Why is the Android Studio app crashing?

Question

Android

The application crashes. Initially, I already had two windows, in addition to the main one. I did the third one, coded everything according to the video tutorial and sources from the git hub. During the test, the assembly was assembled, the application started, all previous windows function, but the last created window, when you click open, crashes the application completely.
If need be, I'll send more.

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button btnW,btnC,btnS,btnP;

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

    public void addListenerOnButton(){
        btnW = (Button)findViewById(R.id.btnweather);
        btnC = (Button)findViewById(R.id.btnclock);
        btnS = (Button)findViewById(R.id.btnstopwatch);
        btnP = (Button)findViewById(R.id.btnplaner);
        btnW.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent("android.intent.action.WeatherAct");
                        startActivity(intent);
                    }
                }
        );

        btnC.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast toast = Toast.makeText(getApplicationContext(),
                                "Тут ДОЛЖЕН БЫТЬ будильник!", Toast.LENGTH_SHORT);
                        toast.show();
                    }
                }
        );

        btnS.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent("android.intent.action.StopwatchActivity");
                        startActivity(intent);
                    }
                }
        );

        btnP.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent("android.intent.action.planer");
                        startActivity(intent);
                    }
                }
        );
    }
}

import android.os.Bundle;

import com.example.diplomchik.R;
import com.example.diplomchik.model.Note;
import com.example.diplomchik.screens.details.NoteDetailsActivity;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;
import androidx.recyclerview.widget.DividerItemDecoration;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

import java.util.List;

public class planer extends AppCompatActivity {

    private RecyclerView recyclerView;

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

        recyclerView = findViewById(R.id.list);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, RecyclerView.VERTICAL, false);
        recyclerView.setLayoutManager(linearLayoutManager);
        recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));

        final Adapter adapter = new Adapter();
        recyclerView.setAdapter(adapter);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                NoteDetailsActivity.start(planer.this, null);
            }
        });

        MainViewModel mainViewModel = ViewModelProviders.of(this).get(MainViewModel.class);
        mainViewModel.getNoteLivedata().observe(this, new Observer<List<Note>>() {
            @Override
            public void onChanged(List<Note> notes) {
                adapter.setItems(notes);
            }
        });
    }
}

2021-06-04 11:14:50.932 30947-30947/com.example.diplomchik D/AndroidRuntime: Shutting down VM
2021-06-04 11:14:50.934 30947-30947/com.example.diplomchik E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.diplomchik, PID: 30947
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.diplomchik/com.example.diplomchik.screens.main.planer}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3534)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3689)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:140)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:100)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2239)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:227)
        at android.app.ActivityThread.main(ActivityThread.java:7822)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1026)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference
        at com.example.diplomchik.screens.main.planer.onCreate(planer.java:38)
        at android.app.Activity.performCreate(Activity.java:7963)
        at android.app.Activity.performCreate(Activity.java:7952)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1306)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3505)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3689) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:140) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:100) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2239) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:227) 
        at android.app.ActivityThread.main(ActivityThread.java:7822) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1026) 
2021-06-04 11:14:50.972 30947-30947/com.example.diplomchik I/Process: Sending signal. PID: 30947 SIG: 9

Answer 1

<b>recyclerView = findViewById(R.id.list);</b>
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, RecyclerView.VERTICAL, false);
<b>recyclerView.setLayoutManager</b>(linearLayoutManager);

Check if you were able to get the expected recyclerView object, and only then do the work. You have an error about trying to call the setLayoutManager method on a non-existent object.

Answer 2

I am attaching the logs, I doubt that it will be visible on the screen

2021-06-04 11:14:45.926 30947-30947/? E/mple.diplomchi: Unknown bits set in runtime_flags: 0x8000
2021-06-04 11:14:46.636 30947-30947/com.example.diplomchik W/mple.diplomchi: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed)
2021-06-04 11:14:46.637 30947-30947/com.example.diplomchik W/mple.diplomchi: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
2021-06-04 11:14:46.728 30947-30947/com.example.diplomchik I/SurfaceFactory: [static] sSurfaceFactory = [email protected]35bb057
2021-06-04 11:14:46.747 30947-30947/com.example.diplomchik D/WindowManager: Add to mViews: DecorView@faf3[MainActivity], this = [email protected]7d313b0,pkg= com.example.diplomchik
2021-06-04 11:14:46.757 30947-30947/com.example.diplomchik D/ViewRootImpl[MainActivity]: hardware acceleration = true , fakeHwAccelerated = false, sRendererDisabled = false, forceHwAccelerated = false, sSystemRendererDisabled = false
2021-06-04 11:14:46.765 30947-30947/com.example.diplomchik I/InputTransport: Create ARC handle: 0x7ca58fb000
2021-06-04 11:14:46.766 30947-30947/com.example.diplomchik V/PhoneWindow: DecorView setVisiblity: visibility = 0, Parent = [email protected]8a709ae, this = DecorView@faf3[MainActivity]
2021-06-04 11:14:46.856 30947-31037/com.example.diplomchik E/EGL-gift: Cannot load register apis
2021-06-04 11:14:46.865 30947-31037/com.example.diplomchik D/Surface: Surface::connect(this=0x7d3d9d8000,api=1)
2021-06-04 11:14:46.869 30947-31037/com.example.diplomchik D/mali_winsys: EGLint new_window_surface(egl_winsys_display *, void *, EGLSurface, EGLConfig, egl_winsys_surface **, EGLBoolean) returns 0x3000
2021-06-04 11:14:46.870 30947-31037/com.example.diplomchik D/Surface: Surface::setBufferCount(this=0x7d3d9d8000,bufferCount=4)
2021-06-04 11:14:46.870 30947-31037/com.example.diplomchik D/Surface: Surface::allocateBuffers(this=0x7d3d9d8000)
2021-06-04 11:14:46.912 30947-31037/com.example.diplomchik W/Gralloc3: mapper 3.x is not supported
2021-06-04 11:14:46.916 30947-31037/com.example.diplomchik E/gralloc: Arm Module v1.0
2021-06-04 11:14:46.917 30947-31037/com.example.diplomchik E/ion: ioctl c0044901 failed with code -1: Invalid argument
2021-06-04 11:14:46.918 30947-31037/com.example.diplomchik W/gralloc: WARNING: internal format modifier bits not mutually exclusive. AFBC basic bit is always set, so extended AFBC support bits must always be checked.
2021-06-04 11:14:47.151 30947-30947/com.example.diplomchik I/Choreographer: Skipped 32 frames!  The application may be doing too much work on its main thread.
2021-06-04 11:14:47.181 30947-30947/com.example.diplomchik I/Choreographer: Skipped 1 frames!  The application may be doing too much work on its main thread.
2021-06-04 11:14:50.788 30947-30947/com.example.diplomchik D/ColorViewRootUtil: nav bar mode ignore false downX 841 downY 1504 mScreenHeight 2400 mScreenWidth 1080 mStatusBarHeight 54 globalScale 1.125 nav mode 0 rotation 0 event MotionEvent { action=ACTION_DOWN, actionButton=0, id[0]=0, x[0]=841.0, y[0]=1504.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, classification=NONE, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=603551068, downTime=603551068, deviceId=4, source=0x1002, displayId=0 }
2021-06-04 11:14:50.854 30947-30947/com.example.diplomchik I/Choreographer: Skipped 1 frames!  The application may be doing too much work on its main thread.
2021-06-04 11:14:50.874 30947-30947/com.example.diplomchik W/ActivityThread: handleWindowVisibility: no activity for token [email protected]56737a4
2021-06-04 11:14:50.932 30947-30947/com.example.diplomchik D/AndroidRuntime: Shutting down VM
2021-06-04 11:14:50.934 30947-30947/com.example.diplomchik E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.diplomchik, PID: 30947
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.diplomchik/com.example.diplomchik.screens.main.planer}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3534)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3689)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:140)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:100)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2239)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:227)
        at android.app.ActivityThread.main(ActivityThread.java:7822)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1026)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference
        at com.example.diplomchik.screens.main.planer.onCreate(planer.java:38)
        at android.app.Activity.performCreate(Activity.java:7963)
        at android.app.Activity.performCreate(Activity.java:7952)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1306)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3505)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3689) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:140) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:100) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2239) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:227) 
        at android.app.ActivityThread.main(ActivityThread.java:7822) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1026) 
2021-06-04 11:14:50.972 30947-30947/com.example.diplomchik I/Process: Sending signal. PID: 30947 SIG: 9