Android 启动其他程序 Android 中启动自己另一个程序的activity怎样实现

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:<a href="http://lib.csdn.net/base/android" rel="external nofollow" class='replace_word' title="Android知识库" target='_blank' style='color:#df3434; font-weight:bold;'>Android</a>="http://schemas.android.com/apk/res/android" 
   package="net.devdiv.activity4" 
   android:versionCode="1" 
   android:versionName="1.0"> 
  <application android:icon="@drawable/icon" android:label="@string/app_name"> 
    <activity android:name=".activity4" 
         android:label="@string/app_name"> 
      <intent-filter> 
        <action android:name="android.intent.action.MAIN" /> 
        <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
      <intent-filter> 
        <action android:name="devdiv.intent.action.activity4" /> 
        <category android:name="android.intent.category.DEFAULT" /> 
      </intent-filter> 
    </activity> 
  </application> 
  <uses-sdk android:minSdkVersion="7" /> 
</manifest>  

    Intent intent = new Intent("devdiv.intent.action.activity4"); 
      startActivity(intent);