java - Alert Dialog not displaying due to IllegalStateException -

when click on listview row, instead of showing alert dialog box, gives illegalstateexception. says use theme.appcompat theme. dont know , new plese me understand these appcompat activity , reason trouble.

java.lang.illegalstateexception: need use theme.appcompat theme (or descendant) activity.                   @ android.support.v7.app.appcompatdelegateimplv9.createsubdecor(appcompatdelegateimplv9.java:355)                   @ android.support.v7.app.appcompatdelegateimplv9.ensuresubdecor(appcompatdelegateimplv9.java:324)                   @ android.support.v7.app.appcompatdelegateimplv9.setcontentview(appcompatdelegateimplv9.java:285)                   @ android.support.v7.app.appcompatdialog.setcontentview(appcompatdialog.java:83)                   @ android.support.v7.app.alertcontroller.installcontent(alertcontroller.java:225)                   @ android.support.v7.app.alertdialog.oncreate(alertdialog.java:257)                   @ android.app.dialog.dispatchoncreate(dialog.java:397)                   @ android.app.dialog.show(dialog.java:298)                   @ com.example.stark.messenger.showdatabase$1.onitemclick(showdatabase.java:93)                   @ android.widget.adapterview.performitemclick(adapterview.java:310)                   @ android.widget.abslistview.performitemclick(abslistview.java:1145)                   @ android.widget.abslistview$performclick.run(abslistview.java:3081)                   @ android.widget.abslistview$3.run(abslistview.java:3947)                   @ android.os.handler.handlecallback(handler.java:739)                   @ android.os.handler.dispatchmessage(handler.java:95)                   @ android.os.looper.loop(looper.java:148)                   @ android.app.activitythread.main(activitythread.java:5441)                   @ java.lang.reflect.method.invoke(native method)                   @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:738)                   @ com.android.internal.os.zygoteinit.main(zygoteinit.java:628) 

the code main activity is:

import android.content.dialoginterface; import android.database.cursor; import android.database.sqlite.sqlitedatabase; import android.database.sqlite.sqliteopenhelper; import android.os.bundle; import android.support.v7.app.appcompatactivity; import android.view.view; import android.widget.adapterview; import android.widget.listview;  import java.util.arraylist;   public class showdatabase extends appcompatactivity { sqliteopenhelper expensedatabase; sqlitedatabase db; cursor cursor; listview lv; arraylist<datamodel> datamodels; private static customadapter adapter;   @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_show_database);     lv=(listview) findviewbyid(r.id.lv_custom_list);     expensedatabase = new expensedatabase(this);     db = expensedatabase.getreadabledatabase();  } protected void onstart() {     super.onstart();     datamodels = new arraylist<datamodel>();     datamodels.clear();     cursor = db.rawquery("select * expenserecord strftime('%y-%m', date) = '2017-04';",null);     if (cursor != null && cursor.getcount() != 0) {     if (cursor.movetofirst()) {         {             datamodel datamodelitems = new datamodel();             datamodelitems.setpayee(cursor.getstring(cursor                     .getcolumnindex("payee")));             datamodelitems.setamount(cursor.getstring(cursor                     .getcolumnindex("amount")));             datamodelitems.setcategory(cursor.getstring(cursor                     .getcolumnindex("category")));             datamodelitems.setnotes(cursor.getstring(cursor                     .getcolumnindex("notes")));             datamodelitems.setdate(cursor.getstring(cursor                     .getcolumnindex("date")));             datamodelitems.settime(cursor.getstring(cursor                     .getcolumnindex("time")));             datamodels.add(datamodelitems);          } while (cursor.movetonext());     }         }     cursor.close();     customadapter customadapter = new customadapter(datamodels,getapplicationcontext());     lv.setadapter(customadapter);      lv.setonitemclicklistener(itemlistener); }  adapterview.onitemclicklistener itemlistener = new adapterview.onitemclicklistener() {     @override     public void onitemclick(adapterview<?> parent, view view, int position, long id) {          final android.support.v7.app.alertdialog.builder builder = new android.support.v7.app.alertdialog.builder(getapplicationcontext());         builder.setview(r.layout.dialog_box)                 .setpositivebutton("update", new dialoginterface.onclicklistener() {                     public void onclick(final dialoginterface dialog, final int id) {                         //update click                     }                 })                 .setneutralbutton("disable", new dialoginterface.onclicklistener() {                     public void onclick(final dialoginterface dialog, final int id) {                         //disable click                     }                 })                 .setnegativebutton("cancel", new dialoginterface.onclicklistener() {                     public void onclick(final dialoginterface dialog, final int id) {                         //cancel click                     }                 });         if(position>-1) {             android.support.v7.app.alertdialog alert = builder.create();             alert.show();         }      } };  public void ondestroy(){     super.ondestroy();     cursor.close();     db.close(); } 

}

try adding

android:theme="@style/theme.appcompat.light"  

to application tag in androidmanifest.xml file.

as suggested in post.

you need use theme.appcompat theme (or descendant) activity