TextView.setText 抛出 NullPointerException 尽管给定的字符串不为空
TextView.setText throws NullPointerException despite given String not being null
当我尝试为我的程序设置作者和日期时，TextView.setText 方法抛出 NullPointerException：
Content of the Custom Object
错误 1：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jokestarapplication, PID: 10886
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jokestarapplication/com.example.jokestarapplication.ActivityJokeDetail}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.example.jokestarapplication.ActivityJokeDetail.onCreate(ActivityJokeDetail.java:44)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
错误 2：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jokestarapplication, PID: 11116
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jokestarapplication/com.example.jokestarapplication.ActivityJokeDetail}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.example.jokestarapplication.ActivityJokeDetail.onCreate(ActivityJokeDetail.java:45)
at android.app.Activity.performCreate(Activity.java:7136)
at android.app.Activity.performCreate(Activity.java:7127)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Activity
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.util.List;
public class ActivityJokeDetail extends AppCompatActivity {
public static final String KEY_JOKEDETAILS = "JOKEDETAILS";
private Joke joke;
private TextView tvJokeText, tvJokeVote, tvAuthor, tvPostedDate;
private EditText etNewComment;
private Button btJokeUp, btJokeDown, btSendComment ;
private RecyclerView recyclerView;
private View include;
private AdapterJokeDetail mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_joke_detail);
joke = getIntent().getParcelableExtra(KEY_JOKEDETAILS);
include = findViewById(R.id.include);
tvJokeText = include.findViewById(R.id.tvCommentText);
tvJokeVote = include.findViewById(R.id.tvCommentVotes);
tvAuthor = include.findViewById(R.id.tvAuthor);
tvPostedDate = include.findViewById(R.id.tvPostDate);
btJokeUp = include.findViewById(R.id.btCommentUp);
btJokeDown = include.findViewById(R.id.btCommentDown);
tvJokeText.setText(joke.getText());
tvJokeVote.setText(Integer.toString(joke.getVotes()));
// TODO: tvAuthor.setText(joke.getAuthor());
// TODO: tvPostedDate.setText(joke.getPostedDate().toString());
etNewComment = findViewById(R.id.etNewComment);
btSendComment = findViewById(R.id.btSendComment);
recyclerView = findViewById(R.id.rvComments);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
mAdapter = new AdapterJokeDetail(joke.getComments());
recyclerView.setAdapter(mAdapter);
btSendComment.setOnClickListener(v -> {
SendComment();
mAdapter.notifyDataSetChanged();
});
}
private void SendComment() {
Comment comment = new Comment(etNewComment.getText().toString(),0,"author"); //TODO: add author
joke.getComments().add(comment);
}
}
笑话
package com.example.jokestarapplication;
import android.os.Parcel;
import android.os.Parcelable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class Joke implements Parcelable {
private String text;
private int votes;
private Date postedDate;
private String author;
private String authorId;
private String category;
private List<Comment> comments;
public Joke(String text, Date postedDate, String category, String author, String authorId, List<Comment> arrayList) {
this.text = text;
this.votes = 0;
this.postedDate = postedDate;
this.author = author;
this.authorId = authorId;
this.category = category;
this.comments = arrayList;
}
protected Joke(Parcel in) {
text = in.readString();
votes = in.readInt();
postedDate = new Date(in.readLong());
author = in.readString();
authorId = in.readString();
category = in.readString();
comments = in.createTypedArrayList(Comment.CREATOR);
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(text);
dest.writeInt(votes);
dest.writeLong(postedDate.getTime());
dest.writeString(author);
dest.writeString(authorId);
dest.writeString(category);
dest.writeTypedList(comments);
}
public static final Creator<Joke> CREATOR = new Creator<Joke>() {
@Override
public Joke createFromParcel(Parcel in) {
return new Joke(in);
}
@Override
public Joke[] newArray(int size) {
return new Joke[size];
}
};
public String getText() {
return text;
}
public int getVotes() {
return votes;
}
public Date getPostedDate() {
return postedDate;
}
public String getAuthor() {
return author;
}
public String getAuthorId() {
return authorId;
}
public String getCategory() {
return category;
}
public List<Comment> getComments() {
return comments;
}
@Override
public int describeContents() {
return 0;
}
public void JokeVoteUp(){
votes+=1;
}
public void JokeVoteDown(){
votes-=1;
}
}
有问题的行在 // TODO:
更新
布局
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".ActivityJokeDetail">
<include
android:id="@+id/include"
layout="@layout/list_item_comment"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginLeft="24dp"
android:layout_marginTop="32dp"
android:layout_marginEnd="24dp"
android:layout_marginRight="24dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvPostedFrom"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginLeft="32dp"
android:layout_marginTop="32dp"
android:text="@string/DEPostedFrom"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/include" />
<TextView
android:id="@+id/tvPostedOn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginLeft="32dp"
android:layout_marginTop="16dp"
android:text="@string/DEPostedOn"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvPostedFrom" />
<TextView
android:id="@+id/tvAuthor"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="32dp"
app:layout_constraintStart_toEndOf="@+id/tvPostedFrom"
app:layout_constraintTop_toBottomOf="@+id/include" />
<TextView
android:id="@+id/tvPostDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="16dp"
app:layout_constraintStart_toEndOf="@+id/tvPostedFrom"
app:layout_constraintTop_toBottomOf="@+id/tvAuthor" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rvComments"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="32dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/etNewComment" />
<EditText
android:id="@+id/etNewComment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="32dp"
android:ems="10"
android:hint="@string/DEAddComment"
android:inputType="textPersonName"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvPostDate" />
<Button
android:id="@+id/btSendComment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="32dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:text="@string/DESend"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvPostDate" />
</androidx.constraintlayout.widget.ConstraintLayout>
假设您在一个文件中有 activity 的整个布局，并假设它们确实存在于布局中。
你真的不需要使用 include 变量。
而不是：
tvAuthor = include.findViewById(R.id.tvAuthor);
使用：
tvAuthor = findViewById(R.id.tvAuthor);
当我尝试为我的程序设置作者和日期时，TextView.setText 方法抛出 NullPointerException： Content of the Custom Object
错误 1：
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.jokestarapplication, PID: 10886 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jokestarapplication/com.example.jokestarapplication.ActivityJokeDetail}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.example.jokestarapplication.ActivityJokeDetail.onCreate(ActivityJokeDetail.java:44) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.java:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
错误 2：
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.jokestarapplication, PID: 11116 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jokestarapplication/com.example.jokestarapplication.ActivityJokeDetail}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.example.jokestarapplication.ActivityJokeDetail.onCreate(ActivityJokeDetail.java:45) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.java:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Activity
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.util.List;
public class ActivityJokeDetail extends AppCompatActivity {
public static final String KEY_JOKEDETAILS = "JOKEDETAILS";
private Joke joke;
private TextView tvJokeText, tvJokeVote, tvAuthor, tvPostedDate;
private EditText etNewComment;
private Button btJokeUp, btJokeDown, btSendComment ;
private RecyclerView recyclerView;
private View include;
private AdapterJokeDetail mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_joke_detail);
joke = getIntent().getParcelableExtra(KEY_JOKEDETAILS);
include = findViewById(R.id.include);
tvJokeText = include.findViewById(R.id.tvCommentText);
tvJokeVote = include.findViewById(R.id.tvCommentVotes);
tvAuthor = include.findViewById(R.id.tvAuthor);
tvPostedDate = include.findViewById(R.id.tvPostDate);
btJokeUp = include.findViewById(R.id.btCommentUp);
btJokeDown = include.findViewById(R.id.btCommentDown);
tvJokeText.setText(joke.getText());
tvJokeVote.setText(Integer.toString(joke.getVotes()));
// TODO: tvAuthor.setText(joke.getAuthor());
// TODO: tvPostedDate.setText(joke.getPostedDate().toString());
etNewComment = findViewById(R.id.etNewComment);
btSendComment = findViewById(R.id.btSendComment);
recyclerView = findViewById(R.id.rvComments);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
mAdapter = new AdapterJokeDetail(joke.getComments());
recyclerView.setAdapter(mAdapter);
btSendComment.setOnClickListener(v -> {
SendComment();
mAdapter.notifyDataSetChanged();
});
}
private void SendComment() {
Comment comment = new Comment(etNewComment.getText().toString(),0,"author"); //TODO: add author
joke.getComments().add(comment);
}
}
笑话
package com.example.jokestarapplication;
import android.os.Parcel;
import android.os.Parcelable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class Joke implements Parcelable {
private String text;
private int votes;
private Date postedDate;
private String author;
private String authorId;
private String category;
private List<Comment> comments;
public Joke(String text, Date postedDate, String category, String author, String authorId, List<Comment> arrayList) {
this.text = text;
this.votes = 0;
this.postedDate = postedDate;
this.author = author;
this.authorId = authorId;
this.category = category;
this.comments = arrayList;
}
protected Joke(Parcel in) {
text = in.readString();
votes = in.readInt();
postedDate = new Date(in.readLong());
author = in.readString();
authorId = in.readString();
category = in.readString();
comments = in.createTypedArrayList(Comment.CREATOR);
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(text);
dest.writeInt(votes);
dest.writeLong(postedDate.getTime());
dest.writeString(author);
dest.writeString(authorId);
dest.writeString(category);
dest.writeTypedList(comments);
}
public static final Creator<Joke> CREATOR = new Creator<Joke>() {
@Override
public Joke createFromParcel(Parcel in) {
return new Joke(in);
}
@Override
public Joke[] newArray(int size) {
return new Joke[size];
}
};
public String getText() {
return text;
}
public int getVotes() {
return votes;
}
public Date getPostedDate() {
return postedDate;
}
public String getAuthor() {
return author;
}
public String getAuthorId() {
return authorId;
}
public String getCategory() {
return category;
}
public List<Comment> getComments() {
return comments;
}
@Override
public int describeContents() {
return 0;
}
public void JokeVoteUp(){
votes+=1;
}
public void JokeVoteDown(){
votes-=1;
}
}
有问题的行在 // TODO:
更新
布局
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".ActivityJokeDetail">
<include
android:id="@+id/include"
layout="@layout/list_item_comment"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginLeft="24dp"
android:layout_marginTop="32dp"
android:layout_marginEnd="24dp"
android:layout_marginRight="24dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvPostedFrom"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginLeft="32dp"
android:layout_marginTop="32dp"
android:text="@string/DEPostedFrom"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/include" />
<TextView
android:id="@+id/tvPostedOn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginLeft="32dp"
android:layout_marginTop="16dp"
android:text="@string/DEPostedOn"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvPostedFrom" />
<TextView
android:id="@+id/tvAuthor"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="32dp"
app:layout_constraintStart_toEndOf="@+id/tvPostedFrom"
app:layout_constraintTop_toBottomOf="@+id/include" />
<TextView
android:id="@+id/tvPostDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="16dp"
app:layout_constraintStart_toEndOf="@+id/tvPostedFrom"
app:layout_constraintTop_toBottomOf="@+id/tvAuthor" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rvComments"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="32dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/etNewComment" />
<EditText
android:id="@+id/etNewComment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="32dp"
android:ems="10"
android:hint="@string/DEAddComment"
android:inputType="textPersonName"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvPostDate" />
<Button
android:id="@+id/btSendComment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="32dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:text="@string/DESend"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvPostDate" />
</androidx.constraintlayout.widget.ConstraintLayout>
假设您在一个文件中有 activity 的整个布局，并假设它们确实存在于布局中。
你真的不需要使用 include 变量。
而不是：
tvAuthor = include.findViewById(R.id.tvAuthor);
使用：
tvAuthor = findViewById(R.id.tvAuthor);