Question

我正在尝试将ListView设置为内部类PinnedSectionListActivity的新实例。但我似乎不断收到ClassCastException的错误。我试过去ListAdapter，但似乎仍然给我一个错误。请帮忙。提前谢谢。

package com.example.android.navigationdrawerexample;

import java.util.Locale;

import com.hb.views.PinnedSectionListView;
import com.hb.views.PinnedSectionListView.PinnedSectionListAdapter;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.ListActivity;
import android.app.SearchManager;
import android.content.Context;
import android.content.Intent;
import android.content.res.Configuration;
import android.graphics.Color;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SectionIndexer;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;

    private CharSequence mDrawerTitle;
    private CharSequence mTitle;
    private String[] mPlanetTitles;

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

        mTitle = mDrawerTitle = getTitle();
        mPlanetTitles = getResources().getStringArray(R.array.planets_array);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        // set a custom shadow that overlays the main content when the drawer opens
        mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);

        // set up the drawer's list view with items and click listener
        mDrawerList.setAdapter((ListAdapter) new PinnedSectionListActivity());
        //mDrawerList.setAdapter(new ArrayAdapter<String>(this,R.layout.drawer_list_item, mPlanetTitles));

        mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

        // enable ActionBar app icon to behave as action to toggle nav drawer
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        // ActionBarDrawerToggle ties together the the proper interactions
        // between the sliding drawer and the action bar app icon
        mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
                ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            selectItem(0);
        }
    }

这是logcat输出错误。

03-04 00:44:41.657: E/AndroidRuntime(17759): FATAL EXCEPTION: main
03-04 00:44:41.657: E/AndroidRuntime(17759): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.navigationdrawerexample/com.example.android.navigationdrawerexample.MainActivity}: java.lang.ClassCastException: com.example.android.navigationdrawerexample.MainActivity$PinnedSectionListActivity cannot be cast to android.widget.ListAdapter
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2266)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.ActivityThread.access$600(ActivityThread.java:150)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.os.Looper.loop(Looper.java:213)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.ActivityThread.main(ActivityThread.java:5225)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at java.lang.reflect.Method.invokeNative(Native Method)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at java.lang.reflect.Method.invoke(Method.java:525)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at dalvik.system.NativeStart.main(Native Method)
03-04 00:44:41.657: E/AndroidRuntime(17759): Caused by: java.lang.ClassCastException: com.example.android.navigationdrawerexample.MainActivity$PinnedSectionListActivity cannot be cast to android.widget.ListAdapter
03-04 00:44:41.657: E/AndroidRuntime(17759):    at com.example.android.navigationdrawerexample.MainActivity.onCreate(MainActivity.java:77)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.Activity.performCreate(Activity.java:5133)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-04 00:44:41.657: E/AndroidRuntime(17759):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2230)

再次感谢。下面是PinnedSectionListActivity的代码。

public class PinnedSectionListActivity extends ListActivity implements OnClickListener {

    static class SimpleAdapter extends ArrayAdapter<Item> implements PinnedSectionListAdapter {

        private static final int[] COLORS = new int[] {
            R.color.green_light, 
            R.color.orange_light,
            R.color.blue_light, 
            R.color.red_light };

        public SimpleAdapter(Context context, int resource, int textViewResourceId) {
            super(context, resource, textViewResourceId);

            //final int sectionsNumber = 'Z' - 'A' + 1;
            final int sectionsNumber = 'Z' - 'A' + 1;

            prepareSections(sectionsNumber);

            int sectionPosition = 0, listPosition = 0;

            for (int i=0; i< sectionsNumber; i++) {

                String title = null;

                final String []country = {
                        "Korean", "Japanese", "Chinese", "Cambodian", "Loas", "Taiwamese"
                };


                final String [] CATEGORY = {
                    "Language",
                    "sports",
                    "love",
                    "luxury",
                    "vacation",
                    "games",
                    "home",
                    "travel",
                    "electronics",
                    "movies",
                };

                switch (('A' + i)) {
                case ('A' + 0):
                    title = country[0];
                    break;
                case ('A' + 1):
                    title = country[1];
                    break;
                case ('A' + 2):
                    title = country[2];
                    break;
                case ('A' + 3):
                    title = country[3];
                    break;
                case ('A' + 4):
                    title = country[4];
                    break;
                case ('A' + 5):
                    title = country[5];
                    break;
                default:
                    break;
                }

                //Create a new Item class with section header and Name
                Item section = new Item(Item.SECTION, title + " " + i);
                //Item section = new Item(Item.SECTION, String.valueOf((char)('A' + i)));

                section.sectionPosition = sectionPosition;
                section.listPosition = listPosition++;
                onSectionAdded(section, sectionPosition);
                add(section);

                final int itemsNumber = CATEGORY.length; 

                //(int) Math.abs((Math.cos(2f*Math.PI/3f * sectionsNumber / (i+1f)) * 25f));

                // For loop to iterate the exact number of itemNumber
                for (int j = 0;j < CATEGORY.length;j++) {
                    //Item item = new Item(Item.ITEM, section.text.toUpperCase(Locale.KOREA) + " - " + j);
                    Item item = new Item(Item.ITEM, CATEGORY[j]);
                    item.sectionPosition = sectionPosition;
                    item.listPosition = listPosition++;
                    add(item);
                }

                sectionPosition++;
            }
        }

        protected void prepareSections(int sectionsNumber) { }
        protected void onSectionAdded(Item section, int sectionPosition) { }

        @Override public View getView(int position, View convertView, ViewGroup parent) {
            TextView view = (TextView) super.getView(position, convertView, parent);
            view.setTextColor(Color.DKGRAY );
            view.setTag("" + position);
            Item item = getItem(position);
            if (item.type == Item.SECTION) {
                //view.setOnClickListener(PinnedSectionListActivity.this);
                view.setBackgroundColor(parent.getResources().getColor(COLORS[item.sectionPosition % COLORS.length]));
            }
            return view;
        }

        @Override public int getViewTypeCount() {
            return 2;
        }

        @Override public int getItemViewType(int position) {
            return getItem(position).type;
        }

        @Override
        public boolean isItemViewTypePinned(int viewType) {
            return viewType == Item.SECTION;
        }

    }

    static class Item {

        public static final int ITEM = 0;
        public static final int SECTION = 1;

        public final int type;
        public final String text;

        public int sectionPosition;
        public int listPosition;

        public Item(int type, String text) {
            this.type = type;
            this.text = text;
        }

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

    }



    static class FastScrollAdapter extends SimpleAdapter implements SectionIndexer {

        private Item[] sections;

        public FastScrollAdapter(Context context, int resource, int textViewResourceId) {
            super(context, resource, textViewResourceId);
        }

        @Override protected void prepareSections(int sectionsNumber) {
            sections = new Item[sectionsNumber];
        }

        @Override protected void onSectionAdded(Item section, int sectionPosition) {
            sections[sectionPosition] = section;
        }

        @Override public Item[] getSections() {
            return sections;
        }

        @Override public int getPositionForSection(int section) {
            if (section >= sections.length) {
                section = sections.length - 1;
            }
            return sections[section].listPosition;
        }

        @Override public int getSectionForPosition(int position) {
            if (position >= getCount()) {
                position = getCount() - 1;
            }
            return getItem(position).sectionPosition;
        }

    }




    private boolean hasHeaderAndFooter;
    private boolean isFastScroll;
    private boolean addPadding;
    private boolean isShadowVisible = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (savedInstanceState != null) {
            isFastScroll = savedInstanceState.getBoolean("isFastScroll");
            addPadding = savedInstanceState.getBoolean("addPadding");
            isShadowVisible = savedInstanceState.getBoolean("isShadowVisible");
            hasHeaderAndFooter = savedInstanceState.getBoolean("hasHeaderAndFooter");
        }
        initializeHeaderAndFooter();
        initializeAdapter();
        initializePadding();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putBoolean("isFastScroll", isFastScroll);
        outState.putBoolean("addPadding", addPadding);
        outState.putBoolean("isShadowVisible", isShadowVisible);
        outState.putBoolean("hasHeaderAndFooter", hasHeaderAndFooter);
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        Item item = (Item) getListView().getAdapter().getItem(position);
        if (item != null) {
            Toast.makeText(this, "Item " + position + ": " + item.text, Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "Item " + position, Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        menu.getItem(0).setChecked(isFastScroll);
        menu.getItem(1).setChecked(addPadding);
        menu.getItem(2).setChecked(isShadowVisible);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_fastscroll:
                isFastScroll = !isFastScroll;
                item.setChecked(isFastScroll);
                initializeAdapter();
                break;
            case R.id.action_addpadding:
                addPadding = !addPadding;
                item.setChecked(addPadding);
                initializePadding();
                break;
            case R.id.action_showShadow:
                isShadowVisible = !isShadowVisible;
                item.setChecked(isShadowVisible);
                ((PinnedSectionListView)getListView()).setShadowVisible(isShadowVisible);
                break;
            case R.id.action_showHeaderAndFooter:
                hasHeaderAndFooter = !hasHeaderAndFooter;
                item.setChecked(hasHeaderAndFooter);
                initializeHeaderAndFooter();
                break;
        }
        return true;
    }

    private void initializePadding() {
        float density = getResources().getDisplayMetrics().density;
        int padding = addPadding ? (int) (16 * density) : 0;
        getListView().setPadding(padding, padding, padding, padding);
    }

    private void initializeHeaderAndFooter() {
        setListAdapter(null);
        if (hasHeaderAndFooter) {
            ListView list = getListView();

            LayoutInflater inflater = LayoutInflater.from(this);
            TextView header1 = (TextView) inflater.inflate(android.R.layout.simple_list_item_1, list, false);
            header1.setText("First header");
            list.addHeaderView(header1);

            TextView header2 = (TextView) inflater.inflate(android.R.layout.simple_list_item_1, list, false);
            header2.setText("Second header");
            list.addHeaderView(header2);

            TextView footer = (TextView) inflater.inflate(android.R.layout.simple_list_item_1, list, false);
            footer.setText("Single footer");
            list.addFooterView(footer);
        }
        initializeAdapter();
    }

    @SuppressLint("NewApi")
    private void initializeAdapter() {
        getListView().setFastScrollEnabled(isFastScroll);
        if (isFastScroll) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
                getListView().setFastScrollAlwaysVisible(true);
            }
            setListAdapter(new FastScrollAdapter(this, android.R.layout.simple_list_item_1, android.R.id.text1));
        } else {
            setListAdapter(new SimpleAdapter(this, android.R.layout.simple_list_item_1, android.R.id.text1));
        }
    }

    @Override
    public void onClick(View v) {
        Toast.makeText(this, "Item: " + v.getTag() , Toast.LENGTH_SHORT).show();
    }

}

Answer 1

这导致错误

mDrawerList.setAdapter((ListAdapter) new PinnedSectionListActivity());

您的PinnedSectionListActivity是Activity的实例，而非Adapter的实例，您需要在ListAdapter设置mDrawerList的实例

您可以SimpleAdapter PinnedSectionListActivity使用public类public static class SimpleAdapter extends ArrayAdapter<Item> implements PinnedSectionListAdapter。

mDrawerList.setAdapter(new PinnedSectionListActivity.SimpleAdapter(context,resource,textViewResource));

并使用

{{1}}

带有导航抽屉的Android ClassCastException

1 个答案: