Android中LayoutInflater的使用

首先對LayoutInflater下一個定義吧，Layoutinflater的作用就是將一個xml布局檔案執行個體化為View對象。

擷取Layoutinflater對象的方法有三種，招不在多，管用就行，跟蹤源碼後發現三種方法的本質都是調用了context.getSystemService()，所以建議以後寫的時候就用context.getSystemService()。具體寫法如下：

[java]
LayoutInflater inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

LayoutInflater inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);接下來重點介紹inflate()方法的使用：

1、傳回值：

View對象，有了View對象我們就能做諸如setContentView()或者在自訂Adapter裡面的getView()方法中擷取item的布局。

2、參數：

[java]
public View inflate (int resource, ViewGroup root) 

public View inflate (int resource, ViewGroup root)
第一個參數是一個xml檔案的R索引，比如R.layout.activity_main。第二個參數如果不為null就是將得到的View對象再放入一個Viewgroup容器中，我這麼說可能有的讀者還不是很清楚，文章的最後會有一個例子來說明問題。
[java]
public View inflate (int resource, ViewGroup root, boolean attachToRoot) 

public View inflate (int resource, ViewGroup root, boolean attachToRoot)

這裡的第三個參數的意思是如果第二個參數不為null，那麼為true則放入第二個參數引用的Viewgroup中，為false則不放入第二個參數的Viewgroup中。

下面用一個執行個體來說明問題。
布局檔案有兩個：
activity_main.xml
[html]
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    android:orientation="vertical" > 
 
    <TextView 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="@string/hello_world" /> 
 
    <RelativeLayout 
        android:id="@+id/viewgroup" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" > 
    </RelativeLayout> 
 
</LinearLayout> 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <RelativeLayout
        android:id="@+id/viewgroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
    </RelativeLayout>

</LinearLayout>inflatertest.xml
[html]
<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" > 
 
    <CheckBox 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="inflatedemo" /> 
 
</LinearLayout> 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="inflatedemo" />

</LinearLayout>當Activity中如是寫：
[java]
<PRE class=java name="code">@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup); 
    mInflater = (LayoutInflater) getApplicationContext().getSystemService( 
            Context.LAYOUT_INFLATER_SERVICE); 
    mInflater.inflate(R.layout.inflatertest, mViewGroup); 
}</PRE> 
<PRE></PRE> 
或者 
<PRE></PRE> 

[java]
@Override  protected void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      setContentView(R.layout.activity_main);      mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup);      mInflater = (LayoutInflater) getApplicationContext().getSystemService(              Context.LAYOUT_INFLATER_SERVICE);      mInflater.inflate(R.layout.inflatertest, mViewGroup);  }  @Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup);
 mInflater = (LayoutInflater) getApplicationContext().getSystemService(
   Context.LAYOUT_INFLATER_SERVICE);
 mInflater.inflate(R.layout.inflatertest, mViewGroup);
}

或者

[java]
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup); 
    mInflater = (LayoutInflater) getApplicationContext().getSystemService( 
            Context.LAYOUT_INFLATER_SERVICE); 
    mInflater.inflate(R.layout.inflatertest, mViewGroup, true); 
} 

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup);
 mInflater = (LayoutInflater) getApplicationContext().getSystemService(
   Context.LAYOUT_INFLATER_SERVICE);
 mInflater.inflate(R.layout.inflatertest, mViewGroup, true);
}結果是這樣子的：

當Activity中如是寫：
[java]
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup); 
    mInflater = (LayoutInflater) getApplicationContext().getSystemService( 
            Context.LAYOUT_INFLATER_SERVICE); 
    mInflater.inflate(R.layout.inflatertest, mViewGroup, false); 
} 

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 mViewGroup = (RelativeLayout) findViewById(R.id.viewgroup);
 mInflater = (LayoutInflater) getApplicationContext().getSystemService(
   Context.LAYOUT_INFLATER_SERVICE);
 mInflater.inflate(R.layout.inflatertest, mViewGroup, false);
}結果是這樣的：

今天就到這裡，學習架構，一定要掌握函數的傳回值和參數的意義，學會總結規律。