Android 不幸的是，OnClickListner已经停止了

我写了一段简单的代码，它导致应用程序停止工作。我找到了错误出现的地方，但我不知道如何解决它

    package com.example.alireza.mygrocerylist.Activities.Activities;

import android.os.Bundle;
import android.os.Handler;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.KeyEvent;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.example.alireza.mygrocerylist.R;

public class MainActivity extends AppCompatActivity {

    private AlertDialog.Builder dialogBuilder;
    private AlertDialog dialog;
    private EditText groceryItem, quantity;
    private Button saveButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                //        .setAction("Action", null).show();
                createPopupDialog();

            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    **private  void createPopupDialog() {
        dialogBuilder = new AlertDialog.Builder(this);
        View view = getLayoutInflater().inflate(R.layout.popup, null);
        groceryItem = (EditText) findViewById(R.id.groceryItem);
        quantity = (EditText) findViewById(R.id.geroceryQty);
        saveButton = (Button) findViewById(R.id.saveButtom);
        dialogBuilder.setView(view);
        dialog = dialogBuilder.create();
        dialog.show();
        saveButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                saveGroceryToDB(v);
            }
        });**



    }

    private void saveGroceryToDB(View v) {

    }

    public boolean onKeyUp (int keyCode, KeyEvent event) {
        //here you can start your activity, i.e. this way:
        //Toast.makeText(MainActivity.this,"First",Toast.LENGTH_LONG).show();
        return true;
    }

}

当代码执行时，在运行到createPopupDialog时，我收到了错误，不幸的是，我的购物清单停止了！但是如果我拿出去 saveButton.setOnClickListenernew View.OnClickListener及其覆盖方法应用程序再次工作！

---

你能帮我解释一下这个错误吗？

对话框的视图不能直接访问。请这样做：-

final AlertDialog dialog = new AlertDialog.Builder(this, R.style.Theme_AppCompat_Light_Dialog_Alert);
dialog.setContentView(R.layout.popup);
groceryItem = view.findViewById(R.id.groceryItem);

---

//同样，对于其他视图，您是否可以重复您的问题？我不明白你的意思。请将此groceryItem=EditText findViewByIdR.id.groceryItem更改为groceryItem=EditText view.findViewByIdR.id.groceryItem。类似地，所有其他视图1我都按照主题所说的做了。2我的意思是，通过这种方法，我的应用程序可以工作，如果我对这种方法发表评论，应用程序也可以工作。3谢谢，但它不起作用05-29 12:08:57.104 12459-12459/com.example.alireza.mygrocerylist E/AndroidRuntime:FATAL EXCEPTION:main Process:com.example.alireza.mygrocerylist，PID:12459 java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法'void android.widget.Button.setOnClickListenerandroid.view.view$OnClickListener'，您应该按-saveButton=Button view.findViewByIdR.id.saveButtom执行；