致命异常+ java.lang.RuntimeException：无法实例化活动ComponentInfo

Question

  

java.lang.RuntimeException：无法实例化活动ComponentInfo

如何解决这个问题？您需要提供什么？还有什么寻找错误？ Android Studio不会在代码中显示错误

如何解决这个问题？您需要提供什么？还有什么寻找错误？ Android Studio不会在代码中显示错误

---

MainActivity.java：

package shabunin.da;

import android.content.Intent;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;


public class MainActivity extends AppCompatActivity {
    private DBHandler dbHandler;
    private SQLiteDatabase database;
    TextView textView = (TextView) findViewById(R.id.textView);
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Thread mainThread = Thread.currentThread();
        Toast.makeText(getApplicationContext(), "Текущий поток " + mainThread.getName(), Toast.LENGTH_LONG).show();
        dbHandler = new DBHandler(this);

        try {
            dbHandler.updateDataBase();
        } catch (IOException mIOException) {
            throw new Error("Error #1: can't connect to DataBase");
        }

        try {
            database = dbHandler.getWritableDatabase();
        } catch (SQLException mSQLException) {
            throw mSQLException;
        }
    }
    public void onClick(View view){

        switch(view.getId()){
            case R.id.pathToRegistrationText:
                Toast.makeText(getApplicationContext(), "Вы перешли на другую активити", Toast.LENGTH_LONG).show();
                Intent intentRegistration = new Intent(MainActivity.this, RegistrationActivity.class);
                startActivity(intentRegistration);
                break;
            case R.id.pathToForgotPassword:
                Toast.makeText(getApplicationContext(), "Вы перешли на другую активитиs", Toast.LENGTH_LONG).show();
                Intent intentForgot = new Intent(MainActivity.this, ForgotActivity.class);
                startActivity(intentForgot);
                break;
            case R.id.enterButton:
                String product = "";
                Cursor cursor = database.rawQuery("SELECT * FROM clients", null);
                cursor.moveToFirst();
                while (!cursor.isAfterLast()) {
                    product += cursor.getString(1) + " | ";
                    cursor.moveToNext();
                }
                cursor.close();
                textView.setText(product);
                break;

        }
    }

}

DBHandler.java：

package shabunin.da;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class DBHandler extends SQLiteOpenHelper {
    private static String       DB_NAME     = "freelance.db";
    private static String       DB_PATH     = "";
    private static final int    DB_VERSION  = 2;

    private SQLiteDatabase mDataBase;
    private final Context mContext;
    private boolean mNeedUpdate = false;

    public DBHandler(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
        if (android.os.Build.VERSION.SDK_INT >= 17)
            DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
        else
            DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
        this.mContext = context;

        copyDataBase();

        this.getReadableDatabase();
    }

    public void updateDataBase() throws IOException {
        if (mNeedUpdate) {
            File dbFile = new File(DB_PATH + DB_NAME);
            if (dbFile.exists())
                dbFile.delete();

            copyDataBase();

            mNeedUpdate = false;
        }
    }

    private boolean checkDataBase() {
        File dbFile = new File(DB_PATH + DB_NAME);
        return dbFile.exists();
    }

    private void copyDataBase() {
        if (!checkDataBase()) {
            this.getReadableDatabase();
            this.close();
            try {
                copyDBFile();
            } catch (IOException mIOException) {
                throw new Error("ErrorCopyingDataBase");
            }
        }
    }

    private void copyDBFile() throws IOException {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        //InputStream mInput = mContext.getResources().openRawResource(R.raw.info);
        OutputStream mOutput = new FileOutputStream(DB_PATH + DB_NAME);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer)) > 0)
            mOutput.write(mBuffer, 0, mLength);
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    public boolean openDataBase() throws SQLException {
        mDataBase = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.CREATE_IF_NECESSARY);
        return mDataBase != null;
    }

    @Override
    public synchronized void close() {
        if (mDataBase != null)
            mDataBase.close();
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (newVersion > oldVersion)
            mNeedUpdate = true;
    }
}

MainActivity.xml：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="217dp"
        android:layout_height="121dp"

        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="60dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/wave" />

    <EditText
        android:id="@+id/loginNameText"
        android:layout_width="300dp"
        android:layout_height="75dp"
        android:layout_marginStart="8dp"

        android:layout_marginLeft="8dp"
        android:layout_marginTop="60dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:backgroundTint="@color/colorBrand"
        android:ems="10"
        android:hint="Логин"
        android:imeOptions="actionDone"
        android:maxLength="24"
        android:singleLine="true"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.505"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

    <EditText
        android:id="@+id/loginPasswordText"
        android:layout_width="300dp"
        android:layout_height="75dp"
        android:layout_marginStart="8dp"

        android:layout_marginLeft="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:backgroundTint="@color/colorBrand"
        android:ems="10"
        android:hint="Пароль"
        android:imeOptions="actionDone"
        android:inputType="textPassword"
        android:maxLength="24"
        android:singleLine="true"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/loginNameText" />

    <Button
        android:id="@+id/enterButton"
        android:layout_width="300dp"
        android:layout_height="50dp"
        android:layout_marginLeft="25dp"
        android:layout_marginTop="60dp"
        android:layout_marginRight="25dp"
        android:background="@color/colorBrand"


        android:text="Войти"
        android:textColor="@color/colorWhite"
        app:layout_constraintHorizontal_bias="0.508"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/loginPasswordText" />

    <TextView
        android:id="@+id/noteToRegistrationText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:text="У вас нет аккаунта?"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/enterButton" />

    <TextView
        android:id="@+id/pathToRegistrationText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:clickable="true"
        android:onClick="onClick"

        android:text="Зарегистрируйтесь"
        android:textColor="@color/colorBrand"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/noteToRegistrationText" />

    <TextView
        android:id="@+id/pathToForgotPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:layout_marginTop="8dp"
        android:layout_marginBottom="8dp"
        android:clickable="true"
        android:onClick="onClick"
        android:text="Забыли пароль?"
        android:textColor="@color/colorBrand"
        app:layout_constraintBottom_toTopOf="@+id/enterButton"
        app:layout_constraintEnd_toEndOf="@+id/enterButton"
        app:layout_constraintTop_toBottomOf="@+id/loginPasswordText"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:text="TextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/pathToRegistrationText" />


</android.support.constraint.ConstraintLayout>

错误：

I/InstantRun: starting instant run server: is main process
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: shabunin.da, PID: 27003
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{shabunin.da/shabunin.da.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2843)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
        at android.support.v7.app.AppCompatDelegateImpl.<init>(AppCompatDelegateImpl.java:249)
        at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:182)
        at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:520)
        at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:191)
        at shabunin.da.MainActivity.<init>(MainActivity.java:19)
        at java.lang.Class.newInstance(Native Method)
        at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:69)
        at android.support.v4.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:43)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1215)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2831)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6669) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)