错误消息：java.lang.IllegalArgumentException

Question

I'm new at coding so I might be not very good at explaining. I'm trying to build chat app with Firebase.

Here is my code for Main activity:

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);
}
}

And code for acitivty_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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">


<android.support.design.widget.FloatingActionButton
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:clickable="true"
    android:src="@drawable/c_send"
    android:id="@+id/fab"
    android:tint="@android:color/white"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="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="Message..."
    android:id="@+id/input"
        />
</android.support.design.widget.TextInputLayout>
<ListView
    android:id="@+id/list_of_message"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:layout_above="@+id/fab"
    android:dividerHeight="16dp"
    android:divider="@android:color/transparent"
    android:layout_marginBottom="16dp"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</ListView>

Error code from the logcat while app says that it keeps stopping tells me that problem is in the snackbar:

 Caused by: java.lang.IllegalArgumentException: No suitable parent found from the given view. Please provide a valid view.
    at android.support.design.widget.Snackbar.make(Snackbar.java:181)
    at com.example.otto.myfirstapplication.MainActivity.onCreate(MainActivity.java:97)
    at android.app.Activity.performCreate(Activity.java:7009)
    at android.app.Activity.performCreate(Activity.java:7000)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)

I updated all dependencies to the latest versions. I was thinking maybe I have to downgrade to solve a problem but I'm not sure.

Anyway I'm super stuck and hope you can help me. Thanks in advance.

Answer 1

Change at all places,

Snackbar.make(activity_main,...

to

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

Cause

You did not initialize activity_main . So it is null when you use it. findViewById(android.R.id.content) gives you root view of current Activity.

Answer 2

First of All you have to create coordinator layout to appear your snackbar. so change your main relativelayout to coordinator layout .

<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>

after that in your activity .

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

and make your Snackbar layout like this

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

 snackbar.show();

Answer 3

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.