我有一个ListView作为文件浏览器：
public class FileChooser extends ListActivity {
private File currentDir;
private FileArrayAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
currentDir = new File("/sdcard/");
fill(currentDir);
registerForContextMenu(getListView());
// get the attachment's filename
SharedPreferences preferences = PreferenceManager
.getDefaultSharedPreferences(this);
String attachmentFileName = preferences.getString("fileName", "");
// save the attachment
try {
InputStream attachment = getContentResolver().openInputStream(
getIntent().getData());
File savedFile = new File(Environment.getExternalStorageDirectory()
.getAbsolutePath(), attachmentFileName);
FileOutputStream f = new FileOutputStream(savedFile);
byte[] buffer = new byte[1024];
int len1 = 0;
while ((len1 = attachment.read(buffer)) > 0) {
f.write(buffer);
}
f.close();
} catch (Exception e) {
}
}
// File Manager Source to view SD Card or Internal Storage Contents
private void fill(File f) {
File[] dirs = f.listFiles();
this.setTitle("Current Dir: " + f.getName());
List<Item> dir = new ArrayList<Item>();
List<Item> fls = new ArrayList<Item>();
try {
for (File ff : dirs) {
Date lastModDate = new Date(ff.lastModified());
DateFormat formater = DateFormat.getDateTimeInstance();
String date_modify = formater.format(lastModDate);
if (ff.isDirectory()) {
File[] fbuf = ff.listFiles();
int buf = 0;
if (fbuf != null) {
buf = fbuf.length;
} else
buf = 0;
String num_item = String.valueOf(buf);
if (buf == 0)
num_item = num_item + " item";
else
num_item = num_item + " items";
// String formated = lastModDate.toString();
dir.add(new Item(ff.getName(), num_item, date_modify, ff
.getAbsolutePath(), "directory_icon"));
} else {
fls.add(new Item(ff.getName(), ff.length() + " Byte",
date_modify, ff.getAbsolutePath(), "file_icon"));
}
}
} catch (Exception e) {
}
Collections.sort(dir);
Collections.sort(fls);
dir.addAll(fls);
if (!f.getName().equalsIgnoreCase("sdcard"))
dir.add(0, new Item("..", "Parent Directory", "", f.getParent(),
"directory_up"));
adapter = new FileArrayAdapter(FileChooser.this, R.layout.file_view,
dir);
this.setListAdapter(adapter);
}
// onClick listener to move back one directory
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
// TODO Auto-generated method stub
super.onListItemClick(l, v, position, id);
Item o = adapter.getItem(position);
if (o.getImage().equalsIgnoreCase("directory_icon")
|| o.getImage().equalsIgnoreCase("directory_up")) {
currentDir = new File(o.getPath());
fill(currentDir);
} else {
onFileClick(o);
}
}
// open file onClick
private void onFileClick(Item o) {
Intent intent = new Intent();
intent.putExtra("GetPath", currentDir.toString());
intent.putExtra("GetFileName", o.getName());
setResult(RESULT_OK, intent);
finish();
}
我添加了一个上下文菜单：
@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
menu.setHeaderTitle("Context Menu");
menu.add(0, v.getId(), 0, "Copy");
menu.add(0, v.getId(), 0, "Paste");
menu.add(0, v.getId(), 0, "Delete");
}
@Override
public boolean onContextItemSelected(MenuItem item) {
if (item.getTitle() == "Copy") {
function1(item.getItemId());
}
if (item.getTitle() == "Paste") {
function2(item.getItemId());
} else if (item.getTitle() == "Delete") {
function3(item.getItemId());
} else {
return false;
}
return true;
}
public void function1(int id) {
Toast.makeText(this, "Copy", Toast.LENGTH_SHORT).show();
try {
copyDirectoryOneLocationToAnotherLocation(currentDir, currentDir);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void function2(int id) {
Toast.makeText(this, "Paste", Toast.LENGTH_SHORT).show();
}
public void function3(int id) {
Toast.makeText(this, "Delete", Toast.LENGTH_SHORT).show();
DeleteRecursive(currentDir);
}
我已经创建了使用上下文菜单删除和复制数据的方法：
private void DeleteRecursive(File fileOrDirectory) {
if (fileOrDirectory.isDirectory())
for (File child : fileOrDirectory.listFiles())
DeleteRecursive(child);
fileOrDirectory.delete();
}
public static void copyDirectoryOneLocationToAnotherLocation(
File sourceLocation, File targetLocation) throws IOException {
if (sourceLocation.isDirectory()) {
if (!targetLocation.exists()) {
targetLocation.mkdir();
}
String[] children = sourceLocation.list();
for (int i = 0; i < sourceLocation.listFiles().length; i++) {
copyDirectoryOneLocationToAnotherLocation(new File(
sourceLocation, children[i]), new File(targetLocation,
children[i]));
}
} else {
InputStream in = new FileInputStream(sourceLocation);
OutputStream out = new FileOutputStream(targetLocation);
// Copy the bits from instream to outstream
byte[] buf = new byte[1024];
int len;
while ((len = in.read(buf)) > 0) {
out.write(buf, 0, len);
}
in.close();
out.close();
}
}
}
我的问题是 - 每次我尝试删除文件时，我都会在第184行遇到强制关闭错误：for (File child : fileOrDirectory.listFiles())
我相信我的DeleteRecursive方法存在问题 - 但我不确定如何解决它。
01-09 11:27:39.491: E/AndroidRuntime(6439): FATAL EXCEPTION: main
01-09 11:27:39.491: E/AndroidRuntime(6439): java.lang.NullPointerException
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.example.project.FileChooser.DeleteRecursive(FileChooser.java:184)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.example.project.FileChooser.DeleteRecursive(FileChooser.java:185)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.example.project.FileChooser.function3(FileChooser.java:178)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.example.project.FileChooser.onContextItemSelected(FileChooser.java:153)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.app.Activity.onMenuItemSelected(Activity.java:2597)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.policy.impl.PhoneWindow$DialogMenuCallback.onMenuItemSelected(PhoneWindow.java:3663)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.view.menu.MenuDialogHelper.onClick(MenuDialogHelper.java:167)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:963)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.widget.AdapterView.performItemClick(AdapterView.java:298)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.widget.AbsListView.performItemClick(AbsListView.java:1128)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2812)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.widget.AbsListView$1.run(AbsListView.java:3571)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.os.Handler.handleCallback(Handler.java:725)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.os.Handler.dispatchMessage(Handler.java:92)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.os.Looper.loop(Looper.java:153)
01-09 11:27:39.491: E/AndroidRuntime(6439): at android.app.ActivityThread.main(ActivityThread.java:5297)
01-09 11:27:39.491: E/AndroidRuntime(6439): at java.lang.reflect.Method.invokeNative(Native Method)
01-09 11:27:39.491: E/AndroidRuntime(6439): at java.lang.reflect.Method.invoke(Method.java:511)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
01-09 11:27:39.491: E/AndroidRuntime(6439): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
01-09 11:27:39.491: E/AndroidRuntime(6439): at dalvik.system.NativeStart.main(Native Method)
01-09 11:27:40.204: D/dalvikvm(6439): threadid=11: interp stack at 0x5f2b8000
01-09 11:27:41.567: I/Process(6439): Sending signal. PID: 6439 SIG: 9
答案 0 :(得分：0)
只需更改此方法：
private void DeleteRecursive(File fileOrDirectory) {
if (fileOrDirectory.isDirectory()) {
File[] children = fileOrDirectory.listFiles();
if(null != children) {
for (File child : children)
DeleteRecursive(child);
}
}
fileOrDirectory.delete();
}