Sqlitedatabase help use of sqliteopenhelper

Sqliteopenhelper is a help class for sqlitedatabse to manage data creation and version updates. The general usage is to define a class that inherits sqliteopenhelper and implement two callback Methods: oncreate (sqlitedatabase dB) and onupgrade (sqlitedatabse, int oldversion, int newversion) to create and update databases, I used the database to provide a function similar to a telephone book, which inserts data, queries data, and deletes data. The interface is ugly. It mainly explains the usage of the sqliteopenhelper class, as shown below:

 

First, we create a dbhelper inherited from sqliteopenhelper, which is a help class of the database.

Package COM. example. utils; import android. content. contentvalues; import android. content. context; import android. database. cursor; import android. database. SQLite. sqlitedatabase; import android. database. SQLite. sqlitedatabase. cursorfactory; import android. database. SQLite. sqliteopenhelper; public class dbhelper extends sqliteopenhelper {private final static int version = 1; private final static string db_name = "Phones. DB "; private final static string table_name =" phone "; private final static string create_tbl =" create table phone (_ id integer primary key autoincrement, Name text, sex text, number text, desc text) "; private sqlitedatabase dB; // a required constructor for the sqliteopenhelper subclass public dbhelper (context, string name, cursorfactory factory, int Version) {// The constructor super (context, name, factory, Ver) of the parent class must be called through Super Sion);} // database constructor. Public dbhelper (context, string name, int version) {This (context, name, null, version);} // database constructor. If a parameter is passed, the database name and version number are all written to public dbhelper (context) {This (context, db_name, null, version);} // callback function. This function is called only during the first creation to create a database @ overridepublic void oncreate (sqlitedatabase dB) {This. DB = dB; system. out. println ("create database" using mongodb.exe csql (create_tbl);} // callback function. When you construct The passed version and previous version call this function @ overridepublic void onupgrade (sqlitedatabase dB, int oldversion, int newversion) {system. out. println ("Update Database");} // Insertion Method public void insert (contentvalues values) {// obtain sqlitedatabase instance sqlitedatabase DB = getwritabledatabase (); // Insert the database. insert (table_name, null, values); dB. close () ;}// query method public cursor query () {sqlitedatabase DB = getreadabledatabase (); // obtain cursorcursor C = dB. query (table_name, null, null); Return C ;}// Delete public void Delete (int id) data based on the unique identifier _ id) {sqlitedatabase DB = getwritabledatabase (); dB. delete (table_name, "_ id =? ", New string [] {string. valueof (ID)});} // update public void Update (contentvalues values, string whereclause, string [] whereargs) {sqlitedatabase DB = getwritabledatabase (); dB. update (table_name, values, whereclause, whereargs);} // close the public void close () {If (DB! = NULL) {dB. Close ();}}}

The first mainactivity

Package COM. example. phonebooks; import android. app. activity; import android. content. contentvalues; import android. content. intent; import android. OS. bundle; import android. view. view; import android. view. view. onclicklistener; import android. widget. button; import android. widget. edittext; import android. widget. radiobutton; import android. widget. radiogroup; import android. widget. radiogroup. oncheckedchangelistener; Import android. widget. toast; import COM. example. utils. dbhelper; public class mainactivity extends activity implements onclicklistener {private dbhelper; // define three input boxes private edittext name, number, DESC; // define two buttons private button submit, look; // define a radiogroupprivate radiogroup radio; private string namestr, numberstr, descstr; private string sexstr = "male"; @ overrideprotected void oncreate (bundle savedinst Ancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. activity_main); // instantiate dbhelperdbhelper = new dbhelper (this); // obtain the corresponding control name = (edittext) findviewbyid (R. id. edittext1); number = (edittext) findviewbyid (R. id. edittext2); DESC = (edittext) findviewbyid (R. id. edittext3); Submit = (button) findviewbyid (R. id. button1); look = (button) findviewbyid (R. id. button2); Radio = (radiogroup) findviewb Yid (R. id. radiogroup1); // click the button to set the listener to submit. setonclicklistener (this); look. setonclicklistener (this); // listener for radio groups. setoncheckedchangelistener (New oncheckedchangelistener () {@ overridepublic void oncheckedchanged (radiogroup group, int checkedid) {If (checkedid = R. id. radio0) {radiobutton r = (radiobutton) group. findviewbyid (checkedid); sexstr = R. gettext (). tostring ();} If (checkedid = R. id. radio1) {radiobutto N r = (radiobutton) group. findviewbyid (checkedid); sexstr = R. gettext (). tostring () ;}}) ;}@ overridepublic void onclick (view v) {Switch (v. GETID () {case R. id. button1: If (name. gettext (). tostring (). length ()! = 0) {namestr = Name. gettext (). tostring ();} else {toast. maketext (getapplication (), "name cannot be blank", toast. length_short ). show (); return;} If (number. gettext (). tostring (). length ()! = 0) {numberstr = number. gettext (). tostring ();} else {toast. maketext (getapplication (), "the phone number cannot be blank", toast. length_short ). show (); return;} If (DESC. gettext (). tostring (). length ()! = 0) {descstr = DESC. gettext (). tostring ();} else {toast. maketext (getapplication (), "remarks cannot be blank", toast. length_short ). show (); return;} // instantiate a contentvalues. contentvalues is in the form of a key-value pair, and the key is the name of the database column, the value is the value contentvalues values = new contentvalues (); values. put ("name", namestr); values. put ("sex", sexstr); values. put ("Number", numberstr); values. put ("DESC", descstr); // call insert to insert database dbhelper. insert (values); // reset the reset (); break; case R. id. button2: intent = new intent (); intent. setflags (intent. flag_activity_clear_top); intent. setclass (this, resultactivity. class); startactivity (intent); break; default: Break ;}// reset edittextprivate void reset () {name. settext (""); number. settext (""); DESC. settext ("");}}

Activity_main.xml

<Relativelayout xmlns: Android = "http://schemas.android.com/apk/res/android" Android: layout_width = "fill_parent" Android: layout_height = "fill_parent" Android: Background = "#000000"> <textview Android: id = "@ + ID/textview1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alignparentleft = "true" Android: layout_alignparenttop = "true" Android: TEXT = "name" Android: textsize = "15 DP "/> <edittext Android: Id =" @ + ID/edittext1 "Android: layout_width =" wrap_content "Android: layout_height =" wrap_content "Android: layout_alignparentleft =" true "Android: layout_alignparentright = "true" Android: layout_below = "@ + ID/textview1" Android: EMS = "10"> <requestfocus/> </edittext> <radiogroup Android: id = "@ + ID/radiogroup1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" android Oid: layout_alignparentleft = "true" Android: layout_below = "@ + ID/edittext1"> <radiobutton Android: Id = "@ + ID/radio0" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: checked = "true" Android: text = "male"/> <radiobutton Android: id = "@ + ID/radio1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_aligntop = "@ + ID/radiogroup1" Android: layout_tor Ightof = "@ + ID/textview2" Android: text = ""/> </radiogroup> <textview Android: Id = "@ + ID/textview2" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alignparentleft = "true" Android: layout_below = "@ + ID/radiogroup1" Android: TEXT = "phone number"/> <edittext Android: Id = "@ + ID/edittext2" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alig Nparentleft = "true" Android: layout_alignparentright = "true" Android: layout_below = "@ + ID/textview2" Android: EMS = "10"/> <textview Android: id = "@ + ID/textview3" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alignparentleft = "true" Android: layout_below = "@ + ID/edittext2" Android: text = "Remarks"/> <edittext Android: Id = "@ + ID/edittext3" Android: layout_width = "wrap_content" Droid: layout_height = "wrap_content" Android: layout_alignparentleft = "true" Android: layout_alignparentright = "true" Android: layout_below = "@ + ID/textview3" Android: lines = "5" Android: EMS = "10" Android: inputtype = "textmultiline"/> <button Android: Id = "@ + ID/button2" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_alignparentbottom = "true" Android: layout_alignparentleft = "True" Android: layout_alignparentright = "true" Android: text = ""/> <button Android: Id = "@ + ID/button1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: Rule = "true" Android: layout_alignparentright = "true" Android: layout_below = "@ + ID/edittext3" Android: TEXT = "insert"/> </relativelayout> uses a person class to encapsulate the data such as name, gender, phone number, and remarks. There are only get () and set () methods.

Package COM. example. mode; public class person {private string name; private string sex; private string number; private string DESC; private int _ id; Public int get_id () {return _ id ;} public void set_id (INT _ id) {This. _ id = _ id;} Public String getname () {return name;} public void setname (string name) {This. name = Name;} Public String getsex () {return sex;} public void setsex (string sex) {This. sex = sex;} Public String getnumber () {return number;} public void setnumber (string number) {This. number = number;} Public String getdesc () {return DESC;} public void setdesc (string DESC) {This. desc = DESC ;}} view the resultactivity of the data

Package COM. example. phonebooks; import Java. util. arraylist; import Java. util. list; import android. app. activity; import android. app. alertdialog; import android. content. context; import android. content. dialoginterface; import android. content. dialoginterface. onclicklistener; import android. database. cursor; import android. OS. bundle; import android. view. layoutinflater; import android. view. view; import android. view. V Iewgroup; import android. widget. adapterview; import android. widget. adapterview. onitemclicklistener; import android. widget. baseadapter; import android. widget. listview; import android. widget. textview; import COM. example. mode. person; import COM. example. utils. dbhelper; public class resultactivity extends activity implements onitemclicklistener {private listview; private dbadapter adapter; dbhelper dbel Per; List <person> booklist = new arraylist <person> (); @ overrideprotected void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. result); // obtain listviewlistview = (listview) findviewbyid (R. id. listview1); booklist = querydata (); // instantiate dbadapteradapter = new dbadapter (getapplication (), booklist); listview. setadapter (adapter); listview. setonitemclicklistener (this );}/ /Query the database, encapsulate each row of data into a person object, and then add the object to the list private list <person> querydata () {list <person> List = new arraylist <person> (); dbhelper = new dbhelper (this); // call query () to obtain cursorcursor c = dbhelper. query (); While (C. movetonext () {int _ id = C. getint (C. getcolumnindex ("_ id"); string name = C. getstring (C. getcolumnindex ("name"); string sex = C. getstring (C. getcolumnindex ("sex"); string number = C. getstring (C. getco Lumnindex ("Number"); string DESC = C. getstring (C. getcolumnindex ("DESC"); // use a person object to encapsulate the queried data person P = new person (); p. set_id (_ id); p. setname (name); p. setsex (sex); p. setnumber (number); p. setdesc (DESC); list. add (p) ;}return list ;}// customize dbadapterpublic class dbadapter extends baseadapter {private list <person> list; private context; private layoutinflater; Public dbadapter (context cont EXT, list <person> List) {layoutinflater = layoutinflater. from (context); this. context = context; this. list = List;} // refresh the adapter public void refresh (list <person> List) {This. list = List; policydatasetchanged () ;}@ overridepublic int getcount () {return list. size () ;}@ overridepublic object getitem (INT position) {return list. get (position) ;}@ overridepublic long getitemid (INT position) {return position ;}@ overridepubli C view getview (INT position, view convertview, viewgroup parent) {person P = List. get (position); viewholder holder; If (convertview = NULL) {holder = new viewholder (); convertview = layoutinflater. inflate (R. layout. item, null); holder. name = (textview) convertview. findviewbyid (R. id. textview1); holder. sex = (textview) convertview. findviewbyid (R. id. textview2); holder. number = (textview) convertview. findvie Wbyid (R. id. textview3); holder. desc = (textview) convertview. findviewbyid (R. id. textview4); convertview. settag (holder);} else {holder = (viewholder) convertview. gettag ();} holder. name. settext (P. getname (); holder. sex. settext (P. getsex (); holder. number. settext (P. getnumber (); holder. desc. settext (P. getdesc (); Return convertview;} public class viewholder {public textview name; Public textview sex; Public textvi EW number; Public textview DESC; Public textview ID; }}@ overridepublic void onitemclick (adapterview <?> Parent, view, final int position, long ID) {final person P = Booklist. get (position); Final long temp = ID; alertdialog. builder = new alertdialog. builder (this); builder. setmessage ("are you sure you want to delete this record? "). Setpositivebutton ("yes", new onclicklistener () {@ overridepublic void onclick (dialoginterface dialog, int which) {// call Delete () to delete a data record dbhelper. delete (P. get_id (); // refresh the adapter. refresh (querydata ());}}). setnegativebutton ("no", new onclicklistener () {@ overridepublic void onclick (dialoginterface dialog, int which ){}}). create (). show (); // disable dbhelper. close () ;}display the Data Layout result. XML, which contains only one listview

<?xml version="1.0" encoding="UTF-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent" >    <ListView        android:id="@+id/listView1"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:layout_alignParentLeft="true"        android:cacheColorHint="#00000000"        android:layout_alignParentTop="true" >    </ListView></RelativeLayout>

Item of listview

<?xml version="1.0" encoding="UTF-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent" >    <TextView        android:id="@+id/textView1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_alignParentTop="true"        android:text="TextView" />    <TextView        android:id="@+id/textView3"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_above="@+id/textView4"        android:layout_alignParentRight="true"        android:text="TextView" />    <TextView        android:id="@+id/textView2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_above="@+id/textView4"        android:layout_centerHorizontal="true"        android:text="TextView" />    <TextView        android:id="@+id/textView4"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_alignParentRight="true"        android:layout_below="@+id/textView1"        android:layout_marginTop="19dp"        android:text="TextView" /></RelativeLayout>

Do not forget to register resultactivity in androidmanifest. xml.

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