Android Learning notes-eighth data storage

Chapter Eighth data storage

2. How data is stored

   Internal Storage Internal Storage

   External Storage External Storage

   SQLite Database Storage

   Http Network Storage

4. shared prefrences parameter sharing

   Storage location: data/data/Package name/shared_prefs/mainacitivy.xml

   Format: xml

   Save data:

   //Get shared Prefrences type Object

   Sharedprefrences sp = getsharedprefrences ("xxx", 0);

   or

   Sharedprefrences sp = getprefrences (0);

   //Get an object of type edit

   Edit edit = Sp.edit ();

   //Write Data

   Edit.putstring ("name", "Xiaoming");

   Edit.putboolean ("IsTrue", "true");

   //Submit data ( must have )

   
   

   
   

   Extract data

   /Get Sharedprefrences type Object

   Sharedprefrences sp = getsharedprefrences ("xxx", 0);

   or

   Sharedprefrences sp = getprefrences (0);

   //Remove the corresponding data based on the key value stored

   String name = sp.getstring ("name", Little Red);

   Boolean B = Sp.getboolean ("IsTrue", false);

6. Internal Storage Internal Storage

   Storage location: data/data/Package Name/files/xxx.xxx

   Format: Custom

   Save data:

   FileOutputStream fos = openfileoutput ("AAA", 0);

   String str = "data store";

   Fos.write (Str.getbytes ());

   Reading data

   FileInputStream FIS = openfileinput ("AAA");

   Bytearraybuffer ArrayBuffer = new Bytearraybuffer (100);

   Byte[] B = new byte[1024];

   int len = 0;

   while ( -1!= (Len=fis.read (b))) {

   Arraybuffer.append (B,0,len);

   }

   String str = new String (Arraybuffer.tobytearray ());

8. External Storage External Storage

   Storage location: Mnt/sdcard

   Read permissions:

   (1) SDcard path:

   Environment.getexternalstoragedirectory (). GetAbsolutePath ();

   (2) Determine if SDcard is available:

   Environment.MEDIA_MOUNTED.equals (Environment.getexternalstoragestate ());

9. SQLite Database Storage

   Android Platform Integration Small database SQLite

   Features: cross-platform, free, lightweight, multi-threaded

   SQL statements:

   Related to table:

   A. Build table: CREATE table table name (ID INTEGER PRIMARY KEY autoincrement,name varchar), phone varchar (20))

   B. Deletion of tables: DROP table name

   C. Change table: ALERT table name ADD age INTEGER

   Related to data: increase, delete, change, check

   A. Adding data: INSERT into table name (field name) values (value)

   B. Deleting data: Delete from table name WHERE condition

   C. Modifying data: UPDATE table name SET field name = value WHERE condition

   D. Querying data: SELECT * FROM table name WHERE condition GROUP BY grouping order by sort

   Steps to create a SQLite database:

   A. Creating an auxiliary class to inherit Sqliteopenhelper

   B. In the OnCreate () method of the auxiliary class, add the statement that creates the table and execute the statement

   String str = "CREATE TABLE student (id integer PRIMARY KEY autoincrement,name varchar (), age INTEGER, phone VARCHAR (20))" ;

   Db.execsql (str);

   C. In activity, create a secondary class object, and then use the helper class object to call getreadabledatabase () or getwriteabledatabase () to create the database object

   Note: When both the database and the table already exist, the OnCreate () method no longer calls the

   When version changes, the Onupgrade () method is called

   SQL statement instance:

   (1) Increase

   String str = "INSERT into student (Name,phone) VALUES (?,?)";

   Mdb.execsql (str,new string[]{"Xiao Ming", "1111"});

   (2) by deleting

   String str = "DELETE from student WHERE name =?";

   Mdb.execsql (str,new string[]{"Xiao Ming"});

   (3) Change

   String str = "UPDATE student SET name =?, phone =?" WHERE id =? ";

   Mdb.execsql (str,new string[]{"Little Red", "2222", "1"});

   (4) Check

   String str = "SELECT * from student";

   cursor cursor = mdb.rawquery (str,null);

   while (Cursor.movetonext ()) {

   Get the index of each field value

   int idindex = Cursor.getcolumnindex ("id");

   int nameindex = Cursor.getcolumnindex ("name");

   int phoneindex = Cursor.getcolumnindex ("Phone");

   Extracting data based on index

   String id = cursor.getstring (idindex);

   String name = cursor.getstring (Nameindex);

   String phone = cursor.getstring (Phoneindex);

   }

   ORM Object Relational Mapping

   (1) Increase

   Contentvalues values = new Contentsvalues ();

   Values.put ("name", "small white");

   Values.put ("Phone", "12356");

   Mdb.insert ("Student",//table name

   null;//Avoiding Insert Errors

   values);//The value inserted

   (2) by deleting

   Mdb.delete ("Student",//table name

   "Name=?", conditional statement

   New string[]{"Small white"}); placeholder padding

   (3) Change

   Contentvalues values = new Contentvalues ();

   Values.put ("Phone", "45621");

   Mdb.update ("Student",//table name

   values,//the value that will be modified

   "Name=?", conditional statement

   New string[]{"Small white"});//Placeholder padding

   (4) Check

   cursor cursor = mdb.query ("Student",//table name

   Fields for null,//queries

   null,//Query criteria

   null,//the fill of a conditional statement placeholder

   null,//grouping statements

   null,//padding for grouping statement placeholders

   NULL);//Sort statement

   while (Cursor.movetonext ()) {

   Get field Index

   int nameindex = Cursor.getcolumnindex ("name");

   Extracting data based on index

   String name = cursor.getstring (Nameindex);

   }

10. CursorAdapter Leng Adapter

    Note: Must contain _id

    Converting a layout XML file into a layout object

    @Override

    Public View Newview (context context, cursor cursor, viewgroup parent) {

    View inflate = Getlayoutinflater (). Inflate (R.layout.list_item, NULL);

    return inflate;

    }

    Set up data display

    @Override

    public void BindView (view view, context context, cursor cursor) {

    TextView textView1 = (TextView) View.findviewbyid (R.ID.TEXTVIEW1);

    TextView textView2 = (TextView) View.findviewbyid (R.ID.TEXTVIEW2);

    Get Data

    String name = cursor.getstring (Cursor.getcolumnindex ("name"));

    String phone = cursor.getstring (Cursor.getcolumnindex ("Phone"));

    Setting property values

    Textview1.settext (name);

    Textview2.settext (phone);

    }

    Update data

    Re-query to get a new cursor object

    cursor cursor = mdb.query ("student", NULL, NULL, NULL, NULL, NULL, NULL);

    To set the latest cursor object to the adapter

    Madapter.changecursor (cursor);

    Refresh Display

    Madapter.notifydatasetchanged ();

Android Learning note-eighth data storage