Android--database Data Display to screen

<span id="Label3"></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><strong>Mainactivity.java</strong></p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><strong>The purpose of this code is to get the data from the database and display it on the Interface.</strong></p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><strong></strong></p></p><pre code_snippet_id="1585325" snippet_file_name="blog_20160223_1_8426703" name="code" class="java"> Import Java.util.arraylist;import java.util.List; Import com.itheima.showdata.domain.Person; Import Android.os.bundle;import Android.app.activity;import Android.database.cursor;import Android.database.sqlite.sqlitedatabase;import Android.view.menu;import Android.widget.linearlayout;import android.widget.TextView; public class Mainactivity extends Activity {list<person> personlist; @Override protected void onCreate (Bundle Savedinstancestate) {super.oncreate (savedinstancestate); Setcontentview (r.layout.activity_main); personlist = new Arraylist<person> (); Query the database data//write this here, because in the Myopenhelper Super constructor, has already written dead three other parameters; myopenhelper oh = new Myopenhelper (this); Sqlitedatabase db = Oh.getwritabledatabase (); cursor cursor = db.query (person, null, null, null, null, null, null, null); While (cursor.movetonext ()) {String _id = cursor.getstring (0); String name = Cursor.getstriNg (1); String salary = cursor.getstring (2); String phone = cursor.getstring (3); To encapsulate these values in a class, this idea must be learned; since p is a local variable here, the container that defines the global variable of the//list to hold the variable p of person type; the key to learn the thought of others; human p = NE W person (_id, name, phone, salary); Personlist.add (p); } linearlayout ll = (linearlayout) Findviewbyid (r.id.ll); Display data to screen for (person P:personlist) {//note that TextView can be created separately, except in Layout,//because It is also a class, is a sub-class below the view class, but at this time the Textview//and layout is not associated, so remember to add the 3rd step//1. each element in the collection is a new TextView TEXTV Iew TV = new TextView (this); 2. Set the Character's information to the text box content Tv.settext (p.tostring ()); Tv.settextsize (18); Setting the above two statements does not display the TextView on the interface,//so a third step is needed to correlate it with layout;//3. set TextView as a sub-node of a linear layout ll.addvi EW (tv); } } }</pre><br><p><p></p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><strong>Note:</strong> When we have a lot of data, then new person is also a lot, at the same time,</p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px">New out of the TextView are also many, then the memory may not be able to carry;</p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px">To do is: what data do we need to create the data when it is displayed on the interface,</p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px">Instead of creating them all at once, so we use the ListView as much as possible</p></p><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px">Further Optimization.</p></p><pre code_snippet_id="1585325" snippet_file_name="blog_20160223_2_2919042" name="code" class="java"><pre code_snippet_id="1585325" snippet_file_name="blog_20160223_2_2919042" name="code" class="java">import java.sql.ResultSet; Import Android.content.context;import Android.database.sqlite.sqlitedatabase;import Android.database.sqlite.sqlitedatabase.cursorfactory;import android.database.sqlite.SQLiteOpenHelper; public class Myopenhelper extends Sqliteopenhelper {public myopenhelper (context context) {super (context, peop le.db, null, 1); TODO auto-generated Constructor}//when The database is created, this method calls @Override public void OnCreate (sqlitedatabase Db) { Db.execsql (create Table Person (_id integer PRIMARY key autoincrement, name Char (ten), salary char), phone intege R (20))); }//database upgrade, This method calls @Override public void Onupgrade (sqlitedatabase db, int oldversion, int Newversion) {Sy Stem.out.println (database upgraded); }}</pre></pre><span style="color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px; text-indent:28px">the <span style="color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px; text-indent:28px">purpose of this code is to add data into the database</span></span><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><p style="border-width:0px; padding-top:0px; padding-bottom:0px; margin-top:0px; margin-bottom:8px; list-style:none; text-indent:2em; color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px"><strong></strong></p></p><pre code_snippet_id="1585325" snippet_file_name="blog_20160223_3_1905287" name="code" class="java">Import com.itheima.showdata.MyOpenHelper; Import Android.content.contentvalues;import Android.database.sqlite.sqlitedatabase;import android.test.AndroidTestCase; public class TestCase extends Androidtestcase {private myopenhelper oh; Private Sqlitedatabase db; After the test framework is initialized, This method calls @Override protected void SetUp () throws Exception {super.setup () before the test method executes; Oh = new Myopenhelper (getcontext ()); db = Oh.getwritabledatabase (); This method calls @Override protected void TearDown () throws Exception {//TODO auto-generated method After the test method has finished Executing) Stub Super.teardown (); Db.close (); } public void Insertapi () {//wrap The data to be inserted into the Contentvalues object for (int i = 0; I <; i++) { Contentvalues values = new Contentvalues (); Values.put (name, Zhao +i); Values.put (phone, 159+i+i); Values.put (salary, 160+i+i); Db.insert (person, null, values); } } }</pre><br><br><br><p><p></p></p><p><p>Android--database Data Display to screen</p></p></span>