Android 本地数据库实现历史记录功能
恩，历史记录实现可以采取网络请求的形式，这样比较耗时；对于存储在本地的方法，我常用的是ShaerdPreferences和数据库；这次主要是通过本地数据库来实现历史记录。
首先要建表，创建需要存储的字段名，为了每次将选中的历史记录置顶，我增加了时间字段
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
//建表(名称记录)：自增长的主键，名称，最后一次更新时间
db.execSQL("create table history(_id integer primary key autoincrement, name varchar(20) , lasttime varchar(50));");
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
}
}
HistoryDao
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.SystemClock;
import java.util.ArrayList;
import java.util.List;
public class HistoryDao {
//创建数据库
private DbHelper dbHelper;
private String tabHistory = "history";
private HistoryDao(Context context) {
dbHelper = new DbHelper(context, "history.db", null, 1);
}
private static HistoryDao instance;
public static synchronized HistoryDao getInstance(Context context) {
if (instance == null) {
instance = new HistoryDao(context);
}
return instance;
}
/**
* 增加历史记录
*/
public void addHistory(String name) {
//获得一个可写的数据库的一个引用
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("lasttime", CommUtil.getCurrentDate());// KEY 是列名，vlaue 是该列的值
if (getIdByName(name)==0) {
values.put("name", name);
db.insert(tabHistory, null, values);
} else {
db.update(tabHistory,values,"name = ?", new String[]{name});
}
}
/**
* 删除历史记录
*/
public void delHistory(int _id) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
//表名 删除的条件
db.delete(tabHistory, "_id = "+_id,null);
}
/**
* 删除全部历史记录
*/
public void delAllHistory(List beans) {
for (int i=0;i getHistoryData() {
//创建集合对象
List data = new ArrayList();
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select * from history order by lasttime desc;", null);
// 返回的 cursor 默认是在第一行的上一行
//遍历
while (cursor.moveToNext()) {// cursor.moveToNext() 向下移动一行,如果有内容，返回true
int id=cursor.getInt(0);
String name = cursor.getString(cursor.getColumnIndex("name"));
HisNameBean bean = new HisNameBean(id, name);
//封装的对象添加到集合中
data.add(bean);
}
//关闭cursor
cursor.close();
SystemClock.sleep(1000);// 休眠2秒，数据比较多，比较耗时的情况
return data;
}
;
/**
* 获得历史记录数量
*/
public int getHistoryCount() {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query(tabHistory, new String[]{"count(*)"}, null, null, null, null, null);
cursor.moveToNext();
int count = cursor.getInt(0);// 仅查了一列，count(*) 这一刻列
cursor.close();
return count;
}
/**
* 根据名称获得_ID
*/
public int getIdByName(String name) {
int id = 0;
//获得一个可读的数据库的一个引用
SQLiteDatabase db = dbHelper.getReadableDatabase();
//查询 表 列 条件
Cursor cursor = db.query(tabHistory, null, "name = ?", new String[]{name}, null, null, null);
if (cursor.moveToNext()) {// 如果查到了，移动成功
id = cursor.getInt(0);
}
cursor.close();
return id;
}
}
表history的基类
public class HisNameBean {
private int id;
private String name;
public HisNameBean (int id, String name ) {
this.id=id;
this.name = name ;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}在Activity中使用
private HistoryDao historyDao; Listbeans = new ArrayList<>(); private NameHisAdapter adapter;
初始化：
historyDao = HistoryDao.getInstance(this);
/**
* 初始化历史记录
*/
private void initHistoryData() {
new Thread() {
public void run() {
if (beans == null) {
beans = historyDao.getHistoryData();
} else {
beans .clear();
beans .addAll(historyDao.getHistoryData());
}
// handler.sendEmptyMessage(100);
Message msg = Message.obtain();
msg.what = 100;
handler.sendMessage(msg);
}
}.start();
tvClean.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// 全部清除
historyDao.delAllHistory(busBeans);
}
});
}
//使用Handler更新主线程（UI线程)
private Handler handler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case 100://子线程获得了数据，开始刷新页面
if (beans.size() == 0) {
// 没有历史记录的情况
} else {
if (adapter == null) { //第一次加载
LinearLayoutManager layoutmanager = new LinearLayoutManager(Activity.this);
//设置RecyclerView 布局
rvHistory.setLayoutManager(layoutmanager);
adapter = new NameHisAdapter(Activity.this, beans);
rvHistory.setAdapter(adapter);
adapter.setOnDelClickListener(new NameHisAdapter.OnDelClickListener() {
@Override
public void onDelClick(View view, int position, int count) {
// 删除当前历史记录 historyDao.delHistory(historyDao.getIDByName(beans.get(position).getName().toString().trim()));
beans.remove(position);
adapter.notifyDataSetChanged();
}
});
adapter.setOnItemClickListener(new NameHisAdapter.OnItemClickListener() {
@Override
public void onItemClick(View view, int position) {
// 获得对应名称
String name= beans.get(position).getName();
// 添加历史记录
historyDao.addHistory(beans.get(position).getName());
}
});
} else {
//追加数据
adapter.notifyDataSetChanged();// 刷新listView 否则仍会从头开始 显示
}
llData.setVisibility(View.VISIBLE);
vNodata.setVisibility(View.GONE);
}
break;
}
}
};
根据实际情况进行增删改查操作