android - can't start activity ,caused maybe by thread/handler/adapter/listview,not for sure -
i'm writing book-searching app on android,something wrong code application force closed when click button start search-activity.from log,i think maybe use handler or thread or adapter incorrectly,but can't figure out.need help,thanks.
activity file:
package com.example.doubanbook.activity; import java.util.arraylist; import java.util.hashmap; import java.util.list; import java.util.map; import android.app.activity; import android.graphics.bitmap; import android.os.bundle; import android.os.handler; import android.os.message; import android.util.log; import android.view.view; import android.view.view.onclicklistener; import android.widget.button; import android.widget.edittext; import android.widget.imageview; import android.widget.listview; import android.widget.simpleadapter; import android.widget.simpleadapter.viewbinder; import com.example.doubanbook.r; import com.example.doubanbook.book.booksearchinfo; import com.example.doubanbook.book.pasesearchreasult; import com.example.doubanbook.book.util; public class searchbookactivity extends activity { private edittext searchedittext = null; private button searchbutton = null; private listview lv = null; private handler hd ; private list<map<string, object>> listitems = new arraylist<map<string, object>>(); private simpleadapter adapt = null; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.searchbook); searchedittext = (edittext) findviewbyid(r.id.search_et); searchbutton = (button) findviewbyid(r.id.search_button); lv = (listview) findviewbyid(r.id.lv); searchbutton.setonclicklistener(new onclicklistener() { @override public void onclick(view v) { string keystr = searchedittext.gettext().tostring(); new downloadthread("https://api.douban.com/v2/book/search?q=" + keystr).start(); } }); hd = new handler() { @override public void handlemessage(message msg) { super.handlemessage(msg); arraylist<booksearchinfo> infos = (arraylist<booksearchinfo>) msg.obj; (int = 0; < infos.size(); i++) { map<string, object> listitem = new hashmap<string, object>(); listitem.put("title", infos.get(i).gettitle()); listitem.put("author", infos.get(i).getauthor()); listitem.put("isbn", infos.get(i).getisbn()); listitem.put("publisher", infos.get(i).getpublisher()); listitem.put("rate", infos.get(i).getrate()); listitem.put("image", infos.get(i).getcover()); listitems.add(listitem); } adapt = new simpleadapter(searchbookactivity.this, listitems, r.layout.search_listitem, new string[] { "title", "author", "isbn", "publisher", "rate", "image" }, new int[] { r.id.tv1, r.id.tv2, r.id.tv3, r.id.tv4, r.id.iv }); adapt.setviewbinder(new viewbinder() { @override public boolean setviewvalue(view view, object data, string textrepresentation) { if ((view instanceof imageview) & (data instanceof bitmap)) { imageview iv = (imageview) view; bitmap bm = (bitmap) data; iv.setimagebitmap(bm); return true; } return false; } }); lv.setadapter(adapt); } }; } class downloadthread extends thread { string url = null; public downloadthread(string urlstr) { url = urlstr; } public void run() { string result = util.download(url); pasesearchreasult mess = new pasesearchreasult(result); arraylist<booksearchinfo> infos = mess.resultcollection(); message msg = message.obtain(); msg.obj = infos; hd.sendmessage(msg); } } } layout xml file:
<?xml version="1.0" encoding="utf-8"?> <scrollview xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" > <linearlayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <textview android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_gravity="center" android:gravity="center" android:text="search" /> <linearlayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <edittext android:id="@+id/search_et" android:layout_width="0dp" android:layout_height="match_parent" android:layout_gravity="center" android:layout_weight="3" android:background="@null" android:gravity="center" android:textcolor="#ffffff" android:hint="type keyword" /> <button android:id="@+id/search_btn" android:layout_width="0dp" android:layout_height="match_parent" android:layout_gravity="center" android:text="search" android:layout_weight="1" /> </linearlayout> <listview android:id="@+id/lv" android:layout_width="match_parent" android:layout_height="wrap_content" > </listview> </linearlayout> </scrollview> list item xml file:
<?xml version="1.0" encoding="utf-8"?> <linearlayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <imageview android:id="@+id/iv" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_weight="1" /> <textview android:id="@+id/lv1" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_weight="1" /> <textview android:id="@+id/lv2" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_weight="1" /> <textview android:id="@+id/lv3" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_weight="1" /> <textview android:id="@+id/lv4" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_weight="1" /> </linearlayout> log information:
04-14 14:33:38.269: e/openglrenderer(1263): getting max_texture_size gradiencache 04-14 14:33:38.273: e/openglrenderer(1263): max_texture_size: 16384 04-14 14:33:38.285: e/openglrenderer(1263): getting max_texture_size caches::initconstraints() 04-14 14:33:38.285: e/openglrenderer(1263): max_texture_size: 16384 04-14 14:33:43.145: e/androidruntime(1263): fatal exception: main 04-14 14:33:43.145: e/androidruntime(1263): process: com.example.doubanbook, pid: 1263 04-14 14:33:43.145: e/androidruntime(1263): java.lang.runtimeexception: unable start activity componentinfo{com.example.doubanbook/com.example.doubanbook.activity.searchbookactivity}: java.lang.nullpointerexception 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activitythread.performlaunchactivity(activitythread.java:2195) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activitythread.handlelaunchactivity(activitythread.java:2245) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activitythread.access$800(activitythread.java:135) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activitythread$h.handlemessage(activitythread.java:1196) 04-14 14:33:43.145: e/androidruntime(1263): @ android.os.handler.dispatchmessage(handler.java:102) 04-14 14:33:43.145: e/androidruntime(1263): @ android.os.looper.loop(looper.java:136) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activitythread.main(activitythread.java:5017) 04-14 14:33:43.145: e/androidruntime(1263): @ java.lang.reflect.method.invokenative(native method) 04-14 14:33:43.145: e/androidruntime(1263): @ java.lang.reflect.method.invoke(method.java:515) 04-14 14:33:43.145: e/androidruntime(1263): @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:779) 04-14 14:33:43.145: e/androidruntime(1263): @ com.android.internal.os.zygoteinit.main(zygoteinit.java:595) 04-14 14:33:43.145: e/androidruntime(1263): @ dalvik.system.nativestart.main(native method) 04-14 14:33:43.145: e/androidruntime(1263): caused by: java.lang.nullpointerexception 04-14 14:33:43.145: e/androidruntime(1263): @ com.example.doubanbook.activity.searchbookactivity.oncreate(searchbookactivity.java:45) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activity.performcreate(activity.java:5231) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1087) 04-14 14:33:43.145: e/androidruntime(1263): @ android.app.activitythread.performlaunchactivity(activitythread.java:2159) 04-14 14:33:43.145: e/androidruntime(1263): ... 11 more
the id wrong here:
searchbutton = (button) findviewbyid(r.id.search_button); because in layout.xml put different id:
android:id="@+id/search_btn" ==> use same id @ layout , activity , should work, otherwise findviewbyid return null because not find id.
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