获取当前默认的launcher包名，并弹出选择launcher的界面

final PackageManager pkgMgt = this.getPackageManager();

Intent intent = new Intent();
				intent.setAction("android.intent.action.MAIN");
				intent.addFlags(0x10200000);
				intent.addCategory("android.intent.category.DEFAULT");
				intent.addCategory("android.intent.category.HOME");
				final ResolveInfo res = pkgMgt.resolveActivity(intent, 0);
				if (res.activityInfo.packageName.equals("android")) {
					// 有多个桌面程序存在，且未指定默认项时；
					startActivity(intent);

				} else {
					pkgMgt.clearPackagePreferredActivities(res.activityInfo.packageName);
					Log.e(TAG, res.activityInfo.packageName);
					startActivity(intent);
				}

这个方法需要系统签名否则

pkgMgt.clearPackagePreferredActivities(res.activityInfo.packageName);

会报权限问题