Android/Firebase-ListView中未显示TextView

Question

我是Android的初学者。在适配器的帮助下，我面临着在卡片列表视图中添加文本视图的问题。我在youtube上学习了一个教程，但它对我不起作用。此外，我还查找了其他类似的问题，但由于我是初学者，我无法理解解决方案。如果有人帮我解决这个问题，我将不胜感激。

这是我的带有文本视图布局的卡片，名为job_row

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView 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:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:cardCornerRadius="3dp"
android:elevation="90dp"
android:layout_margin="15dp">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="112dp"
android:background="#fff"
android:orientation="vertical">

<ImageView
android:id="@+id/prof_pic"
android:layout_width="80dp"
android:layout_height="80dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:scaleType="centerCrop"
android:src="@drawable/prof_pic"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/profName"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="16dp"
android:fontFamily="sans-serif"
android:text="Poster Name"
android:textColor="#000"
android:textSize="16sp"
android:textStyle="normal"
app:layout_constraintStart_toEndOf="@+id/prof_pic"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/jobName"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="8dp"
android:fontFamily="sans-serif-black"
android:text="Job Name"
android:textColor="#000"
android:textSize="16sp"
app:layout_constraintStart_toEndOf="@+id/prof_pic"
app:layout_constraintTop_toBottomOf="@+id/profName" />
<TextView
android:id="@+id/jobLocation"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="24dp"
android:layout_marginTop="8dp"
android:fontFamily="sans-serif-light"
android:text="Job Location"
android:textColor="#000"
android:textSize="14sp"
app:layout_constraintStart_toEndOf="@+id/prof_pic"
app:layout_constraintTop_toBottomOf="@+id/jobName" />
<TextView
android:id="@+id/jobCharge"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:fontFamily="sans-serif-light"
android:text="Job Charge"
android:textColor="#000"
android:textSize="14sp"
app:layout_constraintBaseline_toBaselineOf="@+id/jobLocation"
app:layout_constraintStart_toEndOf="@+id/jobLocation" />
</androidx.constraintlayout.widget.ConstraintLayout>

主页布局，我希望我的卡片视图出现

<?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=".Home"
>
<SearchView
android:id="@+id/search"
android:layout_width="0dp"
android:layout_height="40dp"
android:layout_marginStart="16dp"
android:layout_marginTop="24dp"
android:layout_marginEnd="80dp"
android:background="#fff"
android:iconifiedByDefault="false"
android:queryBackground="@android:color/transparent"
android:queryHint="Search Jobs"
android:textColor="#fff"
android:textSize="10dp"
android:visibility="visible"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/newBtn"
style="@style/TextButton"
android:layout_width="30dp"
android:layout_height="27dp"
android:layout_marginStart="16dp"
android:layout_marginTop="24dp"
android:text="New"
android:textAlignment="viewStart"
android:textSize="14sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/search" />
<Button
android:id="@+id/nearYouBtn"
style="@style/TextButton"
android:layout_width="70dp"
android:layout_height="30dp"
android:layout_marginStart="70dp"
android:layout_marginTop="24dp"
android:text="Near You"
android:textAlignment="viewStart"
android:textSize="14sp"
app:layout_constraintStart_toEndOf="@+id/newBtn"
app:layout_constraintTop_toBottomOf="@+id/search" />
<Button
android:id="@+id/recommendBtn"
style="@style/TextButton"
android:layout_width="96dp"
android:layout_height="25dp"
android:layout_marginStart="70dp"
android:layout_marginTop="24dp"
android:layout_marginEnd="16dp"
android:text="Recommended"
android:textAlignment="viewStart"
android:textSize="14sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/nearYouBtn"
app:layout_constraintTop_toBottomOf="@+id/search" />
<ListView
android:id="@+id/newjob_list"
android:layout_width="329dp"
android:layout_height="446dp"
android:layout_marginStart="16dp"
android:layout_marginTop="32dp"
android:layout_marginEnd="16dp"
android:visibility="visible"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/nearYouBtn" />

主页类

package com.example.oddsynew;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import com.firebase.ui.database.FirebaseListAdapter;
import com.firebase.ui.database.FirebaseListOptions;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
public class Home extends AppCompatActivity {
ListView lv;
FirebaseListAdapter adapter;
DatabaseReference myRef;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
lv = (ListView) findViewById(R.id.newjob_list);
myRef = FirebaseDatabase.getInstance().getReference().child("Job");
FirebaseListOptions<Job> options = new FirebaseListOptions.Builder<Job>()
.setLayout(R.layout.job_row)
.setQuery(myRef, Job.class)
.build();
adapter = new FirebaseListAdapter(options) {
@Override
protected void populateView(View v, Object model, int position) {
TextView recruiterName = v.findViewById(R.id.profName);
TextView jobName = v.findViewById(R.id.jobName);
TextView jobLocation = v.findViewById(R.id.jobLocation);
TextView jobCharge = v.findViewById(R.id.jobCharge);
Job job = (Job) model;
recruiterName.setText(job.getPoster_name());
jobName.setText(job.getJob_name());
jobLocation.setText(job.getLocation());
jobCharge.setText(job.getJob_charge().toString());
}
};
lv.setAdapter(adapter);
}
@Override
protected void onStart() {
super.onStart();
adapter.startListening();
}
@Override
protected void onStop() {
super.onStop();
adapter.stopListening();
}
}

并且我的适配器类

package com.example.oddsynew;
public class Job {
private String job_name;
private String poster_name;
private String location;
private Double job_charge;
public String getJob_name() {
return job_name;
}
public Job(String job_name, String poster_name, String location, Double job_charge) {
this.job_name = job_name;
this.poster_name = poster_name;
this.location = location;
this.job_charge = job_charge;
}
public void setJob_name(String job_name) {
this.job_name = job_name;
}
public String getPoster_name() {
return poster_name;
}
public void setPoster_name(String poster_name) {
this.poster_name = poster_name;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public Double getJob_charge() {
return job_charge;
}
public void setJob_charge(Double job_charge) {
this.job_charge = job_charge;
}
}

Answer 1

您的TextViews没有显示，因为您给了它们0dp宽度，但没有给出完整的约束。

在ConstraintLayout中，给一个子android:layout_width="0dp"意味着您希望使用约束来确定宽度，而不是显式指定宽度。但如果执行此操作，则必须为两个边指定约束：app:layout_constraintStart_*和app:layout_constraintEnd_*。如果不同时指定两者，则视图的宽度将为零，使其不可见。

要解决此问题，请将以下属性添加到所有具有android:layout_width="0dp"的TextViews：

<TextView
...
android:layout_marginEnd="16dp"
app:layout_constraintEnd_toEndOf="parent"
... />