1 <?xml version="1.0" encoding="utf-8"?>
 2 <shape xmlns:android="http://schemas.android.com/apk/res/android">
 3   <!--设置渐变颜色 angle="0"是从左到右  90是从上到下  180是从右到左 -->
 4     <gradient 
 5         android:startColor="#4169E1"
 6         android:endColor="#E6E6FA"
 7         android:angle="0" />
 8     <stroke 
 9         android:width="2dp"
10         android:color="#D2691E"
11         />
12     <corners android:radius="10dip"/>
13     <padding 
14         android:left="10dp"
15            android:top="10dp"
16               android:right="10dp"
17                  android:bottom="10dp"
18         />
19 </shape>

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <shape xmlns:android="http://schemas.android.com/apk/res/android">
 3   <!-- angle="0"是从左到右  90是从上到下  180是从右到左 且必须是45的倍数 -->
 4     <gradient 
 5         android:startColor="#FFD700"
 6         android:endColor="#f5deb3"
 7         android:angle="0" />
 8     <stroke 
 9         android:width="2dp"
10         android:color="#FFB6C1"
11         />
12     <corners android:radius="20dip"/>
13     <padding 
14         android:left="10dp"
15            android:top="10dp"
16               android:right="10dp"
17                  android:bottom="10dp"
18         />
19 </shape>

<LinearLayout 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:gravity="center" 
    android:background="@drawable/asdf"
    tools:context="com.example.top5_4.MainActivity" >

   
<Button 
    android:id="@+id/but"
     android:layout_height="wrap_content"
     android:layout_width="wrap_content"
     android:text="点击按钮改变按钮样式"
     android:background="@drawable/round"
    />
</LinearLayout>

 1 public class MainActivity extends Activity {
 2 private Button but;
 3     @Override
 4     protected void onCreate(Bundle savedInstanceState) {
 5         super.onCreate(savedInstanceState);
 6         setContentView(R.layout.activity_main);
 7        but=(Button) findViewById(R.id.but);
 8     but.setOnClickListener(new OnClickListener() {
 9         
10         @Override
11         public void onClick(View v) {
12             // TODO Auto-generated method stub
13             //点击后更改按钮样式
14             but.setBackgroundResource(R.drawable.newround);
15              //另外设置按钮的透明度setAlpha()里面的值大小为0~255
16             but.getBackground().setAlpha(99);
17         }
18     });
19     }
20 }