Android：自定义ContentProvider
1.创建一个类继承SQLiteOpenHelper（若使用SQLite）:
public class MySQLiteHelper extends SQLiteOpenHelper
{
//重写构造方法
public MySQLiteHelper(Context context, String name, CursorFactory factory,
int version)
{
super(context, name, factory, version);
}
//创建表
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL("CREATE TABLE person(personid INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),phone VARCHAR(20))" );
}
//升级表（当Database的Version低于当前new里的Version，直接执行下面方法）
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
int v = newVersion - oldVersion;
if(v > 0)
{
db.execSQL("ALTER TABLE person ADD salary3 VARCHAR(20)");
}
}
}
2.创建自定义ContentProvider：
public class MyContentProvider extends ContentProvider
{
private MySQLiteHelper mDBHelper;
public MyContentProvider()
{
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
int i = db.delete("person", selection,selectionArgs);
return i;
}
@Override
public String getType(Uri uri)
{
throw new UnsupportedOperationException("Not yet implemented");
}
//创建Uri
private static final Uri URI = Uri.parse("content://com.example.cpone");
@Override//插入
public Uri insert(Uri uri, ContentValues values)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
long id = db.insert("person", null , values);
return ContentUris.withAppendedId(URI, id); //相当于原先的Uri加上插入的行号
}
@Override
public boolean onCreate()//创建表
{
mDBHelper = new MySQLiteHelper(getContext(), "person", null, 1);
return false;
}
@Override//查询
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
Cursor cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder);
return cursor;
}
@Override//修改
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
int i = db.update("person", values, selection, selectionArgs);
return i;
}
}
3.在另一个项目里使用自定义ContentProvider：
public class MyContentProvider extends ContentProvider
{
private MySQLiteHelper mDBHelper;
public MyContentProvider()
{
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
int i = db.delete("person", selection,selectionArgs);
return i;
}
@Override
public String getType(Uri uri)
{
throw new UnsupportedOperationException("Not yet implemented");
}
//创建Uri
private static final Uri URI = Uri.parse("content://com.example.cpone");
@Override//插入
public Uri insert(Uri uri, ContentValues values)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
long id = db.insert("person", null , values);
return ContentUris.withAppendedId(URI, id); //相当于原先的Uri加上插入的行号
}
@Override
public boolean onCreate()//创建表
{
mDBHelper = new MySQLiteHelper(getContext(), "person", null, 1);
return false;
}
@Override//查询
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
Cursor cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder);
return cursor;
}
@Override//修改
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs)
{
SQLiteDatabase db = mDBHelper.getWritableDatabase();
int i = db.update("person", values, selection, selectionArgs);
return i;
}
}
注：
1.ContentProvider仍在主线程上运行，但对他的调用是异步的，不使用消息队列。
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