java.lang.NullPointerException:在androidstudio中

我有一个Android应用。该应用程序有十个活动,其中第一个活动是“启动画面”,并且运行了介绍活动,进入主活动后出现错误,该应用程序关闭且未进入主活动,我得到的错误是:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.myapplication, PID: 28709
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setAlpha(float)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6119)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setAlpha(float)' on a null object reference
        at com.github.hujiaweibujidao.wava.BaseViewAnimator.reset(BaseViewAnimator.java:78)
        at com.github.hujiaweibujidao.wava.BaseViewAnimator.start(BaseViewAnimator.java:55)
        at com.github.hujiaweibujidao.wava.YoYo$Builder.start(YoYo.java:128)
        at com.github.hujiaweibujidao.wava.YoYo$Builder.playOn(YoYo.java:115)
        at com.example.myapplication.MainActivity.onCreate(MainActivity.java:104)
        at android.app.Activity.performCreate(Activity.java:6679)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6119) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

我的xml代码:

<?xml version="1.0" encoding="utf-8"?>
<com.mxn.soul.flowingdrawer_core.FlowingDrawer
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:night="http://schemas.android.com/tools"
    android:id="@+id/drawerlayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clipChildren="false"
    android:clipToPadding="false"
    app:edPosition="2"
    app:edMenuSize="260dp"
    app:edMenuBackground="#dddddd">

    <LinearLayout
        android:id="@+id/lin_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        >
        <androidx.appcompat.widget.Toolbar
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="@color/nephritis"
            android:id="@+id/toolbar"
            >
            <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="horizontal"
                android:gravity="end">

                <androidx.appcompat.widget.AppCompatImageView
                    android:id="@+id/img_night"
                    android:layout_width="35dp"
                    android:layout_height="35dp"
                    android:layout_margin="8dp"
                    android:background="@drawable/moon_icon"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent"
                    android:onClick="set_night"/>


                <TextView
                    android:id="@+id/txt_text"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_margin="4dp"
                    android:layout_marginStart="8dp"
                    android:layout_marginLeft="8dp"
                    android:layout_marginEnd="8dp"
                    android:layout_marginRight="8dp"
                    android:fontFamily="@font/medium"
                    android:gravity="center_vertical"
                    android:lineSpacingExtra="10dp"
                    android:text="@string/martaei"
                    android:textColor="@color/White"
                    android:textSize="26sp"
                    app:layout_constraintEnd_toStartOf="@+id/img_icon"
                    app:layout_constraintStart_toEndOf="@+id/img_night"
                    night:layout_editor_absoluteY="4dp"
                    night:night_textColor="#180101" />

                <androidx.appcompat.widget.AppCompatImageView
                    android:id="@+id/img_icon"
                    android:layout_width="50dp"
                    android:layout_height="50dp"
                    android:layout_centerInParent="true"
                    android:layout_margin="4dp"
                    android:src="@drawable/menu"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintTop_toTopOf="parent" />


            </androidx.constraintlayout.widget.ConstraintLayout>

        </androidx.appcompat.widget.Toolbar>


        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="3"
            android:gravity="center">
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="horizontal"
                android:weightSum="2"
                android:gravity="center">
                <androidx.appcompat.widget.AppCompatImageView
                    android:id="@+id/img_main"
                    android:layout_width="0dp"
                    android:layout_weight="1.5"
                    android:layout_height="match_parent"
                    android:background="@drawable/ic_profile123456"
                    android:layout_gravity="center"
                    android:layout_margin="12sp"/>
            </LinearLayout>

        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="4"
            android:orientation="vertical">
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:orientation="horizontal"
                android:weightSum="2"
                android:layout_marginTop="36dp">
                <Button
                    android:id="@+id/btn_fehrest"
                    android:layout_width="0dp"
                    android:layout_weight="1"
                    android:layout_height="80dp"
                    android:text="@string/listmozo"
                    android:textSize="24sp"
                    android:textColor="@color/White"
                    android:fontFamily="@font/medium"
                    android:onClick="fehrest_intent"
                    android:background="@drawable/back_btn1"
                    android:layout_gravity="center"
                    android:paddingEnd="12dp"/>
            </LinearLayout>
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:orientation="horizontal"
                android:weightSum="2">
                <Button
                    android:id="@+id/btn_last_story"
                    android:layout_width="0dp"
                    android:layout_weight="1"
                    android:layout_height="80dp"
                    android:text="آخرین داستان"
                    android:onClick="text_intent"
                    android:textSize="24sp"
                    android:textColor="@color/White"
                    android:fontFamily="@font/medium"
                    android:background="@drawable/back_btn3"
                    android:layout_gravity="center"
                    android:paddingEnd="12dp"/>
            </LinearLayout>
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:orientation="horizontal"
                android:weightSum="2">
                <Button
                    android:id="@+id/btn_fav"
                    android:layout_width="0dp"
                    android:layout_weight="1"
                    android:layout_height="80dp"
                    android:text="@string/list_of_favorites"
                    android:onClick="fav_intent"
                    android:textSize="24dp"
                    android:textColor="@color/White"
                    android:fontFamily="@font/medium"
                    android:background="@drawable/back_btn2"
                    android:layout_gravity="center"
                    android:paddingRight="12dp"/>
            </LinearLayout>
        </LinearLayout>


        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:layout_margin="8dp">
            <com.akshay.library.CurveBottomBar
                android:layout_width="match_parent"
                android:layout_height="60dp"
                android:layout_alignParentBottom="true"
                app:bottomBarColor="#FFB601"
                app:curveRadius="53dp"
                app:itemIconTint="@color/White"
                android:id="@+id/cbb"/>
        </RelativeLayout>
    </LinearLayout>
    <com.mxn.soul.flowingdrawer_core.FlowingMenuLayout
        android:id="@+id/menulayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        >

        <androidx.appcompat.widget.LinearLayoutCompat
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:gravity="end"
            android:background="@color/White">
            <androidx.appcompat.widget.AppCompatImageView
                android:id="@+id/imgtest"
                android:layout_width="wrap_content"
                android:layout_height="200dp"
                android:scaleType="centerCrop"
                android:background="@drawable/back_nav"/>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">
                <TextView
                    android:id="@+id/txt"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="@string/ghhgkjjjhjl"
                    android:layout_margin="8dp"
                    android:onClick="fehrest_intent"/>
                <androidx.appcompat.widget.AppCompatImageView
                    android:layout_width="20dp"
                    android:layout_height="20dp"
                    android:background="@drawable/content_copy2"/>
            </androidx.appcompat.widget.LinearLayoutCompat>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">
                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="@string/hghjk"
                    android:layout_margin="8dp"
                    android:onClick="fav_intent"/>
                <androidx.appcompat.widget.AppCompatImageView
                    android:layout_width="20dp"
                    android:layout_height="20dp"
                    android:background="@drawable/heart_icon"
                    android:onClick="fav_intent"/>
            </androidx.appcompat.widget.LinearLayoutCompat>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">
                <androidx.appcompat.widget.AppCompatImageView
                    android:layout_width="20dp"
                    android:layout_height="20dp"
                    android:background="@drawable/settings2"/>
            </androidx.appcompat.widget.LinearLayoutCompat>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">

            </androidx.appcompat.widget.LinearLayoutCompat>
            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:background="@color/gray"
                android:layout_margin="8dp"/>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">

            </androidx.appcompat.widget.LinearLayoutCompat>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">
                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="@string/jkhjlkjkl"
                    android:layout_margin="8dp"/>
                <androidx.appcompat.widget.AppCompatImageView
                    android:layout_width="20dp"
                    android:layout_height="20dp"
                    android:background="@drawable/content_copy2"/>
            </androidx.appcompat.widget.LinearLayoutCompat>
            <androidx.appcompat.widget.LinearLayoutCompat
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:gravity="end|center_vertical"
                android:layout_margin="8dp">
                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="@string/klkl"
                    android:layout_margin="8dp"
                    android:onClick="finish"/>
                <ImageView
                    android:layout_width="20dp"
                    android:layout_height="20dp"
                    android:background="@drawable/exit_to_app"/>
            </androidx.appcompat.widget.LinearLayoutCompat>

        </androidx.appcompat.widget.LinearLayoutCompat>

    </com.mxn.soul.flowingdrawer_core.FlowingMenuLayout>
</com.mxn.soul.flowingdrawer_core.FlowingDrawer>

我的Java代码:

package com.example.myapplication;


public class MainActivity extends AppCompatActivity {
    private CurveBottomBar cbb;
    FlowingDrawer mDrawer;
    ImageView img_icon,imgtest,img_music,img_night,img_main,img_setting;
    TextView txt;
    String patch;

    boolean read=false,music=true,night_mode;
    Button btn_fehrest,btn_last_story,btn_fav;
    SharedPreferences sharedP;
    LinearLayout lin_main;
    Toast exit;
    boolean show_intropage;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        cbb = findViewById(R.id.cbb);
        mDrawer = findViewById(R.id.drawerlayout);
        imgtest = findViewById(R.id.imgtest);
        txt = findViewById(R.id.txt);
        btn_fehrest = findViewById(R.id.btn_fehrest);
        img_music = findViewById(R.id.img_music);
        lin_main = findViewById(R.id.lin_main);
        img_night = findViewById(R.id.img_night);
        img_main = findViewById(R.id.img_main);
        btn_fav = findViewById(R.id.btn_fav);
        img_setting = findViewById(R.id.img_setting);

        cbb.inflateMenu(R.menu.menu_scrolling);
        sharedP = getSharedPreferences(Items.SETTINGS, Context.MODE_PRIVATE);
        show_intropage = sharedP.getBoolean(Items.INTROPAGE,true);


        cbb.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {

                switch (menuItem.getItemId()){

                    case R.id.img_setting:
                        // kary ke mikhaym anjam bedim
                        break;

                    case R.id.img_music:
                        //
                        break;
                }

                return true;
            }
        });
        YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(btn_fehrest);
        YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(btn_last_story);
        YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(btn_fav);
        YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(img_music);
        YoYo.with(Techniques.ZoomInDown).duration(1000).playOn(img_setting);

        get_night();
        permission();
        //createFile();
        if (show_intropage){
            taptarget();
        }



        img_icon.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                mDrawer.openMenu(true);
            }
        });

        mDrawer.setTouchMode(ElasticDrawer.TOUCH_MODE_BEZEL);
        mDrawer.setBackgroundColor(Color.WHITE);
        mDrawer.setOnDrawerStateChangeListener(new ElasticDrawer.OnDrawerStateChangeListener() {
            @Override
            public void onDrawerStateChange(int oldState, int newState) {
                if (newState == ElasticDrawer.STATE_CLOSED) {
                    Log.i("MainActivity", "Drawer STATE_CLOSED");
                }
            }

            @Override
            public void onDrawerSlide(float openRatio, int offsetPixels) {
                Log.i("MainActivity", "openRatio=" + openRatio + " ,offsetPixels=" + offsetPixels);
            }
        });
    }


    public void createFile(){

        try {

            patch = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Mbook/";

            File mfile = new File(patch);

            if (!mfile.exists()) {
                mfile.mkdir();
                mfile.createNewFile();
                CopyDB(getBaseContext().getAssets().open("Mbook.db"), new FileOutputStream(patch+"/Mbook.db"));
                //Toast.makeText(this, patch+"", Toast.LENGTH_LONG).show();
            }

        }catch (FileNotFoundException e){
            e.printStackTrace();
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public void CopyDB (InputStream inputStream, OutputStream outputStream) throws IOException {

        byte[] buffer = new byte[1024];
        int file_length;
        while ((file_length = inputStream.read(buffer))>0){

            outputStream.write(buffer,0,file_length);
        }
        inputStream.close();
        outputStream.close();
    }

    public void fehrest_intent(View view) {
        mDrawer.closeMenu(true);
        YoYo.with(Techniques.Pulse).duration(800).playOn(btn_fehrest);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {

                Intent intent = new Intent(getBaseContext(), Fehrest.class);
                intent.putExtra("button","fehrest");
                startActivity(intent);

            }
        },1500);

    }

    private void permission(){

        Dexter.withActivity(MainActivity.this)
                .withPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)

                .withListener(new PermissionListener() {
                    @Override
                    public void onPermissionGranted(PermissionGrantedResponse response) {

                        createFile();
                    }

                    @Override
                    public void onPermissionDenied(PermissionDeniedResponse response) {

                        if (response !=null && response.isPermanentlyDenied()){

                                @Override
                                public void onClick(DialogInterface dialogInterface, int i) {
                                    Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
                                    intent.setData(Uri.fromParts("package",getPackageName(),null));
                                    startActivity(intent);
                                }
                            });
                        }


                    @Override
                    public void onPermissionRationaleShouldBeShown(PermissionRequest permission, final PermissionToken token) {
                        alert();
                    }
                }).check();

    }


        Hoshdar.create().show();
    }

    public void fav_intent(View view) {
        YoYo.with(Techniques.Pulse).duration(600).playOn(btn_fav);
        mDrawer.closeMenu(true);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {

                Intent intent = new Intent(getBaseContext(), Fehrest.class);
                intent.putExtra("button","fav");
                intent.putExtra("activity","main");
                startActivity(intent);

            }
        },1500);
    }


    public void setting_intent(MenuItem item)  {
        mDrawer.closeMenu(true);
        YoYo.with(Techniques.Pulse).duration(600).playOn(img_setting);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {

                startActivity(new Intent(MainActivity.this,Setting.class));

            }
        },1500);

    }

    public void set_music(MenuItem item) {
        YoYo.with(Techniques.Pulse).duration(600).playOn(img_music);

        if (music){
            stopService(new Intent(MainActivity.this,PlayMusic.class));
            img_music.setBackgroundResource(R.drawable.music_off_icon);
            music=false;
            sharedP.edit().putBoolean(Items.MUSIC, false).apply();
        }else {
            startService(new Intent(MainActivity.this,PlayMusic.class));
            img_music.setBackgroundResource(R.drawable.music_on_icon);
            music=true;
            sharedP.edit().putBoolean(Items.MUSIC, true).apply();
        }
    }

上面的代码是用Android Studio编写的。我使用软件的虚拟设备。我希望你能帮助我