通过简单的适配器在 imageview 中显示 bitmap 图像

Question

我从 url 获取图像。 我在列表视图中使用 imageview。 我想将 bitmap 图像列表添加到列表项的每一行中。 我使用了 SimpleAdapter，但 imageview 显示空白。我的代码如下！！

 ArrayList<HashMap<String, Bitmap>> mylist = new ArrayList<HashMap<String, Bitmap>>();

    Bundle bundle = this.getIntent().getExtras();
     get = bundle.getString("name");

     try{
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://www.propertyhookup.com/mobile/propertylist.php");
            nameValuePairs = new ArrayList<NameValuePair>(1);
            nameValuePairs.add(new BasicNameValuePair("zipcode", get.trim()));
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();

    }catch(Exception e){
            Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
    }

  //convert response to string
    try{
            BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                    sb.append(line + "\n");
            }
            is.close();
            result=sb.toString();
    }catch(Exception e){
            Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
    }
    if(result.length()<= 7){
        Toast.makeText(getApplicationContext(), "No properties for this zipcode or check your zipcode ", Toast.LENGTH_LONG).show();
        //text.setText("No properties for this zipcode or check your zipcode");
    }
    else{
    try{

     jArray = new JSONObject(result);            
    }catch(JSONException e){
        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
    }

    //JSONObject json = JSONfunctions.getJSONfromURL("http://192.168.1.111/propertyhookup.com/mobile/propertylist.php");

    try{

        JSONArray  earthquakes = jArray.getJSONArray("earthquakes");

        for(int i=0;i<10;i++){                      
            map = new HashMap<String, Bitmap>();
            //HashMap<String, Drawable> map1 = new HashMap<String, Drawable>();

            JSONObject e = earthquakes.getJSONObject(i);



            if(e.getString("property_type").contains("1")) {
                proptype ="Single Family Home";
            }else if(e.getString("property_type").contains("2")) {
                proptype="Condo";
            }else if(e.getString("property_type").contains("3")) {
                proptype="Townhouse";
            }
            if(e.getString("estimated_price").contains("0")) {
                estimate = "Not Enough Market Value";
                //estimat = (TextView) findViewById(R.id.estimat);
                //estimat.setTextColor(Color.rgb(0, 0, 23));
            }else {
                estimate = "$"+e.getString("estimated_price");
            }

            photo = e.getString("photo1");

            drawable = LoadImageFromWebOperations(photo);

            //text.setImageDrawable(d);

            try
            {
                    aURL = new URL(photo);
            }
            catch (MalformedURLException e1)
            {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
            }
            URLConnection conn = null;
            try
            {
                    conn = aURL.openConnection();
            }
            catch (IOException e1)
            {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
            }
            try
            {
                    conn.connect();
            }
            catch (IOException e1)
            {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
            }
            InputStream is = null;
            try
            {
                    is = conn.getInputStream();
            }
            catch (IOException e1)
            {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
            }
            BufferedInputStream bis = new
    BufferedInputStream(is,8*1024);
            Bitmap bm = BitmapFactory.decodeStream(bis);

            map.put(photos, bm);
            mylist.add(map);


        }       
    }catch(JSONException e)        {
        Toast.makeText(getApplicationContext(),e.getMessage(), Toast.LENGTH_LONG).show();
    }



    SimpleAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main4, 
                   new String[] { "percent","propertyid",  "cityname", "statecode", "propertytype", "footage", "bathroom", "bedroom", "price", "estimated", "photos" }, 
                   new int[] { R.id.percent, R.id.property_id,  R.id.city_name, R.id.state_code, R.id.prop_type, R.id.foot, R.id.bath, R.id.bed, R.id.list, R.id.estimat, R.id.image});
    setListAdapter(adapter);

Answer 1

基本上，简单的适配器会自动将一些资源 ID 或 URI 绑定到行布局的 imageview。 但它不支持 Bitmap。

这是一个问题，因为每个不得不管理bitmap的人都知道，我们经常要减小图片的大小来防止outOfMemory异常。 但是如果你想将图片添加到listView中，如果你只提供URI，你不能减小图片的大小。 所以这里是解决方案：

我已经修改了 simpleAdapter 以便能够处理 bitmap。 将此 class 添加到您的项目中，并使用它代替 simpleAdapter。 然后，不要传递图像的 URI 或 ressourceId，而是传递 Bitmap ！

下面是代码：

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.content.Context;
import android.graphics.Bitmap;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Checkable;
import android.widget.ImageView;
import android.widget.SimpleAdapter;
import android.widget.TextView;



public class ExtendedSimpleAdapter extends SimpleAdapter{
    List<? extends Map<String, ?>> map; // if fails to compile, replace with List<HashMap<String, Object>> map
    String[] from;
    int layout;
    int[] to;
    Context context;
    LayoutInflater mInflater;
    public ExtendedSimpleAdapter(Context context, List<? extends Map<String, ?>> data, // if fails to compile, do the same replacement as above on this line
            int resource, String[] from, int[] to) { 
        super(context, data, resource, from, to);
        layout = resource;
        map = data;
        this.from = from;
        this.to = to;
        this.context = context;
    }


@Override
public View getView(int position, View convertView, ViewGroup parent) {
    mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    return this.createViewFromResource(position, convertView, parent, layout);
}

private View createViewFromResource(int position, View convertView,
        ViewGroup parent, int resource) {
    View v;
    if (convertView == null) {
        v = mInflater.inflate(resource, parent, false);
    } else {
        v = convertView;
    }

    this.bindView(position, v);

    return v;
}


private void bindView(int position, View view) {
    final Map dataSet = map.get(position);
    if (dataSet == null) {
        return;
    }

    final ViewBinder binder = super.getViewBinder();
    final int count = to.length;

    for (int i = 0; i < count; i++) {
        final View v = view.findViewById(to[i]);
        if (v != null) {
            final Object data = dataSet.get(from[i]);
            String text = data == null ? "" : data.toString();
            if (text == null) {
                text = "";
            }

            boolean bound = false;
            if (binder != null) {
                bound = binder.setViewValue(v, data, text);
            }

            if (!bound) {
                if (v instanceof Checkable) {
                    if (data instanceof Boolean) {
                        ((Checkable) v).setChecked((Boolean) data);
                    } else if (v instanceof TextView) {
                        // Note: keep the instanceof TextView check at the bottom of these
                        // ifs since a lot of views are TextViews (e.g. CheckBoxes).
                        setViewText((TextView) v, text);
                    } else {
                        throw new IllegalStateException(v.getClass().getName() +
                                " should be bound to a Boolean, not a " +
                                (data == null ? "<unknown type>" : data.getClass()));
                    }
                } else if (v instanceof TextView) {
                    // Note: keep the instanceof TextView check at the bottom of these
                    // ifs since a lot of views are TextViews (e.g. CheckBoxes).
                    setViewText((TextView) v, text);
                } else if (v instanceof ImageView) {
                    if (data instanceof Integer) {
                        setViewImage((ImageView) v, (Integer) data);                            
                    } else if (data instanceof Bitmap){
                        setViewImage((ImageView) v, (Bitmap)data);
                    } else {
                        setViewImage((ImageView) v, text);
                    }
                } else {
                    throw new IllegalStateException(v.getClass().getName() + " is not a " +
                            " view that can be bounds by this SimpleAdapter");
                }
            }
        }
    }
}



private void setViewImage(ImageView v, Bitmap bmp){
    v.setImageBitmap(bmp);
}



}

此 class 的行为与原始 class (SimpleAdapter) 完全相同

Answer 2

我认为是因为您正在从 web 下载图像，您需要在 ASYNC 中执行这些操作，查看无痛 thrething 下载图像，然后仅刷新图像视图。

Answer 3

最好的方法是创建一个扩展 BaseAdapter 的 class，然后为每个图像实例化一个异步任务（在执行后将 bitmap 设置为对应的 imageView）。 这是一个简单的 function 从 web 下载图像：

private Bitmap loadImageFromNetwork(String url) throws MalformedURLException, IOException {
    HttpURLConnection conn = (HttpURLConnection) (new URL(url)).openConnection();
    conn.connect();
    return BitmapFactory.decodeStream(new FlushedInputStream(conn.getInputStream()));
}