                            .icon(bitmap)                            .zIndex(14)                            .draggable(true);                            marker = (Marker) mBaiduMap.addOverlay(options);                        }                    }                }                //地图状态改变时                @Override                public void onMapStatusChange(MapStatus status) {                    // TODO Auto-generated method stub                    LatLng mCenter = status.target;                    mBaiduMap.clear();                    //画圆                    OverlayOptions ooCircle = new CircleOptions().fillColor(0x384d73b3)                            .center(mCenter).stroke(new Stroke(3, 0x784d73b3))                            .radius(8000);                    mBaiduMap.addOverlay(ooCircle);//                  for (int i = 0; i < length; i++) {//                      String pt = list.get(i).PoleFix;//                      double lat = iml.getLat(pt);//                      double lng = iml.getLng(pt);//                      //marker的经纬度//                      LatLng pt_ll = new LatLng(lat, lng);//                      //获得marker与圆中心点之间的距离。//                      double distance = DistanceUtil.getDistance(pt_ll, mCenter);//                      //圆的半径是8000，这里为美观取7600，距离小于7600的显示//                      if(distance<7600){//                          BitmapDescriptor bitmap = BitmapDescriptorFactory.fromResource(R.drawable.icon_gcoding);//                          OverlayOptions options = new MarkerOptions()//                          .position(pt_ll)//                          .icon(bitmap)//                          .zIndex(14)//                          .draggable(true);//                          //                          marker = (Marker) mBaiduMap.addOverlay(options);//                          //                      }//                  }                }            });        }    }     public class MyLocationListener implements BDLocationListener{        @Override        public void onReceiveLocation(BDLocation location) {            // TODO Auto-generated method stub            if(location == null||isLocationClientStop)                return;            //定位相关数据            MyLocationData locData = new MyLocationData.Builder()            .accuracy(location.getRadius())            .direction(100)            .latitude(location.getLatitude())            .longitude(location.getLongitude())            .build();            mBaiduMap.setMyLocationData(locData);            if(isFirstLoc){                isFirstLoc = false;                //定位点坐标                LatLng ll = new LatLng(location.getLatitude(), location.getLongitude());                //设置地图中心点和缩放级别                MapStatusUpdate u = MapStatusUpdateFactory.newLatLngZoom(ll, 12);                //以动画方式更新地图状态，动画耗时 300 ms                mBaiduMap.animateMapStatus(u);                //画圆                OverlayOptions ooCircle = new CircleOptions().fillColor(0x384d73b3)                        .center(ll).stroke(new Stroke(3, 0x784d73b3))                        .radius(8000);                mBaiduMap.addOverlay(ooCircle);            }        }    }    @Override    public void onDestroy() {        // TODO Auto-generated method stub//      mLocClient.stop();//      mBaiduMap.setMyLocationEnabled(false);//      mMapView = null;        //关闭数据库        mgr.closeDB();        mMapView.onDestroy();        super.onDestroy();    }    @Override    public void onPause() {        // TODO Auto-generated method stub        super.onPause();        mMapView.onPause();    }    @Override    public void onResume() {        // TODO Auto-generated method stub        super.onResume();        mMapView.onResume();    }}

这里有地图定位，地图画圆，显示圆范围内的marker，还有Fragment，这些在我前面的博客中可以看到，这里就不详细讲了。

DBHelper类中：

package com.yds.newpowerbike.db;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBHelper extends SQLiteOpenHelper{    private static final String DATABASE_NAME = "pole.db";    private static final int DATABASE_VERSION = 1;    public DBHelper(Context context){        super(context, DATABASE_NAME, null, DATABASE_VERSION);    }    @Override    public void onCreate(SQLiteDatabase db) {        // TODO Auto-generated method stub        //创建表        db.execSQL("create table if not exists polepoint"+        "(_id integer primary key autoincrement,poleid varchar,poleaddress varchar,polename varchar,polefix varchar,userid varchar)");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        // TODO Auto-generated method stub        //更新表        db.execSQL("ALTER TABLE polepoint ADD COLUMN other STRING");    }}

DBManager类中

package com.yds.newpowerbike.db;import java.util.ArrayList;import java.util.List;import com.yds.newpowerbike.bean.PolePoint;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;public class DBManager {    private DBHelper helper;    private SQLiteDatabase db;    public DBManager(Context context){        helper = new DBHelper(context);        db = helper.getWritableDatabase();    }    public void add(List<PolePoint> list){        db.beginTransaction();        try {            for (PolePoint pp:list) {                db.execSQL("insert into polepoint values(null,?,?,?,?,?)",new Object[]{pp.PoleId,pp.PoleAdress,pp.PoleName,pp.PoleFix,pp.UserId});            }            db.setTransactionSuccessful();        } catch (Exception e) {            // TODO: handle exception        }finally{            db.endTransaction();        }    }//  public void updatePoleAdress(PolePoint pp){//      ContentValues cv = new ContentValues();//      cv.put("PoleAdress", pp.PoleAdress);//      db.update("polepoint", cv, "polename = ?", new String[]{pp.PoleName});//  }    public List<PolePoint> query(){        ArrayList<PolePoint>list = new ArrayList<PolePoint>();        Cursor c = queryTheCursor();        while (c.moveToNext()) {            PolePoint pp = new PolePoint();            pp.PoleId = c.getString(c.getColumnIndex("poleid"));            pp.PoleAdress = c.getString(c.getColumnIndex("poleaddress"));            pp.PoleName = c.getString(c.getColumnIndex("polename"));            pp.PoleFix = c.getString(c.getColumnIndex("polefix"));            pp.UserId = c.getString(c.getColumnIndex("userid"));            list.add(pp);        }        //关闭游标        c.close();        return list;    }    public Cursor queryTheCursor(){        Cursor c = db.rawQuery("select * from polepoint", null);        return c;    }    public void closeDB(){        db.close();    }//  public void deleteOldPerson(PolePoint pp){//      db.delete("polepoint", "age>=?", new String[]{String.valueOf(person.age)});//      //  }}

PolePoint类中

package com.yds.newpowerbike.bean;import java.io.Serializable;/** * { "PoleId": "003f3745-2032-4fa9-afe5-97afde42a89f", "PoleAdress": "鏋附璺?97闄勮繎", "PoleState": 0, "PoleStyle": 0, "PoleFix": "30.884728,121.01502099999999", "PoleName": "鐢靛姩姹借溅鍏呯數妗?", "UserId": "null" }, * @author Administrator * @description 鍏呯數妗╅噷闈㈢殑鐐? */public class PolePoint implements Serializable{    /** * */    private static final long serialVersionUID = 1L;    public int _id;    public String PoleId;    public String PoleAdress;    public String PoleState;    public String PoleStyle;    public String PoleFix;    public String PoleName;    public String UserId;    public PolePoint(){    }    public PolePoint(String poleId,String poleAddress,String poleName,String poleFix,String userId){        this.PoleId = poleId;        this.PoleAdress = poleAddress;        this.PoleName = poleName;        this.PoleFix = poleFix;        this.UserId = userId;    }    public String getPoleId() {        return PoleId;    }    public void setPoleId(String poleId) {        PoleId = poleId;    }    public String getPoleAdress() {        return PoleAdress;    }    public void setPoleAdress(String poleAdress) {        PoleAdress = poleAdress;    }    public String getPoleState() {        return PoleState;    }    public void setPoleState(String poleState) {        PoleState = poleState;    }    public String getPoleStyle() {        return PoleStyle;    }    public void setPoleStyle(String poleStyle) {        PoleStyle = poleStyle;    }    public String getPoleFix() {        return PoleFix;    }    public void setPoleFix(String poleFix) {        PoleFix = poleFix;    }    public String getPoleName() {        return PoleName;    }    public void setPoleName(String poleName) {        PoleName = poleName;    }    public String getUserId() {        return UserId;    }    public void setUserId(String userId) {        UserId = userId;    }}

截图：

Android中sqlite之从网上获取数据更新UI

Android中sqlite之从网上获取数据更新UI

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