| 结果 
 
 Main.XML 
 
 
                  
                    <?
                  
                  
                    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"
                  
                  
                    >
                  
                  
                    <
                  
                  
                    RelativeLayout 
                  
                  
                    android:id
                  
                  
                    ="@+id/Relativelayout01"
                  
                  
                    
       android:background
                  
                  
                    ="@drawable/head_bg"
                  
                  
                    
      android:layout_width
                  
                  
                    ="fill_parent"
                  
                  
                     
      android:layout_height
                  
                  
                    ="42dp"
                  
                  
                    >
                  
                  
                    <
                  
                  
                    ImageButton 
                  
                  
                    android:id
                  
                  
                    ="@+id/a"
                  
                  
                    
        android:layout_width
                  
                  
                    ="36dp"
                  
                  
                     
        android:layout_height
                  
                  
                    ="27dp"
                  
                  
                    
        android:layout_toLeftOf
                  
                  
                    ="@id/Relativelayout01"
                  
                  
                     
        android:src
                  
                  
                    ="@drawable/back"
                  
                  
                    
        android:layout_marginTop
                  
                  
                    ="10dp"
                  
                  
                  
                  
                    />
                  
                  
                    <
                  
                  
                    ImageButton 
                  
                  
                    android:id
                  
                  
                    ="@+id/b"
                  
                  
                     
          android:layout_width
                  
                  
                    ="125dp"
                  
                  
                     
          android:layout_height
                  
                  
                    ="27dp"
                  
                  
                    
          android:layout_centerInParent
                  
                  
                    ="true"
                  
                  
                     
           android:src
                  
                  
                    ="@drawable/logo"
                  
                  
                  
                  
                    />
                  
                  
                    <
                  
                  
                    ImageButton 
                  
                  
                    android:id
                  
                  
                    ="@+id/c"
                  
                  
                    
        android:layout_width
                  
                  
                    ="48dp"
                  
                  
                     
        android:layout_height
                  
                  
                    ="27dp"
                  
                  
                    
         android:layout_alignParentRight
                  
                  
                    ="true"
                  
                  
                    
        android:src
                  
                  
                    ="@drawable/login"
                  
                  
                    
android:layout_marginTop
                  
                  
                    ="10dp"
                  
                  
                  
                  
                    />
                  
                  
                    
                      RelativeLayout
                    
                    
                      >
                    
                    
                      
                        LinearLayout
                      
                      
                        >
                      
                    
                  
                RelativeLayout用到的一些重要的属性: 
                
                  第一类:属性值为true或false
                   
                
                  第二类:属性值必须为id的引用名“@id/id-name”
                
                 
                android:layout_alignTop                      本元素的上边缘和某元素的的上边缘对齐
                 
                
                  第三类:属性值为具体的像素值,如30dip,40px
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