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残念ながら私は解決できない問題があります。だから私はあなたの助けが必要です。新しいユーザーが追加され、userActivity（KontakteActivity）が開いていると、アプリがクラッシュすることがあります。私が忘れてしまった場合は私に知らせてください問題の解決ここでFirebase RecylerviewはpopulateViewでNullPointerExceptionをスローします
するのに役立つ何かがuserActivityのコードです：ここで
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.bumptech.glide.Glide;
import com.bumptech.glide.load.engine.DiskCacheStrategy;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
public class KontakteActivity extends AppCompatActivity {
TextView kontakt_name,kontakt_email;
RecyclerView recyclerView;
FirebaseDatabase firebaseDatabase;
DatabaseReference mDatabaseReference;
public FirebaseRecyclerAdapter<FirebaseDB_helper,Kontakte_Viewholder> mFirebaseAdapter;
ProgressBar progressBar;
LinearLayoutManager linearLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_kontakte);
//DB
firebaseDatabase = FirebaseDatabase.getInstance();
mDatabaseReference = firebaseDatabase.getReference("Users");
mDatabaseReference.keepSynced(true);
//Views
progressBar = (ProgressBar)findViewById(R.id.progressBar_act_kontakte);
recyclerView = (RecyclerView)findViewById(R.id.recylerView_kontakte_act_kontakte);
linearLayoutManager = new LinearLayoutManager(KontakteActivity.this);
recyclerView.setLayoutManager(linearLayoutManager);
}
@Override
protected void onStart() {
super.onStart();
progressBar.setVisibility(ProgressBar.VISIBLE);
mFirebaseAdapter = new FirebaseRecyclerAdapter<FirebaseDB_helper, Kontakte_Viewholder>
(FirebaseDB_helper.class, R.layout.kontakte_card_view, Kontakte_Viewholder.class, mDatabaseReference) {
public void populateViewHolder(final Kontakte_Viewholder viewholder , FirebaseDB_helper model, final int position)
{
progressBar.setVisibility(View.INVISIBLE);
viewholder.Kontakt_Name(model.getName());
viewholder.Kontakt_Image(model.getImage_Url());
if (model.getEmail().equals(MainActivity.User_email))
{
viewholder.Layout_hide();
}else {
viewholder.Kontakt_Email(model.getEmail());
}
}
};
mFirebaseAdapter.notifyDataSetChanged();
recyclerView.setAdapter(mFirebaseAdapter);
}
// /*
public static class Kontakte_Viewholder extends RecyclerView.ViewHolder{
private final TextView kontakt_name,kontakt_email;
private final ImageView kontakt_image;
private final LinearLayout layout;
final LinearLayout.LayoutParams params;
public Kontakte_Viewholder(final View itemView) {
super(itemView);
kontakt_name=(TextView)itemView.findViewById(R.id.txt_name_kontakt_card);
kontakt_email=(TextView)itemView.findViewById(R.id.txtView_email_kontakt_card);
kontakt_image=(ImageView)itemView.findViewById(R.id.imageView_kontakt_card);
layout = (LinearLayout)itemView.findViewById(R.id.linearlayout_kontakt_card_view); //Probleeeeeem
params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);//erforderlich um ein LinearLayout anzupassen
}
private void Kontakt_Name(String name)
{
kontakt_name.setText(name);
}
private void Layout_hide()
{
params.height=0;
layout.setLayoutParams(params);
}
private void Kontakt_Email (String email)
{
kontakt_email.setText(email);
}
private void Kontakt_Image (String Url)
{
if (!Url.equals("Null")){
Glide.with(itemView.getContext())
.load(Url)
.crossFade()
.thumbnail(0.5f)
.placeholder(R.drawable.loading)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.into(kontakt_image);
}
}
}//*/
}
は、Android Studioの
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.zare.ma_firechat, PID: 9510
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at com.example.zare.ma_firechat.KontakteActivity$Kontakte_Viewholder.Kontakt_Image(KontakteActivity.java:129)
at com.example.zare.ma_firechat.KontakteActivity$Kontakte_Viewholder.access$100(KontakteActivity.java:94)
at com.example.zare.ma_firechat.KontakteActivity$1.populateViewHolder(KontakteActivity.java:74)
at com.example.zare.ma_firechat.KontakteActivity$1.populateViewHolder(KontakteActivity.java:61)
at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:184)
at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6356)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6389)
at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5335)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5598)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5440)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5436)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2224)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1551)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1511)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:595)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3583)
at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:3025)
at android.view.View.measure(View.java:19734)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
at android.view.View.measure(View.java:19734)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:1028)
at android.view.View.measure(View.java:19734)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
at android.view.View.measure(View.java:19734)
のクラッシュレポートです
1人以上のユーザーがデータベースにいくつかのプロパティがないようです。 KontakteActivity.java行129に移動して、それがどのプロパティであるかを確認します。デバッガでAndroidスタジオからアプリを実行すると、その行でもアプリが破損します。 https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-itを参照してください。 –