下面介绍一下我的这个demo。
流程简述：
我在raw文件夹下面放了名称为city的数据库，里面包含全国2330个城市，以及所属省，拼音简写等信息。
首先 在进入MainActivity的时候，创建数据库并读入sd卡文件中data/data/databases/city。
然后 我再开启子线程去读取前50条数据，显示在ListView中。
当用户浏览数据， 前50条不够时，他会滑动ListView以查看更多数据，此时，listview的数据源会递增，50 ，100，150，。。。。
以50为增量不断增加.....
这样避免了因一次性加载数据造成ANR，也给用户比较好的体验。
工程目录结构：
cls_city是城市信息类，Common是工具类，ViewHolder是ListView缓存机制帮助类，DataBaseHelper 数据库操作工具类/.....
package com.example.sqlitepagetest;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import android.database.Cursor;
import android.util.Log;
/**
* <p>
* </p>
* 下午9:12:42
*
* @auther dalvikCoder
*/
public class cls_city {
public String _id = "";
public String province = "";
public String name = "";
/**
*
* select _id,province ,name from city order by _id limit perItemNum Offset
* currentPage*perItemNum ;--currentPage 从零开始
* <p>
* 根据条目数量查询
* </p>
*
* @param dbh
* @param num
* num[1]-->每一页显示的条目数量 num[0]--->从第几条开始
* @return List<cls_city>
*/
public static List<cls_city> getCityList(DatabaseHelper dbh, int num[]) {
String sql = "select _id,province ,name from city order by _id limit "
+ num[0] + "," + num[1];
Log.e("select city‘s sql --------------", sql);
Cursor cursor = dbh.rawQuery(sql);
List<cls_city> list = new ArrayList<cls_city>();
cls_city cls = null;
while (cursor.moveToNext()) {
cls = new cls_city();
setClassValueBycursor(cls, cursor);
list.add(cls);
}
return list;
}
/**
* <p>
* 利用反射机制给对象赋值
* </p>
* @param obj
* @param cursor void
*/
public static void setClassValueBycursor(Object obj, Cursor cursor) {
int ColCount = cursor.getColumnCount();
int i = 0;
for (i = 0; i < ColCount; i++) {
String ColName = cursor.getColumnName(i);
try {
Field f = obj.getClass().getField(ColName);
String ret = cursor.getString(i);
if (f == null)
continue;
if (ret == null)
ret = "";
f.set(obj, ret);
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchFieldException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
package com.example.sqlitepagetest;
import android.util.SparseArray;
import android.view.View;
/**
* <p>
* ListView缓存的写法比较多种，下面也是其中一中，
* </p>
* 下午9:45:29
*
* @auther dalvikCoder
*/
public class ViewHolder {
// I added a generic return type to reduce the casting noise in client code
@SuppressWarnings("unchecked")
public static <T extends View> T get(View view, int id) {
SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
if (viewHolder == null) {
viewHolder = new SparseArray<View>();
view.setTag(viewHolder);
}
View childView = viewHolder.get(id);
if (childView == null) {
childView = view.findViewById(id);
viewHolder.put(id, childView);
}
return (T) childView;
}
}
在使用了ViewHolder之后，自定义适配器里面的代码看起来好多了。
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = inflater.inflate(R.layout.city_lv_item, null);
}
TextView cityId = ViewHolder.get(convertView, R.id.cityidtxt);
TextView provincetxt = ViewHolder.get(convertView, R.id.provincetxt);
TextView cityName = ViewHolder.get(convertView, R.id.nametxt);
cls_city city = cityList.get(position);
cityId.setText(city._id);
provincetxt.setText(city.province);
cityName.setText(city.name);
return convertView;
}
下面是总的MainActivity类，里面的注释比较详细，也比较简单。
当然如果有兴趣你可以给ListView添加尾部视图，比如加个状态文字或者加个加个进度条，不过像本地数据，好像用不了多少时间
package com.example.sqlitepagetest;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
public class MainActivity extends Activity {
private ListView cityListView;
private List<cls_city> cityList;
private CityAdapter cityAdapter;
private MyThread thread = null;
/**
* 每页有数据条数 这个数量可以根据需要更改，而不需在程序中更改具体数值
* **/
private int perPageItemNum = 100;
/** 当前是第几页 0表示第一页 **/
private int currentPage = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setUpView();
}
private void setUpView() {
cityList = new ArrayList<cls_city>();
try {
Common.loadCityDatabase(this);
} catch (Exception e) {
e.printStackTrace();
}
Common.dbh = new DatabaseHelper(this, "city");
cityListView = (ListView) findViewById(R.id.citylistview);
cityAdapter = new CityAdapter(this, cityList);
cityListView.setAdapter(cityAdapter);
cityListView.setOnScrollListener(new OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (view.getLastVisiblePosition() == view.getCount() - 1
&& scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
if (thread != null && !thread.isInterrupted()) {
thread.interrupt();
thread = null;
}
currentPage++;
cityListView.setSelection(view.getLastVisiblePosition());// 设置显示位置，这句只是让Listview停留在最后末尾的显示而已，加不加影响不大
thread = new MyThread();
thread.start();
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
}
});
if (thread == null) {
thread = new MyThread();
thread.start();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
class MyThread extends Thread {
@Override
public void run() {
int num[] = new int[2];
num[0] = currentPage * perPageItemNum;// 0*50 1*50 2*50
num[1] = perPageItemNum;
List<cls_city> dataList = cls_city.getCityList(Common.dbh, num);
// try {
// Thread.sleep(1000);
// } catch (InterruptedException e) {
// e.printStackTrace();
// }
Message msg = new Message();
msg.what = 1;
msg.obj = dataList;
mHandler.sendMessage(msg);
}
}
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
List<cls_city> dataList = (List<cls_city>) msg.obj;
if (!dataList.isEmpty()) {
cityAdapter.refresh(dataList);
}
}
};
}
Common类
package com.example.sqlitepagetest;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import android.content.Context;
/**
* <p>
* </p>
* 下午9:02:19
*
* @auther dalvikCoder
*/
public class Common {
public static DatabaseHelper dbh = null;
public static void loadCityDatabase(Context context) throws Exception {
// ------------创建路径
String path = "/data/data/" + context.getPackageName() + "/databases";
File file = new File(path);
if (!file.exists()) {
file.mkdirs();
}
// --------------该路径下创建数据库文件
File f = new File(path, "city");
if (!f.exists()) {
InputStream is = context.getResources().openRawResource(R.raw.city);
FileOutputStream out = new FileOutputStream(path + "/city");
byte buffer[] = new byte[2 * 1024];
int len = 0;
while ((len = is.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
out.close();
is.close();
}
}
}
贴上效果图:
时间： 2024-10-05 05:50:11