public class MainActivity extends Activity
{

 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);

 // 隐藏标题栏
 requestWindowFeature(Window.FEATURE_NO_TITLE);
 // 隐藏状态栏
 getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
  WindowManager.LayoutParams.FLAG_FULLSCREEN);

 setContentView(R.layout.activity_main);
 }

}

<!-- 同时隐藏状态栏和标题栏 -->
<activity
  android:name="com.ysj.demo.MainActivity"
  android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
  android:label="@string/app_name" >
  <intent-filter>
    <action android:name="android.intent.action.MAIN" />


    <category android:name="android.intent.category.LAUNCHER" />
  </intent-filter>
</activity>

<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
  <!-- All customizations that are NOT specific to a particular API-level can go here. -->
  <!-- 隐藏状态栏 -->
  <item name="android:windowFullscreen">true</item>
  <!-- 隐藏标题栏 -->
  <item name="android:windowNoTitle">true</item>
</style>

public class StartupActivity extends Activity
{

 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_startup);
 
 /*
  * 隐藏运行Android 4.0以上系统的平板的屏幕下方的状态栏
  */
 try 
   { 
     String ProcID = "79"; 
     if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) ProcID = "42"; // ICS 
     // 需要root 权限 
     Process proc = Runtime.getRuntime().exec(new String[] { "su", "-c", "service call activity " + ProcID + " s16 com.android.systemui" }); // WAS 
     proc.waitFor(); 
   } 
   catch (Exception ex) 
   { 
     Toast.makeText(getApplicationContext(), ex.getMessage(), Toast.LENGTH_LONG).show(); 
   } 
 }

 @Override
 protected void onDestroy()
 {
 // TODO Auto-generated method stub
 /*
  * 恢复运行Android 4.0以上系统的平板的屏幕下方的状态栏
  */
 try 
   { 
     Process proc = Runtime.getRuntime().exec(new String[] { "am", "startservice", "-n", "com.android.systemui/.SystemUIService" }); 
     proc.waitFor(); 
   } 
   catch (Exception e) 
   { 
     e.printStackTrace(); 
   } 
 super.onDestroy();
 }

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

 @Override
 public boolean onOptionsItemSelected(MenuItem item)
 {
 // TODO Auto-generated method stub
 switch (item.getItemId())
 {
  case R.id.action_exit:
  finish();
  break;
 }
 return true;
 }

}