数据库的使用
作用：
从文本中获取信息存放在数据库中。
SQLActivity主要负责界面控制，六个按钮的摆放以及点击效果。
package com.example.sql;
import java.io.IOException;
import android.app.Activity;
import android.content.ContentValues;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class SQLActivity extends Activity {
private Database db;
private final static String FILE_NAME = "data.txt";
private final static String TXT_TITLE = "标题";
private final static String TXT_CONTENT = "内容";
private final static String TXT_TYPE = "类别";
private final static String TXT_LINK = "链接";
private final static String TXT_ENDSIGN = "#@#";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sql);
db = new Database(getApplicationContext());
// 创建数据库
findViewById(R.id.create).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
db.create();
}
});
// 插入数据
findViewById(R.id.insert).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
GetTxtContentForAssets getTxtContentForAssets = new GetTxtContentForAssets();
String txtContent = null;
try {
txtContent = getTxtContentForAssets.getAllContent(FILE_NAME, getApplicationContext());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (txtContent != null){
String title = new String();
String content = new String();
String type = new String();
String link = new String();
while (txtContent.indexOf(TXT_TITLE) != -1){
title = getTxtContentForAssets.getStringFromXtoY(txtContent, TXT_TITLE, TXT_ENDSIGN);
txtContent = getTxtContentForAssets.getRemainString(txtContent,TXT_ENDSIGN);
content = getTxtContentForAssets.getStringFromXtoY(txtContent, TXT_CONTENT,TXT_ENDSIGN);
txtContent = getTxtContentForAssets.getRemainString(txtContent,TXT_ENDSIGN);
type = getTxtContentForAssets.getStringFromXtoY(txtContent, TXT_TYPE,TXT_ENDSIGN);
txtContent = getTxtContentForAssets.getRemainString(txtContent,TXT_ENDSIGN);
link = getTxtContentForAssets.getStringFromXtoY(txtContent, TXT_LINK,TXT_ENDSIGN);
txtContent = getTxtContentForAssets.getRemainString(txtContent,TXT_ENDSIGN);
// 插入数据title，content，type和link到数据库中。
db.insert(title,content,type,link);
Log.i("database", "insert");
}
}
}
});
// 查询数据
findViewById(R.id.query).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
db.queryAll();
}
});
// 删除数据库
findViewById(R.id.delete).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
db.delete();
}
});
// 修改数据库信息
findViewById(R.id.update).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
db.update();
}
});
// 删除行
findViewById(R.id.deleline).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
db.deleteline();
}
});
}
}
Database类主要完成和数据库相关的各种操作，比如数据库的创建、增删改查等操作，具体看注释。
package com.example.sql;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
public class Database {
private Context mContext;
private SQLiteDatabase db;
private DatabaseSQLiteOpenHelper sqLiteOpenHelper;
private final static String DATABASE_NAME = "legerdemain.db";
private final static int DATABASE_VERSION = 1;
public Database(Context context) {
// TODO Auto-generated constructor stub
mContext = context;
}
// 创建数据库
public void create() {
// TODO Auto-generated method stub
sqLiteOpenHelper = new DatabaseSQLiteOpenHelper(mContext, DATABASE_NAME, null, DATABASE_VERSION);
db = sqLiteOpenHelper.getReadableDatabase();
db.close();
}
/**
* 插入元组到数据库中,各个参数是元组内容
* @param title
* @param content
* @param type
* @param link
*/
public void insert(String title, String content, String type, String link) {
// TODO Auto-generated method stub
sqLiteOpenHelper = new DatabaseSQLiteOpenHelper(mContext, DATABASE_NAME, null, DATABASE_VERSION);
db = sqLiteOpenHelper.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(sqLiteOpenHelper.TABLE_TITLE, title);
cv.put(sqLiteOpenHelper.TABLE_CONTENT, content);
cv.put(sqLiteOpenHelper.TABLE_TYPE, type);
cv.put(sqLiteOpenHelper.TABLE_LINK, link);
db.insert(sqLiteOpenHelper.TABLE_NAME, null, cv);
db.close();
}
/**
* 查询所有数据
*/
public void queryAll() {
// TODO Auto-generated method stub
sqLiteOpenHelper = new DatabaseSQLiteOpenHelper(mContext, DATABASE_NAME, null, DATABASE_VERSION);
db = sqLiteOpenHelper.getReadableDatabase();
Cursor cursor = db.query(sqLiteOpenHelper.TABLE_NAME, new String[]{sqLiteOpenHelper.TABLE_ID,
sqLiteOpenHelper.TABLE_TITLE,sqLiteOpenHelper.TABLE_CONTENT,sqLiteOpenHelper.TABLE_TYPE,sqLiteOpenHelper.TABLE_LINK}, null, null, null, null, null);
String title = null;
String content = null;
String type = null;
String link = null;
while (cursor.moveToNext()){
title = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_TITLE));
content = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_CONTENT));
type = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_TYPE));
link = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_LINK));
Log.i("database","title="+title+"content="+content+"type="+type+"link="+link);
}
db.close();
}
/**
* 查询title列表中的所有包含keyword的数据
* @param keyword
*/
public void queryTitle(String keyword) {
// TODO Auto-generated method stub
sqLiteOpenHelper = new DatabaseSQLiteOpenHelper(mContext, DATABASE_NAME, null, DATABASE_VERSION);
db = sqLiteOpenHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select * from "+sqLiteOpenHelper.TABLE_NAME+" where "+sqLiteOpenHelper.TABLE_TITLE+" LIKE '%"+keyword+"%'", null);
String title = null;
String content = null;
String type = null;
String link = null;
while (cursor.moveToNext()){
title = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_TITLE));
content = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_CONTENT));
type = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_TYPE));
link = cursor.getString(cursor.getColumnIndex(sqLiteOpenHelper.TABLE_LINK));
Log.i("database","title="+title+"content="+content+"type="+type+"link="+link);
}
db.close();
}
/**
* 删除数据库
*/
public void delete() {
// TODO Auto-generated method stub
if (mContext.deleteDatabase(DATABASE_NAME)){
Log.i("database", "deleteDatabase");
}
}
/**
* 修改:将title中含有“天”的title修改为Fred
*/
public void update() {
// TODO Auto-generated method stub
sqLiteOpenHelper = new DatabaseSQLiteOpenHelper(mContext, DATABASE_NAME, null, DATABASE_VERSION);
db = sqLiteOpenHelper.getWritableDatabase();
String sql = "UPDATE "+sqLiteOpenHelper.TABLE_NAME+" SET "+sqLiteOpenHelper.TABLE_TITLE+" = 'Fred' WHERE "+sqLiteOpenHelper.TABLE_TITLE+" LIKE '%天%'" ;
db.execSQL(sql);
db.close();
}
/**
* 删除title中含有“F”的一行
*/
public void deleteline() {
// TODO Auto-generated method stub
sqLiteOpenHelper = new DatabaseSQLiteOpenHelper(mContext, DATABASE_NAME, null, DATABASE_VERSION);
db = sqLiteOpenHelper.getWritableDatabase();
String sql = "DELETE FROM "+sqLiteOpenHelper.TABLE_NAME+" WHERE "+sqLiteOpenHelper.TABLE_TITLE+" LIKE '%F%'";
db.execSQL(sql);
db.close();
}
}
从Asset文件夹中获取信息存入数据库中，作为Insert的一个依赖存在。
package com.example.sql;
import java.io.IOException;
import java.io.InputStream;
import android.content.Context;
import android.content.res.AssetManager;
public class GetTxtContentForAssets {
private final static String ENCODING = "GB2312";
/**
* 读取文件中的所有内容
* @param fileName the fileName which in Asset folder that need to be read
* @param context
* @return the contents of file
* @throws IOException
*/
public String getAllContent(String fileName,Context context) throws IOException{
AssetManager aManager = context.getAssets();
InputStream file = aManager.open(fileName);
int length = file.available();
byte[] buff = new byte[length];
file.read(buff);
file.close();
String content = new String(buff, ENCODING);
return content;
}
/**
* 截取字符串中以startsign和stopsign之中的一段
* @param string String which is pending on
* @param startsign
* @param stopsign
* @return the string which is pending over
*/
public String getStringFromXtoY(String string, String startsign, String stopsign) {
// TODO Auto-generated method stub
int start = string.indexOf(startsign)+startsign.length();
int stop = string.indexOf(stopsign);
return string.substring(start, stop);
}
/**
* 取结束符合之后的一段
* @param string
* @param Endsign
* @return the string which is after endsign
*/
public String getRemainString(String string, String Endsign) {
// TODO Auto-generated method stub
int len = string.indexOf(Endsign)+Endsign.length();
return string.substring(len);
}
}
package com.example.sql;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DatabaseSQLiteOpenHelper extends SQLiteOpenHelper{
public final static String TABLE_NAME = "legerdemain";
public final static String TABLE_ID = "ID";
public final static String TABLE_TITLE = "TITLE";
public final static String TABLE_CONTENT = "CONTENT";
public final static String TABLE_TYPE = "TYPE";
public final static String TABLE_LINK = "LINK";
public DatabaseSQLiteOpenHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("Create table "+TABLE_NAME+" ("+TABLE_ID+" integer primary key autoincrement,"
+TABLE_TITLE+" text,"+TABLE_CONTENT+" text,"+TABLE_TYPE+" text,"+TABLE_LINK+" text);");
Log.i("database", "CreatDatebase");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}