Question

在我的应用中，我使用DrawerLayout。当我切换到包含MapFragment的{{1}}并返回时，Google地图会再次初始化。有没有办法阻止谷歌地图这样做？我正在使用Kotlin。我已经阅读了有关使用WeakReference到MapView的想法，但我不明白它在这种情况下可能会有什么帮助。

SupportMapFragment

Answer 1

使用以下方法，您可以在“片段”关闭时执行任何操作：

@Override
public void onDestroy() {
    super.onDestroy();
    //Anything you wish to do
}

@Override
public void onDetach() {
    super.onDetach();
    //Anything you wish to do
}

Answer 2

您必须通过此代码停止片段重新创建页面：

   mViewPager.setOffscreenPageLimit(NumberOfYourPages);

Answer 3

设置您以这种方式映射，

检查它是否已经存在 findFragmentById(R.id.map_new) 然后加载片段，否则使用已经加载。

childFragmentManager?.run {
        findFragmentById(R.id.map)?.let {
            val mapFragment = childFragmentManager.findFragmentById(R.id.map_new)
            if (mapFragment is SupportMapFragment) {
                mapFragment.getMapAsync(this@MapFragment)
            }
        }
    }

编辑： -

这是活动oncreate： -

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.act_test)

    supportFragmentManager.beginTransaction()
            .replace(R.id.fragment, MapFragment.getInstance())
            .addToBackStack("MapFragment")
            .commit()

    btnBlank.setOnClickListener {
        val frag = supportFragmentManager.findFragmentById(R.id.fragment)
        if(frag !is BlankFragment) {
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment, BlankFragment())
                    .addToBackStack("BlankFragment")
                    .commit()
        }
    }

    btnMap.setOnClickListener {
        supportFragmentManager.popBackStack("MapFragment", 0)
    }

}

和MapFragment： -

class MapFragment : Fragment(), OnMapReadyCallback {

private lateinit var map: GoogleMap

companion object {
    private val INSTANCE = MapFragment()
    fun getInstance() = INSTANCE
}

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? =
        inflater.inflate(R.layout.fragment_map, container, false)

override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    childFragmentManager.run {
        findFragmentById(R.id.map)?.let {
            val mapFragment = childFragmentManager.findFragmentById(R.id.map)
            if (mapFragment is SupportMapFragment) {
                mapFragment.getMapAsync(this@MapFragment)
            }
        }
    }
}

override fun onMapReady(p0: GoogleMap?) {
    p0?.animateCamera(CameraUpdateFactory.newLatLngZoom(LatLng(
            p0.cameraPosition.target.latitude,
            p0.cameraPosition.target.longitude
    ), 14f))
}


}

切换片段时停止重新加载Google Map

3 个答案: