我想用orderbychild过滤所有帖子。但应用程序崩溃了。我调试后显示错误：
final String currentUserId=mAuth.getCurrentUser().getUid(); this line of code.
//我在一台设备上测试但它工作正常，但在其他两个设备中，应用程序崩溃
//这是我的错误报告
java.lang.NullPointerException
at com.soumya.uglypeople.MyPosts.onCreateView(MyPosts.java:80)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2087)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1113)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1295)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1643)
at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1272)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1120)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1646)
at android.view.View.measure(View.java:15518)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:700)
at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1364)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:765)
at android.view.View.measure(View.java:15518)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
at android.view.View.measure(View.java:15518)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
at android.view.View.measure(View.java:15518)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:15518)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
at android.view.View.measure(View.java:15518)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2176)
at android.view.View.measure(View.java:15518)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
at android.view.Choreographer.doCallbacks(Choreographer.java:562)
at android.view.Choreographer.doFrame(Choreographer.java:532)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
//这是我的活动代码：
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.net.Uri;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.facebook.CallbackManager;
import com.facebook.FacebookSdk;
import com.facebook.share.model.ShareLinkContent;
import com.facebook.share.widget.ShareDialog;
import com.firebase.client.Firebase;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;
import com.squareup.picasso.Callback;
import com.squareup.picasso.NetworkPolicy;
import com.squareup.picasso.Picasso;
import static android.R.id.list;
import static com.facebook.FacebookSdk.getApplicationContext;
import static com.squareup.picasso.Picasso.with;
public class MyPosts extends Fragment{
private RecyclerView postList;
private DatabaseReference mDatabase;
private DatabaseReference mDatabaseAppriciate;
private DatabaseReference mDatabaseDisgrace;
private LinearLayoutManager layoutManager;
private FirebaseAuth mAuth;
private DatabaseReference mDatabaseCurrentUser;
private Query mQueryCurrentUser;
//private static final String TAG = "MyActivity";
private boolean mProcessAppriciate=false;
private boolean mProcessDisgrace=false;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
View rootView = inflater.inflate(R.layout.allposts, container, false);
mAuth= FirebaseAuth.getInstance();
mDatabase= FirebaseDatabase.getInstance().getReference().child("Posts");
mDatabaseAppriciate=FirebaseDatabase.getInstance().getReference().child("Appriciate");
mDatabaseDisgrace=FirebaseDatabase.getInstance().getReference().child("Disgrace");
//Below line shows error
final String currentUserId=mAuth.getCurrentUser().getUid();
mDatabaseCurrentUser=FirebaseDatabase.getInstance().getReference().child("Posts");
mQueryCurrentUser=mDatabaseCurrentUser.orderByChild("uid").equalTo(currentUserId);
mDatabase.keepSynced(true);
mDatabaseAppriciate.keepSynced(true);
mDatabaseDisgrace.keepSynced(true);
postList=(RecyclerView) rootView.findViewById(R.id.postList);
postList.setHasFixedSize(true);
layoutManager=new LinearLayoutManager(getActivity());
layoutManager.setReverseLayout(true);
postList.setHasFixedSize(true);
postList.setLayoutManager(layoutManager);
postList.getRecycledViewPool().clear();
return rootView;
}
@Override
public void onStart() {
super.onStart();
FirebaseRecyclerAdapter<Posts,PostViewHolder> firebaseRecyclerAdapter= new FirebaseRecyclerAdapter<Posts,PostViewHolder>(
Posts.class,
R.layout.single_post,
PostViewHolder.class,
mQueryCurrentUser
) {
@Override
protected void populateViewHolder(final PostViewHolder viewHolder, final Posts model, final int position) {
final String post_key=getRef(position).getKey();
viewHolder.setTitle(model.getTitle());
viewHolder.setDescription(model.getDescription());
viewHolder.setProfileName(model.getProfilename());
viewHolder.setImage(getContext(),model.getImage());
viewHolder.getLayoutPosition();
viewHolder.setAppriciateButton(post_key);
viewHolder.setDisgraceButton(post_key);
//Share click code below
viewHolder.Share.setOnClickListener(new View.OnClickListener() {
CallbackManager callbackManager;
ShareDialog shareDialog;
@Override
public void onClick(View v) {
FacebookSdk.sdkInitialize(getApplicationContext());
callbackManager = CallbackManager.Factory.create();
shareDialog = new ShareDialog(MyPosts.this);
if (ShareDialog.canShow(ShareLinkContent.class)) {
ShareLinkContent content = new ShareLinkContent.Builder()
.setContentTitle(model.getTitle())
.setContentDescription(model.getDescription())
.setImageUrl(Uri.parse(model.getImage()))
.setContentUrl(Uri.parse("https://developers.facebook.com"))
.build();
shareDialog.show(content);
}
}
});
viewHolder.Appriciate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mProcessAppriciate=true;
mDatabaseAppriciate.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (mProcessAppriciate) {
if (dataSnapshot.child(post_key).hasChild(mAuth.getCurrentUser().getUid())) {
mDatabaseAppriciate.child(post_key).child(mAuth.getCurrentUser().getUid()).removeValue();
mProcessAppriciate = false;
}else {
mDatabaseAppriciate.child(post_key).child(mAuth.getCurrentUser().getUid()).setValue(mAuth.getCurrentUser().getDisplayName());
viewHolder.Appriciate.setText("APPRICIATED");
mProcessAppriciate = false;
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
viewHolder.Disgrace.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mProcessDisgrace=true;
mDatabaseDisgrace.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (mProcessDisgrace) {
if (dataSnapshot.child(post_key).hasChild(mAuth.getCurrentUser().getUid())) {
mDatabaseDisgrace.child(post_key).child(mAuth.getCurrentUser().getUid()).removeValue();
//
mProcessDisgrace = false;
} else {
mDatabaseDisgrace.child(post_key).child(mAuth.getCurrentUser().getUid()).setValue(mAuth.getCurrentUser().getDisplayName());
//
mProcessDisgrace = false;
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
//Disgrace Button Click code Ends
}
};
postList.setAdapter(firebaseRecyclerAdapter);
//test code
firebaseRecyclerAdapter.notifyDataSetChanged();
}
public static class PostViewHolder extends RecyclerView.ViewHolder{
View mView;
Button Appriciate;
Button Disgrace;
Button Share;
DatabaseReference mDatabaseAppriciate;
DatabaseReference mDatabaseDisgrace;
FirebaseAuth mAuth;
public PostViewHolder(View itemView) {
super(itemView);
mView=itemView;
Appriciate=(Button) mView.findViewById(R.id.appriciate);
Disgrace=(Button) mView.findViewById(R.id.disgraceful);
Share=(Button) mView.findViewById(R.id.share);
mDatabaseAppriciate=FirebaseDatabase.getInstance().getReference().child("Appriciate");
mDatabaseDisgrace=FirebaseDatabase.getInstance().getReference().child("Disgrace");
mAuth=FirebaseAuth.getInstance();
mDatabaseAppriciate.keepSynced(true);
mDatabaseDisgrace.keepSynced(true);
}
public void setAppriciateButton(final String post_key){
mDatabaseAppriciate.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.child(post_key).hasChild(mAuth.getCurrentUser().getUid())){
Appriciate.setBackgroundColor(Color.GRAY);
Appriciate.setText("Appriciated");
}else{
Appriciate.setBackgroundColor(Color.GREEN);
Appriciate.setText("APPRICIATE");
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
public void setDisgraceButton(final String post_key){
mDatabaseDisgrace.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.child(post_key).hasChild(mAuth.getCurrentUser().getUid())){
Disgrace.setBackgroundColor(Color.GRAY);
Disgrace.setText("Disgraced");
}else{
Disgrace.setBackgroundColor(Color.RED);
Disgrace.setText("DISGRACE");
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
public void setTitle(String title){
TextView postTitle=(TextView) mView.findViewById(R.id.allPostTitle);
postTitle.setText(title);
}
public void setDescription(String description){
TextView postDescription=(TextView) mView.findViewById(R.id.allPostDescription);
postDescription.setText(description);
}
public void setProfileName(String profilename){
TextView postName=(TextView) mView.findViewById(R.id.profileName);
postName.setText(profilename);
}
public void setImage(final Context context, final String image) {
final ImageView postImage=(ImageView) mView.findViewById(R.id.allPostImage);
with(context).load(image).networkPolicy(NetworkPolicy.OFFLINE).into(postImage, new Callback() {
@Override
public void onSuccess() {
}
@Override
public void onError() {
Picasso.with(context).load(image).resize(500,700).into(postImage);
}
});
}
}
}
//这里是构建gradle（Module.app）
apply plugin: 'com.android.application'
android {
compileSdkVersion 24
buildToolsVersion "24.0.3"
packagingOptions {
exclude 'META-INF/LICENSE'
exclude 'META-INF/LICENSE-FIREBASE.txt'
exclude 'META-INF/NOTICE'
}
defaultConfig {
minSdkVersion 17
targetSdkVersion 24
multiDexEnabled true
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:24.2.1'
compile 'com.android.support:design:24.2.1'
compile 'com.android.support:recyclerview-v7:24.2.1'
compile 'com.android.support:cardview-v7:24.2.1'
compile 'com.google.firebase:firebase-core:10.0.1'
compile 'com.google.firebase:firebase-database:10.0.1'
compile 'com.google.firebase:firebase-storage:10.0.1'
compile 'com.google.firebase:firebase-auth:10.0.1'
compile 'com.firebase:firebase-client-android:2.5.2'
compile 'com.firebaseui:firebase-ui-database:1.0.1'
compile 'com.squareup.picasso:picasso:2.5.2'
testCompile 'junit:junit:4.12'
compile 'com.google.android.gms:play-services:10.0.1'
compile 'com.android.support:multidex:1.0.1'
compile 'com.squareup.okhttp3:okhttp:3.5.0'
compile 'com.facebook.android:facebook-android-sdk:[4,5)'
}
apply plugin: 'com.google.gms.google-services'
答案 0 :(得分：1)
问题是，在创建用户时，在firebase中，它不会登录用户。
首先检查mAuth是否为null，如果不为空，则获取getUid。
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if (user != null) {
// User is signed in
// Get User details
} else {
// No user is signed in
// create new signin
}
答案 1 :(得分：1)
问题是您正在同步读取当前用户，该用户可能会返回null：
final String currentUserId=mAuth.getCurrentUser().getUid()
当应用启动时，可能还不知道用户的登录状态。在这种情况下，getCurrentUser()将返回null，这会导致代码崩溃。
为防止这种情况发生，您应该listen for the authentication state to be confirmed/changed：
FirebaseAuth.getInstance().addAuthStateListener(new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = firebaseAuth.getCurrentUser();
if (user != null) {
// User is signed in
Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
}
}
});