错误消息：java.lang.IllegalArgumentException

我对编码还不熟悉，所以我可能不太擅长解释。我正在尝试使用Firebase构建聊天应用程序

以下是我的主要活动代码：

Mpackage com.example.otto.myfirstapplication;

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

import com.firebase.ui.auth.AuthUI;
import com.firebase.ui.database.FirebaseListAdapter;
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;


public class MainActivity extends AppCompatActivity {

private static int SIGN_IN_REQUEST_CODE = 1;
private FirebaseListAdapter<ChatClass> adapter;
RelativeLayout activity_main;
FloatingActionButton fab;

@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) {
                 Snackbar.make(activity_main,"You have been signed out.", Snackbar.LENGTH_SHORT).show();
                 finish();
             }
         });
    }
    return true;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main_menu,menu);
    return true;
}

@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)
        {

            Snackbar.make(activity_main,"Successfully sighned in.Welcome!", Snackbar.LENGTH_SHORT).show();
            displayChatMessage();

        }
        else{
            Snackbar.make(activity_main,"Error 1", Snackbar.LENGTH_SHORT).show();
            finish();
        }

    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);



    fab = (FloatingActionButton)findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            EditText input = (EditText)findViewById(R.id.input);
            FirebaseDatabase.getInstance().getReference().push().setValue(new ChatClass(input.getText().toString(),FirebaseAuth.getInstance().getCurrentUser().getEmail()));
            input.setText("");

        }
    });
    if(FirebaseAuth.getInstance().getCurrentUser() == null)
    {
        startActivityForResult(AuthUI.getInstance().createSignInIntentBuilder().build(),SIGN_IN_REQUEST_CODE);
    }
    else
    {
        Snackbar.make(activity_main,"Welcome " +FirebaseAuth.getInstance().getCurrentUser().getEmail(),Snackbar.LENGTH_SHORT).show();
    }
    displayChatMessage();
}

private void displayChatMessage() {
    ListView listOfMessage = (ListView)findViewById(R.id.list_of_message);
    adapter = new FirebaseListAdapter<ChatClass>(this,ChatClass.class,R.layout.list_item,FirebaseDatabase.getInstance().getReference()) {



        @Override
        protected void populateView(View v, ChatClass model, int position) {
            TextView messageText,messageUser,messageTime;
            messageText = (TextView)findViewById(R.id.message_text);
            messageUser = (TextView)findViewById(R.id.message_user);
            messageTime = (TextView)findViewById(R.id.message_time);

            messageText.setText(model.getMessageText());
            messageUser.setText(model.getMessageUser());
            messageTime.setText(DateFormat.format("dd-mm-yy (HH:mm:ss)",model.getMessageTime()));
        }
    };
    listOfMessage.setAdapter(adapter);
}
}

我将所有依赖项更新为最新版本。我在想也许我必须降级才能解决问题，但我不确定

不管怎么说，我被深深地困住了，希望你能帮助我。提前感谢。

在任何地方换车

Snackbar.make(activity_main,...

到

原因

---

您没有初始化

活动\u main

。因此，当您使用它时，它是空的

findviewbyd（android.R.id.content）

提供当前活动的根视图

首先，您必须创建协调器布局以显示snackbar。因此，将您的主要relativelayout更改为coordinator布局

<android.support.design.widget.CoordinatorLayout 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/coordinatorLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


//YOUR CURRENT CODE

</android.support.design.widget.CoordinatorLayout>

让你的Snackbar布局像这样

 Snackbar snackbar = Snackbar.make(coordinatorLayout, "Welcome to AndroidHive", Snackbar.LENGTH_LONG);

 snackbar.show();

与您的代码一样，
相对活动；
您尚未初始化activity_main，请在创建activity时使用findviewbyid
在xml中更改以下代码，在xml中添加id。
在代码中，在活动的onCreate方法中获取id：
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
活动_main=findViewById（R.id.container）；
}
现在在快餐店里使用这个视图（activity_main）。

生成全局变量

查看root\u视图

不再使用

findviewbyd（android.R.id.content）

.RelativeLayout活动\u main；您尚未初始化活动\u main，请在onCreate中使用findviewbyidactivity@OtarJibladze我的回答对你有帮助吗？

Snackbar.make(findViewById(android.R.id.content),...

<android.support.design.widget.CoordinatorLayout 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/coordinatorLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


//YOUR CURRENT CODE

</android.support.design.widget.CoordinatorLayout>

 coordinatorLayout = (CoordinatorLayout) findViewById(R.id
                .coordinatorLayout);

 Snackbar snackbar = Snackbar.make(coordinatorLayout, "Welcome to AndroidHive", Snackbar.LENGTH_LONG);

 snackbar.show();

As in your code, 
RelativeLayout activity_main; 
you haven't initialized the activity_main, use findviewbyid in onCreate of activity
In xml change the below code, add the id in 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/container"
    tools:context=".MainActivity">

and in the code fetch the id in onCreate method of Activity:

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    activity_main=findViewById(R.id.container);
    }

and now use this view(activity_main) in snack bar.