作者:我无眼泪1221 | 来源:互联网 | 2023-05-18 03:02
学android已经有大概一周时间了吧,总感觉自己基础不怎么好,只能通过一点一点积累着敲来巩固平常的知识,有的时候就先不封装的敲一遍,再封装上,有些语句真的记不住,虽然知道他是什么意思,于是
学android已经有大概一周时间了吧 ,总感觉自己基础不怎么好,只能通过一点一点积累着敲来巩固平常的知识,有的时候就先不封装的敲一遍,再封装上,有些语句真的记不住,虽然知道他是什么意思,于是乎就反复的敲着,加油吧!少年,下面进入正题吧
DBConn.java类 主要是将raw写入到DDMS里的data/data/xxx包/下,代码如下:
package com.tp.soft.util;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import com.example.dbcity.R;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.os.Environment;
public class DBConn {
private static String DB_NAME = "test.db";
private static String PACKAGE = "com.example.dbcity";
private static String PATH = "/data" +
Environment.getDataDirectory().getPath()+
File.separator + PACKAGE;
private Context context;
private SQLiteDatabase database;
public DBConn(Context context){
this.cOntext= context;
}
public static final DBConn getInstance(Context context){
DBConn conn = new DBConn(context);
return conn;
}
public SQLiteDatabase getDb(){
database = openDB(PATH + File.separator + DB_NAME);
return database;
}
public SQLiteDatabase openDB(String dbFile){
try{
if(!isExitFile(dbFile)){
InputStream is = context.getResources().openRawResource(R.raw.test);
FileOutputStream fos = new FileOutputStream(dbFile);
byte[] buffer = new byte[1024];
int len = -1;
while((len = is.read(buffer)) != -1){
fos.write(buffer, 0, len);
}
is.close();
fos.close();
}
database = SQLiteDatabase.openOrCreateDatabase(dbFile, null);
return database;
}catch (Exception e) {
e.printStackTrace();
return null;
}
}
public boolean isExitFile(String path){
File file = new File(path);
return file.exists();
}
}
DBManage.java主要是对数据库的封装,目前只做了个查询,待后期完善吧,代码如下:
package com.tp.soft.util;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
public class DBManage {
private SQLiteDatabase db;
public DBManage(Context context) {
DBConn conn = DBConn.getInstance(context);
db = conn.getDb();
}
public List queryData(String sql, String[] selectionArgs, String property){
Cursor cursor = null;
List list = new ArrayList();
try{
cursor = db.rawQuery(sql, selectionArgs);
while(cursor.moveToNext()){
String str = cursor.getString(cursor.getColumnIndex(property));
list.add(str);
}
}catch (Exception e) {
e.printStackTrace();
}finally{
if(null != cursor){
cursor.close();
}
}
return list;
}
}
主入口就是一个下拉列表的显示,然后就是调用sqlite数据库了,部分代码如下:
proSelect = (Spinner) findViewById(R.id.proSelect);
DBManage dbManage = new DBManage(this);
List proList = dbManage.queryData("select * from au_user", null, "username");
ArrayAdapter arrayAdapter = new ArrayAdapter(this, android.R.layout.simple_gallery_item, proList);
proSelect.setAdapter(arrayAdapter);
总结一句话,其实代码敲多了 才去想怎么敲,而不是一点都没敲就去想如何将语句敲到最好 我觉得这个是不可能的,菜鸟自学路程。。。