Android：我的列表视图不会自动更新吗？

大家好，我已经创建了一个自定义列表适配器，我使用JSON填充数据。JSON是通过查询数据库生成的，然后数据显示在列表视图上。我面临的问题是，当我将数据添加到数据库时，它应该立即显示在列表视图上，但我需要的是，它没有这样做若要继续并清除缓存，然后清除数据，则仅显示我添加的内容

这里的片段一活动是使用JSON解析器的地方

public class FragmentOne extends BaseActivity {
private static final String TAG = FragmentOne.class.getSimpleName();
private ListView listView;
private FeedListAdapter listAdapter;
private List<FeedItem> feedItems;
private String URL_FEED = "http://ops.esy.es/android_app_api/json.php";
public  int pid;
private Button b1;
public CursorAdapter me;
public ArrayAdapter my;
int global_position =0;
FeedListAdapter feedi;
public static Integer length;


@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getLayoutInflater().inflate(R.layout.fragment_layout_one, frameLayout);

    session = new SessionManager(getApplicationContext());

    // SQLite database handler
    db = new SQLiteHandler(getApplicationContext());
    mDrawerList.setItemChecked(position, true);
    setTitle(listArray[position]);

    listView = (ListView) findViewById(R.id.feedlist);
    b1 = (Button) findViewById(R.id.button);

    feedItems = new ArrayList<FeedItem>();

    listAdapter = new FeedListAdapter(this, feedItems);
    listView.setAdapter(listAdapter);
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Log.d("Clicked item id", " " + position);

        }
    });


    // These two lines not needed,
    // just to get the look of facebook (changing background color & hiding the icon)
    getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#FF6600")));
    getActionBar().setIcon(
            new ColorDrawable(getResources().getColor(android.R.color.transparent)));

    // We first check for cached request
    Cache cache = AppController.getInstance().getRequestQueue().getCache();
    Entry entry = cache.get(URL_FEED);
    if (entry != null) {
        // fetch the data from cache
        try {
            String data = new String(entry.data, "UTF-8");
            try {
                parseJsonFeed(new JSONObject(data));
            } catch (JSONException e) {
                e.printStackTrace();
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

    } else {
        // making fresh volley request and getting json
        JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
                URL_FEED, null, new Response.Listener<JSONObject>() {

            @Override
            public void onResponse(JSONObject response) {
                VolleyLog.d(TAG, "Response: " + response.toString());
                if (response != null) {
                    parseJsonFeed(response);
                }
            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
            }
        });

        // Adding request to volley request queue
        AppController.getInstance().addToRequestQueue(jsonReq);
    }
     b1.setOnClickListener(new View.OnClickListener(){
         @Override
         public void onClick(View v) {
             Intent myIntent = new Intent(FragmentOne.this, Post.class);

             FragmentOne.this.startActivity(myIntent);
         }
     });
    listView.invalidateViews();
}

/**
 * Parsing json reponse and passing the data to feed view list adapter
 * */
private void parseJsonFeed(JSONObject response) {
    try {
        JSONArray feedArray = response.getJSONArray("feed");

        for (int i = 0 ; i <feedArray.length() ; i++) {
            JSONObject feedObj = (JSONObject) feedArray.get(i);
            int  pid = feedObj.getInt("id");
            String pname = feedObj.getString("name");
            String pimage = feedObj.isNull("image") ? null : feedObj.getString("image");
            String pstatus = feedObj.getString("status");
            String profilep =feedObj.getString("profilePic");
            String timestamp= feedObj.getString("timeStamp");

            db.addpost(pid,pname,pimage,pstatus,profilep,timestamp);



         FeedItem item = new FeedItem();
            item.setId(feedObj.getInt("id"));
            item.setName(feedObj.getString("name"));

            // Image might be null sometimes
            String image = feedObj.isNull("image") ? null : feedObj
                    .getString("image");
            item.setImge(image);
            item.setStatus(feedObj.getString("status"));
            item.setProfilePic(feedObj.getString("profilePic"));
            item.setTimeStamp(feedObj.getString("timeStamp"));




            // url might be null sometimes
            String feedUrl = feedObj.isNull("url") ? null : feedObj
                    .getString("url");
            item.setUrl(feedUrl);

            feedItems.add(item);

        }




        // notify data changes to list adapater

        listAdapter.notifyDataSetChanged();

    } catch (JSONException e) {
        e.printStackTrace();
    }
}


}

---

在为listview设置适配器之前，您必须获得FeedItems列表

当列表被更新或删除时，您应该使用相同的arrayList引用，然后只有notifyDataSetChanged（）可以工作

并为您的适配器使用以下代码

public class FeedListAdapter extends BaseAdapter {
private Activity activity;
private LayoutInflater inflater;
private List<FeedItem> feedItems;
private ListView lv;
private SQLiteHandler db;
public static  Integer pos;


public FragmentOne f2 = new FragmentOne();


public AdapterView.OnItemClickListener onItemClickListener =
        new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            }
        };
ImageLoader imageLoader = AppController.getInstance().getImageLoader();

public FeedListAdapter(Activity activity, List<FeedItem> feedItems) {
    this.activity = activity;
    this.feedItems = feedItems;
    inflater = LayoutInflater.from(activity);
}

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

@Override
public Object getItem(int location) {
    return feedItems.get(location);
}

@Override
public long getItemId(int position) {

    return position;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

final ViewHolder viewHolder;

    if (convertView == null) {
        convertView = inflater.inflate(R.layout.feed_item, null);
        viewHolder =  new ViewHolder();
        viewHolder.name=(TextView) convertView.findViewById(R.id.name);
        viewHolder.timestamp = (TextView) convertView
                .findViewById(R.id.timestamp);
        viewHolder.statusmsg = (TextView) convertView
                .findViewById(R.id.txtStatusMsg);
        viewHolder.url = (TextView) convertView.findViewById(R.id.txtUrl);
        viewHolder.profilePic = (NetworkImageView) convertView
                .findViewById(R.id.profilePic);
        viewHolder.feedImageView = (FeedImageView) convertView
                .findViewById(R.id.feedImage1);
        viewHolder.ops = (Button) convertView.findViewById(R.id.ops);
        convertView.setTag(viewHolder);
    }else {
        viewHolder = (ViewHolder) convertView.getTag();
     }


    if (imageLoader == null)
        imageLoader = AppController.getInstance().getImageLoader();

    TextView name = (TextView) convertView.findViewById(R.id.name);
    TextView timestamp = (TextView) convertView
            .findViewById(R.id.timestamp);
    TextView statusMsg = (TextView) convertView
            .findViewById(R.id.txtStatusMsg);
    TextView url = (TextView) convertView.findViewById(R.id.txtUrl);
    NetworkImageView profilePic = (NetworkImageView) convertView
            .findViewById(R.id.profilePic);
    FeedImageView feedImageView = (FeedImageView) convertView
            .findViewById(R.id.feedImage1);
    db = new SQLiteHandler(activity);

    final FeedItem item = feedItems.get(position);
    Button ops= (Button) convertView.findViewById(R.id.ops);
    name.setText(item.getName());
    ops.setTag(position);
    ops.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            pos = (Integer) v.getTag();
            db.deletecom();
            pos = pos+1;
            String posi = String.valueOf(pos);
            Intent i = new Intent(activity.getApplicationContext(), CommentMain.class);
            i.putExtra("position",posi);

            activity.startActivity(i);

            Log.d("Clicked item id", " " + pos);


                        }
    });

    // Converting timestamp into x ago format
    CharSequence timeAgo = DateUtils.getRelativeTimeSpanString(
            Long.parseLong(item.getTimeStamp()),
            System.currentTimeMillis(), DateUtils.SECOND_IN_MILLIS);
    timestamp.setText(timeAgo);


    // Chcek for empty status message
    if (!TextUtils.isEmpty(item.getStatus())) {
        statusMsg.setText(item.getStatus());
        statusMsg.setVisibility(View.VISIBLE);
    } else {
        // status is empty, remove from view
        statusMsg.setVisibility(View.GONE);
    }

    // Checking for null feed url
    if (item.getUrl() != null) {
        url.setText(Html.fromHtml("<a href=\"" + item.getUrl() + "\">"
                + item.getUrl() + "</a> "));

        // Making url clickable
        url.setMovementMethod(LinkMovementMethod.getInstance());
        url.setVisibility(View.VISIBLE);
    } else {
        // url is null, remove from the view
        url.setVisibility(View.GONE);
    }

    // user profile pic
    profilePic.setImageUrl(item.getProfilePic(), imageLoader);

    // Feed image
    if (item.getImge() != null) {
        feedImageView.setImageUrl(item.getImge(), imageLoader);
        feedImageView.setVisibility(View.VISIBLE);
        feedImageView
                .setResponseObserver(new FeedImageView.ResponseObserver() {
                    @Override
                    public void onError() {
                    }

                    @Override
                    public void onSuccess() {
                    }
                });
    } else {
        feedImageView.setVisibility(View.GONE);
    }

    return convertView;
}
public void setMyList(List myListOfObjects) {
    this.feedItems = myListOfObjects;
    this.notifyDataSetChanged();
}


public class ViewHolder {
    TextView name;
    TextView timestamp;
    TextView statusmsg;
    TextView url;
    FeedImageView feedImageView;
    NetworkImageView profilePic;
    Button ops;
}
}

公共类FeedListAdapter扩展了BaseAdapter{
私人活动；
私人充气机；
私人物品清单；
私有ListView lv；
私有SQLiteHandler数据库；
公共静态整数pos；
公共FragmentOne f2=新FragmentOne（）；
public AdapterView.OnItemClickListener OnItemClickListener=
新的AdapterView.OnItemClickListener（）{
@凌驾
public void onItemClick（AdapterView父对象、视图、整型位置、长id）{
}
};
ImageLoader ImageLoader=AppController.getInstance（）.getImageLoader（）；
公共FeedListAdapter（活动，列出feedItems）{
这个。活动=活动；
此项。feedItems=feedItems；
充气机=从（活动）开始的充气机；
}
@凌驾
public int getCount（）{
返回feedItems.size（）；
}
@凌驾
公共对象getItem（int位置）{
返回feedItems.get（位置）；
}
@凌驾
公共长getItemId（int位置）{
返回位置；
}
@凌驾
公共视图getView（最终整数位置、视图转换视图、视图组父视图）{
最终持票人；
if（convertView==null）{
convertView=充气机。充气（R.layout.feed_项，空）；
viewHolder=新的viewHolder（）；
viewHolder.name=（TextView）convertView.findViewById（R.id.name）；
viewHolder.timestamp=（TextView）convertView
.findviewbyd（R.id.时间戳）；
viewHolder.statusmsg=（文本视图）convertView
.findViewById（R.id.txtStatusMsg）；
viewHolder.url=（TextView）convertView.findViewById（R.id.txtrl）；
viewHolder.profilePic=（网络图像视图）convertView
.findviewbyd（R.id.profilePic）；
viewHolder.feedImageView=（feedImageView）convertView
.findViewById（R.id.feedImage1）；
viewHolder.ops=（按钮）convertView.findViewById（R.id.ops）；
convertView.setTag（viewHolder）；
}否则{
viewHolder=（viewHolder）convertView.getTag（）；
}
如果（imageLoader==null）
imageLoader=AppController.getInstance（）.getImageLoader（）；
TextView name=（TextView）convertView.findViewById（R.id.name）；
TextView时间戳=（TextView）convertView
.findviewbyd（R.id.时间戳）；
TextView statusMsg=（TextView）convertView
.findViewById（R.id.txtStatusMsg）；
TextView url=（TextView）convertView.findViewById（R.id.txtrl）；
NetworkImageView配置文件PIC=（NetworkImageView）convertView
.findviewbyd（R.id.profilePic）；
FeedImageView FeedImageView=（FeedImageView）convertView
.findViewById（R.id.feedImage1）；
db=新的SQLiteHandler（活动）；
最终饲料项目=饲料项目。获取（位置）；
按钮操作=（按钮）convertView.findViewById（R.id.ops）；
name.setText（item.getName（））；
操作设置标签（位置）；
ops.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
pos=（整数）v.getTag（）；
db.deletecom（）；
pos=pos+1；
String posi=String.valueOf（pos）；
Intent i=新的Intent（activity.getApplicationContext（），CommentMain.class）；
i、 putExtra（“位置”，posi）；
活动性、触觉性（i）；
Log.d（“单击的项目id”，“”+pos）；
}
});
//将时间戳转换为x ago格式
CharSequence timeAgo=DateUtils.getRelativeTimeSpanString(
Long.parseLong（item.getTimeStamp（）），
System.currentTimeMillis（），DateUtils.SECOND（单位：毫秒）；
timestamp.setText（timeAgo）；
//空状态消息的Chcek
如果（！TextUtils.isEmpty（item.getStatus（）））{
statusMsg.setText（item.getStatus（））；
statusMsg.setVisibility（View.VISIBLE）；
}否则{
//状态为空，请从视图中删除
statusMsg.setVisibility（View.GONE）；
}
//正在检查空提要url
if（item.getUrl（）！=null）{
url.setText（Html.fromHtml（“”）；
//使url可点击
setMovementMethod（LinkMovementMethod.getInstance（））；
setVisibility（View.VISIBLE）；
}否则{
//url为空，请从视图中删除
setVisibility（View.GONE）；
}
//用户档案图片
profilePic.setImageUrl（item.getProfilePic（），imageLoader）；
//馈送图像
if（item.getImge（）！=null）{
setImageUrl（item.getImge（），imageLoader）；
feedImageView.setVisibility（View.VISIBLE）；
feedImageView
.setResponseObserver（新的FeedImageView.ResponseObserver（）{
@凌驾
公开无效{
}
@凌驾
成功时的公共无效（）{
}
});
}否则{
feedImageView.setVisibility（View.GONE）；
}
返回视图；
}
public void setMyList（列出MyListFobjects）{
this.feedItems=myListOfObjects；
this.notifyDataSetChanged（）；
}
公共类视图持有者{
文本视图名称；
文本视图时间戳；
文本视图状态消息；
文本视图url；
FeedImageView FeedImageView；
NetworkImageView profilePi
  <?php

    $con = mysql_connect($host, $uname, $pwd) or die ("connection failed");
    mysql_select_db($db,$con) or die(" db selection failed");

    $result = mysql_query("select * from thoughts order by id desc", $con);
    $json_response =array();
    while($row = mysql_fetch_array($result, MYSQL_ASSOC)){
        $row_array['id'] = utf8_encode($row['id']);
        $row_array['name'] = utf8_encode($row['name']);
        $row_array['image'] =utf8_encode( $row['image']);
        $row_array['status'] = utf8_encode($row['status']);
        $row_array['profilePic'] = utf8_encode($row['profilepic']);
        $row_array['timeStamp'] =utf8_encode($row['timestamp']);
        $row_array['url'] = utf8_encode($row['url']);
        array_push($json_response,$row_array);

    }
    $my= json_encode(array('feed' =>$json_response));

    echo $my;
   $fp = fopen('results.json', 'w');
fwrite($fp, $my);
fclose($fp);


?>

public class FeedItem {


    private int id;
    private String name, status, image, profilePic, timeStamp, url;

    public FeedItem() {
    }

    public FeedItem(int id, String name, String image, String status,
                    String profilePic, String timeStamp, String url) {
        super();
        this.id = id;
        this.name = name;
        this.image = image;
        this.status = status;
        this.profilePic = profilePic;
        this.timeStamp = timeStamp;
        this.url = url;

    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getImge() {
        return image;
    }

    public void setImge(String image) {
        this.image = image;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getProfilePic() {
        return profilePic;
    }

    public void setProfilePic(String profilePic) {
        this.profilePic = profilePic;
    }

    public String getTimeStamp() {
        return timeStamp;
    }

    public void setTimeStamp(String timeStamp) {
        this.timeStamp = timeStamp;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

}

public class FeedListAdapter extends BaseAdapter {
private Activity activity;
private LayoutInflater inflater;
private List<FeedItem> feedItems;
private ListView lv;
private SQLiteHandler db;
public static  Integer pos;


public FragmentOne f2 = new FragmentOne();


public AdapterView.OnItemClickListener onItemClickListener =
        new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            }
        };
ImageLoader imageLoader = AppController.getInstance().getImageLoader();

public FeedListAdapter(Activity activity, List<FeedItem> feedItems) {
    this.activity = activity;
    this.feedItems = feedItems;
    inflater = LayoutInflater.from(activity);
}

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

@Override
public Object getItem(int location) {
    return feedItems.get(location);
}

@Override
public long getItemId(int position) {

    return position;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

final ViewHolder viewHolder;

    if (convertView == null) {
        convertView = inflater.inflate(R.layout.feed_item, null);
        viewHolder =  new ViewHolder();
        viewHolder.name=(TextView) convertView.findViewById(R.id.name);
        viewHolder.timestamp = (TextView) convertView
                .findViewById(R.id.timestamp);
        viewHolder.statusmsg = (TextView) convertView
                .findViewById(R.id.txtStatusMsg);
        viewHolder.url = (TextView) convertView.findViewById(R.id.txtUrl);
        viewHolder.profilePic = (NetworkImageView) convertView
                .findViewById(R.id.profilePic);
        viewHolder.feedImageView = (FeedImageView) convertView
                .findViewById(R.id.feedImage1);
        viewHolder.ops = (Button) convertView.findViewById(R.id.ops);
        convertView.setTag(viewHolder);
    }else {
        viewHolder = (ViewHolder) convertView.getTag();
     }


    if (imageLoader == null)
        imageLoader = AppController.getInstance().getImageLoader();

    TextView name = (TextView) convertView.findViewById(R.id.name);
    TextView timestamp = (TextView) convertView
            .findViewById(R.id.timestamp);
    TextView statusMsg = (TextView) convertView
            .findViewById(R.id.txtStatusMsg);
    TextView url = (TextView) convertView.findViewById(R.id.txtUrl);
    NetworkImageView profilePic = (NetworkImageView) convertView
            .findViewById(R.id.profilePic);
    FeedImageView feedImageView = (FeedImageView) convertView
            .findViewById(R.id.feedImage1);
    db = new SQLiteHandler(activity);

    final FeedItem item = feedItems.get(position);
    Button ops= (Button) convertView.findViewById(R.id.ops);
    name.setText(item.getName());
    ops.setTag(position);
    ops.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            pos = (Integer) v.getTag();
            db.deletecom();
            pos = pos+1;
            String posi = String.valueOf(pos);
            Intent i = new Intent(activity.getApplicationContext(), CommentMain.class);
            i.putExtra("position",posi);

            activity.startActivity(i);

            Log.d("Clicked item id", " " + pos);


                        }
    });

    // Converting timestamp into x ago format
    CharSequence timeAgo = DateUtils.getRelativeTimeSpanString(
            Long.parseLong(item.getTimeStamp()),
            System.currentTimeMillis(), DateUtils.SECOND_IN_MILLIS);
    timestamp.setText(timeAgo);


    // Chcek for empty status message
    if (!TextUtils.isEmpty(item.getStatus())) {
        statusMsg.setText(item.getStatus());
        statusMsg.setVisibility(View.VISIBLE);
    } else {
        // status is empty, remove from view
        statusMsg.setVisibility(View.GONE);
    }

    // Checking for null feed url
    if (item.getUrl() != null) {
        url.setText(Html.fromHtml("<a href=\"" + item.getUrl() + "\">"
                + item.getUrl() + "</a> "));

        // Making url clickable
        url.setMovementMethod(LinkMovementMethod.getInstance());
        url.setVisibility(View.VISIBLE);
    } else {
        // url is null, remove from the view
        url.setVisibility(View.GONE);
    }

    // user profile pic
    profilePic.setImageUrl(item.getProfilePic(), imageLoader);

    // Feed image
    if (item.getImge() != null) {
        feedImageView.setImageUrl(item.getImge(), imageLoader);
        feedImageView.setVisibility(View.VISIBLE);
        feedImageView
                .setResponseObserver(new FeedImageView.ResponseObserver() {
                    @Override
                    public void onError() {
                    }

                    @Override
                    public void onSuccess() {
                    }
                });
    } else {
        feedImageView.setVisibility(View.GONE);
    }

    return convertView;
}
public void setMyList(List myListOfObjects) {
    this.feedItems = myListOfObjects;
    this.notifyDataSetChanged();
}


public class ViewHolder {
    TextView name;
    TextView timestamp;
    TextView statusmsg;
    TextView url;
    FeedImageView feedImageView;
    NetworkImageView profilePic;
    Button ops;
}
}