mainactivity.java
package com.example.newsplash;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.CheckBox; import android.widget.Toast;
public class MainActivity extends AppCompatActivity { CheckBox Chapathi, Dosai, Biriyani, Coffee; Button order;`enter code here` @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); addListenerOnButtonClick(); } public void addListenerOnButtonClick() { Chapathi = (CheckBox) findViewById(R.id.Chapathi); Biriyani = (CheckBox) findViewById(R.id.Biriyani); Dosai = (CheckBox) findViewById(R.id.Dosai); Coffee = (CheckBox) findViewById(R.id.Coffee); order.setOnClickListener(new View.OnClickListener() { @Override public void onClick (View view) { int totalamount = 0; StringBuilder result = new StringBuilder(); result.append("Selected Items:"); if (Chapathi.isChecked()) { result.append("\nChapathi 10RS"); totalamount += 10; } if (Biriyani.isChecked()) { result.append("\nBiriyani is 100RS"); totalamount += 100; } if (Dosai.isChecked()) { result.append("\nDosai is 10RS"); totalamount += 10; } if (Coffee.isChecked()) { result.append("\n Coffee is 10RS"); totalamount += 10; } result.append(("\nTotal"+totalamount +"RS")); Toast.makeText(getApplicationContext(), result.toString(), Toast.LENGTH_LONG).show(); } }); }}logcat 2020-11-05 00:33:48.523 27490-27966/com.example.newsplash D/mmscene: getHint applicationScene=com.example.newsplash,idx=0 none 2020-11-05 00:33:48.577 27490-27490/com.example.newsplash I/Choreographer: Skipped 7 frames! The application may be doing too much work on its main thread. 2020-11-05 00:33:51.378 27490-27490/com.example.newsplash W/ActivityThread: handleWindowVisibility: no activity for token android.os.BinderProxy@3268ab0 2020-11-05 00:33:51.928 27490-27490/com.example.newsplash D/AndroidRuntime: Shutting down VM 2020-11-05 00:33:51.938 27490-27490/com.example.newsplash E/AndroidRuntime: FATAL EXCEPTION: mainProcess: com.example.newsplash, PID: 27490java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.newsplash/com.example.newsplash.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object referenceat android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3146)at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3296)at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:114)at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:74)at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1994)at android.os.Handler.dispatchMessage(Handler.java:106)at android.os.Looper.loop(Looper.java:226)at android.app.ActivityThread.main(ActivityThread.java:7224)at java.lang.reflect.Method.invoke(Native Method)at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:500)at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:913)Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object referenceat com.example.newsplash.MainActivity.addListenerOnButtonClick(MainActivity.java:36)at com.example.newsplash.MainActivity.onCreate(MainActivity.java:23)at android.app.Activity.performCreate(Activity.java:7337)at android.app.Activity.performCreate(Activity.java:7328)at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3126)at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3296) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:114) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:74) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1994) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:226) at android.app.ActivityThread.main(ActivityThread.java:7224) at java.lang.reflect.Method.invoke(Native Method)