我正在尝试通过调用各自的URL来加载列表视图中的图像。我通过拨打在线网络服务获取网址。我的应用程序因NullPointerException而崩溃。
这是我的listview适配器
public class NewsListingActivity extends ListActivity{
final Context context = this;
//NewsItem currentNewsItem;
Category currentCategory;
View view;
NewsItems myNewsItemList = new NewsItems();
public JSONArray newsItems;
public LinkedList<NewsItem> m_newsItems = null;
public NewsItemAdapter m_adapter;
public Runnable viewNewsItems;
public ProgressDialog m_ProgressDialog = null;
public ListView lv;
NewsItem o;
URL url;
ImageLoader imageLoader;
Bitmap bmImg;
public String [] currentNewsItem;
// called when activity is first created
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_newslist);
//Recieves a Seriablzble Object passed from previous activity - with the tag selectedBook
currentCategory = (Category) getIntent().getSerializableExtra("selectedCategory");
final ListView lv = getListView(); //find listview in activity layout
lv.setTextFilterEnabled(true);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> list, View v, int position, long id) {
//Log.v("test","Item clicked: "+ position);
//on click proceed to the next activity while passing an object of the clicked item - Book
Intent intent = new Intent(getApplicationContext() , NewsItemView.class);
intent.putExtra("selectedCategory", m_adapter.getItem(position)); // pass Object - Book
startActivity(intent);
}
});
//Log.v("test","currentCategory is: " + currentCategory.getCategoryName()+ " "+ currentCategory.getId());
setUpViews();
}
private void setUpViews(){
final ListView lv = getListView(); //find listview in activity layout
lv.setTextFilterEnabled(true);
m_newsItems = new LinkedList<NewsItem>(); //create LinkedList of type NewsItem
this.m_adapter = new NewsItemAdapter(this, R.layout.row_news, m_newsItems); // ItemListView Holder
setListAdapter(this.m_adapter); //attach adapter to ListView
viewNewsItems = new Runnable(){
@Override
public void run() {
getNewsItems(); // run in background
}
};
//create a thread and a progress dialog to handle processes in background
//avoid lagging or freezing app-phone
Thread thread = new Thread(null, viewNewsItems, "MagentoBackground");
thread.start();
m_ProgressDialog = ProgressDialog.show(NewsListingActivity.this,
"Please wait...", "Retrieving data ...", true);
}
private Runnable returnRes = new Runnable() {
// loop through list of type newsItems to update UI
@Override
public void run() {
if(m_newsItems != null && m_newsItems.size() > 0){
m_adapter.notifyDataSetChanged();
for(int i=0;i<m_newsItems.size();i++)
m_adapter.add(m_newsItems.get(i));
}
m_ProgressDialog.dismiss();
m_adapter.notifyDataSetChanged();
}
};
private void getNewsItems(){
try{
updateNewsItemList();
m_newsItems = myNewsItemList.getNewsItemList();
Thread.sleep(5000);
Log.i("ARRAY", ""+ m_newsItems.size());
} catch (Exception e) {
Log.e("BACKGROUND_PROC", e.getMessage());
}
runOnUiThread(returnRes);
}
//Contacts server to retrive JSON object containing all BOOKS and their related information
public void updateNewsItemList(){
//String request = "http://xxxxx/RestServiceImpl.svc/GetNews/1";
String request= "http://xxxxxx/RestServiceImpl.svc/GetNews/" + currentCategory.getId();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(request);
Log.v("test","request is made");
try {
// Getting Array of Contacts
newsItems = json.getJSONArray("GetNewsResult");
//Log.v("test","content is: "+ newsItems.length());
// looping through All newsItems
for(int i = 0; i < newsItems.length(); i++){
// Log.v("test","inside loop");
currentNewsItem = new String[5];
JSONObject c = newsItems.getJSONObject(i);
currentNewsItem[0] = c.getString("NewsId");
currentNewsItem[1] = c.getString("NewsCategory");
currentNewsItem[2] = c.getString("NewsDesc");
currentNewsItem[3] = "http://xxxxxxxx/CMS/Management/News/Images/" + c.getString("NewsImage");
currentNewsItem[4] = c.getString("NewsTitle");
myNewsItemList.getNewsItemList().add(new NewsItem(currentNewsItem));
currentNewsItem = null; //clear array after each loop
}
} catch (JSONException e) {
Log.v("test","no array found");
}};
//ListView Adapter
private class NewsItemAdapter extends ArrayAdapter<NewsItem> {
private LinkedList<NewsItem> items;
public NewsItemAdapter(Context context, int textViewResourceId, LinkedList<NewsItem> items) {
super(context, textViewResourceId, items);
this.items = items;
}
@Override
public int getCount() {
return items.size();
//return number of items in array
}
@Override
public NewsItem getItem(int position) {
return items.get(position);
// return task by passing position
}
@Override
public long getItemId(int position) {
return position; //return item id by passing position
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.row_news, null);
}
o = items.get(position);
if (o != null) { //listView attributes - nodes - views
TextView newsTitle = (TextView) v.findViewById(R.id.title);
ImageView newsImage = (ImageView) v.findViewById(R.id.newsImage);
newsTitle.setText(o.getNewsTitle());
// Log.v("test","this is url to call: " + o.getNewsImage());
imageLoader.DisplayImage(o.getNewsImage(), NewsListingActivity.this, newsImage);
/**
newsImage.setImageBitmap(bmImg);
try {
url = new URL(o.getNewsImage());
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setDoInput(true);
conn.connect();
InputStream is = conn.getInputStream();
bmImg = BitmapFactory.decodeStream(is);
//Here u will set image in imageview
newsImage.setImageBitmap(bmImg);
}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
*/
}
return v;
}
}
}
这是我的ImageLoader类
public class ImageLoader {
//the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();
private File cacheDir;
public ImageLoader(Context context){
//Make the background thead low priority. This way it will not affect the UI performance
photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
//Find the dir to save cached images
if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"LazyList");
else
cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
final int stub_id=R.drawable.ic_action_search;
public void DisplayImage(String url, Activity activity, ImageView imageView)
{
if(cache.containsKey(url))
imageView.setImageBitmap(cache.get(url));
else
{
queuePhoto(url, activity, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView)
{
//This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p=new PhotoToLoad(url, imageView);
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
//start thread if it's not started yet
if(photoLoaderThread.getState()==Thread.State.NEW)
photoLoaderThread.start();
}
private Bitmap getBitmap(String url)
{
//I identify images by hashcode. Not a perfect solution, good for the demo.
String filename=String.valueOf(url.hashCode());
File f=new File(cacheDir, filename);
//from SD cache
Bitmap b = decodeFile(f);
if(b!=null)
return b;
//from web
try {
Bitmap bitmap=null;
DataInputStream input = null;
InputStream is=new URL(url).openStream();
// String auth = android.util.Base64.encodeToString(("devneoauto" + ":" + "2kk0rnpnpvir")
// .getBytes("UTF-8"), android.util.Base64.NO_WRAP);
HttpClient client = new DefaultHttpClient();
HttpGet getmethod = new HttpGet(url);
// getmethod.addHeader("Authorization", "Basic " + auth);
// getmethod.addHeader("X-ZFWS-Accept", "text/json");
HttpResponse responseGet = client.execute(getmethod);
HttpEntity resEntityGet = responseGet.getEntity();
if (resEntityGet != null) {
input = new DataInputStream(responseGet.getEntity().getContent());
}
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(input, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
return null;
}
}
//decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f){
try {
//decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);
//Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE=70;
int width_tmp=o.outWidth, height_tmp=o.outHeight;
int scale=1;
while(true){
if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
break;
width_tmp/=2;
height_tmp/=2;
scale++;
}
//decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize=scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
return null;
}
//Task for the queue
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}
PhotosQueue photosQueue=new PhotosQueue();
public void stopThread()
{
photoLoaderThread.interrupt();
}
//stores list of photos to download
class PhotosQueue
{
private Stack<PhotoToLoad> photosToLoad=new Stack<PhotoToLoad>();
//removes all instances of this ImageView
public void Clean(ImageView image)
{
for(int j=0 ;j<photosToLoad.size();){
if(photosToLoad.get(j).imageView==image)
photosToLoad.remove(j);
else
++j;
}
}
}
class PhotosLoader extends Thread {
public void run() {
try {
while(true)
{
//thread waits until there are any images to load in the queue
if(photosQueue.photosToLoad.size()==0)
synchronized(photosQueue.photosToLoad){
photosQueue.photosToLoad.wait();
}
if(photosQueue.photosToLoad.size()!=0)
{
PhotoToLoad photoToLoad;
synchronized(photosQueue.photosToLoad){
photoToLoad=photosQueue.photosToLoad.pop();
}
Bitmap bmp=getBitmap(photoToLoad.url);
cache.put(photoToLoad.url, bmp);
if(((String)photoToLoad.imageView.getTag()).equals(photoToLoad.url)){
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad.imageView);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if(Thread.interrupted())
break;
}
} catch (InterruptedException e) {
//allow thread to exit
}
}
}
PhotosLoader photoLoaderThread=new PhotosLoader();
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;}
public void run()
{
if(bitmap!=null)
{
imageView.setImageBitmap(bitmap);
}
else
imageView.setImageResource(R.drawable.ic_action_search);
}
}
public void clearCache() {
//clear memory cache
cache.clear();
//clear SD cache
File[] files=cacheDir.listFiles();
for(File f:files)
f.delete();
}
}
LogCat输出：
06-10 21:29:00.771: E/AndroidRuntime(25339): FATAL EXCEPTION: main
06-10 21:29:00.771: E/AndroidRuntime(25339): Process: com.saeedjoul.hayatnews, PID: 25339
06-10 21:29:00.771: E/AndroidRuntime(25339): java.lang.NullPointerException
06-10 21:29:00.771: E/AndroidRuntime(25339): at com.saeedjoul.hayatnews.NewsListingActivity$NewsItemAdapter.getView(NewsListingActivity.java:239)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.AbsListView.obtainView(AbsListView.java:2720)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.ListView.makeAndAddView(ListView.java:1801)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.ListView.fillDown(ListView.java:697)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.ListView.fillFromTop(ListView.java:763)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.ListView.layoutChildren(ListView.java:1627)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.AbsListView.onLayout(AbsListView.java:2533)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.View.layout(View.java:15655)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewGroup.layout(ViewGroup.java:4856)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1677)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1531)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.onLayout(LinearLayout.java:1440)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.View.layout(View.java:15655)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewGroup.layout(ViewGroup.java:4856)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1677)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1531)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.onLayout(LinearLayout.java:1440)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.View.layout(View.java:15655)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewGroup.layout(ViewGroup.java:4856)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.View.layout(View.java:15655)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewGroup.layout(ViewGroup.java:4856)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1677)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1531)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.LinearLayout.onLayout(LinearLayout.java:1440)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.View.layout(View.java:15655)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewGroup.layout(ViewGroup.java:4856)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.View.layout(View.java:15655)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewGroup.layout(ViewGroup.java:4856)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2284)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2004)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1234)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6467)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:803)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.Choreographer.doCallbacks(Choreographer.java:603)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.Choreographer.doFrame(Choreographer.java:573)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:789)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.os.Handler.handleCallback(Handler.java:733)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.os.Handler.dispatchMessage(Handler.java:95)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.os.Looper.loop(Looper.java:157)
06-10 21:29:00.771: E/AndroidRuntime(25339): at android.app.ActivityThread.main(ActivityThread.java:5356)
06-10 21:29:00.771: E/AndroidRuntime(25339): at java.lang.reflect.Method.invokeNative(Native Method)
06-10 21:29:00.771: E/AndroidRuntime(25339): at java.lang.reflect.Method.invoke(Method.java:515)
06-10 21:29:00.771: E/AndroidRuntime(25339): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
06-10 21:29:00.771: E/AndroidRuntime(25339): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
06-10 21:29:00.771: E/AndroidRuntime(25339): at dalvik.system.NativeStart.main(Native Method)
记录2
06-10 23:00:46.196: W/System.err(30836): java.net.MalformedURLException: Protocol not found: 162.13.166.28/CMS/Management/News/Images/3.jpg 06-10 23:00:46.196: W/System.err(30836): at java.net.URL.<init>(URL.java:176) 06-10 23:00:46.196: W/System.err(30836): at java.net.URL.<init>(URL.java:125) 06-10 23:00:46.196: W/System.err(30836): at com.saeedjoul.hayatnews.ImageLoader.getBitmap(ImageLoader.java:88) 06-10 23:00:46.196: W/System.err(30836): at com.saeedjoul.hayatnews.ImageLoader.access$0(ImageLoader.java:72) 06-10 23:00:46.196: W/System.err(30836): at com.saeedjoul.hayatnews.ImageLoader$PhotosLoader.run(ImageLoader.java:197) 06-10 23:00:46.196: W/dalvikvm(30836): threadid=11: thread exiting with uncaught exception (group=0x4183bc08) 06-10 23:00:46.196: E/AndroidRuntime(30836): FATAL EXCEPTION: Thread-31698 06-10 23:00:46.196: E/AndroidRuntime(30836): Process: com.saeedjoul.hayatnews, PID: 30836 06-10 23:00:46.196: E/AndroidRuntime(30836): java.lang.NullPointerException 06-10 23:00:46.196: E/AndroidRuntime(30836): at com.saeedjoul.hayatnews.ImageLoader$PhotosLoader.run(ImageLoader.java:199)
答案 0 :(得分：0)
它是null，因为您没有从类中实例化imageLoader，因此在此行中为您提供了 NPE ：imageLoader.DisplayImage(o.getNewsImage(), NewsListingActivity.this, newsImage);
<强>解决方案：
在使用imageLoader方法之前实例化DisplayImage。
imageLoader = new ImageLoader(NewsListingActivity.this);
imageLoader.DisplayImage(o.getNewsImage(), NewsListingActivity.this, newsImage);