android应用面试宝典（上）；公共基类管理公共头尾页；公共activity的参数问题；SQLite存数据；前提先将txt数据保存在项目的assets文件下；

本文链接：https://blog.youkuaiyun.com/needkane/article/details/22405635

本文详细介绍了SQLite数据库的连接操作及CRUD（增删改查）功能，包括创建数据库、表，以及插入、删除、查询数据的方法。同时，展示了如何在Android应用中集成并使用SQLite数据库，以实现数据持久化存储。

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SQLite连接操作

package com.kane.interviewcollection.dbc;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class SqliteConnection extends SQLiteOpenHelper {
private static final int DBVERSION=1;
private static final String DBNAME="question.db";

//简化构造方法,哪个类需要调用数据库，就传参进来
public SqliteConnection(Context ctx){
super(ctx,DBNAME, null,DBVERSION);
}
public SqliteConnection(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}

@Override
public void onCreate(SQLiteDatabase db) {
//安装时只建立一次，以后不执行了，主键id默认自增长，当然也可以写autoIncrement
String sql="CREATE TABLE question("+
"id integer primary key," +
"question text not null," +
"answer text not null" +
")";
db.execSQL(sql);
}

/**
* 当检测与前一次创建数据库版本不一样时，先删除表再创建新表才回进来
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS question");
//先删除旧表，再创建新表，必须版本号比以前高
onCreate(db);
}

}

SQLite的CRUD操作

package com.kane.interviewcollection.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.database.Cursor;

public class QuesstionDAOUtils {
public static void insert(Map<String,Object> map) {
String sql="INSERT INTO question(question,answer) VALUES(?,?>)";
Globals.dbc.getWritableDatabase().execSQL(sql,new Object[]{
map.get("question"),map.get("answer")
});
}

public static void deleteAll() {
String sql="DELETE FROM question";
Globals.dbc.getWritableDatabase().execSQL(sql);
}

public static List<Map<String,Object>> listDataPage (int pageNo,int pageSize,String keyword) {
List<Map<String,Object>> allValues=new ArrayList<Map<String,Object>>();

String sql = "SELECT id,question,answer FROM question WHERE question LIKE ? LIMIT ?,?";
Cursor c = Globals.dbc.getReadableDatabase().rawQuery(
sql,
new String[] { "%" + keyword + "%",
(pageNo - 1) * pageSize + "", String.valueOf(pageSize) });
c.moveToFirst();
while (!c.isAfterLast()) {
Map<String, Object> map = new HashMap<String, Object>();
map.put("id", c.getInt(0));
map.put("question", c.getInt(0) + "、" + c.getString(1));
map.put("answer", c.getString(2));

map.put("showFlag",false);//默认不显示答案，只有点击的显示答案
allValues.add(map);
c.moveToNext();
}
c.close();
return allValues;

}
public static int getAllCount(String keyword) {
String sql="SELECT COUNT(*) FROM question WHERE question LIKE ?";
Cursor c=Globals.dbc.getReadableDatabase().rawQuery(sql,
new String[]{"%"+keyword+"%"} );
c.moveToFirst();
int count =c.getInt(0);
c.close();
return count;

}
}

公共初始类

package com.kane.interviewcollection.util;

import com.kane.interviewcollection.dbc.SqliteConnection;

import android.app.Activity;

public class Globals {
public static int SCREEN_WIDTH;
public static int SCERRN_HEIGHT;

public static SqliteConnection dbc;

public static void init(Activity a){
dbc=new SqliteConnection(a);//对应需要的activity类
SCERRN_HEIGHT=a.getWindowManager().getDefaultDisplay().getHeight();
SCREEN_WIDTH=a.getWindowManager().getDefaultDisplay().getWidth();
}
}