android 数据存储技术

1.私有数据存储xml形式(SharedPreferences)

SharedPreferences settins = getSharedPreferences("文件名",0) //获取一个SharedPreferences对象

读取数据：
String name = settings.get("KEY","");

写入/更新数据
settings.edit().putString("KEY","VALUE").commit();


数据保存位置：
在DDMS中的File Explorer中的展开到/data/data/<package name>/shared_prefs下<文件名>.xml


2.文件存储

String FILE_NAME = "tempfile.tmp";
FileOutputStream fos = openFileOutput(FILE_NAME , Context.MODE_PRIVATE);//初始化

Context.MODE_PRIVATE：写入的时候覆盖原有的内容。
Context.MODE_APPEND：写入的时候在原有的内容后面添加内容。

FileInputStream fis = openFileInput(FILE_NAME);//创建写入流

其他资源文件的使用：
例如mp3
资源文件放在/res/raw下
使用时：
Resources myResources = getResources();
InputStream myFile = myResources.openRawResource(R.raw.myfilename);

3.数据库的运用

定义SQLiteOpenHelper 并完成 创建 更新 功能


public class DBHelper extends SQLiteOpenHelper {  
      
    public static final String TB_NAME = "mycountry";  
    public static final String ID = "_id";  
    public static final String COUNTRY = "country";  
    public static final String CODE = "code";  
      
      //数据库对象构造函数
    public DBHelper(Context context, String name,   
            CursorFactory factory,int version) {  
        super(context, name, factory, version);  
    }  

    //数据库创建函数
    public void onCreate(SQLiteDatabase db) {  
          
        db.execSQL("CREATE TABLE IF NOT EXISTS "   
                + TB_NAME + " ("   
                + ID + " INTEGER PRIMARY KEY,"   
                + COUNTRY + " VARCHAR,"  
                + CODE + " INTEGER)");  
    } 

    //数据库升级时候调用函数
    public void onUpgrade(SQLiteDatabase db,   
            int oldVersion, int newVersion) {  
          
        db.execSQL("DROP TABLE IF EXISTS "+TB_NAME);  
        onCreate(db);  
    }  

}

从SQLiteOpenHelper 得到SQLiteDatabase的实例

DBHelper helper = new DBHelper(this, DB_NAME, null, VERSION);  

//得到一个可写的数据库对象
SQLiteDatabase db = helper.getWritableDatabase();  

//得到一个可读的数据库对象
SQLiteDatabase db = helper.getReadableDatabase();  


SQLiteDatabase 的一些操作：

插入数据：
ContentValues values = new ContentValues();  
        values.put(DBHelper.COUNTRY, "中国");  
        values.put(DBHelper.CODE, 86);  
        db.insert(DBHelper.TB_NAME,DBHelper.ID, values);

改动数据
1. db.insert(DBHelper.TB_NAME,DBHelper.ID,null);  
2.         values.clear();  
3.         values.put(DBHelper.COUNTRY, "意大利");  
4.         values.put(DBHelper.CODE, 39);  
5.         db.update(DBHelper.TB_NAME, values,DBHelper.ID + " = 2",null);  

execSQL 执行SQL语言
1. db.execSQL("INSERT INTO "  
2.                 + DBHelper.TB_NAME + "("  
3.                 + DBHelper.COUNTRY + ","  
4.                 + DBHelper.CODE + ") VALUES "  
5.                 + "('洪都拉斯',504)");  

查询数据
1. Cursor c = db.query(DBHelper.TB_NAME,null,null,null,null,null,  
2.                 DBHelper.CODE+" DESC");  

第一个参数为表名，
第二个字段是我们想要返回数据包含的列的信息，字符串数组形式
第三个参数是selection
第四个是selectionArgs
第五个是groupBy
第六个是having
第七个是orderBy

删除数据
1. db.delete(DBHelper.TB_NAME,null,null);  
第一个参数是表名
第二个是selection
第三个是selectionArgs

如果存在这个表，就删除表
DROP TABLE IF EXISTS 表名

SimpleCursorAdapter notes = new SimpleCursorAdapter(this,R,layout.listview,myCursor,from,to)
第一个参数是context
第二个是ListView中每一项的布局
第三个是cursor
第四个是cursor列名
第五个是ListView中的组件ID

listview.setListAdapter(notes);

4.程序间数据共享ContentProvider Content provider

package com.eoeAndroid.contentProvider;

import java.util.Calendar;
import java.util.HashMap;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

import com.eoeAndroid.contentProvider.Diary.DiaryColumns;

public class DiaryContentProvider extends ContentProvider {

private static final String DATABASE_NAME = "database";
private static final int DATABASE_VERSION = 3;
private static final String DIARY_TABLE_NAME = "diary";

private static final int DIARIES = 1;
private static final int DIARY_ID = 2;

private static final UriMatcher sUriMatcher;

private static class DatabaseHelper extends SQLiteOpenHelper {

DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
Log.i("jinyan", "DATABASE_VERSION=" + DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
Log.i("jinyan", "onCreate(SQLiteDatabase db)");
String sql = "CREATE TABLE " + DIARY_TABLE_NAME + " ("
+ DiaryColumns._ID + " INTEGER PRIMARY KEY,"
+ DiaryColumns.TITLE + " TEXT," + DiaryColumns.BODY
+ " TEXT," + DiaryColumns.CREATED + " TEXT" + ");";
//
sql ="CREATE TABLE " + DIARY_TABLE_NAME + " ("
+ DiaryColumns._ID + " INTEGER PRIMARY KEY,"
+ DiaryColumns.TITLE + " varchar(255)," + DiaryColumns.BODY
+ " TEXT," + DiaryColumns.CREATED + " TEXT" + ");";
//
Log.i("jinyan", "sql="+sql);
db.execSQL(sql);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.i("jinyan",
onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)=
+ newVersion);
db.execSQL("DROP TABLE IF EXISTS diary");
onCreate(db);
}
}

private DatabaseHelper mOpenHelper;

static {
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
sUriMatcher.addURI(Diary.AUTHORITY, "diaries", DIARIES);
sUriMatcher.addURI(Diary.AUTHORITY, "diaries/#", DIARY_ID);

}

@Override
public boolean onCreate() {
mOpenHelper = new DatabaseHelper(getContext());
return true;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

switch (sUriMatcher.match(uri)) {
case DIARIES:
qb.setTables(DIARY_TABLE_NAME);
break;

case DIARY_ID:
qb.setTables(DIARY_TABLE_NAME);
qb.appendWhere(DiaryColumns._ID + "="
+ uri.getPathSegments().get(1));
break;

default:
throw new IllegalArgumentException("Unknown URI " + uri);
}

String orderBy;
if (TextUtils.isEmpty(sortOrder)) {
orderBy = Diary.DiaryColumns.DEFAULT_SORT_ORDER;
} else {
orderBy = sortOrder;
}

SQLiteDatabase db = mOpenHelper.getReadableDatabase();
Cursor c = qb.query(db, projection, selection, selectionArgs, null,
null, orderBy);
return c;
}

@Override
public String getType(Uri uri) {
switch (sUriMatcher.match(uri)) {
case DIARIES:
return DiaryColumns.CONTENT_TYPE;

case DIARY_ID:
return DiaryColumns.CONTENT_ITEM_TYPE;

default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
}

@Override
public Uri insert(Uri uri, ContentValues initialValues) {
if (sUriMatcher.match(uri) != DIARIES) {
throw new IllegalArgumentException("Unknown URI " + uri);
}

ContentValues values;
if (initialValues != null) {
values = new ContentValues(initialValues);
} else {
values = new ContentValues();
}

if (values.containsKey(Diary.DiaryColumns.CREATED) == false) {
values.put(Diary.DiaryColumns.CREATED, getFormateCreatedDate());
}

if (values.containsKey(Diary.DiaryColumns.TITLE) == false) {
Resources r = Resources.getSystem();
values.put(Diary.DiaryColumns.TITLE, r
.getString(android.R.string.untitled));
}

if (values.containsKey(Diary.DiaryColumns.BODY) == false) {
values.put(Diary.DiaryColumns.BODY, "");
}

SQLiteDatabase db = mOpenHelper.getWritableDatabase();
long rowId = db.insert(DIARY_TABLE_NAME, DiaryColumns.BODY, values);
if (rowId > 0) {
Uri diaryUri = ContentUris.withAppendedId(
Diary.DiaryColumns.CONTENT_URI, rowId);
return diaryUri;
}

throw new SQLException("Failed to insert row into " + uri);
}

@Override
public int delete(Uri uri, String where, String[] whereArgs) {
SQLiteDatabase db = mOpenHelper.getWritableDatabase();
String rowId = uri.getPathSegments().get(1);
return db
.delete(DIARY_TABLE_NAME, DiaryColumns._ID + "=" + rowId, null);

}

@Override
public int update(Uri uri, ContentValues values, String where,
String[] whereArgs) {
SQLiteDatabase db = mOpenHelper.getWritableDatabase();
String rowId = uri.getPathSegments().get(1);
return db.update(DIARY_TABLE_NAME, values, DiaryColumns._ID + "="
+ rowId, null);

}

public static String getFormateCreatedDate() {
Calendar calendar = Calendar.getInstance();
String created = calendar.get(Calendar.YEAR) + "年"
+ calendar.get(Calendar.MONTH) + "月"
+ calendar.get(Calendar.DAY_OF_MONTH) + "日"
+ calendar.get(Calendar.HOUR_OF_DAY) + "时"
+ calendar.get(Calendar.MINUTE) + "分";
return created;
}
}



package com.eoeAndroid.contentProvider;

import android.net.Uri;
import android.provider.BaseColumns;


public final class Diary {
    public static final String AUTHORITY = "com.ex09_2_contentprovider.diarycontentprovider";

    private Diary() {}
   
    /**
     * Notes table
     */
    public static final class DiaryColumns implements BaseColumns {
        // This class cannot be instantiated
        private DiaryColumns() {}

        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/diaries");


        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.google.diary";


        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.google.diary";


        public static final String DEFAULT_SORT_ORDER = "created DESC";

        public static final String TITLE = "title";

        public static final String BODY = "body";

        public static final String CREATED = "created";


    
    }