Android 试图从listview中删除的空指针异常
我在Android 试图从listview中删除的空指针异常,android,android-listview,nullpointerexception,Android,Android Listview,Nullpointerexception,我在文件列表中的deleteIt方法中得到一个空指针异常 我需要一些帮助,试图删除该文件,请友好。如何添加longclick方法花了我几个小时。这可能会被人使用,但我需要帮助从列表中删除项目 public class AndroidExplorer extends ListActivity { private List<String> item = null; private List<String> path = null; private TextView myP
文件列表中的deleteIt
方法中得到一个空指针异常代码>
我需要一些帮助,试图删除该文件,请友好。如何添加longclick
方法花了我几个小时。这可能会被人使用,但我需要帮助从列表中删除项目
public class AndroidExplorer extends ListActivity
{
private List<String> item = null;
private List<String> path = null;
private TextView myPath;
ArrayAdapter filelist = null;
File myFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/GV-Skynet");
String root2 = myFile.getAbsolutePath();;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myPath = (TextView)findViewById(R.id.path);
getDir(root2);
ListView list = getListView();
list.setOnItemLongClickListener(new OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view,
int position, long id)
{
File file = new File(path.get(position));
deleteIt("Do you want to Delete", file.getName(), file );
return true;
}
});
}
private void showToast(String msg)
{
Toast error = Toast.makeText(getBaseContext(), msg, Toast.LENGTH_LONG);
error.show();
}
private void getDir(String dirPath)
{
myPath.setText("Location: " + dirPath);
item = new ArrayList<String>();
path = new ArrayList<String>();
File f = new File(dirPath);
File[] files = f.listFiles();
if(!dirPath.equals(root2))
{
item.add("Return to GV-Skynet Directory");
path.add(f.getParent());
}
for(int i=0; i < files.length; i++)
{
File file = files[i];
path.add(file.getPath());
if(file.isDirectory())
item.add(file.getName() + "/");
else
item.add(file.getName());
}
ArrayAdapter<String> fileList =
new ArrayAdapter<String>(this, R.layout.row, item);
setListAdapter(fileList);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id)
{
File file = new File(path.get(position));
if (file.isDirectory())
{
if(file.canRead())
getDir(path.get(position));
else
{
new AlertDialog.Builder(this)
.setIcon(R.drawable.icon)
.setTitle("[" + file.getName() + "] folder can't be read!")
.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
}
}).show();
}
}
else
{
String fileName = file.getName();
String fname="";
String ext="";
int mid= fileName.lastIndexOf(".");
fname=fileName.substring(0,mid);
ext=fileName.substring(mid+1,fileName.length());
if(ext.equals("jpg"))
{
Intent intent = new Intent("android.intent.action.VIEW");
intent.addCategory("android.intent.category.DEFAULT");
intent.addFlags (Intent.FLAG_ACTIVITY_NEW_TASK);
Uri uri = Uri.fromFile(file);
intent.setDataAndType (uri, "image/*");
this.startActivity(intent);
}
if(ext.equals("3gp"))
{
Intent intent = new Intent("android.intent.action.VIEW");
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.putExtra ("oneshot", 0);
intent.putExtra ("configchange", 0);
Uri uri = Uri.fromFile(file);
intent.setDataAndType (uri, "video/*");
this.startActivity(intent);
}
}
}
public void deleteIt( String title, String name, File file )
{
final String name1 = name;
final File tmFile = file;
new AlertDialog.Builder(this)
.setTitle(title)
.setMessage(name1)
.setPositiveButton("YES", new DialogInterface.OnClickListener() // OnClickListener()
{
public void onClick(DialogInterface arg0, int arg1)
{
//item = new ArrayList<String>();
item.remove(tmFile.getName()); // remove the item
filelist.notifyDataSetChanged(); // let the adapter know to update
showToast("File Deleted: " + tmFile.getName() );
}
})
.setNegativeButton("NO", new DialogInterface.OnClickListener() // OnClickListener()
{
public void onClick(DialogInterface arg0, int arg1) {
// do stuff onclick of CANCEL
showToast("CANCELLING DELETE");
}
}).show();
}
}
公共类AndroidExplorer扩展了ListActivity
{
私有列表项=null;
私有列表路径=null;
私有文本视图myPath;
ArrayAdapter文件列表=空;
File myFile=新文件(Environment.getExternalStorageDirectory().getAbsolutePath()+“/GV Skynet”);
字符串root2=myFile.getAbsolutePath();;
/**在首次创建活动时调用*/
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myPath=(TextView)findViewById(R.id.path);
getDir(root2);
ListView list=getListView();
list.setOnItemLongClickListener(新的OnItemLongClickListener(){
@凌驾
长单击(AdapterView父视图、视图、,
内部位置,长id)
{
File File=新文件(path.get(position));
deleteIt(“是否要删除”,file.getName(),file);
返回true;
}
});
}
私有void showtoos(字符串msg)
{
Toast error=Toast.makeText(getBaseContext(),msg,Toast.LENGTH_LONG);
error.show();
}
私有void getDir(字符串dirPath)
{
setText(“位置:“+dirPath”);
item=newarraylist();
路径=新的ArrayList();
文件f=新文件(dirPath);
File[]files=f.listFiles();
如果(!dirPath.equals(root2))
{
添加(“返回GV天网目录”);
add(f.getParent());
}
对于(int i=0;i
试试这个改变你的陈述
ArrayAdapter filelist = null;
与
ArrayAdapter filelist=null;
而且您正在getDir方法中重新声明filelist,所以将其更改为
filelist = new ArrayAdapter<String>(this,R.layout.row, item);
setListAdapter(filelist);
filelist=newarrayadapter(此,R.layout.row,项);
setListAdapter(文件列表);
长点击(AdapterView父项、视图、int位置、长id){
File File=新文件(path.get(position));
if(file.exists()){
deleteIt(“是否要删除”,file.getName(),file);
}否则{
Toast.makeText(此“文件不存在”,Toast.LENGTH_SHORT).show();
}
}
您能否编辑您的帖子以提供LogCat错误输出?是否确实要在getDir()中声明局部变量ArrayAdapter文件列表?它覆盖类中声明的“ArrayAdapter文件列表”。
filelist = new ArrayAdapter<String>(this,R.layout.row, item);
setListAdapter(filelist);
onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
File file = new File(path.get(position));
if (file.exists()) {
deleteIt("Do you want to Delete", file.getName(), file);
} else {
Toast.makeText(this, "File not Exist", Toast.LENGTH_SHORT).show();
}
}