Android ListView _ displays database data, androidlistview

Android ListView _ displays database data, androidlistview

Xml

<? Xml version = "1.0"?> -<LinearLayout tools: context = ". mainActivity "android: orientation =" vertical "android: paddingTop =" @ dimen/activity_vertical_margin "android: paddingRight =" @ dimen/activity_horizontal_margin "android: paddingLeft = "@ dimen/users" android: paddingBottom = "@ dimen/activity_vertical_margin" android: layout_height = "match_parent" android: layout_width = "match_parent" xmlns: tools = "http://schemas.android.com/tools" xmlns: android = "http://schemas.android.com/apk/res/android"> <Button android: id = "@ + id/bt_add" android: layout_height = "wrap_content" android: layout_width = "fill_parent" android: text = "@ string/add"/> <Button android: id = "@ + id/bt_del" android: layout_height = "wrap_content" android: layout_width = "fill_parent" android: text = "@ string/del"/> <Button android: id = "@ + id/bt_update" android: layout_height = "wrap_content" android: layout_width = "fill_parent" android: text = "@ string/update"/> <Button android: id = "@ + id/bt_query" android: layout_height = "wrap_content" android: layout_width = "fill_parent" android: text = "@ string/query"/> <ListView android: id = "@ + id/lv_databases" android: layout_height = "match_parent" android: layout_width = "fill_parent"/> </LinearLayout>Database button Design

 

Java

Package com. itheima. crud; import java. util. arrayList; import android. app. activity; import android. content. context; import android. database. sqlite. SQLiteDatabase; import android. OS. bundle; import android. view. view; import android. view. view. onClickListener; import android. widget. listView; import android. widget. toast; import com. itheima. crud2_listview.R; import com. itheima. crud. adapter. queryAdapter; import com. itheima. crud. bean. infoBean; import com. itheima. crud. dao. infoDao; public class MainActivity extends Activity implements OnClickListener {private Context mContext; private ListView lv_databases; @ Override protected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. activity_main); mContext = this; // create a help Class Object MySqliteOpenHelper mySqliteOpenHelper = new helper (mContext); // call the getReadableDatabase method to initialize the database creation SQLiteDatabase db = MySqliteOpenHelper. getReadableDatabase (); // find the findViewById (R. id. bt_add ). setOnClickListener (this); findViewById (R. id. bt_del ). setOnClickListener (this); findViewById (R. id. bt_update ). setOnClickListener (this); findViewById (R. id. bt_query ). setOnClickListener (this); // find listview lv_databases = (ListView) findViewById (R. id. lv_databases) ;}@ Override public void onClick (View v) {InfoDao infoDao = new InfoDao (mContext); // create a dao object for addition, deletion, modification, and query switch (v. getId () {case R. id. bt_add: InfoBean bean = new InfoBean (); bean. name = "Zhang San"; bean. phone = "110"; boolean result = infoDao. add (bean); if (result) {Toast. makeText (mContext, "added successfully", 0 ). show ();} else {Toast. makeText (mContext, "failed to add", 0 ). show ();} break; case R. id. bt_del: int del = infoDao. del ("James"); Toast. makeText (mContext, "successfully deleted" + del + "row", 0 ). show (); break; case R. id. bt_update: InfoBean bean2 = new InfoBean (); bean2.name = "zhangsan"; bean2.phone = "119"; int update = infoDao. update (bean2); Toast. makeText (mContext, "modified successfully" + update + "row", 0 ). show (); break; case R. id. bt_query: // obtain the queried data ArrayList <InfoBean> arrayList = infoDao. query ("Zhang San"); // encapsulate adapter QueryAdapter queryAdapter = new QueryAdapter (mContext, arrayList); // set the adapter to listview lv_databases.setAdapter (queryAdapter); break; default: break ;}}}MainActivity

 

Package com. itheima. crud; import android. content. context; import android. database. sqlite. SQLiteDatabase; import android. database. sqlite. SQLiteDatabase. cursorFactory; import android. database. sqlite. SQLiteOpenHelper; public class MySqliteOpenHelper extends SQLiteOpenHelper {public MySqliteOpenHelper (Context context) {// context: Context, name: database file name factory: used to create a cursor object, the default value is null // version: the database version number. The onUpgrade method will be called if it changes from 1. After 4.0, the super (context, "info. db ", null, 1);} // The oncreate method is called when the database is created for the first time. It is especially suitable for table structure initialization and SQL statements need to be executed; SQLiteDatabase db can be used to execute SQL statements @ Override public void onCreate (SQLiteDatabase db) {// execute the SQL statement db.exe cSQL ("create table info (_ id integer primary key autoincrement, name varchar (20), phone varchar (11) for creating a table through SQLiteDatabase )) ");} // The onUpgrade database will be executed only when the version number of the database changes. It is particularly suitable for modifying the table structure @ Override public void onUpgrade (SQLiteDatabase db, int oldVersion, int newVersion) {// add a phone field // db.exe cSQL ("alter table info add phone varchar (11 )");}}MySqliteOpenHelper

 

Package com. itheima. crud. dao; import java. util. arrayList; import android. content. contentValues; import android. content. context; import android. database. cursor; import android. database. sqlite. SQLiteDatabase; import com. itheima. crud. mySqliteOpenHelper; import com. itheima. crud. bean. infoBean; public class InfoDao {private MySqliteOpenHelper mySqliteOpenHelper; public InfoDao (Context context) {// create a help class Object mySq LiteOpenHelper = new MySqliteOpenHelper (context);} public boolean add (InfoBean bean) {// sqliteDatabase object is required to execute the SQL statement // call the getReadableDatabase method, to initialize SQLiteDatabase db = mySqliteOpenHelper. getReadableDatabase (); ContentValues values = new ContentValues (); // It is an object encapsulated by map and used to store value values. put ("name", bean. name); values. put ("phone", bean. phone); // table: table Name, nullColumnHack: Can be empty, indicating that a blank row is added. values: the value of a Data row, Returned value: indicates the Id of the new row to be added.-1 indicates that the addition failed long result = db. insert ("info", null, values); // The underlying layer is to assemble SQL statements // close the database object db. close (); if (result! =-1) {//-1 indicates failed return true;} else {return false;} public int del (String name) {// sqliteDatabase object is required to execute the SQL statement // call the getReadableDatabase method to initialize the database creation SQLiteDatabase db = mySqliteOpenHelper. getReadableDatabase (); // table: table Name, whereClause: delete condition, whereArgs: parameter of the placeholder condition; Return Value: number of rows deleted successfully int result = db. delete ("info", "name =? ", New String [] {name}); // closes the database object db. close (); return result;} public int update (InfoBean bean) {// The sqliteDatabase object is required to execute the SQL statement // call the getReadableDatabase method to initialize the database creation SQLiteDatabase db = mySqliteOpenHelper. getReadableDatabase (); ContentValues values = new ContentValues (); // It is an object encapsulated by map and used to store value values. put ("phone", bean. phone); // table: table Name, values: updated value, whereClause: Updated condition, whereArgs: The placeholder value of the updated condition, return value: successfully modified number of rows int r Esult = db. update ("info", values, "name =? ", New String [] {bean. name}); // closes the database object db. close (); return result;} public ArrayList <InfoBean> query (String name) {ArrayList <InfoBean> list = new ArrayList <InfoBean> (); // The sqliteDatabase object is required to execute the SQL statement // call the getReadableDatabase method to initialize the database creation SQLiteDatabase db = mySqliteOpenHelper. getReadableDatabase (); // table: table Name, columns: column name to be queried. If null represents all columns to be queried. selection: Query condition, selectionArgs: parameter value of the condition placeholder, // groupBy: by which field group, havi Ng: grouping condition. orderBy: sort by field. Cursor cursor = db. query ("info", new String [] {"_ id", "name", "phone"}, "name =? ", New String [] {name}, null, null," _ id asc "); // parse the data in Cursor if (cursor! = Null & cursor. getCount ()> 0) {// checks whether data exists in the cursor. // traverses the result set cyclically and obtains the content of each row while (cursor. moveToNext () {// condition, can the cursor locate the next line of InfoBean bean = new InfoBean (); // obtain the data bean. id = cursor. getInt (0) + ""; bean. name = cursor. getString (1); bean. phone = cursor. getString (2); list. add (bean);} cursor. close (); // close the result set} // close the database object db. close (); return list ;}}Package dao

 

Package com. itheima. crud. bean; public class InfoBean {public String id; public String name; public String phone ;}Package bean

 

Package com. itheima. crud. adapter; import java. util. arrayList; import com. itheima. crud. bean. infoBean; import com. itheima. crud2_listview.R; import android. content. context; import android. view. view; import android. view. viewGroup; import android. widget. baseAdapter; import android. widget. textView; public class QueryAdapter extends BaseAdapter {private Context mContext; private ArrayList <InfoBean> arrayList; publ Ic QueryAdapter (Context mContext, ArrayList <InfoBean> arrayList) {this. mContext = mContext; this. arrayList = arrayList;} @ Override public int getCount () {return arrayList. size () ;}@ Override public Object getItem (int position) {return arrayList. get (position) ;}@ Override public long getItemId (int position) {return position ;}@ Override public View getView (int position, View convertView, ViewG Roup parent) {// reuse convertView View view = null; if (convertView! = Null) {view = convertView;} else {view = View. inflate (mContext, R. layout. item_database_layout, null);} // find the control TextView item_ TV _id = (TextView) view. findViewById (R. id. item_ TV _id); TextView item_ TV _name = (TextView) view. findViewById (R. id. item_ TV _name); TextView item_ TV _phone = (TextView) view. findViewById (R. id. item_ TV _phone); // find the content InfoBean infoBean = arrayList. get (position); // set the content item_ TV _id.setText (infoBean. id); item_ TV _name.setText (infoBean. name); item_ TV _phone.setText (infoBean. phone); return view ;}}Package adapter

 

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