手把手教你打造一个Material Design风格的App(四)

——接上文。

3.3实现导航抽屉菜单项的选择

尽管导航抽屉已经实现了，但是你会发现选择抽屉列表项并没有反应，这是因为我们还没有实现RecycleView items的点击监听。

因为我们在导航抽屉里有3个菜单（Home，Friends & Messages），所以需要为每一个菜单项创建一个独立的Fragment。

（24）在res-->layout里面，创建一个名为fragment_home.xml的文件并添加如下代码。

fragment_home.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="androidhive.info.materialdesign.activity.HomeFragment">

    <TextView
        android:id="@+id/label"
        android:layout_alignParentTop="true"
        android:layout_marginTop="100dp"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:textSize="45dp"
        android:text="HOME"
        android:textStyle="bold"/>

    <TextView
        android:layout_below="@id/label"
        android:layout_centerInParent="true"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textSize="12dp"
        android:layout_marginTop="10dp"
        android:gravity="center_horizontal"
        android:text="Edit fragment_home.xml to change the appearance" />

</RelativeLayout>

（25）在activity包下，创建一个名为HomeFragment.java的类，并添加如下代码。

HomeFragment.java
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class HomeFragment extends Fragment {

    public HomeFragment() {
        // Required empty public constructor
    }

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

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_home, container, false);

        // Inflate the layout for this fragment
        return rootView;
    }

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

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

（26）同样，创建FriendsFragment.java和MessagesFragment.java两个fragment类，并创建fragment_friends.xml和fragment_messages.xml布局文件，代码请参考前两步。

（27）打开MainActivity.java并作如下修改。

>displayView()方法会显示当导航菜单选中时对应的fragment视图，这个方法应该在某个导航菜单选中时，在onDrawerItemSelected()中调用，来展示对应的视图。

MainActivity.java
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity implements FragmentDrawer.FragmentDrawerListener {

    private static String TAG = MainActivity.class.getSimpleName();

    private Toolbar mToolbar;
    private FragmentDrawer drawerFragment;

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

        mToolbar = (Toolbar) findViewById(R.id.toolbar);

        setSupportActionBar(mToolbar);
        getSupportActionBar().setDisplayShowHomeEnabled(true);

        drawerFragment = (FragmentDrawer)
                getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
        drawerFragment.setUp(R.id.fragment_navigation_drawer, (DrawerLayout) findViewById(R.id.drawer_layout), mToolbar);
        drawerFragment.setDrawerListener(this);

        // display the first navigation drawer view on app launch
        displayView(0);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        if(id == R.id.action_search){
            Toast.makeText(getApplicationContext(), "Search action is selected!", Toast.LENGTH_SHORT).show();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onDrawerItemSelected(View view, int position) {
            displayView(position);
    }

    private void displayView(int position) {
        Fragment fragment = null;
        String title = getString(R.string.app_name);
        switch (position) {
            case 0:
                fragment = new HomeFragment();
                title = getString(R.string.title_home);
                break;
            case 1:
                fragment = new FriendsFragment();
                title = getString(R.string.title_friends);
                break;
            case 2:
                fragment = new MessagesFragment();
                title = getString(R.string.title_messages);
                break;
            default:
                break;
        }

        if (fragment != null) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.replace(R.id.container_body, fragment);
            fragmentTransaction.commit();

            // set the toolbar title
            getSupportActionBar().setTitle(title);
        }
    }
}

好了，再次运行App，你可以看到选择导航菜单起作用了，点击会在toolbar下方显示对应的视图。

全文完。

原文地址：http://www.androidhive.info/2015/04/android-getting-started-with-material-design/