Question

我在build.gradle中使用以下依赖项：

compile 'com.google.firebase:firebase-database:11.4.2'
compile 'com.firebaseui:firebase-ui-database:3.1.0'
compile 'com.firebaseui:firebase-ui-auth:3.1.0'

我的目标是使用Firebase数据库中的数据填充Listview。我按照Github Firebase上的指南进行操作以下方法应将数据绑定到listview：

private void showMessages() {

        Query query = FirebaseDatabase.getInstance()
                .getReference("notfication/unread/" + userMailAddress.replace(".", ","))
                .orderByKey();


        FirebaseListOptions<Message> options = new FirebaseListOptions.Builder<Message>()
                .setLayout(R.layout.fbmessage_listitem)//Note: The guide doesn't mention this method, without it an exception is thrown that the layout has to be set.
                .setQuery(query, Message.class)
                .build();


        FirebaseListAdapter<Message> adapter = new FirebaseListAdapter<Message>(options) {
            @Override
            protected void populateView(View v, Message model, int position) {

                TextView tvMessage = v.findViewById(R.id.tv_message);
                tvMessage.setText(model.getDateTimeCreated());

            }
        };

        ListView readMessageList = findViewById(R.id.lvReadMessageList);
        readMessageList.setAdapter(adapter);
}

这是包含TextViews的布局。

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="0.6"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tv_created_on"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="start"
        android:gravity="start"
        android:paddingStart="5dp"
        android:paddingEnd="0dp"
        android:textColor="@android:color/black" />

    <TextView
        android:id="@+id/tv_message"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="start"
        android:gravity="start"
        android:paddingStart="5dp"
        android:paddingEnd="0dp"
        android:textColor="@android:color/black" />

</LinearLayout>


<ImageView
    android:id="@+id/iv_message_read"
    android:layout_width="200dp"
    android:layout_height="30dp"
    android:layout_weight="0.2"
    android:contentDescription="@string/message_read"
    android:elevation="2dp"
    app:srcCompat="@drawable/android_ok_sign" />

<ImageView
    android:id="@+id/iv_delete"
    android:layout_width="200dp"
    android:layout_height="30dp"
    android:layout_weight="0.2"
    android:contentDescription="@string/abc_delete"
    android:elevation="2dp"
    android:src="@drawable/ic_delete_red_48dp" />

模特：

public class Message {

    private String message;
    private String sender;
    private String receiver;
    private long timestamp;
    private boolean isRead;
    private String userMailAddress;

    public Message() {
    }

    public Message(String message, String sender, String receiver, long timestamp, boolean isRead) {
        this.message = message;
        this.sender = sender;
        this.receiver = receiver;
        this.timestamp = timestamp;
        this.isRead = isRead;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public String getSender() {
        return sender;
    }

    public void setSender(String sender) {
        this.sender = sender;
    }

    public String getReceiver() {
        return receiver;
    }

    public void setReceiver(String receiver) {
        this.receiver = receiver;
    }

    public long getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(long timestamp) {
        this.timestamp = timestamp;
    }

    public boolean isRead() {
        return isRead;
    }

    public void setRead(boolean read) {
        isRead = read;
    }

    public String getUserMailAddress() {
        return userMailAddress;
    }

    public void setUserMailAddress(String userMailAddress) {
        this.userMailAddress = userMailAddress;
    }

    public String getDateTimeCreated() {

        Calendar calendar = Calendar.getInstance(Locale.getDefault());
        calendar.setTimeInMillis(timestamp);
        String date = DateFormat.format("dd-MM-yyyy", calendar).toString();
        String time = DateFormat.format("HH:mm", calendar).toString();
        return date + "\r\n" + time;
    }
}

无论我尝试什么，设置断点或记录TAG，方法populateView将模型中的数据绑定到文本域都不被调用。我在之前的FirebaseUI中使用相同的布局（仍然在我的生产应用程序中），一切都在那里正常工作。

有谁知道为什么覆盖方法populateView没有被调用？

Answer 1

我遇到了同样的问题，修复了：

@Override
protected void onStart() {
    super.onStart();
    mAdapter.startListening();
}

然后

@Override
protected void onStop() {
    super.onStop();
    mAdapter.stopListening();
}

像更新前一样工作： - ）

Answer 2

我遇到了同样的问题。我尝试了接受的答案，但代码在startListening语句中失败并且空指针异常（适配器为空！）。

经过大量研究后，我在示例代码中添加了.setLifecycleOwner(this)（例如，参见下面的代码）。它就像一个魅力！

FirebaseListOptions<Message> options = new FirebaseListOptions.Builder<Message>()
    .setLayout(R.layout.fbmessage_listitem)//Note: The guide doesn't mention this method, without it an exception is thrown that the layout has to be set.
    .setQuery(query, Message.class)
    .setLifecycleOwner(this)   //Added this
    .build();

Answer 3

这可能是查询中的拼写错误吗？ notifications代替notification？尝试在FirebaseListAdapter#onChildChanged()中放置一个断点，看看是否有任何事件进入。

最有可能的原因是你没有打电话给FirebaseListAdapter#startListening()。除非您使用FirebaseListOptions#setLifecycleOwner(...)的Android架构组件，否则必须手动manage your adapter's lifecycle。这意味着调用startListening()中的onStart()和stopListening()中的onStop()。

PS：我建议您查看性能优于ListView的RecyclerView。

Android使用FirebaseUI和FirebaseListOptions填充ListView不会调用populateView

3 个答案: