DrawerLayout實現的簡易的側滑效果

開始用Android Studio了，之前沒有用Android Studio是由於還不太穩定，現在已經很穩定了，尤其是最近的2.0版，加入很多特性，本人剛開始用，很多特性不是很清楚，也在慢慢摸索，今天第一次用，寫了個側滑的效果，下面是代碼和個人的一點理解

 第一步，創建一個Navigation Drawer Activity,命名爲SliderActivity

public class SliderActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);    
        setContentView(R.layout.activity_slider);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

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

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

        } else if (id == R.id.nav_slideshow) {

        } else if (id == R.id.nav_manage) {

        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }

 SliderActivity是創建的第一個Activity ，而且是唯一一個Activity。 它實現了Navigation.onNavigationItemSelectedListener，看官網上的解釋如下：

       這個接口是用來監聽NavigationView的Menu選中事件的，NavigationView會在側滑出的菜單中用到，後面會出現

      現在來看一下SliderActivity的佈局文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools" android:id="@+id/drawer_layout"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:fitsSystemWindows="true" tools:openDrawer="start">

    <include layout="@layout/app_bar_slider" android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.NavigationView android:id="@+id/nav_view"
        android:layout_width="wrap_content" android:layout_height="match_parent"
        android:layout_gravity="start" android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_slider" app:menu="@menu/activity_slider_drawer" />
     <!--menu裏是一個數組列表，在側滑出的菜單頁顯示
       nav_header_slider是-->
</android.support.v4.widget.DrawerLayout>

   最外層是DrawerLayout佈局  內部的app_bar_slider是側滑菜單未滑出時的佈局，下面的NavigationView是側滑菜單的佈局，SliderActivity實現的Navigation.onNavigationItemSelectedListener正是監聽NavigationView裏的菜單選中的

  下面看看app_bar_slider的佈局代碼

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:fitsSystemWindows="true"
    tools:context="ly.com.testslider.SliderActivity">

    <android.support.design.widget.AppBarLayout android:layout_width="match_parent"
        android:layout_height="wrap_content" android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar android:id="@+id/toolbar"
            android:layout_width="match_parent" android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary" app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_slider" />

    <android.support.design.widget.FloatingActionButton android:id="@+id/fab"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:layout_gravity="bottom|end" android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>

它用了CoordinatorLayout作爲最外面的佈局，下面是google對CoordinatorLayout的描述，CoordinatorLayout是一個繼承自ViewGroup子類，這裏用到了官方描述裏的第一個功能，我

CoordinatorLayout is a super-powered FrameLayout.

CoordinatorLayout is intended for two primary use cases:

1. As a top-level application decor or chrome layout
2. As a container for a specific interaction with one or more child views

側滑的效果如下圖：