public class Main2Activity extends AppCompatActivity {
    private EditText editText1, editText2, editText3, editText4;
    private Button button;

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

        editText1 = (EditText) findViewById(R.id.editText);
        editText2 = (EditText) findViewById(R.id.editText2);
        editText3 = (EditText) findViewById(R.id.editText3);
        editText4 = (EditText) findViewById(R.id.editText4);

        button = (Button) findViewById(R.id.button3);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String un, pw, cpw, ph;

                un = editText1.getText().toString();
                pw = editText2.getText().toString();
                cpw = editText3.getText().toString();
                ph = editText4.getText().toString();

                DbHelper dbHelpero = new DbHelper(Main2Activity.this);
                SQLiteDatabase db = dbHelpero.getWritableDatabase();

                ContentValues values = new ContentValues();
                values.put(Entry.C_UNAME, un);
                values.put(Entry.C_PASS, pw);
                values.put(Entry.C_CPASS, cpw);
                values.put(Entry.C_PNO, ph);

                long newRowId = db.insert(Entry.TABLE_NAME, null, values);

                if (newRowId == -1) {
                    Toast.makeText(getApplicationContext(), "Error while adding", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(getApplicationContext(), "Yo Registration is complete", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

这是Contract.java

public class Contract {

    private Contract() {

    }

    public static final class Entry implements BaseColumns {
        public final static String TABLE_NAME = "details";
        public final static String _ID = BaseColumns._ID;
        public final static String C_UNAME = "uname";
        public final static String C_PASS = "pw";
        public final static String C_CPASS = "cpw";
        public final static String C_PNO = "pno";

    }
}

还有DbHelper.java

public class DbHelper extends SQLiteOpenHelper {
    public static final String LOG_TAG = DbHelper.class.getSimpleName();
    public final static String DATABASE_NAME = "contacts.db";
    private static final int DATABASE_VERSION = 1;

    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_TABLE = "CREATE TABLE " + Entry.TABLE_NAME + " ("
                + Entry._ID + " TEXT PRIMARY KEY AUTOINCREMENT, "
                + Entry.C_UNAME + " TEXT, "
                + Entry.C_PASS + " TEXT, "
                + Entry.C_CPASS + " TEXT, "
                + Entry.C_PNO + " TEXT" + ")";

        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

没有语法错误，但应用仍然崩溃。