1 Introduction Database
sqlite
Under what circumstances the use of database
There are large amounts of data need to be stored similar structure when
Creating a database of 2
Define a class that inherits sqliteOpenhelper
OpenHelper used to open the database
Rewrite abstract methods
/ **
*
* @param context SA
* name: Ming word database
* factory aim to create a cursor object
* version version of the database from the beginning 1
* /
public MyOpenHelper (Context context) {
Super (context, "suzuna.db", null , 1);
}
create objects of OpenHelper
MyOpenHelper helper = new MyOpenHelper(getApplicationContext());
调用
.getWritableDatabase ();
method to open or create a database, and if the first call is to create a database, such as:
SQLiteDatabase database = helper.getWritableDatabase();
transfer
.getReadableDatabase ();
method to open or create a database, and if the first call is to create a database, if the disk is full read-only database object is returned, such as:
SQLiteDatabase database = helper.getReadableDatabase();
SQLiteDatabase object provides a method of operation of the database management
default constructor
Method 3 OnCreate method database and OnUpgrade
OnCreate: when the database was first created is called, this method is particularly suitable for initialization table structure
You need to use sql statement to create table
id usually begins with an underscore _
db.execSQL( "create table info (_id integer primary key autoincrement , name varchar(20) )" );
Db file generated using SQLite Expert Professional Open
OnGrade: when the database is upgraded version, which will be called
This method is suitable for the update table structure
For example, to increase a data table information, perform the following sql statement
db.execSQL("alter table info add phone varchar(20)");
When you open the same directory db file must have wal shm file and read the contents of less than or database (
4 Use the sql statement to the database additions and deletions to change search
Enter the execution of SQL in SQLite Expert Professional interface
Insert data insert into info (name, phone) values ( 'www', '1377770')
Modify the data update info set phone = '2313123' where name = 'www'
Query data select name, phone from info query name and phone columns from the table info
Or select * from info query all the columns from the table info
You can also limit the scope of what line of inquiry
Returns a cursor object that can traverse a query to a database table
Delete data delete from info where name = 'www' delete information from the called www info table
SQL parameter placeholders -?> Then use an array to replace bit
Contents of the database can be operated directly write sql statement is executed, you can also use the direct method APi provided by Google engineer database operation
Disadvantages: 1 sql statement is easy to mistake
Sql statement 2 performs no return value is not easily determined
Advantages: easy multi-table query
supplement:
Using the command line tool can open a database Sqlite3
Enter the command sql database operations
Changing dos encoding chcp 936 adapted for encoding GBK
Dos change chco 65001 encoding changed to utf-8 encoded
5 api packaged using Google database search changes, additions or deletions
Call the object's method of operation SqlitDatabase
Add a record
db.insert(table,nullColimnHack,values);
Name of the table: table
nullComlimnHack may be null
ContentValues inside a package name map in which the map is to insert a column key, value the value of this row is inserted
ContentValues values = new ContentValues();
values.put(name,values);
....
After inserting the return value represents a successful new line of id, data type is long
Delete Record
db.delete(tablename,whereClause,WhereArg);
"name=?"
update record
db.update(table,values,whereClause,whereArgs);
Returns the number of deleted rows int
inquiry record
Cursor c = db.query(...)
The method is passed underlying parameters Assembling sql
Advantages: simple and does not require writing complex and error-prone sql statement not return a value may be determined whether the operation is successful
Cons: If you have multiple tables using Google api can not be easily packaged inquiry
62 Species deletions search changed disadvantages
Services introduced 7 Android in the database
Services: the implementation of a logic, either all succeed or fail
Call the method
db.beginTransition ()
Using a template provided by Google write the business logic, if an error occurs logic is automatically rolled back to before execution, otherwise success.
The entry-8 listview
0 define the layout listView
1 find control by id
findViewById
2 shows the data and common controls are not the same, data from the data adapter ListAdapter
ListViewAdapter is the interface can not be used directly, so you can own or use his implementation class
For example, can be inherited from BaseAdapter and four abstract methods
1 definition of a data adapter listView
2 getCount getView method and the method implemented baseAdapter
GetCount method is responsible for controlling the number of entries to be displayed
getView method is responsible for controlling each entry to show what controls
The adapter 3 is disposed listView
9 listview optimization
GetView method will be called upon when listView entry into the screen is displayed, but if the entry is a lot of fast display, memory overflow error occurs, because the new View object has not been enough time to clean up, the program stops running
This is when you need to use converVew argument, he represented the previously used View, called the history cache object, if it is empty, that is first displayed, you can only create a new View to display content, and content to be displayed after ConverView can be used directly without re-created, so as to avoid because creating too many objects cause memory overflow View
10 listview display principle data
MVC
JavaWeb:
M: mode data
V: View View jsp
C: controller controller servlet
Android：
M: mode data (javaBean)
V：View listView
C: adapter adapter
The best listView high to match the parent space
11 listview display complex pages
The preparation of the interface to be displayed as a layout file, then through the pump api View this layout file into a file, and then returns the process getView displayed as entry listView
Linear layout relative layout inherits from ViewGroup, description of these components can have their own sub-layout, which can be put in other components and sub-layout, rather than inherited from ViewGroup controls such as TextView, etc. can not put other controls inside
Use View.inflate methods
12 pump used to obtain api
Pump method for obtaining services
1。 View v = View.inflate（）
2. View view = LayoutInflater.from（）.inflate（）
3. LayoutInflater inflater = getSystemService（LAYOUT_INFLATER_SERVICE）;
View v = inflater.inflate（）；
13 arrayAdapter use
1 Definitions listView
2 declaration Adapter
如 ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.item,objects)
item layout file is a list of items for displaying data
3 Set adapter
14 simpleAdapter use
1 Definitions listView
2 Prepare the required data, List <? Extends Map <String,? >> data
2 declaration Adapter
如 SimpleAdapter adapter = new SimpleAdapter(context,data,resource,from,to);
context is the context where listView
data is the data to be displayed, he is a collection of a set of map objects
resource is a list of items item layout file
from a String [] object stored key map key pairs
It is to int [] id item stored inside each component, id corresponding key that corresponds to the content for display
item layout file is a list of items for displaying data
3 Set adapter
Data out 15 query the database to display on listView
0 lv Found
1 from the database to check out the data, encapsulated in javabean
2 javabean data displayed on listview
Setting data adapter 3
16 summary
How to create a database
Define a class that inherits SqliteOpenHelper
SQLiteDatabase; operation of the database
oncreate method: When you first create a database call, suitable for a database table initialization
onupgrade: When the database is updated version is called
The first way to change the database search deletions
Traditional sql statement
Google engineers provided us with api master the operation of the database
Command-line tool can open a database sqlite3 practice
Transaction database, practice
listview display master data
baseAdapter master
Gets pump grasp of common api
1 View.inflate
2 LayoutInflater.from(...).inflate()
3 LayoutInflater inflater = context.getSystemService(LAYOUT_INFLATE_SERVICE);
view = inflater.inflate(...);
ArrayAdapter master
simpleAdapter understand