Question

我想将背景图片放在“图片网址”不存在的地方。

我没有得到图片网址不存在的背景图片。为什么没有出现？

请在图片中看到一个图像网址在json中不存在，它应该替换为“bc.jpeg”，我已放置在可绘制的文件夹中。

但是为什么它没有显示呢？

主要活动

public class MainActivity extends Activity {
    // Log tag
    private static final String TAG = MainActivity.class.getSimpleName();
    private static final String url = "http://qzrbzpztcd.localtunnel.me/api/v1/restaurants?per_page=10&page=1&sort_col=average_ratings";
    // Movies json url
    //private static final String url = "http://api.androidhive.info/json/movies.json";
    private ProgressDialog pDialog;
    private List<Movie> movieList = new ArrayList<Movie>();
    private ListView listView;
    private CustomListAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.list);
        adapter = new CustomListAdapter(this, movieList);
        listView.setAdapter(adapter);
        pDialog = new ProgressDialog(this);
        // Showing progress dialog before making http request
        pDialog.setMessage("Loading...");
        pDialog.show();
        // changing action bar color
        getActionBar().setBackgroundDrawable(
                new ColorDrawable(Color.parseColor("#1b1b1b")));
        // Creating volley request obj
        JsonArrayRequest movieReq = new JsonArrayRequest(url,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, response.toString());
                        hidePDialog();
                        // Parsing json
                        for (int i = 0; i < response.length(); i++) {
                            try {
                                JSONObject obj = response.getJSONObject(i);
                                Movie movie = new Movie();
                                //movie.setTitle(obj.getString("title"));
                                movie.setName(obj.getString("name"));
                                //movie.setThumbnailUrl(obj.getString("image"));
                                movie.setThumbnailUrl(obj.getString("image_url"));
                                movie.setAverage_ratings(obj.getString("average_ratings"));
                                movie.setCuisine(obj.getString("cuisine"));
                                movie.setAddress(obj.getJSONObject("address").getString("area"));
                                //movie.setAddress(obj.getString("address"));
                                //movie.setYear(obj.getInt("releaseYear"));
                                // Genre is json array
                                /*JSONArray genreArry = obj.getJSONArray("genre");
                                ArrayList<String> genre = new ArrayList<String>();
                                for (int j = 0; j < genreArry.length(); j++) {
                                    genre.add((String) genreArry.get(j));
                                }
                                movie.setGenre(genre);*/
                                // adding movie to movies array
                                movieList.add(movie);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }

                        // notifying list adapter about data changes
                        // so that it renders the list view with updated data
                        adapter.notifyDataSetChanged();
                    }
                }, new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        hidePDialog();

                    }
                });

        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(movieReq);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        hidePDialog();
    }

    private void hidePDialog() {
        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

列出row.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/list_row_selector"
    android:padding="8dp" >

    <!-- Thumbnail Image -->
    <com.android.volley.toolbox.NetworkImageView
        android:id="@+id/thumbnail"
        android:layout_width="120dp"
        android:layout_height="80dp"
        android:layout_alignParentLeft="true"
        android:layout_marginRight="8dp" />

    <!-- Restaurant name  -->
    <TextView
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:layout_toRightOf="@+id/thumbnail"
        android:textSize="@dimen/title"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/area"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/name"

        android:layout_toRightOf="@+id/thumbnail"
        android:textSize="@dimen/rating" />

    <!-- Rating -->
    <TextView
        android:id="@+id/average_ratings"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/area"
        android:layout_toRightOf="@+id/thumbnail"

        android:textSize="@dimen/rating" />

    <TextView
        android:id="@+id/cuisine"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/average_ratings"

        android:layout_toRightOf="@+id/thumbnail"
        android:textSize="@dimen/rating" />

    <!-- Genre -->
   <!-- <TextView
        android:id="@+id/genre"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/rating"
        android:layout_marginTop="5dp"
        android:layout_toRightOf="@+id/thumbnail"
        android:textColor="@color/genre"
        android:textSize="@dimen/genre" />-->
<!--
    &lt;!&ndash; Release Year &ndash;&gt;
    <TextView
        android:id="@+id/releaseYear"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:textColor="@color/year"
        android:textSize="@dimen/year" />-->

</RelativeLayout>

Customlist Adapter.java

public class CustomListAdapter extends BaseAdapter {
    private Activity activity;
    private LayoutInflater inflater;
    private List<Movie> movieItems;
    ImageLoader imageLoader = AppController.getInstance().getImageLoader();

    public CustomListAdapter(Activity activity, List<Movie> movieItems) {
        this.activity = activity;
        this.movieItems = movieItems;
    }

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

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

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

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

        if (inflater == null)
            inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null)
            convertView = inflater.inflate(R.layout.list_row, null);

        if (imageLoader == null)
            imageLoader = AppController.getInstance().getImageLoader();
        NetworkImageView thumbNail = (NetworkImageView) convertView
                .findViewById(R.id.thumbnail);
        TextView name = (TextView) convertView.findViewById(R.id.name);
        TextView average_ratings = (TextView) convertView.findViewById(R.id.average_ratings);
        TextView address=(TextView) convertView.findViewById(R.id.area);
        TextView cuisine =(TextView) convertView.findViewById(R.id.cuisine);
        //TextView genre = (TextView) convertView.findViewById(R.id.genre);
        //TextView year = (TextView) convertView.findViewById(R.id.releaseYear);

        // getting movie data for the row
        Movie m = movieItems.get(position);

        // thumbnail image
        //thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader);
        if (m.getThumbnailUrl().compareTo("")!=0)
            thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader);
        else{
        thumbNail.setImageResource(R.drawable.bc);
        }


        // title
        name.setText(m.getName());

        // rating
        average_ratings.setText("Rating: " + String.valueOf(m.getAverage_ratings()));
        address.setText("Area: " + String.valueOf(m.getAddress()));
        cuisine.setText("Cusine: " + String.valueOf(m.getCuisine()));
        /*// genre
        String genreStr = "";
        for (String str : m.getGenre()) {
            genreStr += str + ", ";
        }
        genreStr = genreStr.length() > 0 ? genreStr.substring(0,
                genreStr.length() - 2) : genreStr;
        genre.setText(genreStr);

        // release year
        year.setText(String.valueOf(m.getYear()));*/

        return convertView;
    }

}

Movie.java

public class Movie {
    private String name, thumbnailUrl;
    //private int year;
    private String average_ratings,area,cuisine,address;
//  private ArrayList<String> genre;

    public Movie() {
    }

    public Movie(String name, String thumbnailUrl, String average_ratings,String area,String cuisine,String address
            ) {
        this.name = name;
        this.thumbnailUrl = thumbnailUrl;
        //this.year = year;
        this.average_ratings = average_ratings;
        this.area=area;
        this.cuisine=cuisine;
this.address=address;
        //this.genre = genre;
    }

    public String getName() {
        return name;
    }

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

    public String getThumbnailUrl() {
        return thumbnailUrl;
    }

    public void setThumbnailUrl(String thumbnailUrl) {
        this.thumbnailUrl = thumbnailUrl;
    }

    /*public int getYear() {
        return year;
    }*/

    /*public void setYear(int year) {
        this.year = year;
    }*/

    public String getAverage_ratings() {
        return average_ratings;
    }

    public void setAverage_ratings(String average_ratings) {
        this.average_ratings = average_ratings;
    }
    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getCuisine() {
        return cuisine;
    }

    public void setCuisine(String cuisine) {
        this.cuisine = cuisine;
    }
    /*public ArrayList<String> getGenre() {
        return genre;
    }

    public void setGenre(ArrayList<String> genre) {
        this.genre = genre;
    }
*/
}

Answer 1

要在加载图像时显示占位符，请使用：

thumbNail.setDefaultImageResId(R.drawable.your_placeholder);

如果图像没有加载任何错误，要显示图像错误，请使用：

thumbNail.setErrorImageResId(R.drawable.your_error);

如何使用Glide？

＆＃34; Glide是一个快速高效的Android开源媒体管理和图像加载框架，它将媒体解码，内存和磁盘缓存以及资源池包装成一个简单易用的界面。＆＃34; < / p>

它的使用太容易了。

滑翔。随着（上下文） .load（URL） .placeholder（R.drawable.loading_spinner） .into（myImageView）;

使用此功能，Glide会为您处理所有事情。

Answer 2

尝试检查网址是否为空或

if TextUtils.isEmpty(m.getThumbnailUrl())

您的JSON无法获取URL的密钥，但我不认为obj.getString("image_url")返回空字符串。 obj.getOptString("image_url")可能（如果您使用该方法使用JSON API）

Answer 3

而不是

thumbNail.setImageResource(R.drawable.bc);

您可以使用默认和错误方法

else {
  thumbNail.setDefaultImageResId(R.drawable.bc);
  thumbNail.setErrorImageResId(R.drawable.bc);
}

Answer 4

尝试使用方法setDefaultImageResId（int defaultImage）而不是setImageResource，如thumbNail.setDefaultImageResId（R.drawable.bc）;

我想将背景图像放在“图像网址”不存在的地方

4 个答案: