android listview添加出现问题

Question

我是一枚新手，在写添加listview并对数据库进行增删改查时遇到了问题，添加listview时我想添加一个item可是一添加就添加了好多行，还有插入数据后不能listview没有显示之前插入的值，求大神给看看！这是我的代码：

 public class DLXMainActivity extends AppCompatActivity {
    private Toolbar mToolbar;
    public static EditText mDlxInput1, mDlxInput2;//输入框
    public TextView mTitle, mContent, mTime;//显示内容
    DatabaseHelper mDatabaseHelper = new DatabaseHelper(this);
    static List<Comment> mList = new ArrayList<>();
    static Comment mComment = new Comment();
    MyAdapter mAdapter;
    ListView mListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dlx_task3_dlxmain);
        initViewValue();
    }

    public void initViewValue() {
        findViews();
        setSupportActionBar(mToolbar);
        setOnclicklistener();
    }

    //数据库的初始化和按下删除的监听事件
    public void setOnclicklistener() {
        mDatabaseHelper = new DatabaseHelper(this);
        mAdapter = new MyAdapter(this, mList);
        mListView.setAdapter(mAdapter);
        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                mComment = mList.get(position);
                int positioncurrent = mComment.getId();
                mDatabaseHelper.databaseDelete(positioncurrent);
                mList.remove(mComment);
                mAdapter.notifyDataSetChanged();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.dlx_task3_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_add:
                showDialog_Layout(DLXMainActivity.this);
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    //对话框
    private void showDialog_Layout(final Context context) {
        LayoutInflater inflater = LayoutInflater.from(this);
        final View textEntryView = inflater.inflate(R.layout.dlx_task3_dialoglayout, null);
        final AlertDialog.Builder builder = new AlertDialog.Builder(context);
        mDlxInput1 = (EditText) textEntryView.findViewById(R.id.dlx_Input1);
        mDlxInput2 = (EditText) textEntryView.findViewById(R.id.dlx_Input2);
        builder.setCancelable(false);
        builder.setTitle(R.string.dlx_add);
        builder.setView(textEntryView);
        builder.setNegativeButton(android.R.string.cancel,
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                        setTitle("");
                    }
                });
        builder.setPositiveButton(android.R.string.ok,
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                        mDatabaseHelper.databaseInsert();
                        mDatabaseHelper.databaseFind(context);
                        mAdapter.notifyDataSetChanged();
                    }
                });
        builder.show();
    }

    public void findViews() {
        mToolbar = (Toolbar) findViewById(R.id.toolbar);
        mTitle = (TextView) findViewById(R.id.dlx_maintitle);
        mContent = (TextView) findViewById(R.id.dlx_maincontent);
        mTime = (TextView) findViewById(R.id.dlx_maintime);
        mListView = (ListView) findViewById(R.id.dlx_lv);
    }

}

public class MyAdapter extends BaseAdapter {
    public List<Comment> list;
    public LayoutInflater mInflater = null;
    Context context;
    DatabaseHelper mDatabaseHelper = new DatabaseHelper(context);

    public MyAdapter(Context context, List<Comment> list) {
        this.mInflater = LayoutInflater.from(context);
        this.context = context;
        this.list = list;
    }


    //ViewHolder静态类
    static class ViewHolder {
        public TextView title;
        public TextView content;
        public TextView time;
    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    //获取一个在数据集中指定索引的视图来显示数据
    public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        //如果缓存convertView为空，则需要创建View
        if (convertView == null) {
            holder = new ViewHolder();
            //根据自定义的Item布局加载布局
            convertView = mInflater.inflate(R.layout.dlx_task3_commentlayout, null);
            holder.title = (TextView) convertView.findViewById(R.id.dlx_maintitle);
            holder.content = (TextView) convertView.findViewById(R.id.dlx_maincontent);
            holder.time = (TextView) convertView.findViewById(R.id.dlx_maintime);
            //将设置好的布局保存到缓存中，并将其设置在Tag里，以便后面方便取出Tag
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.title.setText(list.get(position).getTitle());
        holder.content.setText(list.get(position).getContent());
        holder.time.setText(mDatabaseHelper.getTimeShow(context, (list.get(position).getTime())));
        return convertView;
    }
}

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "Comment.db";
    public static final String TABLE_NAME = " comment";
    public long mDatetimecurrent;
    Context context;
    public long mDatetime;

    // TODO: 2016/5/18  
    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL("CREATE TABLE" + TABLE_NAME + "(" +
                Comment.Commentinter.EVENT_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                Comment.Commentinter.EVENT_TITLE + " TEXT NOT NULL, " +
                Comment.Commentinter.EVENT_CONTENT + " TEXT NOT NULL, " +
                Comment.Commentinter.EVENT_TIME + " INTEGER NOT NULL);");
    }

    public void databaseInsert() {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues values = new ContentValues();
        mDatetime = System.currentTimeMillis();
        //开始组装第一条数据
        values.put("title", String.valueOf(DLXMainActivity.mDlxInput1.getText()));
        values.put("content", String.valueOf(DLXMainActivity.mDlxInput2.getText()));
        values.put("time", mDatetime);
        db.insert(TABLE_NAME, null, values);//插入第一条数据
        db.close();
    }

    /**
     * 删除数据库元素
     *
     * @param
     */
    public void databaseDelete(int positioncurrent) {
        SQLiteDatabase db = getWritableDatabase();
        String[] args = {String.valueOf(positioncurrent)};
        db.delete("comment", Comment.Commentinter.EVENT_ID + "=?", args);
        db.close();
    }

    /**
     * 从数据库中取值并放到listview中
     * @param context
     */
    public void databaseFind(Context context) {
        this.context = context;
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.query(DatabaseHelper.TABLE_NAME,new String[]
                {Comment.Commentinter.EVENT_ID, Comment.Commentinter.EVENT_TITLE,
                        Comment.Commentinter.EVENT_CONTENT,Comment.Commentinter.EVENT_TIME},
                null, null, null, null, null, null);
            //DLXMainActivity.mList.clear();
            while (cursor.moveToNext()) {
                String title = cursor.getString(cursor.getColumnIndex(Comment.Commentinter.EVENT_TITLE));
                String content = cursor.getString(cursor.getColumnIndex(Comment.Commentinter.EVENT_CONTENT));
                long time = cursor.getLong(cursor.getColumnIndex(Comment.Commentinter.EVENT_TIME));
                int id = cursor.getInt(cursor.getColumnIndex(Comment.Commentinter.EVENT_ID));
                DLXMainActivity.mComment.setTitle(title);
                DLXMainActivity.mComment.setContent(content);
                DLXMainActivity.mComment.setTime(time);
                DLXMainActivity.mComment.setId(id);
                DLXMainActivity.mList.add(DLXMainActivity.mComment);
            }
            cursor.close();
            db.close();
    }

    public String getTimeShow(Context context, long datetime) {
        mDatetimecurrent = System.currentTimeMillis();
        long time = mDatetimecurrent - datetime;
        if (time / 1000 != 0) {
            if (time / 60000 != 0) {
                if (time / 3600000 != 0) {
                    if (time / 86400000 != 0) {
                        return time / 86400000 + context.getString(R.string.dlx_day1);
                    } else {
                        return time / 3600000 + context.getString(R.string.dlx_hour);
                    }
                } else {
                    return time / 60000 + context.getString(R.string.dlx_minute);
                }
            } else {
                return time / 1000 + context.getString(R.string.dlx_second);
            }

        } else {
            return context.getString(R.string.dlx_gang);
        }
    }

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

    @Override
    public void onOpen(SQLiteDatabase db) {
        super.onOpen(db);
    }