我正在制作一个家庭作业计划器应用程序，我正在寻找一种方法来只显示包含Task对象的ArrayList中的某些元素。用户单击课程标题列表中的课程后，应显示与该课程相关的任务列表。目前，无论选择哪个课程，它都会显示所有任务的列表。每个Task对象在名为mBelongsToCourse的字段中存储它所属的过程。我希望能够过滤我在TaskAdapter中使用的所有任务的ArrayList，只显示属于特定课程的任务，但我的所有尝试都没有结果。
下面是我的TaskListFragment类，其中包含TaskAdapter：
public class TaskListFragment extends ListFragment {
private ArrayList<Task> mTasks;
private static String courseName;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
courseName = getActivity().getIntent().getStringExtra("name");
getActivity().setTitle(courseName);
mTasks = TaskLab.get(getActivity()).getTasks();
TaskAdapter adapter = new TaskAdapter(mTasks);
setListAdapter(adapter);
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
//Get the Task from the adapter
Task t = ((TaskAdapter)getListAdapter()).getItem(position);
// Start TaskActivity for this task
Intent i = new Intent(getActivity(), TaskActivity.class);
i.putExtra(TaskFragment.EXTRA_TASK_ID, t.getId());
startActivity(i);
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.fragment_task_list, menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.menu_item_new_task:
Task task = new Task();
task.setBelongsToCourse(courseName);
TaskLab.get(getActivity()).addTask(task);
Intent i = new Intent(getActivity(), TaskActivity.class);
i.putExtra(TaskFragment.EXTRA_TASK_ID, task.getId());
//i.putExtra("cn", task.getBelongsToCourse());
startActivityForResult(i, 0);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
getActivity().getMenuInflater().inflate(R.menu.task_list_item_context, menu);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup parent,
Bundle savedInstanceState) {
View v = super.onCreateView(inflater, parent, savedInstanceState);
ListView listView = (ListView)v.findViewById(android.R.id.list);
listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);
listView.setMultiChoiceModeListener(new MultiChoiceModeListener() {
public void onItemCheckedStateChanged(ActionMode mode, int position,
long id, boolean checked) {
// Required, but not used in this implementation
}
// ActionMode.Callback methods
public boolean onCreateActionMode(ActionMode mode, Menu menu) {
MenuInflater inflater = mode.getMenuInflater();
inflater.inflate(R.menu.task_list_item_context, menu);
return true;
}
public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
return false;
// Required, but not used in this implementation
}
public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
switch (item.getItemId()) {
case R.id.menu_item_delete_task:
TaskAdapter adapter = (TaskAdapter)getListAdapter();
TaskLab taskLab = TaskLab.get(getActivity());
for (int i = adapter.getCount() - 1; i >= 0; i--) {
if (getListView().isItemChecked(i)) {
taskLab.deleteTask(adapter.getItem(i));
}
}
mode.finish();
adapter.notifyDataSetChanged();
return true;
default:
return false;
}
}
public void onDestroyActionMode(ActionMode mode) {
// Required, but not used in this implementation
}
});
return v;
}
@Override
public boolean onContextItemSelected(MenuItem item) {
AdapterContextMenuInfo info = (AdapterContextMenuInfo)item.getMenuInfo();
int position = info.position;
TaskAdapter adapter = (TaskAdapter)getListAdapter();
Task task = adapter.getItem(position);
switch (item.getItemId()) {
case R.id.menu_item_delete_task:
TaskLab.get(getActivity()).deleteTask(task);
adapter.notifyDataSetChanged();
return true;
}
return super.onContextItemSelected(item);
}
@Override
public void onResume() {
super.onResume();
((TaskAdapter)getListAdapter()).notifyDataSetChanged();
}
private class TaskAdapter extends ArrayAdapter<Task> {
public TaskAdapter(ArrayList<Task> tasks) {
super(getActivity(), 0, tasks);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// If we weren't given a view, inflate one
if (convertView == null) {
convertView = getActivity().getLayoutInflater()
.inflate(R.layout.list_item_task, null);
}
// Configure the view for this Task
Task t = getItem(position);
TextView titleTextView =
(TextView)convertView.findViewById(R.id.task_list_item_titleTextView);
titleTextView.setText(t.getTitle());
TextView dateTextView =
(TextView)convertView.findViewById(R.id.task_list_item_dateTextView);
dateTextView.setText(t.getDate().toString());
CheckBox completedCheckBox =
(CheckBox)convertView.findViewById(R.id.task_list_item_completedCheckBox);
completedCheckBox.setChecked(t.isCompleted());
return convertView;
}
}
}
非常感谢任何帮助。
编辑：我遵循了Ravind Maurya和Embattled Swag的建议并更新了我的TaskAdapter：private class TaskAdapter extends ArrayAdapter<Task> implements Filterable {
private ArrayList<Task> taskList;
private Filter taskFilter;
public TaskAdapter(ArrayList<Task> tasks) {
super(getActivity(), 0, tasks);
this.taskList = tasks;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// If we weren't given a view, inflate one
if (convertView == null) {
convertView = getActivity().getLayoutInflater()
.inflate(R.layout.list_item_task, null);
}
// Configure the view for this Task
Task t = getItem(position);
TextView titleTextView =
(TextView)convertView.findViewById(R.id.task_list_item_titleTextView);
titleTextView.setText(t.getTitle());
TextView dateTextView =
(TextView)convertView.findViewById(R.id.task_list_item_dateTextView);
dateTextView.setText(t.getDate().toString());
CheckBox completedCheckBox =
(CheckBox)convertView.findViewById(R.id.task_list_item_completedCheckBox);
completedCheckBox.setChecked(t.isCompleted());
return convertView;
}
@Override
public Filter getFilter() {
if (taskFilter == null)
taskFilter = new TaskFilter();
return taskFilter;
}
private class TaskFilter extends Filter {
@Override
protected FilterResults performFiltering (CharSequence constraint) {
FilterResults results = new FilterResults();
if (constraint == null | constraint.length() == 0) {
results.values = taskList;
results.count = taskList.size();
} else {
ArrayList<Task> newTaskList = new ArrayList<Task>();
for (Task t : taskList) {
if (t.getBelongsToCourse().toUpperCase().startsWith(constraint.toString().toUpperCase())) {
newTaskList.add(t);
}
}
results.values = newTaskList;
results.count = newTaskList.size();
} return results;
}
@SuppressWarnings("unchecked")
@Override
protected void publishResults(CharSequence constraint,
FilterResults results) {
// Now we have to inform the adapter about the new list filtered
if (results.count == 0)
notifyDataSetInvalidated();
else {
taskList = (ArrayList<Task>)results.values;
notifyDataSetChanged();
}
}
}
}
现在我遇到的问题是我不知道在哪里调用.getFilter（）。filter（courseName）来过滤ArrayList。
答案 0 :(得分：0)
昨天我按照这个例子直接提出了一个固体过滤器：http://www.survivingwithandroid.com/2012/10/android-listview-custom-filter-and.html
然而;此示例不包括您使用退格键的情况，因此列表视图必须重新填充。您可以在此处关注通用过滤器的实际源代码（它位于底部...基本上您只需创建一个副本，然后减少其中一个列表的项目）：http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/1.5_r4/android/widget/ArrayAdapter.java#ArrayAdapter.0mOriginalValues