08-20 17:19:33.200: D / AndroidRuntime (938): Shutting down VM
08-20 17:19:33.200: W / dalvikvm (938): threadid = 1: thread exiting with uncaught exception (group = 0x40020560)
08-20 17:19:33.210: E / AndroidRuntime (938): FATAL EXCEPTION: main
08-20 17:19:33.210: E / AndroidRuntime (938): java.lang.RuntimeException: Unable to start activity ComponentInfo {com.example.suishoukan / com . example.suishoukan.MainActivity}: java.lang.NullPointerException
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.ActivityThread.performLaunchActivity (ActivityThread.java: 1834)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java: 1850)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.ActivityThread.access $ 1500 (ActivityThread.java: 125)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.ActivityThread $ H.handleMessage (ActivityThread.java: 941)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.os.Handler.dispatchMessage (Handler.java: 99)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.os.Looper.loop (Looper.java: 130)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.ActivityThread.main (ActivityThread.java: 3962)
08-20 17:19:33.210: E / AndroidRuntime (938): at java.lang.reflect.Method.invokeNative (Native Method)
08-20 17:19:33.210: E / AndroidRuntime (938): at java.lang.reflect.Method.invoke (Method.java: 507)
08-20 17:19:33.210: E / AndroidRuntime (938): at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java: 864)
08-20 17:19:33.210: E / AndroidRuntime (938): at com.android.internal.os.ZygoteInit.main (ZygoteInit.java: 622)
08-20 17:19:33.210: E / AndroidRuntime (938): at dalvik.system.NativeStart.main (Native Method)
08-20 17:19:33.210: E / AndroidRuntime (938): Caused by: java.lang.NullPointerException
08-20 17:19:33.210: E / AndroidRuntime (938): at com.example.suishoukan.MainActivity.show (MainActivity.java: 85)
08-20 17:19:33.210: E / AndroidRuntime (938): at com.example.suishoukan.MainActivity.onCreate (MainActivity.java: 54)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.Instrumentation.callActivityOnCreate (Instrumentation.java: 1047)
08-20 17:19:33.210: E / AndroidRuntime (938): at android.app.ActivityThread.performLaunchActivity (ActivityThread.java: 1788)
08-20 17:19:33.210: E / AndroidRuntime (938): ... 11 more
package com.example.suishoukan;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import com.example.domain.Film;
import com.example.service.FilmService;
import com.example.test.FilmServiceTest;
import android.app.TabActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TabHost;
import android.widget.TabHost.OnTabChangeListener;
public class MainActivity extends TabActivity
{
//声明TabHost对象
TabHost mTabHost;
Button button1,button2,button3,button4;
FilmService filmService;
List<Film> films;
ListView listView;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//取得TabHost对象
mTabHost = getTabHost();
/* 为TabHost添加标签 */
//新建一个newTabSpec(newTabSpec)
//设置其标签和图标(setIndicator)
//设置内容(setContent)
mTabHost.addTab(mTabHost.newTabSpec("tab_test1")
.setIndicator("榜单")
.setContent(R.id.textview1));
mTabHost.addTab(mTabHost.newTabSpec("tab_test2")
.setIndicator("节目表")
.setContent(R.id.textview2));
mTabHost.addTab(mTabHost.newTabSpec("tab_test3")
.setIndicator("收藏")
.setContent(R.id.textview3));
//设置当前显示哪一个标签
mTabHost.setCurrentTab(0);
filmService = new FilmService(this);
films = filmService.getScrollData(0,10);
listView = (ListView) this.findViewById(R.id.listView) ;
button1 = (Button) this.findViewById(R.id.button1);
button2 = (Button) this.findViewById(R.id.button2);
button3 = (Button) this.findViewById(R.id.button3);
button4 = (Button) this.findViewById(R.id.button4);
OnClickListener o = new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(button1.getId()==v.getId()){
films = filmService.getScrollData(0,10);
}
else if(button2.getId()==v.getId()){
films = filmService.getScrollData(10,10);
}
else if(button3.getId()==v.getId()){
films = filmService.getScrollData(20,10);
}
else{
films = filmService.getScrollData(30,10);
}
}
};
button1.setOnClickListener(o);
button2.setOnClickListener(o);
button3.setOnClickListener(o);
button4.setOnClickListener(o);
show();
}
private void show() {
// TODO Auto-generated method stub
List<HashMap<String, Object>> data = new ArrayList<HashMap<String,Object>>();
for(Film film : films){
HashMap<String,Object> item = new HashMap<String,Object>();
item.put("title", film.getTitle());
item.put("score", film.getScore());
data.add(item);
}
SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,
new String[]{"title","score"}, new int[]{R.id.title,R.id.score});
listView.setAdapter(adapter);
}
}
------ Solution ------------------------------------- -------
films caused no data ,
private void show() {
// TODO Auto-generated method stub
if(films != null)
{
List<HashMap<String, Object>> data = new ArrayList<HashMap<String,Object>>();
for(Film film : films){
HashMap<String,Object> item = new HashMap<String,Object>();
item.put("title", film.getTitle());
item.put("score", film.getScore());
data.add(item);
}
SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,
new String[]{"title","score"}, new int[]{R.id.title,R.id.score});
listView.setAdapter(adapter);
}
}
------ Solution ------------------------------------- -------
else {
films = filmService . getScrollData (30,10);
}
show ();
}
a problem here . . .
------ For reference only -------------------------------------- -
line 54 or 85 rows must have a variable is empty, so look at the code is very troublesome, 54 and 85 lines of code which specifically I do not see it ...... you have a good look at it, a null pointer exception solved the
------ For reference only ------------------------------------- -
I was not initialized in front of the Well
films = filmService.getScrollData (0,10);
------ For reference only -------------------- -------------------
then you have to check getScrollDat part code
------ For reference only -------- -------------------------------
public List<Film> getScrollData(int offset, int maxResult){
List<Film> films = new ArrayList<Film>();
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select * from film order by filmid asc limit ?,?",
new String[]{String.valueOf(offset), String.valueOf(maxResult)});
while(cursor.moveToNext()){
int filmid = cursor.getInt(cursor.getColumnIndex("filmid"));
float score = cursor.getFloat(cursor.getColumnIndex("score"));
String title = cursor.getString(cursor.getColumnIndex("title"));
films.add(new Film(filmid, title,score));
}
cursor.close();
return films;
}
------ For reference only ----------------------------------- ----
this case recommended by the Log output detection Why films is null
For example, in
while (cursor.moveToNext ()) {
preceded by
Log.i ("test", " number of records :" + cursor.getCount ());
to detect the query results
will
button4.setOnClickListener (o);
behind
show ();
deleted, and then show (); put
else {
films = filmService . getScrollData (30,10);
}
code behind .
------ For reference only ---------------------------------- -----
Great God , I do as you say , a start on Showing 1-10 record , Click the button
But why it is not responding ?
------ For reference only -------------------------------------- -
in the show () inside
listView.setAdapter (adapter);
followed by a
listView.setSelection (0);
------ For reference only --------------------------- ------------
your original onClick event there is no plus show ();
inside the onClick
else {
films = filmService.getScrollData (30,10);
}
code followed by
show ();
------ For reference only ------------------------------ ---------
Great God , I added a show () , but does not work .
Do not listen for multiple buttons to set the same event do ? On certain score to write ?
------ For reference only -------------------------------------- -
current code Tieshanglai see
------ For reference only --------------------------- ------------
package com.example.suishoukan;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import com.example.domain.Film;
import com.example.service.FilmService;
import com.example.test.FilmServiceTest;
import android.app.TabActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TabHost;
import android.widget.TabHost.OnTabChangeListener;
public class MainActivity extends TabActivity
{
//声明TabHost对象
TabHost mTabHost;
Button button1,button2,button3,button4;
FilmService filmService;
List<Film> films;
ListView listView;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//取得TabHost对象
mTabHost = getTabHost();
/* 为TabHost添加标签 */
//新建一个newTabSpec(newTabSpec)
//设置其标签和图标(setIndicator)
//设置内容(setContent)
mTabHost.addTab(mTabHost.newTabSpec("tab_test1")
.setIndicator("榜单")
.setContent(R.id.textview1));
mTabHost.addTab(mTabHost.newTabSpec("tab_test2")
.setIndicator("节目表")
.setContent(R.id.textview2));
mTabHost.addTab(mTabHost.newTabSpec("tab_test3")
.setIndicator("收藏")
.setContent(R.id.textview3));
//设置当前显示哪一个标签
mTabHost.setCurrentTab(0);
filmService = new FilmService(this);
//films = filmService.getScrollData(0,10);
listView = (ListView) this.findViewById(R.id.listView) ;
button1 = (Button) this.findViewById(R.id.button1);
button2 = (Button) this.findViewById(R.id.button2);
button3 = (Button) this.findViewById(R.id.button3);
button4 = (Button) this.findViewById(R.id.button4);
OnClickListener o = new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(button1.getId()==v.getId()){
films = filmService.getScrollData(0,10);
}
else if(button2.getId()==v.getId()){
films = filmService.getScrollData(10,10);
}
else if(button3.getId()==v.getId()){
films = filmService.getScrollData(20,10);
}
else{
films = filmService.getScrollData(30,10);
}
show();
}
};
button1.setOnClickListener(o);
button2.setOnClickListener(o);
button3.setOnClickListener(o);
button4.setOnClickListener(o);
}
private void show() {
// TODO Auto-generated method stub
if(films!=null){
List<HashMap<String, Object>> data = new ArrayList<HashMap<String,Object>>();
for(Film film : films){
HashMap<String,Object> item = new HashMap<String,Object>();
item.put("title", film.getTitle());
item.put("score", film.getScore());
data.add(item);
}
SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,
new String[]{"title","score"}, new int[]{R.id.title,R.id.score});
listView.setAdapter(adapter);
listView.setSelection(0);
}
}
}
------ For reference only -------------------- -------------------
you neither setId is called getId.
Each button will be added setId
package com.example.suishoukan;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import com.example.domain.Film;
import com.example.service.FilmService;
import com.example.test.FilmServiceTest;
import android.app.TabActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TabHost;
import android.widget.TabHost.OnTabChangeListener;
public class MainActivity extends TabActivity
{
//声明TabHost对象
TabHost mTabHost;
Button button1,button2,button3,button4;
FilmService filmService;
List<Film> films;
ListView listView;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//取得TabHost对象
mTabHost = getTabHost();
/* 为TabHost添加标签 */
//新建一个newTabSpec(newTabSpec)
//设置其标签和图标(setIndicator)
//设置内容(setContent)
mTabHost.addTab(mTabHost.newTabSpec("tab_test1")
.setIndicator("榜单")
.setContent(R.id.textview1));
mTabHost.addTab(mTabHost.newTabSpec("tab_test2")
.setIndicator("节目表")
.setContent(R.id.textview2));
mTabHost.addTab(mTabHost.newTabSpec("tab_test3")
.setIndicator("收藏")
.setContent(R.id.textview3));
//设置当前显示哪一个标签
mTabHost.setCurrentTab(0);
filmService = new FilmService(this);
//films = filmService.getScrollData(0,10);
listView = (ListView) this.findViewById(R.id.listView) ;
button1 = (Button) this.findViewById(R.id.button1);
button1.setId(1);
button2 = (Button) this.findViewById(R.id.button2);
button2.setId(2);
button3 = (Button) this.findViewById(R.id.button3);
button3.setId(3);
button4 = (Button) this.findViewById(R.id.button4);
button4.setId(4);
OnClickListener o = new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(button1.getId()==v.getId()){
films = filmService.getScrollData(0,10);
}
else if(button2.getId()==v.getId()){
films = filmService.getScrollData(10,10);
}
else if(button3.getId()==v.getId()){
films = filmService.getScrollData(20,10);
}
else{
films = filmService.getScrollData(30,10);
}
show();
}
};
button1.setOnClickListener(o);
button2.setOnClickListener(o);
button3.setOnClickListener(o);
button4.setOnClickListener(o);
}
private void show() {
// TODO Auto-generated method stub
if(films!=null){
List<HashMap<String, Object>> data = new ArrayList<HashMap<String,Object>>();
for(Film film : films){
HashMap<String,Object> item = new HashMap<String,Object>();
item.put("title", film.getTitle());
item.put("score", film.getScore());
data.add(item);
}
SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.item,
new String[]{"title","score"}, new int[]{R.id.title,R.id.score});
listView.setAdapter(adapter);
listView.setSelection(0);
}
}
}
------ For reference only ----------------------------------- ----
Great God , does not seem like it, ,
That v.getId () is to get the currently clicked button id value ah, you are in front of each button setId ()
------ For reference only ------ ---------------------------------
Thank you, ah , the problem solved.
------ For reference only -------------------------------------- -
------ For reference only ---------------------------------- -----
Hello , I am also learning android, development and you encounter the same problem : SimpleAdapter, NullPointerException encountered the problem that bothers me one day , and I ask you how to solve, code, and you almost the same ! Thank you !
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