我正在开发一个项目，该项目向 Web 服务器发布请求，并且 Web 服务器以 XML 格式响应。这是真正的故事开始。实际上，我在同一活动中向 Web 服务器发送请求并在同一活动中获得响应，响应包含分辨率为 500X800 的图像和一些纯文本。
public class Home extends Activity implements AdapterView.OnItemClickListener {
/** Called when the activity is first created. */
Context context = Home.this;
ArrayList<String> BookTitle = new ArrayList<String>();
ArrayList<String> BookCoverPhotos = new ArrayList<String>();
ArrayList<String> BookAuther = new ArrayList<String>();
ArrayList<String> BookPublishDate = new ArrayList<String>();
URL bookImageURL = null;
Bitmap bitMapImage = null;
View homeTabLayout;
View reviewLayout;
ImageButton btnBack;
// All static variables
static final String URL = "http://www.shiaislamiclibrary.com/requesthandler.ashx";
// XML node keys
static final String KEY_ITEM = "Book"; // parent node
static final String KEY_BOOKAUTHOR = "BookAuthor";
static final String KEY_BOOKDATEPUBLISHED = "DatePublished";
static final String KEY_BOOKTITLE = "BookTitle";
static final String KEY_BOOKCODE = "BookCode";
static final String KEY_BOOKIMAGE = "BookImage";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home_activity);
// Get XML Data in a Array List
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL, "Imam Ali"); // getting
// XML
Log.i("XML FORMAT", xml);
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
// looping through all item nodes <item>
for (int i = 0; i < nl.getLength(); i++) {
Element e = (Element) nl.item(i);
BookTitle.add(parser.getValue(e, KEY_BOOKTITLE));
BookCoverPhotos.add("http://shiaislamicbooks.com/books_Snaps/"
+ parser.getValue(e, KEY_BOOKCODE) + "/1.jpg");
BookAuther.add(parser.getValue(e, KEY_BOOKAUTHOR));
BookPublishDate.add(parser.getValue(e, KEY_BOOKDATEPUBLISHED));
Log.i("URLs", BookPublishDate + "::" + BookAuther + "::"
+ BookTitle + BookCoverPhotos.toString());
}
// OverView Page Views...
final ImageView imgOverVuBookCoverPhoto = (ImageView) findViewById(R.id.img_OverVuBookCoverPhoto);
final TextView txtOverVuBookTitle = (TextView) findViewById(R.id.txt_revwBookTitle);
final TextView txtOverVuBookAuthor = (TextView) findViewById(R.id.txt_revwAutherName);
final TextView txtBookPublishDate = (TextView) findViewById(R.id.txt_PublishDate);
homeTabLayout = findViewById(R.id.rel_HomeLayout);
reviewLayout = findViewById(R.id.scroll_ReviewLayout);
reviewLayout.setVisibility(View.GONE);
btnBack = (ImageButton) findViewById(R.id.btnBack);
btnBack.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
reviewLayout.setVisibility(View.GONE);
homeTabLayout.setVisibility(View.VISIBLE);
}
});
final GridView gridView = (GridView) findViewById(R.id.gridview);
gridView.setAdapter(new ImageAdapter(this));
gridView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
long arg3) {
reviewLayout.setVisibility(View.VISIBLE);
homeTabLayout.setVisibility(View.GONE);
Toast.makeText(context, BookTitle.get(pos), Toast.LENGTH_SHORT)
.show();
txtOverVuBookTitle.setText(BookTitle.get(pos));
txtOverVuBookAuthor.setText(BookAuther.get(pos));
txtBookPublishDate.setText(BookPublishDate.get(pos));
try {
bookImageURL = new URL(BookCoverPhotos.get(pos));
} catch (MalformedURLException e) {
e.printStackTrace();
Toast.makeText(context, "Network Error", Toast.LENGTH_LONG)
.show();
Log.i("URL", "ERROR");
}
try {
bitMapImage = BitmapFactory.decodeStream(bookImageURL
.openConnection().getInputStream());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Toast.makeText(context, "Bitmap Error", Toast.LENGTH_LONG)
.show();
Log.i("BITMAP", "ERROR");
}
imgOverVuBookCoverPhoto.setImageBitmap(bitMapImage);
}
});
}
public class ImageAdapter extends BaseAdapter {
private Context context;
public ImageAdapter(Context c) {
context = c;
}
// ---returns the number of images---
public int getCount() {
// return imageIDs.length;
return BookCoverPhotos.size();
// return 6;
}
// ---returns the ID of an item---
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
// ---returns an ImageView view---
public View getView(int position, View convertView, ViewGroup parent) {
// ImageView bmImage;
ImageView img_BookCoverPhoto;
img_BookCoverPhoto = new ImageView(context);
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View row = inflater.inflate(R.layout.grid_style, parent, false);
TextView txt_BooksTitle = (TextView) row
.findViewById(R.id.txt_BookTitle);
txt_BooksTitle.setText(BookTitle.get(position) + "");
img_BookCoverPhoto = (ImageView) row
.findViewById(R.id.imgBookCover);
try {
bookImageURL = new URL(BookCoverPhotos.get(position));
} catch (MalformedURLException e) {
e.printStackTrace();
Toast.makeText(context, "Network Error", Toast.LENGTH_LONG)
.show();
Log.i("URL", "ERROR");
}
try {
bitMapImage = BitmapFactory.decodeStream(bookImageURL
.openConnection().getInputStream());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Toast.makeText(context, "Bitmap Error", Toast.LENGTH_LONG)
.show();
Log.i("BITMAP", "ERROR");
}
// img_BookCoverPhoto.setImageResource(imageIDs[position]);
img_BookCoverPhoto.setImageBitmap(bitMapImage);
return row;
}
}
public class AsyncTaskForUI extends AsyncTask<String, Integer, String> {
ProgressDialog progressDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog = ProgressDialog
.show(context,
"Loading...",
"This may take a few minuts\nDepending Upon your Internet Connection Speed",
true);
}
@Override
protected String doInBackground(String... params) {
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
progressDialog.dismiss();
Toast.makeText(context, "Completed", Toast.LENGTH_SHORT).show();
}
}
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
}
}
我在包含 ImageView 和 textView 的自定义 GridView 中加载图像和文本。这是布局的XML
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/widget44"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:orientation="vertical" >
<ImageView
android:id="@+id/imgBookCover"
android:layout_width="150dp"
android:layout_height="180dp"
android:scaleType="center"
android:adjustViewBounds="true"
android:src="@drawable/book1">
</ImageView>
<TextView
android:id="@+id/txt_BookTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="TextView"
android:layout_margin="5dp"
android:textColorHighlight="#656565"
android:textColor="@color/White">
</TextView>
</LinearLayout>
这也是我的 XMLParser.java 类代码
public class XMLParser {
// constructor
public XMLParser() {
}
/**
* Getting XML from URL making HTTP request
*
* @param url
* string
* */
public String getXmlFromUrl(String url, String SearchKeywords) {
String xml = null;
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
/*ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(
3);
nameValuePairs.add(new BasicNameValuePair("type", "Free Books"));
nameValuePairs.add(new BasicNameValuePair("lang", "English"));
nameValuePairs.add(new BasicNameValuePair("book_title", "hasan"));
try {
httpPost.setEntity(new UrlEncodedFormEntity(
nameValuePairs));
} catch (UnsupportedEncodingException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}*/
String postParameter = "type=Free Books&lang=English&book_title="+SearchKeywords;
try {
httpPost.setEntity(new StringEntity(postParameter));
}catch (Exception e) {
// TODO: handle exception
}
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
xml = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// return XML
return xml;
}
/**
* Getting XML DOM element
*
* @param XML
* string
* */
public Document getDomElement(String xml) {
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(xml));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (SAXException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Error: ", e.getMessage());
return null;
}
return doc;
}
/**
* Getting node value
*
* @param elem
* element
*/
public final String getElementValue(Node elem) {
Node child;
if (elem != null) {
if (elem.hasChildNodes()) {
for (child = elem.getFirstChild(); child != null; child = child
.getNextSibling()) {
if (child.getNodeType() == Node.TEXT_NODE) {
return child.getNodeValue();
}
}
}
}
return "";
}
/**
* Getting node value
*
* @param Element
* node
* @param key
* string
* */
public String getValue(Element item, String str) {
NodeList n = item.getElementsByTagName(str);
return this.getElementValue(n.item(0));
}
}
代码工作得很好，但是它会挂起应用程序，直到服务器发送响应并且我的应用程序显示黑屏，直到它将所有图像和文本加载到所需的视图中。当我滚动 gridView 有时它会给出异常
java.lang.OutOfMemoryError: bitmap size exceeds VM budget
- 但问题是现在我想在 AsyncTask 中进行 XML 解析和位图解码。如何在 AsynTask 类的单个 doInbackground() 方法中实现这两项任务。
- 还给出了使用 AsyncTask 类将高分辨率图像调整为低分辨率的代码片段。