FirebaseListAdapter <>已更新为Firebase 4+的较新版本

时间：2018-12-30 05:31:07

标签： android firebase firebase-realtime-database

我关注了following tutorial 我从MainActivity.java运行代码时，Android Studio坏了。

代码的主要部分：

build.gradle （模块：应用）

    android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.samcompany.samichatting2"
        minSdkVersion 17
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }  ...                                                                            
      dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.google.firebase:firebase-core:16.0.6'
    implementation 'com.android.support:design:28.0.0'
   implementation 'com.firebaseui:firebase-ui-auth:4.3.0'
    implementation "com.google.firebase:firebase-database:16.0.5"
    implementation 'com.firebaseui:firebase-ui-database:4.3.0'
}

build.gradle （项目：30dec2018_update1）

...
dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
        classpath 'com.google.gms:google-services:4.0.1'
...

在MainActivity.java中，这部分代码是主要问题：

private void displayChatMessages() {
        ListView listOfMessages = (ListView)findViewById(R.id.list_of_messages);
        Query query = FirebaseDatabase.getInstance().getReference().child("chats");
        FirebaseListOptions<ChatMessage> options = new FirebaseListOptions.Builder<ChatMessage>()
                .setQuery(query, ChatMessage.class)
                .build();
        FirebaseListAdapter<ChatMessage> adapter = new FirebaseListAdapter<ChatMessage>(options) {...}};

我看到了有关此主题的一些链接，但没人帮我，因为现在Firebase版本是4 +。

即使该应用程序没有错误，为什么本节代码也会破坏我的应用程序？

这是堆栈跟踪：

 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.samcompany.samichatting2, PID: 5617
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.samcompany.samichatting2/com.samcompany.samichatting2.MainActivity}: java.lang.RuntimeException: Layout cannot be null. Call setLayout.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2442)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2502)
        at android.app.ActivityThread.-wrap11(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1348)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:5648)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
     Caused by: java.lang.RuntimeException: Layout cannot be null. Call setLayout.
        at com.firebase.ui.common.Preconditions.assertNonNull(Preconditions.java:27)
        at com.firebase.ui.database.FirebaseListOptions$Builder.build(FirebaseListOptions.java:162)
        at com.samcompany.samichatting2.MainActivity.displayChatMessages(MainActivity.java:138)
        at com.samcompany.samichatting2.MainActivity.onCreate(MainActivity.java:54)
        at android.app.Activity.performCreate(Activity.java:6269)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2395)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2502) 
        at android.app.ActivityThread.-wrap11(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1348) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:148) 
        at android.app.ActivityThread.main(ActivityThread.java:5648) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

ChatMessage.Java 

package com.samcompany.samichatting2;
import java.util.Date;

public class ChatMessage {

    private String messageText;
    private String messageUser;
    private long messageTime;

    public ChatMessage(String messageText, String messageUser) {
        this.messageText = messageText;
        this.messageUser = messageUser;

        // Initialize to current time
        messageTime = new Date().getTime();
    }

    public ChatMessage(){

    }

    public String getMessageText() {
        return messageText;
    }

    public void setMessageText(String messageText) {
        this.messageText = messageText;
    }

    public String getMessageUser() {
        return messageUser;
    }

    public void setMessageUser(String messageUser) {
        this.messageUser = messageUser;
    }

    public long getMessageTime() {
        return messageTime;
    }

    public void setMessageTime(long messageTime) {
        this.messageTime = messageTime;
    }
}

MainActivity.Java 

package com.samcompany.samichatting2;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.text.format.DateFormat;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.firebase.ui.auth.AuthUI;
import com.firebase.ui.database.FirebaseListOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.FirebaseDatabase;
import com.firebase.ui.database.FirebaseListAdapter;
import com.google.firebase.database.Query;

public class MainActivity extends AppCompatActivity {

    private static final int SIGN_IN_REQUEST_CODE = 1;
    private FirebaseListAdapter<ChatMessage> adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if(FirebaseAuth.getInstance().getCurrentUser() == null) {
            // Start sign in/sign up activity
            startActivityForResult(
                    AuthUI.getInstance()
                            .createSignInIntentBuilder()
                            .build(),
                    SIGN_IN_REQUEST_CODE
            );
        } else {
            // User is already signed in. Therefore, display
            // a welcome Toast
            Toast.makeText(this,
                    "Welcome " + FirebaseAuth.getInstance()
                            .getCurrentUser()
                            .getDisplayName(),
                    Toast.LENGTH_LONG)
                    .show();

            // Load chat room contents
            displayChatMessages();
        }
        FloatingActionButton fab =
                (FloatingActionButton)findViewById(R.id.fab);

        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                EditText input = (EditText)findViewById(R.id.input);

                // Read the input field and push a new instance
                // of ChatMessage to the Firebase database
                FirebaseDatabase.getInstance()
                        .getReference()
                        .push()
                        .setValue(new ChatMessage(input.getText().toString(),
                                FirebaseAuth.getInstance()
                                        .getCurrentUser()
                                        .getDisplayName())
                        );

                // Clear the input
                input.setText("");
            }
        });
    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode,
                                    Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if(requestCode == SIGN_IN_REQUEST_CODE) {
            if(resultCode == RESULT_OK) {
                Toast.makeText(this,
                        "Successfully signed in. Welcome!",
                        Toast.LENGTH_LONG)
                        .show();
                displayChatMessages();
            } else {
                Toast.makeText(this,
                        "We couldn't sign you in. Please try again later.",
                        Toast.LENGTH_LONG)
                        .show();

                // Close the app
                finish();
            }
        }

    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if(item.getItemId() == R.id.menu_sign_out) {
            AuthUI.getInstance().signOut(this)
                    .addOnCompleteListener(new OnCompleteListener<Void>() {
                        @Override
                        public void onComplete(@NonNull Task<Void> task) {
                            Toast.makeText(MainActivity.this,
                                    "You have been signed out.",
                                    Toast.LENGTH_LONG)
                                    .show();

                            // Close activity
                            finish();
                        }
                    });
        }
        return true;
    }


    //Code issues
    private void displayChatMessages() {
        ListView listOfMessages = (ListView)findViewById(R.id.list_of_messages);
        Query query = FirebaseDatabase.getInstance().getReference().child("chats");
        FirebaseListOptions<ChatMessage> options = new FirebaseListOptions.Builder<ChatMessage>()
                .setQuery(query, ChatMessage.class)
                .build();
        FirebaseListAdapter<ChatMessage> adapter = new FirebaseListAdapter<ChatMessage>(options) {
            @Override
            protected void populateView(View v, ChatMessage model, int position) {
                // Get references to the views of message.xml
                TextView messageText = (TextView)v.findViewById(R.id.message_text);
                TextView messageUser = (TextView)v.findViewById(R.id.message_user);
                TextView messageTime = (TextView)v.findViewById(R.id.message_time);
                // Set their text
                messageText.setText(model.getMessageText());
                messageUser.setText(model.getMessageUser());
                messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",
                        model.getMessageTime()));
            }
        };

        listOfMessages.setAdapter(adapter); //Stop here
    }
}

activity_main.xml 

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.samcompany.samichatting2.MainActivity">

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:clickable="true"
        android:src="@drawable/ic_send_black_24dp"
        android:id="@+id/fab"
        android:tint="@android:color/white"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        app:fabSize="mini" />

    <android.support.design.widget.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/fab"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true">

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Input"
            android:id="@+id/input"
            />
    </android.support.design.widget.TextInputLayout>

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:layout_above="@id/fab"
        android:dividerHeight="16dp"
        android:divider="@android:color/transparent"
        android:id="@+id/list_of_messages"
        android:layout_marginBottom="16dp"/>
</RelativeLayout>

message.xml 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:id="@+id/message_user"
        android:textStyle="normal|bold" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/message_user"
        android:layout_alignParentEnd="true"
        android:id="@+id/message_time" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/message_user"
        android:layout_alignParentStart="true"
        android:layout_marginTop="5dp"
        android:id="@+id/message_text"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1"
        android:textSize="18sp" />
</RelativeLayout>

我将RemixOS用作运行该应用程序的仿真器。 该项目已使用API​​17创建。 我注意到主要的问题是private void displayChatMessages()中的代码。当我从那里删除代码时，该应用程序正在运行，但不显示消息。

0 个答案:

没有答案
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