List中的ImageView不会清空之前的图片

Question

我有 ListView 接受 ArrayAdapter。 ArrayAdapter 有一个 ImageView，在共享图像时由 Picasso（来自 Square 的库）填充。但是，在共享带有图像的消息并将其放置在该列表项的 ImageView 中之后，如果共享了另一条没有图像的消息，则先前的相同图像将填充到 ImageView 中，而不是是空白的，如果没有共享图像，它应该是空白的。

我已经研究并尝试将 ImageView 设置为空或透明，如果没有共享图像但没有任何效果。到目前为止我已经尝试过：

sharedSpecial.setImageBitmap(null); 和 sharedSpecial.setImageResource(0); 但都不起作用。

如果没有共享当前图像，我如何"clear" ImageView 显示 ListView 中的上一张图像？

ArrayAdapter class 设置分享类型的图片如下：

public class DiscussArrayAdapter extends ArrayAdapter<OneComment> {

private TextView countryName;
private ImageView sharedSpecial;

private MapView locationMap;
private GoogleMap map;

private List<OneComment> countries = new ArrayList<OneComment>();
private LinearLayout wrapper;


String getSharedSpecialURL = null;
String getSharedSpecialWithLocationURL = null;

String specialsActionURL = "http://" + Global.getIpAddress()
        + ":3000/getSharedSpecial/";

String specialsLocationActionURL = "http://" + Global.getIpAddress()
        + ":3000/getSharedSpecialWithLocation/";

String JSON = ".json";

@Override
public void add(OneComment object) {
    countries.add(object);
    super.add(object);
}

public DiscussArrayAdapter(Context context, int textViewResourceId) {
    super(context, textViewResourceId);
}

public int getCount() {
    return this.countries.size();
}

public OneComment getItem(int index) {
    return this.countries.get(index);
}

public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;
    if (row == null) {
        LayoutInflater inflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(R.layout.message_list_item, parent, false);
    }

    wrapper = (LinearLayout) row.findViewById(R.id.wrapper);

    OneComment comment = getItem(position);

    countryName = (TextView) row.findViewById(R.id.comment);

    sharedSpecial = (ImageView) row.findViewById(R.id.sharedSpecial);

    countryName.setText(comment.comment);

    // Initiating Volley
    final RequestQueue requestQueue = VolleySingleton.getsInstance().getRequestQueue();

    // Check if message has campaign or campaign/location attached
    if (comment.campaign_id == "0" && comment.location_id == "0") {

        sharedSpecial.setImageBitmap(null);

    } else if (comment.campaign_id != "0" && comment.location_id != "0") {

        // If both were shared
        getSharedSpecialWithLocationURL = specialsLocationActionURL + comment.campaign_id + "/" + comment.location_id + JSON;


        // GET JSON data and parse
        JsonObjectRequest getCampaignLocationData = new JsonObjectRequest(Request.Method.GET, getSharedSpecialWithLocationURL, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        // Parse the JSON:
                        try {
                            resultObject = response.getJSONObject("shared");

                            imageObject = resultObject.getJSONObject("image");
                            adImageURL = imageObject.getString("url");


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

                        // Get and set image
                        Picasso.with(getContext()).load("http://" + Global.getIpAddress() + ":3000" + adImageURL).into(sharedSpecial);
                        sharedSpecial.setImageResource(0);

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("Error.Response", error.toString());
                    }
                }
        );

        requestQueue.add(getCampaignLocationData);


    } else if (comment.campaign_id != "0" && comment.location_id == "0") {

        // Just the campaign is shared
        getSharedSpecialURL = specialsActionURL + comment.campaign_id + JSON;

        // Test Campaign id = 41

        // GET JSON data and parse

        JsonObjectRequest getCampaignData = new JsonObjectRequest(Request.Method.GET, getSharedSpecialURL, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        // Parse the JSON:
                        try {
                            resultObject = response.getJSONObject("shared");

                            imageObject = resultObject.getJSONObject("image");
                            adImageURL = imageObject.getString("url");

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

                        // Get and set image
                        Picasso.with(getContext()).load("http://" + Global.getIpAddress() + ":3000" + adImageURL).into(sharedSpecial);
                        sharedSpecial.setImageResource(0);

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("Error.Response", error.toString());
                    }
                }
        );

        requestQueue.add(getCampaignData);

        // Location set to empty
    }

    // If left is true, then yello, if not then set to green bubble
    countryName.setBackgroundResource(comment.left ? R.drawable.bubble_yellow : R.drawable.bubble_green);
    wrapper.setGravity(comment.left ? Gravity.LEFT : Gravity.RIGHT);

    return row;
}

}

Answer 1

您的 getView 方法有问题。您没有将膨胀的 xml 附加到该行。您正在全局声明组件（textview 等），同时最好创建一个可以附加的持有人 class。

能否为您的适配器尝试以下操作：

更新添加了将列表作为参数的构造函数。现在你像这样调用适配器：

DiscussArrayAdapter adapter = new DiscussArrayAdapter(context, R.layout.message_list_item, countries);

listView.setAdapter(adapter);

那么信任适配器 notifyDataSetChanged 很重要。

在 activity 中全局创建国家/地区列表和适配器，每当您从列表中添加/删除项目时，只需调用 adapter.notifyDataSetChanged();

适配器：

public class DiscussArrayAdapter extends ArrayAdapter<OneComment>{


private MapView locationMap;
private GoogleMap map;

private List<OneComment> countries;

public DiscussArrayAdapter(Context context, int resource, List<OneComment> objects) {
    super(context, resource, objects);

    this.countries = objects;
}
String getSharedSpecialURL = null;
String getSharedSpecialWithLocationURL = null;

String specialsActionURL = "http://" + Global.getIpAddress()
        + ":3000/getSharedSpecial/";

String specialsLocationActionURL = "http://" + Global.getIpAddress()
        + ":3000/getSharedSpecialWithLocation/";

String JSON = ".json";

@Override
public void add(OneComment object) {
    countries.add(object);
    super.add(object);
}

public DiscussArrayAdapter(Context context, int textViewResourceId) {
    super(context, textViewResourceId);
}

public int getCount() {
    return this.countries.size();
}

public OneComment getItem(int index) {
    return this.countries.get(index);
}

public View getView(int position, View row, ViewGroup parent) {

     //Create instance of inflated view holder
    Holder holder;

    if (row == null) {

        //Its the first time we are going to inflate the view, get new instance of Holder            
        holder = new Holder();

        //Inflate view
        LayoutInflater inflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(R.layout.message_list_item, parent, false);

        //Put components in the holder
        holder.countryName = (TextView) row.findViewById(R.id.comment);
        holder.sharedSpecial = (ImageView) row.findViewById(R.id.sharedSpecial);
        holder.wrapper = (LinearLayout) row.findViewById(R.id.wrapper);

        //Attach holder to the row
        row.setTag(holder);

    }else{

        //Row was inflated before get holder 
        holder = (Holder)row.getTag();
    }



    OneComment comment = getItem(position);
    countryName.setText(comment.comment);

    // Initiating Volley
    final RequestQueue requestQueue = VolleySingleton.getsInstance().getRequestQueue();

    // Check if message has campaign or campaign/location attached
    if (comment.campaign_id.equals("0") && comment.location_id.equals("0")) {

        sharedSpecial.setImageBitmap(null);

    } else if (!comment.campaign_id.equals("0") && !comment.location_id.equals("0")) {

        // If both were shared
        getSharedSpecialWithLocationURL = specialsLocationActionURL + comment.campaign_id + "/" + comment.location_id + JSON;


        // GET JSON data and parse
        JsonObjectRequest getCampaignLocationData = new JsonObjectRequest(Request.Method.GET, getSharedSpecialWithLocationURL, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        // Parse the JSON:
                        try {
                            resultObject = response.getJSONObject("shared");

                            imageObject = resultObject.getJSONObject("image");
                            adImageURL = imageObject.getString("url");


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

                        // Get and set image
                        Picasso.with(getContext()).load("http://" + Global.getIpAddress() + ":3000" + adImageURL).into(sharedSpecial);
                        sharedSpecial.setImageResource(0);

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("Error.Response", error.toString());
                    }
                }
        );

        requestQueue.add(getCampaignLocationData);


    } else if (!comment.campaign_id.equals("0") && comment.location_id.equals("0")) {

        // Just the campaign is shared
        getSharedSpecialURL = specialsActionURL + comment.campaign_id + JSON;

        // Test Campaign id = 41

        // GET JSON data and parse

        JsonObjectRequest getCampaignData = new JsonObjectRequest(Request.Method.GET, getSharedSpecialURL, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        // Parse the JSON:
                        try {
                            resultObject = response.getJSONObject("shared");

                            imageObject = resultObject.getJSONObject("image");
                            adImageURL = imageObject.getString("url");

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

                        // Get and set image
                        Picasso.with(getContext()).load("http://" + Global.getIpAddress() + ":3000" + adImageURL).into(sharedSpecial);
                        sharedSpecial.setImageResource(0);

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("Error.Response", error.toString());
                    }
                }
        );

        requestQueue.add(getCampaignData);

        // Location set to empty
    }

    // If left is true, then yello, if not then set to green bubble
    countryName.setBackgroundResource(comment.left ? R.drawable.bubble_yellow : R.drawable.bubble_green);
    wrapper.setGravity(comment.left ? Gravity.LEFT : Gravity.RIGHT);

    return row;
}

private class Holder{
    TextView countryName;
    ImageView sharedSpecial;
    LinearLayout wrapper;
}

}

List中的ImageView不会清空之前的图片

ImageView in List will not clear previous image

android

listview

imageview