LongClick删除列表项（在Master-Detail中使用片段）

Question

我已经创建了Master-Detail Flow应用程序，并且我使用了Eclipse / Android创建的所有默认文件。我使用模板创建了一个项目，并且没有对其中的任何内容进行修改，除了添加下面讨论的删除项目的方法。

我需要实现一个onItemLongClickListener，这样当我长按列表中的某个项目时，该项目就会被删除。我不想要提醒或确认或选择多个项目，我只想要一个我长篇大论消失的那个。

我已经找到了几个关于这个主题的教程，但我的问题是他们没有使用片段，所以我对哪些方法去哪里感到有点困惑。 （这是我主要使用的那个：AndroidForBeginners）

如果我理解正确，我应该只使用ItemListActivity和ItemListFragment。我知道片段中的方法将在Activity中调用（例如模板附带的默认onItemSelected）。据我所知，removeItemFromList方法（来自链接教程）从数组中删除该项，并通知适配器更新列表。我的问题是，我不知道数组和适配器在Master-Detail片段和活动中的位置。 DummyContent中有一个ArrayList，所以我想如果我在片段中调用removeItem，然后将它发送到Activity，然后从DummyContent类调用它就可以了。但它并没有，而且我被卡住了。

非常感谢任何建议！

根据要求，这是我目前正在使用的代码。正如我所说，只是默认的Android模板。

ItemListActivity.java

package Andrea.deletelistitem;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

/**
 * An activity representing a list of Items. This activity
 * has different presentations for handset and tablet-size devices. On
 * handsets, the activity presents a list of items, which when touched,
 * lead to a {@link ItemDetailActivity} representing
 * item details. On tablets, the activity presents the list of items and
 * item details side-by-side using two vertical panes.
 * <p>
 * The activity makes heavy use of fragments. The list of items is a
 * {@link ItemListFragment} and the item details
 * (if present) is a {@link ItemDetailFragment}.
 * <p>
 * This activity also implements the required
 * {@link ItemListFragment.Callbacks} interface
 * to listen for item selections.
 */
public class ItemListActivity extends FragmentActivity
        implements ItemListFragment.Callbacks {

    /**
     * Whether or not the activity is in two-pane mode, i.e. running on a tablet
     * device.
     */
    private boolean mTwoPane;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_item_list);

        if (findViewById(R.id.item_detail_container) != null) {
            // The detail container view will be present only in the
            // large-screen layouts (res/values-large and
            // res/values-sw600dp). If this view is present, then the
            // activity should be in two-pane mode.
            mTwoPane = true;

            // In two-pane mode, list items should be given the
            // 'activated' state when touched.
            ((ItemListFragment) getSupportFragmentManager()
                    .findFragmentById(R.id.item_list))
                    .setActivateOnItemClick(true);
        }

        // TODO: If exposing deep links into your app, handle intents here.
    }

    /**
     * Callback method from {@link ItemListFragment.Callbacks}
     * indicating that the item with the given ID was selected.
     */
    @Override
    public void onItemSelected(String id) {
        if (mTwoPane) {
            // In two-pane mode, show the detail view in this activity by
            // adding or replacing the detail fragment using a
            // fragment transaction.
            Bundle arguments = new Bundle();
            arguments.putString(ItemDetailFragment.ARG_ITEM_ID, id);
            ItemDetailFragment fragment = new ItemDetailFragment();
            fragment.setArguments(arguments);
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.item_detail_container, fragment)
                    .commit();

        } else {
            // In single-pane mode, simply start the detail activity
            // for the selected item ID.
            Intent detailIntent = new Intent(this, ItemDetailActivity.class);
            detailIntent.putExtra(ItemDetailFragment.ARG_ITEM_ID, id);
            startActivity(detailIntent);
        }
    }
}

ItemListFragment.java

package Andrea.deletelistitem;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import Andrea.deletelistitem.dummy.DummyContent;

/**
 * A list fragment representing a list of Items. This fragment
 * also supports tablet devices by allowing list items to be given an
 * 'activated' state upon selection. This helps indicate which item is
 * currently being viewed in a {@link ItemDetailFragment}.
 * <p>
 * Activities containing this fragment MUST implement the {@link Callbacks}
 * interface.
 */
public class ItemListFragment extends ListFragment {

    /**
     * The serialization (saved instance state) Bundle key representing the
     * activated item position. Only used on tablets.
     */
    private static final String STATE_ACTIVATED_POSITION = "activated_position";

    /**
     * The fragment's current callback object, which is notified of list item
     * clicks.
     */
    private Callbacks mCallbacks = sDummyCallbacks;

    /**
     * The current activated item position. Only used on tablets.
     */
    private int mActivatedPosition = ListView.INVALID_POSITION;

    /**
     * A callback interface that all activities containing this fragment must
     * implement. This mechanism allows activities to be notified of item
     * selections.
     */
    public interface Callbacks {
        /**
         * Callback for when an item has been selected.
         */
        public void onItemSelected(String id);
    }

    /**
     * A dummy implementation of the {@link Callbacks} interface that does
     * nothing. Used only when this fragment is not attached to an activity.
     */
    private static Callbacks sDummyCallbacks = new Callbacks() {
        @Override
        public void onItemSelected(String id) {
        }
    };

    /**
     * Mandatory empty constructor for the fragment manager to instantiate the
     * fragment (e.g. upon screen orientation changes).
     */
    public ItemListFragment() {
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // TODO: replace with a real list adapter.
        setListAdapter(new ArrayAdapter<DummyContent.DummyItem>(
                getActivity(),
                android.R.layout.simple_list_item_activated_1,
                android.R.id.text1,
                DummyContent.ITEMS));
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        // Restore the previously serialized activated item position.
        if (savedInstanceState != null
                && savedInstanceState.containsKey(STATE_ACTIVATED_POSITION)) {
            setActivatedPosition(savedInstanceState.getInt(STATE_ACTIVATED_POSITION));
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // Activities containing this fragment must implement its callbacks.
        if (!(activity instanceof Callbacks)) {
            throw new IllegalStateException("Activity must implement fragment's callbacks.");
        }

        mCallbacks = (Callbacks) activity;
    }

    @Override
    public void onDetach() {
        super.onDetach();

        // Reset the active callbacks interface to the dummy implementation.
        mCallbacks = sDummyCallbacks;
    }

    @Override
    public void onListItemClick(ListView listView, View view, int position, long id) {
        super.onListItemClick(listView, view, position, id);

        // Notify the active callbacks interface (the activity, if the
        // fragment is attached to one) that an item has been selected.
        mCallbacks.onItemSelected(DummyContent.ITEMS.get(position).id);
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        if (mActivatedPosition != ListView.INVALID_POSITION) {
            // Serialize and persist the activated item position.
            outState.putInt(STATE_ACTIVATED_POSITION, mActivatedPosition);
        }
    }

    /**
     * Turns on activate-on-click mode. When this mode is on, list items will be
     * given the 'activated' state when touched.
     */
    public void setActivateOnItemClick(boolean activateOnItemClick) {
        // When setting CHOICE_MODE_SINGLE, ListView will automatically
        // give items the 'activated' state when touched.
        getListView().setChoiceMode(activateOnItemClick
                ? ListView.CHOICE_MODE_SINGLE
                : ListView.CHOICE_MODE_NONE);
    }

    private void setActivatedPosition(int position) {
        if (position == ListView.INVALID_POSITION) {
            getListView().setItemChecked(mActivatedPosition, false);
        } else {
            getListView().setItemChecked(position, true);
        }

        mActivatedPosition = position;
    }
}

DummyContent.java

package Andrea.deletelistitem.dummy;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Helper class for providing sample content for user interfaces created by
 * Android template wizards.
 * <p>
 * TODO: Replace all uses of this class before publishing your app.
 */
public class DummyContent {

    /**
     * An array of sample (dummy) items.
     */
    public static List<DummyItem> ITEMS = new ArrayList<DummyItem>();

    /**
     * A map of sample (dummy) items, by ID.
     */
    public static Map<String, DummyItem> ITEM_MAP = new HashMap<String, DummyItem>();

    static {
        // Add 3 sample items.
        addItem(new DummyItem("1", "Item 1"));
        addItem(new DummyItem("2", "Item 2"));
        addItem(new DummyItem("3", "Item 3"));
    }

    private static void addItem(DummyItem item) {
        ITEMS.add(item);
        ITEM_MAP.put(item.id, item);
    }

    /**
     * A dummy item representing a piece of content.
     */
    public static class DummyItem {
        public String id;
        public String content;

        public DummyItem(String id, String content) {
            this.id = id;
            this.content = content;
        }

        @Override
        public String toString() {
            return content;
        }
    }
}

这是教程中的方法：

protected void removeItemFromList(int position) {
final int deletePosition = position;

AlertDialog.Builder alert = new AlertDialog.Builder(
        MainActivity.this);

alert.setTitle("Delete");
alert.setMessage("Do you want delete this item?");
alert.setPositiveButton("YES", new OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        // TOD O Auto-generated method stub

            // main code on after clicking yes
            arr.remove(deletePosition);
            adapter.notifyDataSetChanged();
            adapter.notifyDataSetInvalidated();
    }
});
alert.setNegativeButton("CANCEL", new OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        // TODO Auto-generated method stub
        dialog.dismiss();
    }
});

alert.show();
}

这是我修改的方法，用于删除确认提醒：

protected void removeItemFromList(int position) {
    arr.remove(position);
    adapter.notifyDataSetChanged();
    adapter.notifyDataSetInvalidated();
}

在这种方法中，我认为DummyContent中的ITEMS会替换arr数组，因为它是一个ArrayList。但是，我不确定适配器。

Answer 1

在任何名为onActivityCreated的片段上都有一个方法你想要@Override那个方法。

然后，在其中，使用getListView()您可以附加onLongItemClickListener()。

像这样：

getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
          @Override
          public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                //Here you implement your code. Basically delete an item from 
                // the underlying data structure of your adapter, and then...
                setListAdapter(.....); //re-set the list adapter.
                return false;

          }
});