我正在从网址获取图像。我在listview中使用imageview。我想将位图图像列表添加到列表项的每一行。我使用SimpleAdapter但是imageview显示为空白。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);
我认为是因为你从网上下载图像，你需要在ASYNC中看到无痛的线索下载图像，然后刷新图像视图。
基本上，简单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，因为每个必须管理位图的人都知道我们经常需要减小图片的大小以防止outOfMemory异常。但是，如果要将图像添加到listView中，如果仅提供URI，则无法缩小图像的大小。所以这是解决方案：
我修改了simpleAdapter以便能够处理位图。将此类添加到项目中，并使用它而不是simpleAdapter。然后传递一个位图，而不是传递图像的URI或ressourceId！
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);
}
}
这个类的行为与原始类（SimpleAdapter）完全相同
最好的方法是创建一个扩展BaseAdapter的类，然后为每个图像实例化异步任务（在后执行时将位图设置为相应的imageView）。这是从web下载图像的简单功能：
private Bitmap loadImageFromNetwork(String url) throws MalformedURLException, IOException {
HttpURLConnection conn = (HttpURLConnection) (new URL(url)).openConnection();
conn.connect();
return BitmapFactory.decodeStream(new FlushedInputStream(conn.getInputStream()));
}