imsdroid启动Activity的方式很独特

　　近来在调试imsdroid，想限制转屏。结果发现常用的办法无效。这是为什么呢？后来研究了一下启动Activity的代码，有点独特。具体代码是：

	@Override
	public boolean show(Class<? extends Activity> cls, String id) {
		final Main mainActivity = (Main)Engine.getInstance().getMainActivity();
		
		String screen_id = (id == null) ? cls.getCanonicalName() : id;
		Intent intent = new Intent(mainActivity, cls);
		intent.putExtra("id", screen_id);
		intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
		final Window window = mainActivity.getLocalActivityManager().startActivity(screen_id, intent);
		if(window != null){
			View view = mainActivity.getLocalActivityManager().startActivity(screen_id, intent).getDecorView();
			
			LinearLayout layout = (LinearLayout) mainActivity.findViewById(R.id.main_linearLayout_principal);
			layout.removeAllViews();
			layout.addView(view, new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
			
			// add to stack
			this.mLastScreens[(++this.mLastScreensIndex % this.mLastScreens.length)] = screen_id;
			this.mLastScreensIndex %= this.mLastScreens.length;
			return true;
		}
		return false;
	}

　　初步分析来说，相当于把一个Activity作为容器，然后把另外一个Activity放进去。也就是说，要想设置，就必须在主Activity中（或者在Manifest.xml）。