空指针问题：Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)

做一晚上了，有没有大佬帮帮我，万分感谢
报错E/AndroidRuntime: FATAL EXCEPTION: main
Process: main_activity.diary, PID: 11800
java.lang.NullPointerException: Attempt to invoke virtual method ‘void android.widget.TextView.setText(java.lang.CharSequence)’ on a null object reference
at main_activity.diary.Memo$1.getView(Memo.java:87)atandroid.widget.AbsListView.obtainView(AbsListView.java:2360)atandroid.widget.ListView.measureHeightOfChildren(ListView.java:1326)atandroid.widget.ListView.onMeasure(ListView.java:1233)atandroid.view.View.measure(View.java:19731)atandroid.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)atandroid.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)atandroid.view.View.measure(View.java:19731)atandroid.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)atandroid.widget.FrameLayout.onMeasure(FrameLayout.java:185)atandroid.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)atandroid.view.View.measure(View.java:19731)atandroid.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)atandroid.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:389)atandroid.view.View.measure(View.java:19731)atandroid.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)atandroid.widget.FrameLayout.onMeasure(FrameLayout.java:185)atandroid.view.View.measure(View.java:19731)atandroid.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)atandroid.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)atandroid.widget.LinearLayout.measureVertical(LinearLayout.java:758)atandroid.widget.LinearLayout.onMeasure(LinearLayout.java:640)atandroid.view.View.measure(View.java:19731)atandroid.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6120)atandroid.widget.FrameLayout.onMeasure(FrameLayout.java:185)atcom.android.internal.policy.DecorView.onMeasure(DecorView.java:687)atandroid.view.View.measure(View.java:19731)atandroid.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2271)atandroid.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1358)atandroid.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1607)atandroid.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1246)atandroid.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6301)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871)atandroid.view.Choreographer.doCallbacks(Choreographer.java:683)atandroid.view.Choreographer.doFrame(Choreographer.java:619)atandroid.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)

.java文件：
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
public class Memo extends AppCompatActivity {
private TextView welcome;
private ImageButton btn_add;
private ListView listView;
private DBHelper dbHelper;
private ArrayList MemoList;
SQLiteDatabase db;
private int id;
private String name;
private String strid;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn_add=(ImageButton)findViewById(R.id.btn_add);
listView=(ListView)findViewById(R.id.lv_memoList);
dbHelper=new DBHelper(this);
db=dbHelper.getReadableDatabase();
welcome=(TextView)findViewById(R.id.welcome_word);
final Intent intent=getIntent();
MemoList=new ArrayList<>();
id=Integer.parseInt(intent.getStringExtra(“id”));
String sql_name=“select username from tb_user where user_id=?”;
Cursor c=db.rawQuery(sql_name,new String[]{Integer.toString(id)});
while(c.moveToNext()){
name=c.getString(c.getColumnIndex(“username”));
}
strid=Integer.toString(id);
welcome.setText(name+“欢迎你！”);
String sql=“select * from tb_memo where userID=?”;
Cursor cursor = db.rawQuery(sql,new String[]{Integer.toString(id)});
while(cursor.moveToNext()){
if(id==cursor.getInt(2)){
String title=cursor.getString(cursor.getColumnIndex(“title”));
String createDate=cursor.getString(cursor.getColumnIndex(“createDate”));
int id=cursor.getInt(0);
Memo_info memo=new Memo_info(title,createDate,id);
System.out.println(“title:”+title+“createDate:”+createDate+“id:”+id);
MemoList.add(memo);
}
}
listView.setAdapter(new BaseAdapter() {
@Override
public int getCount() {
return MemoList.size();
}

        @Override
        public Object getItem(int i) {
            return i;
        }

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

        @Override
        public View getView(int i, View convertView, ViewGroup viewGroup) {
            View view;
            if (convertView==null){
                view = View.inflate(getBaseContext(),R.layout.list_item_memo,null);
            }else{
                view = convertView;
            }
            Memo_info memo=MemoList.get(i);
            TextView title=(TextView)view.findViewById(R.id.title);
            TextView content=(TextView)view.findViewById(R.id.content);
            TextView getsqlId=(TextView)view.findViewById(R.id.getsqlId);
            TextView createDate=(TextView)view.findViewById(R.id.noticeDate);
            title.setText(memo.getTitle());
            content.setText(memo.getContent());
            createDate.setText(memo.getCreateDate());
            getsqlId.setText(Integer.toString(memo.getId()));
            return view;
        }
    });
    btn_add.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent1=new Intent(Memo.this,SaveMemo.class);
            intent1.putExtra("userID",strid);
            startActivity(intent1);
        }
    });
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView adapterView, View view, int i, long l) {
            TextView view1=(TextView)view.findViewById(R.id.getsqlId);
            String memoid=view1.getText().toString();
            Intent intent2=new Intent(Memo.this,showmemo.class);
            intent2.putExtra("memoid",memoid);
            intent2.putExtra("user_id",strid);
            startActivity(intent2);
        }
    });
    listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        @Override
        public boolean onItemLongClick(AdapterView adapterView, View view, int i, long l) {
            Button btn_del=(Button)view.findViewById(R.id.btn_del);
            btn_del.setVisibility(View.VISIBLE);
            TextView view1=(TextView)view.findViewById(R.id.getsqlId);
            final String memoid=view1.getText().toString();
            btn_del.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    db=dbHelper.getWritableDatabase();
                    db.delete("tb_memo","id=?",new String[]{memoid});
                    Intent intent3=new Intent(Memo.this,Memo.class);
                    System.out.println("调用删除方法");
                    intent3.putExtra("id",strid);
                    startActivity(intent3);
                }
            });

            return true;
        }

    });

}

}

.xml文件

这是在做一个记事本，一开始是没问题的，写入数据保存后就闪退了，后面一到跳转到另一个activity时就直接闪退了。这到底怎么回事啊，之前也是报空指针我给解决了，可是这次报的是at main_activity.diary.Memo$1.getView(Memo.java:87)直接给我整懵了，它指示位置代码为title.setText(memo.getTitle()); 布局也没错的感觉啊，现在很无解。 help！