NullPointerException - 安卓谷歌地图街景

Question

我试图在片段中显示街景。

public class StreetDisplay extends Fragment implements OnStreetViewPanoramaReadyCallback{ 

SupportStreetViewPanoramaFragment streetFrag; 

static final LatLng PosOne = new LatLng(43.771925, -79.512460); 

@Override 
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    View v = inflater.inflate(R.layout.street_display, container, false); 
    initialize(); 
    return v; 

} 

private void initialize() { 

    streetFrag = 
      (SupportStreetViewPanoramaFragment) getFragmentManager() 
        .findFragmentById(R.id.street); 
    streetFrag.getStreetViewPanoramaAsync(this); 
} 

//this method is needed for using a ViewPager swiping feature 
public static StreetDisplay newInstance(){ 
    StreetDisplay sd = new StreetDisplay(); 
    return sd; 
} 

@Override 
public void onStreetViewPanoramaReady(StreetViewPanorama panorama) { 
    panorama.setPosition(PosOne); 
} 
} 

这里的错误消息时我跑我的应用程序，我得到

Process: com.example.nikhilbhaskar.mapplayground, PID: 22406 
java.lang.NullPointerException 
     at com.example.nikhilbhaskar.mapplayground.StreetDisplay.initialize(StreetDisplay.java:43) 
     at com.example.nikhilbhaskar.mapplayground.StreetDisplay.onCreateView(StreetDisplay.java:33) 

管线33

initialize(); 

第43行是

streetFrag.getStreetViewPanoramaAsync(this); 

我不知道是什么问题是 - 你能帮忙吗？

Answer 1

streetFrag = 
      (SupportStreetViewPanoramaFragment) getFragmentManager() 
        .findFragmentById(R.id.street); 

此声明可能不会为StreetFrag创建对象。

检查streetFrag是否为null。

Answer 2

我试着从官方的文档，它的工作完美。

我的示例代码：

StreetViewActivity

import android.os.Bundle; 
import android.support.v4.app.FragmentActivity; 

import com.google.android.gms.maps.OnStreetViewPanoramaReadyCallback; 
import com.google.android.gms.maps.StreetViewPanorama; 
import com.google.android.gms.maps.StreetViewPanoramaFragment; 
import com.google.android.gms.maps.model.LatLng; 


public class StreetViewActivity extends FragmentActivity 
     implements OnStreetViewPanoramaReadyCallback { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_street_view); 
     StreetViewPanoramaFragment streetViewPanoramaFragment = 
       (StreetViewPanoramaFragment) getFragmentManager() 
         .findFragmentById(R.id.streetviewpanorama); 
     streetViewPanoramaFragment.getStreetViewPanoramaAsync(this); 
    } 


    @Override 
    public void onStreetViewPanoramaReady(StreetViewPanorama streetViewPanorama) { 
     streetViewPanorama.setPosition(new LatLng(-33.87365, 151.20689)); 
    } 
} 

而对于activity_street_view.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
       xmlns:tools="http://schemas.android.com/tools" 
       android:layout_width="match_parent" 
       android:layout_height="match_parent" 
       android:paddingLeft="@dimen/activity_horizontal_margin" 
       android:paddingRight="@dimen/activity_horizontal_margin" 
       android:paddingTop="@dimen/activity_vertical_margin" 
       android:paddingBottom="@dimen/activity_vertical_margin" 
       tools:context="com.bjiang.map_ex.StreetViewActivity"> 

    <fragment 
     android:name="com.google.android.gms.maps.StreetViewPanoramaFragment" 
     android:id="@+id/streetviewpanorama" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent"/> 

</RelativeLayout> 

有关详细信息，请参阅here。

编辑：

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 

import com.google.android.gms.maps.OnStreetViewPanoramaReadyCallback; 
import com.google.android.gms.maps.StreetViewPanorama; 
import com.google.android.gms.maps.SupportStreetViewPanoramaFragment; 
import com.google.android.gms.maps.model.LatLng; 

public class StreetDisplay extends FragmentActivity implements OnStreetViewPanoramaReadyCallback { 

    static SupportStreetViewPanoramaFragment streetViewPanoramaFragment; 

    static final LatLng PosOne = new LatLng(43.771925, -79.512460); 

    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.street_display); 
     streetViewPanoramaFragment = 
       ((SupportStreetViewPanoramaFragment)getSupportFragmentManager().findFragmentById(R.id.street)); 

     streetViewPanoramaFragment.getStreetViewPanoramaAsync(this); 
    } 

    //this method is needed for using a ViewPager swiping feature 
    public static Fragment newInstance(){ 
     return streetViewPanoramaFragment.newInstance(); 
    } 

    @Override 
    public void onStreetViewPanoramaReady(StreetViewPanorama streetViewPanorama) { 
     streetViewPanorama.setPosition(new LatLng(-33.87365, 151.20689)); 
    } 

} 

Answer 3

在片段使用getChildFragmentManager()代替。

streetFrag = (SupportStreetViewPanoramaFragment) getChildFragmentManager() 
                .findFragmentById(R.id.street);