空指针异常而做搜索功能的ListView控件随着BaseAdapter [英] NullPointer Exception While Doing Search Feature for ListView With BaseAdapter
问题描述
我刚刚完成了添加一个搜索功能,以我的Android窗口小部件,通过安装的应用程序的用户的列表中搜索。我的应用程序安装很好,一切,但是当我去寻找一些应用程序的力量关闭,我得到这个错误:
十一月10日至18日:10:49.393:E / AndroidRuntime(10901):致命异常:主要
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):显示java.lang.NullPointerException
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在com.example.awesomefilebuilderwidget.AppInfoAdapter.getCount(AppInfoAdapter.java:33)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.widget.AdapterView $ AdapterDataSetObserver.onChanged(AdapterView.java:778)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.database.DataSetObservable.notifyChanged(DataSetObservable.java:31)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.widget.BaseAdapter.notifyDataSetChanged(BaseAdapter.java:50)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在com.example.awesomefilebuilderwidget.AppInfoAdapter $ 1.publishResults(AppInfoAdapter.java:98)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.widget.Filter $ ResultsHandler.handleMessage(Filter.java:282)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.os.Handler.dispatchMessage(Handler.java:99)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.os.Looper.loop(Looper.java:150)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在android.app.ActivityThread.main(ActivityThread.java:4333)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在java.lang.reflect.Method.invokeNative(本机方法)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在java.lang.reflect.Method.invoke(Method.java:507)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:839)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
十一月10号至18日:10:49.393:E / AndroidRuntime(10901):在dalvik.system.NativeStart.main(本机方法)
下面是我的AppInfoAdapter,所以我可能会搞砸了某处沿线:
包com.example.awesomefilebuilderwidget;
进口的java.util.ArrayList;
进口的java.util.List;
进口android.content.Context;
进口android.content.pm.ApplicationInfo;
进口android.content.pm.PackageManager;
进口android.view.LayoutInflater;
进口android.view.View;
进口android.view.ViewGroup;
进口android.widget.BaseAdapter;
进口android.widget.Filter;
进口android.widget.Filterable;
进口android.widget.ImageView;
进口android.widget.TextView;
公共类AppInfoAdapter扩展了BaseAdapter实现过滤的{
私人语境mContext;
私人列表< ApplicationInfo> mListAppInfo;
私人PackageManager mPackManager;
私人列表< ApplicationInfo> originalListAppInfo;
私人过滤器过滤;
公共AppInfoAdapter(上下文C,名单,其中,ApplicationInfo> listApp,PackageManager时){
mContext = C;
this.originalListAppInfo = this.mListAppInfo = listApp;
mPackManager =时;
}
@覆盖
公众诠释getCount将(){
返回mListAppInfo.size();
}
@覆盖
公共对象的getItem(INT位置){
返回mListAppInfo.get(位置);
}
@覆盖
众长getItemId(INT位置){
返回的位置;
}
@覆盖
公共查看getView(INT位置,查看convertView,ViewGroup中父){
//获取选定的条目
ApplicationInfo进入=(ApplicationInfo)mListAppInfo.get(位置);
//参照convertView
视图V = convertView;
//膨胀,如果空的新布局
如果(V == NULL){
LayoutInflater充气= LayoutInflater.from(mContext);
V = inflater.inflate(R.layout.layout_appinfo,NULL);
}
从布局资源//负荷控制
ImageView的ivAppIcon =(ImageView的)v.findViewById(R.id.ivIcon);
TextView的tvAppName =(TextView中)v.findViewById(R.id.tvName);
TextView的tvPkgName =(TextView中)v.findViewById(R.id.tvPack);
//设置要显示的数据
ivAppIcon.setImageDrawable(entry.loadIcon(mPackManager));
tvAppName.setText(entry.loadLabel(mPackManager));
tvPkgName.setText(entry.packageName);
//返回查看
返回伏;
}
@覆盖
公共过滤用getFilter(){
如果(过滤== NULL){
过滤器=新的过滤器(){
@覆盖
保护FilterResults performFiltering(CharSequence的约束){
FilterResults结果=新FilterResults();
名单< ApplicationInfo> myFilteredAppList =新的ArrayList< ApplicationInfo>();
约束= constraint.toString()与toLowerCase()。
对于(ApplicationInfo APPINFO:originalListAppInfo){
字符串somefield = appInfo.name;
如果(somefield.toLowerCase()。包含(constraint.toString())){
myFilteredAppList.add(APPINFO);
}
}
results.count = myFilteredAppList.size();
results.values = myFilteredAppList;
返回结果;
}
@覆盖
保护无效publishResults(CharSequence的约束,FilterResults结果){
mListAppInfo =(名单< ApplicationInfo>)results.values;
notifyDataSetChanged();
}
};
}
返回过滤器;
}
}
这是什么问题?
增加:这是我的Drag_and_Drop_App.java:
包com.example.awesomefilebuilderwidget;
进口的java.util.List;
进口android.app.Activity;
进口android.content.Intent;
进口android.content.pm.ApplicationInfo;
进口android.os.Bundle;
进口android.text.Editable;
进口android.text.TextWatcher;
进口android.util.Log;
进口android.view.View;
进口android.widget.AdapterView;
进口android.widget.AdapterView.OnItemClickListener;
进口android.widget.AdapterView.OnItemLongClickListener;
进口android.widget.Button;
进口android.widget.EditText;
进口android.widget.ListView;
公共类Drag_and_Drop_App延伸活动{
私人的ListView mListAppInfo;
//搜索的EditText
的EditText inputSearch;
公共静态AppInfoAdapter适配器;
@覆盖
公共无效的onCreate(包savedInstanceState){
super.onCreate(savedInstanceState);
//主画面设置布局
的setContentView(R.layout.drag_and_drop_app);
//导入按钮
按钮btnLinkToFeedback =(按钮)findViewById(R.id.btnLinkToFeedback);
//链接反馈屏幕
btnLinkToFeedback.setOnClickListener(新View.OnClickListener(){
公共无效的onClick(视图查看){
意图I =新的意图(getApplicationContext()
Feedback.class);
startActivity(ⅰ);
完();
}
});
//创建新的适配器
适配器=新AppInfoAdapter(这一点,(名单< ApplicationInfo>)Utilities.getInstalledApplication(本),getPackageManager());
//加载列表应用
mListAppInfo =(ListView控件)findViewById(R.id.lvApps);
//设置适配器列表视图
mListAppInfo.setAdapter(适配器);
//搜索栏
inputSearch =(EditText上)findViewById(R.id.inputSearch);
inputSearch.addTextChangedListener(新TextWatcher(){
@覆盖
公共无效onTextChanged(CharSequence的CS,诠释ARG1,诠释ARG2,诠释ARG3){
//当用户更改文本
// Drag_and_Drop_App.this.adapter.getFilter()过滤器(CS)。
如果(Drag_and_Drop_App.this.adapter == NULL){
//某些打印声明说,这是空
Log.d(msg_error,adapter_is_null);
}
。Drag_and_Drop_App.this.adapter.getFilter()过滤器(CS);
}
@覆盖
公共无效beforeTextChanged(CharSequence的arg0中,诠释ARG1,INT ARG2,
INT ARG3){
// TODO自动生成方法存根
}
@覆盖
公共无效afterTextChanged(编辑为arg0){
// TODO自动生成方法存根
}
});
当列表视图中选择了一个项目//实现事件
mListAppInfo.setOnItemClickListener(新OnItemClickListener(){
@覆盖
公共无效onItemClick(适配器视图<>母公司视图中查看,INT POS,长ID){
//获取列表适配器
AppInfoAdapter appInfoAdapter =(AppInfoAdapter)parent.getAdapter();
//获取选择列表中的项目
ApplicationInfo APPINFO =(ApplicationInfo)appInfoAdapter.getItem(POS);
//启动所选择的应用
Utilities.launchApp(parent.getContext(),getPackageManager(),appInfo.packageName);
}
});
//当列表视图中的项目,通过选择实现事件长期点击拖放
mListAppInfo.setOnItemLongClickListener(新OnItemLongClickListener(){
@覆盖
公共布尔onItemLongClick(适配器视图<>母公司视图中查看,
INT POS,长ID){
// TODO自动生成方法存根
//获取列表适配器
AppInfoAdapter appInfoAdapter =(AppInfoAdapter)parent.getAdapter();
//获取选择列表中的项目
ApplicationInfo APPINFO =(ApplicationInfo)appInfoAdapter.getItem(POS);
//启动所选择的应用
Utilities.launchApp(parent.getContext(),getPackageManager(),appInfo.packageName);
返回true;
}
});
}
}
添加的类:这是我的实用工具类:
包com.example.awesomefilebuilderwidget;
进口的java.util.List;
进口android.content.ActivityNotFoundException;
进口android.content.Context;
进口android.content.Intent;
进口android.content.pm.PackageManager;
进口android.widget.Toast;
公共类公用事业{
/ *
*获取移动所有已安装的应用程序,并返回一个列表
*参数C应用程序的语境
* @返回安装的应用程序列表
* /
公共静态列表<> getInstalledApplication(上下文C){
。返回c.getPackageManager()getInstalledApplications(PackageManager.GET_META_DATA);
}
/ *
*启动应用程序
*参数C应用程序的语境
* @参数时的上下文的相关包管理
*包跑了@参数PKGNAME名称
* /
公共静态布尔launchApp(上下文C,PackageManager时许,串PKGNAME){
//查询意图空空
意向意图= pm.getLaunchIntentForPackage(包名称);
//如果意图是可用
如果(意向!= NULL){
尝试 {
//启动应用程序
c.startActivity(意向);
//如果成功
返回true;
//如果失败
}赶上(ActivityNotFoundException前){
//快速消息通知
吐司面包= Toast.makeText(C,应用程序未找到,Toast.LENGTH_LONG);
//显示消息
toast.show();
}
}
//默认情况下,无法启动
返回false;
}
}
您的列表中包含 appInfo.packageName
不是 appInfo.name
。
在performFiltering方法要添加 appInfo.name
来过滤列表。相反,你应该添加 appInfo.packageName
。
您的for循环应该是这样的。
的(ApplicationInfo APPINFO:originalListAppInfo){
字符串somefield = appInfo.packageName;
如果(somefield.toLowerCase()。包含(constraint.toString())){
myFilteredAppList.add(APPINFO);
}
}
这应该工作。
永远不要忘记检查空值 publishResults
方法
@覆盖
保护无效publishResults(CharSequence的约束,FilterResults结果){
如果(results.values!= NULL)
{
mListAppInfo =(名单< ApplicationInfo>)results.values;
notifyDataSetChanged();
}
}
I just finished adding a search feature to my android widget to search through a list of the users installed applications. My app installs fine and everything but when I go to search something the app force closes and I get this error:
10-18 11:10:49.393: E/AndroidRuntime(10901): FATAL EXCEPTION: main
10-18 11:10:49.393: E/AndroidRuntime(10901): java.lang.NullPointerException
10-18 11:10:49.393: E/AndroidRuntime(10901): at com.example.awesomefilebuilderwidget.AppInfoAdapter.getCount(AppInfoAdapter.java:33)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.widget.AdapterView$AdapterDataSetObserver.onChanged(AdapterView.java:778)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.database.DataSetObservable.notifyChanged(DataSetObservable.java:31)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.widget.BaseAdapter.notifyDataSetChanged(BaseAdapter.java:50)
10-18 11:10:49.393: E/AndroidRuntime(10901): at com.example.awesomefilebuilderwidget.AppInfoAdapter$1.publishResults(AppInfoAdapter.java:98)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:282)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.os.Handler.dispatchMessage(Handler.java:99)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.os.Looper.loop(Looper.java:150)
10-18 11:10:49.393: E/AndroidRuntime(10901): at android.app.ActivityThread.main(ActivityThread.java:4333)
10-18 11:10:49.393: E/AndroidRuntime(10901): at java.lang.reflect.Method.invokeNative(Native Method)
10-18 11:10:49.393: E/AndroidRuntime(10901): at java.lang.reflect.Method.invoke(Method.java:507)
10-18 11:10:49.393: E/AndroidRuntime(10901): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-18 11:10:49.393: E/AndroidRuntime(10901): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-18 11:10:49.393: E/AndroidRuntime(10901): at dalvik.system.NativeStart.main(Native Method)
Here is my AppInfoAdapter so I might have messed up somewhere along the line:
package com.example.awesomefilebuilderwidget;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ImageView;
import android.widget.TextView;
public class AppInfoAdapter extends BaseAdapter implements Filterable {
private Context mContext;
private List<ApplicationInfo> mListAppInfo;
private PackageManager mPackManager;
private List<ApplicationInfo> originalListAppInfo;
private Filter filter;
public AppInfoAdapter(Context c, List<ApplicationInfo> listApp, PackageManager pm) {
mContext = c;
this.originalListAppInfo = this.mListAppInfo = listApp;
mPackManager = pm;
}
@Override
public int getCount() {
return mListAppInfo.size();
}
@Override
public Object getItem(int position) {
return mListAppInfo.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// get the selected entry
ApplicationInfo entry = (ApplicationInfo) mListAppInfo.get(position);
// reference to convertView
View v = convertView;
// inflate new layout if null
if(v == null) {
LayoutInflater inflater = LayoutInflater.from(mContext);
v = inflater.inflate(R.layout.layout_appinfo, null);
}
// load controls from layout resources
ImageView ivAppIcon = (ImageView)v.findViewById(R.id.ivIcon);
TextView tvAppName = (TextView)v.findViewById(R.id.tvName);
TextView tvPkgName = (TextView)v.findViewById(R.id.tvPack);
// set data to display
ivAppIcon.setImageDrawable(entry.loadIcon(mPackManager));
tvAppName.setText(entry.loadLabel(mPackManager));
tvPkgName.setText(entry.packageName);
// return view
return v;
}
@Override
public Filter getFilter() {
if(filter == null) {
filter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
FilterResults results = new FilterResults();
List<ApplicationInfo> myFilteredAppList = new ArrayList<ApplicationInfo>();
constraint = constraint.toString().toLowerCase();
for (ApplicationInfo appInfo : originalListAppInfo) {
String somefield = appInfo.name;
if (somefield.toLowerCase().contains(constraint.toString())) {
myFilteredAppList.add(appInfo);
}
}
results.count = myFilteredAppList.size();
results.values = myFilteredAppList;
return results;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
mListAppInfo = (List<ApplicationInfo>)results.values;
notifyDataSetChanged();
}
};
}
return filter;
}
}
What's the problem?
ADDED: Here is my Drag_and_Drop_App.java:
package com.example.awesomefilebuilderwidget;
import java.util.List;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
public class Drag_and_Drop_App extends Activity {
private ListView mListAppInfo;
// Search EditText
EditText inputSearch;
public static AppInfoAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// set layout for the main screen
setContentView(R.layout.drag_and_drop_app);
// import buttons
Button btnLinkToFeedback = (Button) findViewById(R.id.btnLinkToFeedback);
// Link to Feedback Screen
btnLinkToFeedback.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
Feedback.class);
startActivity(i);
finish();
}
});
// create new adapter
adapter = new AppInfoAdapter(this, (List<ApplicationInfo>) Utilities.getInstalledApplication(this), getPackageManager());
// load list application
mListAppInfo = (ListView)findViewById(R.id.lvApps);
// set adapter to list view
mListAppInfo.setAdapter(adapter);
// search bar
inputSearch = (EditText) findViewById(R.id.inputSearch);
inputSearch.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
// When user changed the Text
// Drag_and_Drop_App.this.adapter.getFilter().filter(cs);
if (Drag_and_Drop_App.this.adapter == null){
// some print statement saying it is null
Log.d ("msg_error", "adapter_is_null");
}
Drag_and_Drop_App.this.adapter.getFilter().filter(cs);
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
});
// implement event when an item on list view is selected
mListAppInfo.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int pos, long id) {
// get the list adapter
AppInfoAdapter appInfoAdapter = (AppInfoAdapter)parent.getAdapter();
// get selected item on the list
ApplicationInfo appInfo = (ApplicationInfo)appInfoAdapter.getItem(pos);
// launch the selected application
Utilities.launchApp(parent.getContext(), getPackageManager(), appInfo.packageName);
}
});
// implement event when an item on list view is selected via long-click for drag and drop
mListAppInfo.setOnItemLongClickListener(new OnItemLongClickListener(){
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view,
int pos, long id) {
// TODO Auto-generated method stub
// get the list adapter
AppInfoAdapter appInfoAdapter = (AppInfoAdapter)parent.getAdapter();
// get selected item on the list
ApplicationInfo appInfo = (ApplicationInfo)appInfoAdapter.getItem(pos);
// launch the selected application
Utilities.launchApp(parent.getContext(), getPackageManager(), appInfo.packageName);
return true;
}
});
}
}
ADDED CLASS: Here is my Utilities class:
package com.example.awesomefilebuilderwidget;
import java.util.List;
import android.content.ActivityNotFoundException;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.widget.Toast;
public class Utilities {
/*
* Get all installed application on mobile and return a list
* @param c Context of application
* @return list of installed applications
*/
public static List<?> getInstalledApplication(Context c) {
return c.getPackageManager().getInstalledApplications(PackageManager.GET_META_DATA);
}
/*
* Launch an application
* @param c Context of application
* @param pm the related package manager of the context
* @param pkgName Name of the package to run
*/
public static boolean launchApp(Context c, PackageManager pm, String pkgName) {
// query the intent for lauching
Intent intent = pm.getLaunchIntentForPackage(pkgName);
// if intent is available
if(intent != null) {
try {
// launch application
c.startActivity(intent);
// if succeed
return true;
// if fail
} catch(ActivityNotFoundException ex) {
// quick message notification
Toast toast = Toast.makeText(c, "Application Not Found", Toast.LENGTH_LONG);
// display message
toast.show();
}
}
// by default, fail to launch
return false;
}
}
Your list contains appInfo.packageName
not appInfo.name
.
In performFiltering method you are adding appInfo.name
to filtered list. Instead you should add appInfo.packageName
.
Your for loop should be like this
for (ApplicationInfo appInfo : originalListAppInfo) {
String somefield = appInfo.packageName;
if (somefield.toLowerCase().contains(constraint.toString())) {
myFilteredAppList.add(appInfo);
}
}
This should work.
And never forget to check for null values in publishResults
method
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
if(results.values != null)
{
mListAppInfo = (List<ApplicationInfo>)results.values;
notifyDataSetChanged();
}
}
这篇关于空指针异常而做搜索功能的ListView控件随着BaseAdapter的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!