Android 使用BaseAdapter搜索ListView时出现NullPointer异常
我刚刚在我的android小部件中添加了一个搜索功能，用于搜索已安装应用程序的用户列表。我的应用程序安装良好，但当我去搜索某个内容时，应用程序强制关闭，我得到以下错误：Android 使用BaseAdapter搜索ListView时出现NullPointer异常,android,nullpointerexception,Android,Nullpointerexception,我刚刚在我的android小部件中添加了一个搜索功能，用于搜索已安装应用程序的用户列表。我的应用程序安装良好，但当我去搜索某个内容时，应用程序强制关闭，我得到以下错误： 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/
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)
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;
}
}
package com.example.awesomefilebuilderwidget；
导入java.util.ArrayList；
导入java.util.List；
导入android.content.Context；
导入android.content.pm.ApplicationInfo；
导入android.content.pm.PackageManager；
导入android.view.LayoutInflater；
导入android.view.view；
导入android.view.ViewGroup；
导入android.widget.BaseAdapter；
导入android.widget.Filter；
导入android.widget.Filterable；
导入android.widget.ImageView；
导入android.widget.TextView；
公共类AppInfoAdapter扩展BaseAdapter实现可过滤{
私有上下文；
私人名单；
专用软件包管理器mPackManager；
私人名单原件；
专用滤波器；
公共AppInfoAdapter（上下文c、列表listApp、PackageManager pm）{
mContext=c；
this.originalListAppInfo=this.mListAppInfo=listApp；
mPackManager=pm；
}
@凌驾
public int getCount（）{
返回mListAppInfo.size（）；
}
@凌驾
公共对象getItem（int位置）{
返回mlistapingfo.get（位置）；
}
@凌驾
公共长getItemId（int位置）{
返回位置；
}
@凌驾
公共视图getView（int位置、视图转换视图、视图组父视图）{
//获取所选条目
ApplicationInfo条目=（ApplicationInfo）mListAppInfo.get（位置）；
//对convertView的引用
视图v=转换视图；
//如果为空，则为新布局充气
如果（v==null）{
LayoutFlater充气机=LayoutFlater.from（mContext）；
v=充气机充气（R.layout.layout_appinfo，空）；
}
//从布局资源加载控件
ImageView ivAppIcon=（ImageView）v.findViewById（R.id.ivIcon）；
TextView-tvAppName=（TextView）v.findviewbyd（R.id.tvName）；
TextView-tvPkgName=（TextView）v.findviewbyd（R.id.tvPack）；
//设置要显示的数据
setImageDrawable（entry.loadIcon（mPackManager））；
tvAppName.setText（entry.loadLabel（mPackManager））；
tvPkgName.setText（entry.packageName）；
//返回视图
返回v；
}
@凌驾
公共过滤器getFilter（）{
if（filter==null）{
过滤器=新过滤器（）{
@凌驾
受保护的筛选器结果性能筛选（CharSequence约束）{
FilterResults results=新的FilterResults（）；
List myfilteredaplist=new ArrayList（）；
constraint=constraint.toString（）.toLowerCase（）；
对于（应用程序信息appInfo:originalListAppInfo）{
字符串somefield=appInfo.name；
if（somefield.toLowerCase（）.contains（constraint.toString（）））{
添加（appInfo）；
}
}
results.count=myfilteredaplist.size（）；
results.values=myFilteredAppList；
返回结果；
}
@凌驾
受保护的void publishResults（CharSequence约束、FilterResults结果）{
mlistapingfo=（列表）results.values；
notifyDataSetChanged（）；
}
};
}
回流过滤器；
}
}
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;
}
});
}
}
package com.example.awesomefilebuilderwidget；
导入java.util.List；
导入android.app.Activity；
导入android.content.Intent；
导入android.content.pm.ApplicationInfo；
导入android.os.Bundle；
导入android.text.Editable；
导入android.text.TextWatcher；
导入android.util.Log；
导入android.view.view；
导入android.widget.AdapterView；
导入android.widget.AdapterView.OnItemClickListener；
导入android.widget.AdapterView.OnItemLongClickListener；
导入android.widget.Button；
导入android.widget.EditText；
导入android.widget.ListView；
公共类拖放应用程序扩展活动{
私有ListView MListapInfo；
//搜索编辑文本
编辑文本输入搜索；
公共静态AppInfoAdapter；
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
//设置主屏幕的布局
setContentView（R.layout.拖放应用程序）；
//导入按钮
按钮btnLinkToFeedback=（按钮）findViewById（R.id.btnLinkToFeedback）；
//链接到反馈屏幕
btnLinkToFeedback.setOnClickListener（新视图.OnClickListener（）{
公共void onClick（视图）{
意图i=新意图（getApplicationContext（），
反馈（课堂）；
星触觉（i）；
完成（）；
}
});
//创建新适配器
adapter=新的AppInfoAdapter（此，（列表）实用程序.getInstalledApplication（此），getPackageManager（））；
//加载列表应用程序
mListAppInfo=（ListView）findViewById（R.id.lvApps）；
//将适配器设置为列表视图
mListAppInfo.setAdapter（适配器）；
//搜索栏
inputSearch=（EditText）findViewById（R.id.inputSearch）；
inputSearch.addTextChangedListener（新的TextWatcher（）{
@凌驾
public void onTextChanged（字符序列cs、int arg1、int arg2、int arg3）{
//当用户更改文本时
//拖放App.this.adapter.getFilter（）.filter（cs）；
if（拖放App.this.adapter==null）{
//一些打印声明说它是空的
Log.d（“消息错误”，“适配器为空”）；
}
拖放App.this.adapter.getFilter（）.filter（cs）；
}
@凌驾
更改前的公共void（字符序列arg0、int arg1、int arg2、，
int arg3）{
//TODO自动生成的方法存根
}
@O
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;
}
}
if (constraint.length() == 0) {
myFilteredAppList.addAll(originalListAppInfo);
}
@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();
if (constraint.length() == 0) {
myFilteredAppList.addAll(originalListAppInfo);
}
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;
}
@Override
public int getCount() {
return mListAppInfo.size();
}
for (ApplicationInfo appInfo : originalListAppInfo) {
String somefield = appInfo.packageName;
if (somefield.toLowerCase().contains(constraint.toString())) {
myFilteredAppList.add(appInfo);
}
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
if(results.values != null)
{
mListAppInfo = (List<ApplicationInfo>)results.values;
notifyDataSetChanged();
}
}