Android 类未定义无参数构造函数。如果您使用的是ProGuard，请确保未剥离这些构造函数

我正在尝试在android studio上创建聊天应用程序。我的应用程序没有生成错误，我可以启动该应用程序。但是，当我使用

listOfMessage.setAdapter（adapter）时我的应用程序正在崩溃。不过，它确实启动了应用程序，在我说1-2秒之后，它正在崩溃应用程序。在
logcat
上，我发现
类没有定义无参数构造函数。如果您使用的是ProGuard，请确保这些构造函数没有删除错误消息。
您能告诉我如何解决此问题吗

当我不使用
listOfMessage.setAdapter（适配器）时
，无论我在应用程序上写下什么，都不会显示在
列表视图上，但我看到条目在firebase上运行良好。代码如下：

public class MainActivity extends AppCompatActivity {



private static int SIGN_IN_REQUEST_CODE = 1;
private FirebaseListAdapter<ChatMessage> adapter;
RelativeLayout activity_main;
FloatingActionButton sendButton;


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

    activity_main =(RelativeLayout)findViewById(R.id.activiy_main);
    sendButton = (FloatingActionButton) findViewById(R.id.sendButton);
    sendButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            EditText input = (EditText)findViewById(R.id.input);
            FirebaseDatabase.getInstance().getReference().push().setValue(new ChatMessage(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<ChatMessage>(this,ChatMessage.class,R.layout.list_item,FirebaseDatabase.getInstance().getReference())
    {
        @Override
        protected void populateView(View v, ChatMessage model, int position) {
            TextView messageText, messageUser,messageTime;
            messageText = (TextView)v.findViewById(R.id.message_text);
            messageUser = (TextView)v.findViewById(R.id.message_user);
            messageTime = (TextView)v.findViewById(R.id.message_time);

            messageText.setText(model.getMessageText());
            messageUser.setText(model.getMessageText());
            messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",model.getMessageTime()));
        }
    };


    //BELOW ONE NEEDS TO BE ACTIVE...TO MAKE ENTRIES VISIBLE

    //listOfMessage.setAdapter(adapter);



}

@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 signed in. Welcome !", Snackbar.LENGTH_SHORT).show();
            displayChatMessage();
        }
        else {
            Snackbar.make(activity_main, "we couldn't sign you in. Please try again", Snackbar.LENGTH_SHORT).show();
            finish();
        }
    }
}


@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;
}

}

logcat上出现完全错误
：

com.google.firebase.database.DatabaseException: Class com.example.cagrik.chat.ChatMessage does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped.
        at com.google.android.gms.internal.firebase_database.zzku.zza(Unknown Source:44)
        at com.google.android.gms.internal.firebase_database.zzkt.zzb(Unknown Source:196)
        at com.google.android.gms.internal.firebase_database.zzkt.zza(Unknown Source:0)
        at com.google.firebase.database.DataSnapshot.getValue(Unknown Source:10)
        at com.firebase.ui.database.FirebaseListAdapter.parseSnapshot(FirebaseListAdapter.java:120)
        at com.firebase.ui.database.FirebaseListAdapter.getItem(FirebaseListAdapter.java:109)
        at com.firebase.ui.database.FirebaseListAdapter.getView(FirebaseListAdapter.java:137)
        at android.widget.AbsListView.obtainView(AbsListView.java:3189)
        at android.widget.ListView.makeAndAddView(ListView.java:2197)
        at android.widget.ListView.fillDown(ListView.java:824)
        at android.widget.ListView.fillFromTop(ListView.java:885)
        at android.widget.ListView.layoutChildren(ListView.java:1924)
        at android.widget.AbsListView.onLayout(AbsListView.java:2961)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1080)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:443)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:945)
        at android.view.View.layout(View.java:20854)
        at android.view.ViewGroup.layout(ViewGroup.java:6401)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2956)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2643)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1780)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7827)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
        at android.view.Choreographer.doCallbacks(Choreographer.java:723)
        at android.view.Choreographer.doFrame(Choreographer.java:658)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
        at android.os.Handler.handleCallback(Handler.java:789)
        at android.os.Handler.dispatchMessage(Handler.java:98)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6944)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

我只是错过了：

public ChatMessage（）{}
关于我的
ChatMessage.class
-感谢@Michael为我找到解决方案。
如果您使用的是内部类，您也可以获得该消息。然后最好是将该内部类提取到它自己的文件中，在本例中：ChatMessage.java
在声明所有变量（即

public ChatMessage() { }

Kotlin的解决方案

您需要放置辅助构造函数

public ChatMessage(){}

在ChatMessage.kt中添加以下代码

 constructor(
    messageText: String,
    messageUser: String,
    messageUserId: String) {
    this.messageText = messageText
    this.messageUser = messageUser
    messageTime = Date().getTime()
    this.messageUserId = messageUserId
}

constructor()   // **Add this**

我也犯了同样的错误，我忘记了构造函数：

public ChatMessage() { }

您必须添加一个默认构造函数：

public ChatMessage（）{}
在kotlin代码的数据类中添加一个默认参数，并将每个参数设置为null。例如

数据类消息（val名称：String？=null，val用户名：String？=null）
只需添加此构造函数即可

public ChatMessage(){}

这已经晚了，但可能会在将来帮助别人
Kotlin

**change your from**

data class ChatMessage(
   var messageText: String?,
   var messageUser: String?,
   var messageTime: Long?)

到此

data class ChatMessage(
   var messageText: String? = "",
   var messageUser: String? = "",
   var messageTime: Long? = 0)

“i'm getting类未定义无参数构造函数”。哪一班？请发布完整的堆栈跟踪。@Michael com.google.firebase.database.DatabaseException:Class com.example.cagrik.chat.ChatMessage未定义无参数构造函数。如果您使用的是ProGuard，请确保com.google.android.gms.internal.firebase_database.zzku.zza（未知源代码：44）com.google.android.gms.internal.firebase_database.zzkt.zzb（未知源代码：196）com.google.android.gms.internal.firebase_database.zzkt.zz（未知源代码：0）上没有剥离这些构造函数位于com.firebase.ui.database.database.DataSnapshot.getValue（未知来源：10）位于com.firebase.ui.database.FirebaseListAdapter.parseSnapshot（FirebaseListAdapter.java:120）位于com.firebase.ui.database.FirebaseListAdapter.getItem（FirebaseListAdapter.java:109）位于com.FirebaseListAdapter.ui.database.FirebaseListAdapter.java:137）通过编辑，在你的问题中以正确的格式发布。另外，
ChatMessage
类的代码在哪里，因为这就是错误所指的？正如错误消息所说，您的
ChatMessage
类没有无参数构造函数。所以你需要添加一个。我不理解你的解决方案，因为在你的问题代码中你已经有了ChatMessage构造函数？？？如果我在数据类中这样做呢？