RecyclerView未显示所有项目

Question

我创建了一个RecyclerView来显示我的应用程序的一些测试帖子。但当我运行我的应用程序时，当我在资源文件上创建时，我只能看到用户名，而不能看到测试后的imageView。我今天开始学习RecyclerView，我对这个观点有很多问题。

注意：我现在不想显示任何url中的任何图像，只想显示我已经保存在可绘制文件夹中的图像。我知道什么时候不需要在模型中添加getImageUrl方法，但也许我在生产中需要它，这就是我不删除这种方法的原因

主页活动代码：

public class HomeActivity extends AppCompatActivity {
public Uri imguri;
DatabaseReference mRef;
final StorageReference mStorageRef = FirebaseStorage.getInstance().getReference("images");
List<PostModel> postList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);

final RecyclerView recyclerView = findViewById(R.id.recyclerView);
RecyclerView.Adapter recyclerAdapter;
final FirebaseAuth mAuth = FirebaseAuth.getInstance();
final FirebaseUser user = mAuth.getCurrentUser();
final ImageButton new_post = findViewById(R.id.new_post_btn);
final ImageButton settings = findViewById(R.id.settingsButton);

if (user == null) {
finish();
startActivity(new Intent(HomeActivity.this, MainActivity.class));
}
mRef = FirebaseDatabase.getInstance().getReference("users");
postList = new ArrayList<>();
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
for (int i = 0; i < 3; i++) {
PostModel postModel = new PostModel("user " + i, "hello world");
postList.add(postModel);
}
recyclerAdapter = new RecyclerAdapter(postList, this);
recyclerView.setAdapter(recyclerAdapter);

settings.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(HomeActivity.this,SettingsActivity.class));
}
});
new_post.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
fileChoose();
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable @org.jetbrains.annotations.Nullable Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == 1 && resultCode == RESULT_OK && data != null && data.getData() != null){
imguri = data.getData();
}
}
public String getFileExtension(Uri uri){
ContentResolver cr = getContentResolver();
MimeTypeMap typeMap = MimeTypeMap.getSingleton();
return typeMap.getExtensionFromMimeType(cr.getType(uri));
}
public void FileUpload(){
StorageReference ref = mStorageRef.child(System.currentTimeMillis() + "." + getFileExtension(imguri));
ref.putFile(imguri)
.addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
@Override
public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
// Get a URL to the uploaded content
//Uri downloadUrl = taskSnapshot.getDownloadUrl();
Toast.makeText(HomeActivity.this, "Meme image successfully uploaded.", Toast.LENGTH_SHORT).show();
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception exception) {
// Handle unsuccessful uploads
// ...
Toast.makeText(HomeActivity.this, "error: " + exception, Toast.LENGTH_SHORT).show();
}
});
}
public void fileChoose(){
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(intent.ACTION_GET_CONTENT);
startActivityForResult(intent,1);
}

}

适配器代码：

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder>{
List<PostModel> postList;
Context context;
public RecyclerAdapter(List<PostModel> postList, Context context) {
this.postList = postList;
this.context = context;
}
@NonNull
@NotNull
@Override
public ViewHolder onCreateViewHolder(@NonNull @NotNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.post_item,parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull @NotNull ViewHolder holder, int position) {
PostModel postModel = postList.get(position);
holder.username.setText(postModel.getName());
}
@Override
public int getItemCount() {
return postList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder{
TextView username;
ImageView postImg;
public ViewHolder(@NonNull @NotNull View itemView) {
super(itemView);
username = itemView.findViewById(R.id.post_username);
postImg = itemView.findViewById(R.id.post_image);
}
}

}

XML资源文件：

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:padding="15dp"
app:cardCornerRadius="20dp"
android:layout_gravity="center_horizontal"
app:cardElevation="20dp"
android:outlineSpotShadowColor="@color/teal_200">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="wrap_content"
android:layout_height="match_parent">
<TextView
android:id="@+id/post_username"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="start"
android:layout_marginStart="10dp"
android:layout_marginTop="5dp"
android:clickable="true"
android:focusable="true"
android:text="By george sepetadelis"
android:textColor="@color/black"
android:textSize="17sp"
android:textStyle="bold"
app:layout_constraintBottom_toTopOf="@+id/post_image"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0" />
<ImageView
android:id="@+id/post_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="10dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/post_username"
tools:srcCompat="@drawable/m1" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>

还有我的型号代码：

public class PostModel {
String name;
String imgUrl;
public PostModel(String name, String imgUrl) {
this.name = name;
this.imgUrl = imgUrl;
}
public String getName() {
return name;
}
public String getImgUrl() {
return imgUrl;
}
}

Answer 1

将tools:srcCompat更改为app:scrCompat，因为tools命名空间仅用于预览Android studio预览选项卡中的内容，并且在运行应用程序时，具有tools命名空间的属性将从xml文件中删除

有关toolsns 的更多信息，请查看官方文档