java - 使用 sax 解析器和 imageloader 类将图像解析为 listview

Question

将图像 url 解析为图像并将其显示在我的 listview 中时出现错误。我已经发现了错误，但无法纠正它....(发现=知道错误在哪里-_-)

首先我使用SAX。其次，我进行了各种解析，所以我在一项 Activity 中粉碎了所有内容。第三，我将在没有捕获异常的情况下发送日志。

错误是最后一段代码...其中有 try 和 catch。

    public class MainActivity extends Activity {
    URL url;
    ListView list;

    ArrayList<String> titles = new ArrayList<String>();
    ArrayList<String> artists = new ArrayList<String>();
    ArrayList<String> countries = new ArrayList<String>();
    ArrayList<String> companies = new ArrayList<String>();
    ArrayList<String> prices = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        list = (ListView) findViewById(R.id.listView1);
        MyAsync ma = new MyAsync();
        ma.execute();

        list.setOnItemClickListener(new OnItemClickListener() {

    @Override
    public void onItemClick(AdapterView<?> parent, View view,
    int position, long id) {
    // getting values from selected ListItem

    if(position == 0){

    Intent a = new Intent(MainActivity.this , custom.class);
    tartActivity(a);

    }

    }
    });

        }

        class MyAsync extends AsyncTask<Void, Void, Void> {
        ProgressDialog pd;

        @Override
        protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();

        pd = ProgressDialog.show(MainActivity.this, "", "loading pc parts");
        }

        @Override
        protected Void doInBackground(Void... params) {
            // TODO Auto-generated method stub
        try {
                url = new        URL("https://dl.dropboxusercontent.com/u/74662678/graphicscards.xml");

                // Create an instance for SAXParserFactory
                SAXParserFactory mySAXParserFactory = SAXParserFactory
                        .newInstance();

                // Create an instance for SAXParser
                SAXParser mySAXParser = mySAXParserFactory.newSAXParser();

                // Create an instance for XMLReader
                XMLReader myXMLReader = mySAXParser.getXMLReader();

                // Create an instance for customized handler class
                XMLHandler myXMLHandler = new XMLHandler();

                // apply handler to the XMLReader
                myXMLReader.setContentHandler(myXMLHandler);

                // open the connection
                InputSource is = new InputSource(url.openStream());



                // parse the data
                myXMLReader.parse(is);

            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (ParserConfigurationException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (SAXException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);

            pd.cancel();
            CustomAdapter ca = new CustomAdapter();
            list.setAdapter(ca);

        }

    }

    class XMLHandler extends DefaultHandler {

        boolean TITLE = false;
        boolean BRAND = false;
        boolean USE = false;
        boolean URL = false;
        boolean COST = false;


        @Override
        public void startElement(String uri, String localName, String qName,
                Attributes attributes) throws SAXException {
            // TODO Auto-generated method stub
            super.startElement(uri, localName, qName, attributes);

            if (localName.equals("TITLE")) {
                this.TITLE = true;
            } else if (localName.equals("BRAND")) {
                this.BRAND = true;
            } else if (localName.equals("USE")) {
                this.USE = true;
            } else if (localName.equals("URL")) {
                this.URL = true;
            } else if (localName.equals("COST")) {
                this.COST = true;
            } 
        }

        @Override
        public void characters(char[] ch, int start, int length)
                throws SAXException {
            // TODO Auto-generated method stub
            super.characters(ch, start, length);
            if (this.TITLE) {
                titles.add(new String(ch, start, length));
            } else if (this.BRAND) {
                artists.add(new String(ch, start, length));

            } else if (this.USE) {
                countries.add(new String(ch, start, length));

            } else if (this.URL) {
                companies.add(new String(ch, start, length));

            } else if (this.COST) {
                prices.add(new String(ch, start, length));

            }

        }

        @Override
        public void endElement(String uri, String localName, String qName)
                throws SAXException {
            // TODO Auto-generated method stub
            super.endElement(uri, localName, qName);
            if (localName.equals("TITLE")) {
                this.TITLE = false;
            } else if (localName.equals("BRAND")) {
                this.BRAND = false;
            } else if (localName.equals("USE")) {
                this.USE = false;
            } else if (localName.equals("URL")) {
                this.URL = false;
            } else if (localName.equals("COST")) {
                this.COST = false;
            } 
        }
    }

    class CustomAdapter extends BaseAdapter {

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return titles.size();
        }

        @Override
        public Object getItem(int arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public long getItemId(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public View getView(int index, View v, ViewGroup arg2) {
            // TODO Auto-generated method stub
            v = getLayoutInflater().inflate(R.layout.custom, null);

            TextView t1 = (TextView) v.findViewById(R.id.title);
            TextView t2 = (TextView) v.findViewById(R.id.artist);
            TextView t3 = (TextView) v.findViewById(R.id.textView1);
            TextView t4 = (TextView) v.findViewById(R.id.duration);

            String song = new String();
            song = titles.get(index);


            t1.setText(titles.get(index).toString());
            t2.setText(artists.get(index).toString());
            t3.setText(countries.get(index).toString());
            t4.setText(prices.get(index).toString());

            //loading list picture

            String a = companies.get(index).toString();
            ImageView lblThumb = (ImageView) findViewById(R.id.thumbie);

            try{

            int loader = R.drawable.loader;
            ImageLoader imgLoader = new ImageLoader(getApplicationContext());
            imgLoader.DisplayImage(a, loader, lblThumb);

            }catch(Exception e){
                Log.d("error" , "lol");
            }


            return v;
        }

    }
}

日志:-

03-19 08:28:34.635: E/AndroidRuntime(3635): FATAL EXCEPTION: main
03-19 08:28:34.635: E/AndroidRuntime(3635): java.lang.NullPointerException
03-19 08:28:34.635: E/AndroidRuntime(3635):     at com.ram.saxparserexample.ImageLoader.DisplayImage(ImageLoader.java:48)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at com.ram.saxparserexample.MainActivity$CustomAdapter.getView(MainActivity.java:273)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.AbsListView.obtainView(AbsListView.java:2159)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.ListView.makeAndAddView(ListView.java:1831)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.ListView.fillDown(ListView.java:674)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.ListView.fillFromTop(ListView.java:735)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.ListView.layoutChildren(ListView.java:1652)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.AbsListView.onLayout(AbsListView.java:1994)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.View.layout(View.java:14008)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewGroup.layout(ViewGroup.java:4373)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1663)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1521)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.View.layout(View.java:14008)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewGroup.layout(ViewGroup.java:4373)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.View.layout(View.java:14008)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewGroup.layout(ViewGroup.java:4373)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1663)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1521)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.View.layout(View.java:14008)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewGroup.layout(ViewGroup.java:4373)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.View.layout(View.java:14008)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewGroup.layout(ViewGroup.java:4373)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1892)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1711)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.Choreographer.doFrame(Choreographer.java:532)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.os.Handler.handleCallback(Handler.java:725)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.os.Looper.loop(Looper.java:137)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at android.app.ActivityThread.main(ActivityThread.java:5041)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at java.lang.reflect.Method.invokeNative(Native Method)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at java.lang.reflect.Method.invoke(Method.java:511)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-19 08:28:34.635: E/AndroidRuntime(3635):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

您必须更改此设置

 ImageView lblThumb = (ImageView) findViewById(R.id.thumbie);

至

 ImageView lblThumb = (ImageView) v.findViewById(R.id.thumbie);

因为每当您在 getView() 方法中找到 UI 控件的 ID 时，您都需要传递 View 对象的引用来查找 ID。