Android DrawerMenu. A different approach using Enums.

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Android DrawerMenu. A different approach using Enums.

This is an example of a drawer menu using enums to define view types and actions.

DrawerAction.java

package com.ahuralab.shakeacocktail.drawer;

/**
 * Menu actions used as events identifiers to propagate events.
 *
 * Created by msama on 14/02/2015.
 */
public enum DrawerAction {
    NONE,
    COCKTAILS_FILTER_ALL,
    COCKTAILS_FILTER_USER_RATED,
    // All the other actions
}

DrawerAdapter.java

package com.ahuralab.shakeacocktail.drawer;

import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.ahuralab.shakeacocktail.R;


/**
 * Instantiate the various items views.
 *
 * Created by msama on 02/02/2015.
 */
public class DrawerAdapter extends ArrayAdapter<DrawerItem> {

    public DrawerAdapter(final Context context) {
        super(context, 0);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // Delegate view initialization to a sub function.
        // Android automatically pass a convertView of the right type
        // using getItemViewType(int position)
        switch(DrawerItem.Type.values()[getItemViewType(position)]) {
            case TOP:
                return getTopView(position, convertView, parent);
            case HEADER:
                return getHeaderView(position, convertView, parent);
            case ITEM:
                return getItemView(position, convertView, parent);
        }
        return null;
    }

    // Delegate method to build the view for Top elements
    private View getTopView(int position, View convertView, ViewGroup parent) {
        DrawerItem.Top item = (DrawerItem.Top)getItem(position);
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) getContext()
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.drawer_top, parent, false);
        }
        TextView text = (TextView) convertView
                .findViewById(R.id.name);
        text.setText(item.getName());
        text = (TextView) convertView
                .findViewById(R.id.email);
        text.setText(item.getEmail());
        return convertView;
    }

    // Delegate method to build the view for Header views
    private View getHeaderView(int position, View convertView, ViewGroup parent) {
        DrawerItem.Header item = (DrawerItem.Header)getItem(position);
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) getContext()
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.drawer_list_header, parent, false);
        }
        TextView text = (TextView) convertView
                .findViewById(R.id.title);
        text.setText(item.getName());
        return convertView;
    }

    // Delegate method to build the view for Item views
    private View getItemView(int position, View convertView, ViewGroup parent) {
        DrawerItem.Item item = (DrawerItem.Item)getItem(position);
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) getContext()
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.drawer_list_item, parent, false);
        }
        TextView text = (TextView) convertView
                .findViewById(R.id.title);
        text.setText(item.getName());

        if (item.getIcon() != 0) {
            ImageView icon = (ImageView) convertView
                    .findViewById(R.id.icon);
            icon.setImageDrawable(convertView.getResources()
                    .getDrawable(item.getIcon()));
        }
        return convertView;
    }

    /**
     * Specifies that not all the items are enabled and forces
     * the view to check them one by one.
     *
     * @return <code>false</code>.
     */
    @Override
    public boolean areAllItemsEnabled() {
        return false;
    }

    /**
     * Specify that only items defined as {link DrawerItem.Type.ITEM}
     * are enabled.
     *
     * @param position the element position being enquired.
     * @return <code>true</code> if the element is enabled,
     *      <code>false</code> otherwise.
     */
    @Override
    public boolean isEnabled(int position) {
        return getItem(position).getItemType() == DrawerItem.Type.ITEM;
    }

    /**
     * Defines how many view types this adapter requires.
     *
     * @return the number of view types.
     */
    @Override
    public int getViewTypeCount() {
        return DrawerItem.Type.values().length;
    }

    /**
     * Returns a unique identifier for each different view type. This will be used by the
     * {link #getView(int, View, ViewGroup)} method
     *
     * @param position the element position being enquired.
     * @return a unique identifier.
     */
    @Override
    public int getItemViewType(int position) {
        return getItem(position).getItemType().ordinal();
    }

}

DrawerItem.java

package com.ahuralab.shakeacocktail.drawer;

/**
 * Defines the various types of drawer menu elements and provides
 * static factory methods.
 * 
 * Created by msama on 02/02/2015.
 */
public abstract class DrawerItem {

    public static Top CreateTop(String name, String email) {
        return new Top(name, email);
    }

    public static Header CreateHeader(String name) {
        return new Header(name);
    }

    public static Item CreateItem(String name, DrawerAction action, int icon) {
        return new Item(name, action, icon);
    }

    /**
     * Menu type used to help the adapter to distinguish which view to use.
     */
    public static enum Type {
        TOP,
        HEADER,
        ITEM
    }

    private final Type itemType;

    private DrawerItem(Type itemType) {
        this.itemType = itemType;
    }

    public Type getItemType() {
        return itemType;
    }

    /**
     * Menu top banner showing the user identity.
     */
    public static final class Top extends DrawerItem {
        private String name;
        private String email;

        private Top(String name, String email) {
            super(Type.TOP);
            this.name = name;
            this.email = email;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getEmail() {
            return email;
        }

        public void setEmail(String email) {
            this.email = email;
        }
    }

    /**
     * Menu section header to be used as a title.
     */
    public static final class Header extends DrawerItem {
        private final String name;

        private Header(String name) {
            super(Type.HEADER);
            this.name = name;
        }

        public String getName() {
            return name;
        }
    }

    /**
     * Clickable drawer item which triggers a
     * {link com.ahuralab.shakeacocktail.drawer.DrawerAction}.
     */
    public static final class Item extends DrawerItem {
        private final String name;
        private final DrawerAction action;
        private final int icon;

        private Item(String name, DrawerAction action, int icon) {
            super(Type.ITEM);
            this.name = name;
            this.action = action;
            this.icon = icon;
        }

        public String getName() {
            return name;
        }

        public DrawerAction getAction() {
            return action;
        }

        public int getIcon() {
            return icon;
        }
    }
}

MyActivity.java

// Pseudo code
public class MyActivity extends Activity {

    private ListView mDrawerList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //...
        final DrawerAdapter adapter = new DrawerAdapter(this);
        adapter.addAll(createDraver());
        mDrawerList.setAdapter(adapter);
        mDrawerList.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                handleDrawerAction(((DrawerItem.Item) adapter.getItem(position)).getAction());
            }
        });
        //...
    }

    private List<DrawerItem> createDraver() {
        List<DrawerItem> drawerItems = new ArrayList<>();
        drawerItems.add(DrawerItem.CreateTop(
                "Username", "foo@email.org"));

        // Menu events
        drawerItems.add(DrawerItem.CreateHeader(
                getResources().getString(R.string.drawer_header_cocktails)));
        drawerItems.add(DrawerItem.CreateItem(
                getResources().getString(R.string.drawer_item_filter_cocktails_all),
                DrawerAction.COCKTAILS_FILTER_ALL, R.drawable.ic_glass));
        drawerItems.add(DrawerItem.CreateItem(
                getResources().getString(R.string.drawer_item_filter_user_rated),
                DrawerAction.COCKTAILS_FILTER_USER_RATED, R.drawable.ic_star));
                
        // Add other items
        return drawerItems;
    }
    
    private void handleDrawerAction(DrawerAction action) {
        switch(action) {
            case COCKTAILS_FILTER_ALL: {
                // Handle this case
                break;
            }
            case COCKTAILS_FILTER_USER_RATED: {
                // Handle this case
                break;
            }
            // Handle other cases
        }
        // Close the drawer layout
        mDrawerLayout.closeDrawer(Gravity.LEFT);
    }
}