Android Listview适配器在片段中提供空指针异常
这里使用的代码是我从另一个片段类中提取出来的,它工作得非常好 我想从Android Listview适配器在片段中提供空指针异常,android,file,listview,Android,File,Listview,这里使用的代码是我从另一个片段类中提取出来的,它工作得非常好 我想从data/data/目录中提取文件列表,并在列表视图中显示它们 抛出的错误在第58行。lv.setAdapter 我已经从Eclipse切换到Android studio,所以这可能与此有关 日志: 02-04 12:21:48.535 7433-7433/com.super8bit.singoffbeta E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.Null
data/data/
目录中提取文件列表,并在列表视图中显示它们
抛出的错误在第58行。lv.setAdapter
我已经从Eclipse切换到Android studio,所以这可能与此有关
日志:
02-04 12:21:48.535 7433-7433/com.super8bit.singoffbeta E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at com.super8bit.singoffbeta.UserGamesHandler.SetListViewAdapter(UserGamesHandler.java:58)
at com.super8bit.singoffbeta.UserGamesHandler.onCreateView(UserGamesHandler.java:33)
我的代码是:
public class UserGamesHandler extends android.support.v4.app.Fragment implements
android.view.View.OnClickListener {
File path = new File(Environment.getRootDirectory().getAbsolutePath().toString());
ArrayList<String> fileList = new ArrayList<String>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_user_games, container,
false);
getVideos(path);
SetListViewAdapter();
return view;
}
@Override
public void onClick(View view) {
}
private void getVideos(File f){
File[] files = f.listFiles();
//fileList.clear();
for (File file : files){
fileList.add(file.getName().toString()+".MP4 ");
}
}
private void SetListViewAdapter() {
ListView lv = (ListView) getActivity().findViewById(R.id.listViewTest);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
R.layout.custom_listview, fileList);
lv.setAdapter(adapter);
Toast.makeText(getActivity().getApplicationContext(), fileList.toString(), Toast.LENGTH_LONG).show();
}
}
public类UserGamesHandler扩展了android.support.v4.app.Fragment实现
android.view.view.OnClickListener{
文件路径=新文件(Environment.getRootDirectory().getAbsolutePath().toString());
ArrayList fileList=新建ArrayList();
@凌驾
创建视图上的公共视图(布局、充气机、视图组容器、,
Bundle savedInstanceState){
//为该碎片膨胀布局
视图=充气机。充气(R.layout.fragment\u user\u游戏,容器,
假);
获取视频(路径);
SetListViewAdapter();
返回视图;
}
@凌驾
公共void onClick(视图){
}
私人视频(文件f){
File[]files=f.listFiles();
//fileList.clear();
用于(文件:文件){
添加(file.getName().toString()+“.MP4”);
}
}
私有void SetListViewAdapter(){
ListView lv=(ListView)getActivity().findViewById(R.id.listViewTest);
ArrayAdapter=新的ArrayAdapter(getActivity(),
R.layout.custom_列表视图、文件列表);
低压设置适配器(适配器);
Toast.makeText(getActivity().getApplicationContext(),fileList.toString(),Toast.LENGTH_LONG).show();
}
}
声明您在创建视图上查看变量,并替换此行
ListView lv = (ListView) getActivity().findViewById(R.id.listViewTest);
与
在创建视图上声明查看变量,并替换此行
ListView lv = (ListView) getActivity().findViewById(R.id.listViewTest);
与
public类UserGamesHandler扩展了android.support.v4.app.Fragment实现
android.view.view.OnClickListener{
文件路径=新文件(Environment.getRootDirectory().getAbsolutePath().toString());
ArrayList fileList=新建ArrayList();
@凌驾
创建视图上的公共视图(布局、充气机、视图组容器、,
Bundle savedInstanceState){
//为该碎片膨胀布局
视图=充气机。充气(R.layout.fragment\u user\u游戏,容器,
假);
获取视频(路径);
SetListViewAdapter();
返回视图;
}
@凌驾
已创建ActivityState上的公共无效(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
获取视频(路径);
SetListViewAdapter();
}
私人视频(文件f){
File[]files=f.listFiles();
//fileList.clear();
用于(文件:文件){
添加(file.getName().toString()+“.MP4”);
}
}
私有void SetListViewAdapter(){
ListView lv=(ListView)getView().findViewById(R.id.listViewTest);
ArrayAdapter=新的ArrayAdapter(getActivity(),
R.layout.custom_列表视图、文件列表);
低压设置适配器(适配器);
Toast.makeText(getActivity().getApplicationContext(),fileList.toString(),Toast.LENGTH_LONG).show();
}
}
}
公共类UserGamesHandler扩展了android.support.v4.app.Fragment实现
android.view.view.OnClickListener{
文件路径=新文件(Environment.getRootDirectory().getAbsolutePath().toString());
ArrayList fileList=新建ArrayList();
@凌驾
创建视图上的公共视图(布局、充气机、视图组容器、,
Bundle savedInstanceState){
//为该碎片膨胀布局
视图=充气机。充气(R.layout.fragment\u user\u游戏,容器,
假);
获取视频(路径);
SetListViewAdapter();
返回视图;
}
@凌驾
已创建ActivityState上的公共无效(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
获取视频(路径);
SetListViewAdapter();
}
私人视频(文件f){
File[]files=f.listFiles();
//fileList.clear();
用于(文件:文件){
添加(file.getName().toString()+“.MP4”);
}
}
私有void SetListViewAdapter(){
ListView lv=(ListView)getView().findViewById(R.id.listViewTest);
ArrayAdapter=新的ArrayAdapter(getActivity(),
R.layout.custom_列表视图、文件列表);
低压设置适配器(适配器);
Toast.makeText(getActivity().getApplicationContext(),fileList.toString(),Toast.LENGTH_LONG).show();
}
}
}
getView()
在onActivityCreated
中,我确实尝试过getView(),但它随后在该行抛出一个空指针。还有其他建议吗?您必须重写onActivityCreated,然后才能使用getView()方法。它可以工作!我删除了getVideos(路径);和SetListViewAdapter();从onCreateView。谢谢你的解决方案<代码>getView()在创建的活动中,我确实尝试过getView(),但它随后在该行抛出一个空指针。还有其他建议吗?您必须重写onActivityCreated,然后才能使用getView()方法。它可以工作!我删除了getVideos(路径);和SetListViewAdapter();从onCreateView。谢谢你的解决方案!
public class UserGamesHandler extends android.support.v4.app.Fragment implements
android.view.View.OnClickListener {
File path = new File(Environment.getRootDirectory().getAbsolutePath().toString());
ArrayList<String> fileList = new ArrayList<String>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_user_games, container,
false);
getVideos(path);
SetListViewAdapter();
return view;
}
@Override
public void onActivityCreated (Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
getVideos(path);
SetListViewAdapter();
}
private void getVideos(File f){
File[] files = f.listFiles();
//fileList.clear();
for (File file : files){
fileList.add(file.getName().toString()+".MP4 ");
}
}
private void SetListViewAdapter() {
ListView lv = (ListView) getView().findViewById(R.id.listViewTest);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
R.layout.custom_listview, fileList);
lv.setAdapter(adapter);
Toast.makeText(getActivity().getApplicationContext(), fileList.toString(), Toast.LENGTH_LONG).show();
}
}
}