尝试调用虚拟方法'void android.widget.TextView.setText（java.lang.CharSequence）'ON机器人应用程序

Question

ProfileDisplay.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".Profiledisplay">
<RelativeLayout
android:layout_width="match_parent"
android:background="@color/colorPrimaryDark"
android:layout_height="match_parent">
<de.hdodenhof.circleimageview.CircleImageView
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/profilimg"
    android:layout_width="160dp"
    android:elevation="20dp"
    android:layout_height="160dp"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="40dp"
    app:civ_border_width="2dp"
    android:src="@drawable/progileicon"
    app:civ_border_color="#FF000000"/>
    <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="26dp"
    android:textColor="@color/white"
    android:text="[email protected]"
    android:id="@+id/mailid"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="220dp"
    android:textStyle="bold"></TextView>
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="name"
    android:id="@+id/name1"
    android:textColor="@color/white"
    android:layout_marginTop="260dp"
    android:layout_centerHorizontal="true"
    android:textStyle="bold"
    android:textSize="20dp"/>
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/bloggerorweiter"
    android:textSize="20dp"
    android:textColor="@color/white"
    android:layout_marginTop="280dp"
    android:layout_centerHorizontal="true"
    android:textStyle="bold"
    android:text="Blogger or Writer"
     />
<TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:id="@+id/City"
        android:textColor="@color/white"
        android:layout_marginTop="300dp"
        android:layout_centerHorizontal="true"
        android:textStyle="bold"
        android:text="City"
        />
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="20dp"
    android:id="@+id/state"
    android:textColor="@color/white"
    android:layout_marginTop="320dp"
    android:layout_centerHorizontal="true"
    android:textStyle="bold"
    android:text="State"
    />
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="20dp"
    android:id="@+id/Country"
    android:textColor="@color/white"
    android:layout_marginTop="340dp"
    android:layout_centerHorizontal="true"
    android:textStyle="bold"
    android:text="Country"
    />
</RelativeLayout>
<com.google.android.material.navigation.NavigationView
    android:id="@+id/navigation"
    android:background="#97145C"
    android:layout_width="240dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    app:menu="@menu/nav_items"
    app:headerLayout="@layout/header">
</com.google.android.material.navigation.NavigationView>

ProfileDisplay.java

package com.example.myapplication;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.media.Image;
import android.nfc.Tag;
import android.os.Bundle;
import android.util.Log;
import android.view.MenuItem;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.bumptech.glide.Glide;
import com.google.android.material.navigation.NavigationView;
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.ValueEventListener;
import org.w3c.dom.Text;
import java.util.concurrent.ExecutionException;
public class Profiledisplay extends AppCompatActivity {
NavigationView navigationView;
ImageView imgview;
FirebaseAuth mauth;
String currentuserID;
private DatabaseReference userref1;
TextView name,country,mailid,city,state,blog_writer;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    imgview=findViewById(R.id.profilimg);
    name=(TextView) findViewById(R.id.name1);
    country=(TextView)findViewById(R.id.Country);
    mailid=(TextView)findViewById(R.id.mailid);
    city=(TextView)findViewById(R.id.City);
    state=(TextView)findViewById(R.id.state);
    mauth=FirebaseAuth.getInstance();
    blog_writer=(TextView)findViewById(R.id.bloggerorweiter);
    currentuserID=mauth.getCurrentUser().getUid();
    userref1 = FirebaseDatabase.getInstance().getReference().child("Users");
   try{
    userref1.child(currentuserID).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            if(dataSnapshot.exists()){
                if(dataSnapshot.hasChild("username")){
                        String fullname1 = dataSnapshot.child("username").getValue().toString();
                        **name.setText(fullname1);**
                }
                if(dataSnapshot.hasChild("urlimage")){
                    String imageurl=dataSnapshot.child("urlimage").getValue().toString();
                    Glide.with(getApplicationContext()).load(imageurl).into(imgview);
                }else{
                    Toast.makeText(Profiledisplay.this, "username or profile not exist", 
   Toast.LENGTH_SHORT).show();
                }
                String Email="[email protected]";
                mailid.setText(Email);
            }
        }
        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
        }
    });}
   catch(Exception e){
   }
    setContentView(R.layout.activity_profiledisplay);
    navigationView=findViewById(R.id.navigation);
    navigationView.setNavigationItemSelectedListener(new 
    NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
            switch (menuItem.getItemId()){
                case R.id.home:
                    Toast.makeText(Profiledisplay.this, "CLicked Home", Toast.LENGTH_SHORT).show();
                    startActivity(new Intent(getApplicationContext(),Home.class));
                    break;
                case R.id.Profile:
                    Toast.makeText(Profiledisplay.this, "CLicked profile",Toast.LENGTH_SHORT).show();
                    startActivity(new Intent(getApplicationContext(),Profiledisplay.class));
                    break;
                case R.id.Post:
                    Toast.makeText(Profiledisplay.this, "CLicked Post", Toast.LENGTH_SHORT).show();
                    startActivity(new Intent(getApplicationContext(),forgotpass.class));
                    break;
            }
            return false;
        }
    });
    }
}

错误

E / AndroidRuntime：致命异常：主要流程：com.example.myapplication，PID：25982java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'void android.widget.TextView.setText（java.lang.CharSequence）'在com.example.myapplication.Profiledisplay $ 1.onDataChange（Profiledisplay.java:51）com.google.firebase.database.core.ValueEventRegistration.fireEvent（com.google.firebase：firebase-database @@ 16.0.4：75）com.google.firebase.database.core.view.DataEvent.fire（com.google.firebase：firebase-database @@ 16.0.4：63）com.google.firebase.database.core.view.EventRaiser $ 1.run（com.google.firebase：firebase-database @@ 16.0.4：55）在android.os.Handler.handleCallback（Handler.java:790）在android.os.Handler.dispatchMessage（Handler.java:99）在android.os.Looper.loop（Looper.java:198）在android.app.ActivityThread.main（ActivityThread.java:7055）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:523）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:836）

我每次尝试执行SetText（）方法时都会遇到此错误，请帮帮我。预先感谢。

build.gradel文件

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'
android {
compileSdkVersion 29
buildToolsVersion '24.0.2'
defaultConfig {
    applicationId "com.example.myapplication"
    minSdkVersion 21
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android- 
optimize.txt'), 'proguard-rules.pro'
    }
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'com.squareup.picasso:picasso:2.71828'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'com.google.firebase:firebase-auth:16.0.5'
implementation 'com.google.firebase:firebase-database:16.0.4'
implementation 'com.google.firebase:firebase-storage:16.0.4'
implementation 'com.github.bumptech.glide:glide:4.10.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.10.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test.ext:junit:1.1.0'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
implementation 'com.google.android.gms:play-services-auth:17.0.0'
api 'com.theartofdev.edmodo:android-image-cropper:2.8.+'
implementation 'com.google.android.material:material:1.0.0'
implementation 'de.hdodenhof:circleimageview:3.0.1'
implementation 'com.github.bumptech.glide:glide:4.11.0'
implementation 'com.makeramen:roundedimageview:2.3.0'
}
apply plugin: 'com.google.gms.google-services'

Answer 1

您需要在调用findViewbyID之前设置setContentView。

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_profiledisplay); // move setContentView here
    imgview=findViewById(R.id.profilimg);
    name=(TextView) findViewById(R.id.name1);
 ....

您的问题是，当您尝试查找它时，视图为空。