java-在片段上的GridView中显示从Firebase下载的图像在打开片段时不断崩溃
我正在使用我们位于导航抽屉中的一个片段上的GridView为我们的android应用创建图库.我为图像视图创建了一个自定义适配器,该适配器使用Picasso在图像视图中显示图像.我制作了一种名为DohvatiSlike()的方法,该方法从firebase下载图像并将其保存在File变量中.当我构建应用程序并运行它时,每当我从导航抽屉中打开图库时,应用程序都会崩溃.如果我在onCreateView中排除设置GalleryGridAdapter的行,则不会崩溃,但显然不起作用.谁能帮我发现问题?
这是GalleryFragment代码:
public class GalleryFragment extends Fragment implements NavigationItem { private DatabaseReference mDatabaseRef; private List<File> slike; private int position; GridView galleryGridView; @Override public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) { View v = inflater.inflate(R.layout.gallery_fragment,container,false); super.onCreateView(inflater,savedInstanceState); galleryGridView = (GridView)v.findViewById(R.id.gallery_gridview); DohvatiSlike(); galleryGridView.setAdapter(new GalleryGridAdapter(getActivity(),slike)); return v; } public void DohvatiSlike(){ mDatabaseRef=FirebaseDatabase.getInstance().getReference("images"); mDatabaseRef.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { for(DataSnapshot postSnapshot: dataSnapshot.getChildren()){ File slika = postSnapshot.getValue(File.class); slike.add(slika); } } @Override public void onCancelled(DatabaseError databaseError) { Toast.makeText((AppCompatActivity)getActivity(),databaseError.getMessage(),Toast.LENGTH_SHORT).show(); } });} @Override public void onAttach(Activity activity){ super.onAttach(activity); }
这是适配器代码:
public class GalleryGridAdapter extends BaseAdapter { private Context mContext; public List<File> slike; public GalleryGridAdapter(Context context,List<File> slikice){ slike = slikice; mContext = context; } @Override public int getCount() { return slike.size(); } @Override public Object getItem(int position) { return slike.indexOf(position); } @Override public long getItemId(int position) { return 0; } @Override public View getView(int position,View convertView,ViewGroup parent) { ImageView imageView; if (convertView == null) { imageView = new ImageView(mContext); imageView.setLayoutParams(new GridView.LayoutParams(500,500)); imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); } else{ imageView = (ImageView) convertView; } Picasso.with(mContext).load(slike.indexOf(position)).into(imageView); return imageView; }
}
编辑*
这是崩溃日志
Process: hr.foi.air1817.botanico,PID: 26065 java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at hr.foi.air1817.botanico.adapters.GalleryGridAdapter.getCount(GalleryGridAdapter.java:26) at android.widget.GridView.setAdapter(GridView.java:211) at hr.foi.air1817.botanico.fragments.GalleryFragment$1.onDataChange(GalleryFragment.java:62) at com.google.firebase.database.obfuscated.zzap.zza(com.google.firebase:firebase-database@@16.0.3:75) at com.google.firebase.database.obfuscated.zzca.zza(com.google.firebase:firebase-database@@16.0.3:63) at com.google.firebase.database.obfuscated.zzcd$1.run(com.google.firebase:firebase-database@@16.0.3:55) at android.os.Handler.handleCallback(Handler.java:873) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6863) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:537) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
我已经连续两天在这里工作了,只是无法正常工作,建议或想法受到赞赏
DohvatiSlike(); galleryGridView.setAdapter(new GalleryGridAdapter(getActivity(),slike));
方法DohvatiSlike();仍在请求数据,并且可能无法在您拥有的类似数组上添加元素.
而是在您的DohvatiSlike()中移动适配器的设置.方法
public void DohvatiSlike(){ slike = new List<>(); mDatabaseRef = FirebaseDatabase.getInstance().getReference("images"); mDatabaseRef.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { for(DataSnapshot postSnapshot: dataSnapshot.getChildren()){ File slika = postSnapshot.getValue(File.class); slike.add(slika); } galleryGridView.setAdapter(new GalleryGridAdapter(getActivity(),slike)); } @Override public void onCancelled(DatabaseError databaseError) { Toast.makeText((AppCompatActivity)getActivity(),Toast.LENGTH_SHORT).show(); } }); }
当执行DohvatiSlike()时,您将需要等待,具体取决于您的Internet连接以获取该数据,在获取数据之后,您将填充阵列,在这种情况下,您是在请求数据并立即用可能没有配置的数据设置适配器.尚未获取,而是只需在解析所有数据并将其添加到onDataChange内部之后再设置适配器.
另外,在显示视图时,请在onViewCreated()内进行操作,因为onCreateView()仅用于放大视图元素
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