public class NewMovie extends Activity {
GridView lv;
Vibrator vibrator;
SimpleAdapter adapter ;
Button b;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
enter code heresuper.onCreate(savedInstanceState);
Log.i("Category", MainActivity.movie_Category);
setContentView(R.layout.new_movie);
LayoutInflater li = getLayoutInflater();
View layout = li.inflate(R.layout.customtoast, (ViewGroup) findViewById(R.id.custom_toast_layout));
Toast toast = new Toast(getApplicationContext());
toast.setDuration(Toast.LENGTH_LONG);
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setView(layout);
toast.show();
vibrator=(Vibrator)getSystemService(Context.VIBRATOR_SERVICE);
lv=(GridView)findViewById(R.id.grid_view);
b=(Button)findViewById(R.id.profile_button);
// URL to the JSON data
String strUrl = "http://vaibhavtech.com/work/android/movie_list.php? category="+MainActivity.movie_Category+"&sub_category=new";
// Creating a new non-ui thread task to download json data
DownloadTask downloadTask = new DownloadTask();
// Starting the download processt
downloadTask.execute(strUrl);
// Getting a reference to ListView of activity_main
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
// // TODO Auto-generated method stub
vibrator.vibrate(40);
LayoutInflater inflater=getLayoutInflater();
View view=inflater.inflate(R.layout.customtoast, (ViewGroup)findViewById(R.id.custom_toast_layout));
Toast toast=new Toast(getApplicationContext());
toast.setDuration(Toast.LENGTH_LONG);
toast.setGravity(Gravity.CENTER_HORIZONTAL, 0, 0);
toast.setView(view);
toast.show();
MainActivity.movie_Id= ((TextView)arg1.findViewById(R.id.tv_girdview_content_id)).getText().toString();
Log.i("Name is", MainActivity.movie_Id);
startActivity(new Intent(NewMovie.this,MovieDescription.class));
}
});
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
}
return data;
}
/** AsyncTask to download json data */
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
@Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
// The parsing of the xml data is done in a non-ui thread
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
// Start parsing xml data
listViewLoaderTask.execute(result);
}
}
/** AsyncTask to parse json data and load ListView */
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
// Doing the parsing of xml data in a non-ui thread
@Override
protected SimpleAdapter doInBackground(String... strJson) {
try{
jObject = new JSONObject(strJson[0]);
MovieParser countryJsonParser = new MovieParser();
countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("JSON Exception1",e.toString());
}
// Instantiating json parser class
MovieParser countryJsonParser = new MovieParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> countries = null;
try{
// Getting the parsed data as a List construct
countries = countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("Exception",e.toString());
}
// Keys used in Hashmap
String[] from = { "image","id","year","duration","name"};
// Ids of views in listview_layout
// int[] to = { R.id.iv_radio_data_image,R.id.tv_radio_data_id,R.id.tv_radio_data_like,R.id.tv_radio_data_rating,R.id.tv_radio_data_listner,R.id.tv_radio_data_radio_url,R.id.tv_radio_data_name};
int[] to = { R.id.iv_girdview_content_image,R.id.tv_girdview_content_id,R.id.tv_girdview_content_like,R.id.tv_girdview_content_listner,R.id.tv_girdview_content_name};
// Instantiating an adapter to store each items
// R.layout.listview_layout defines the layout of each item
adapter = new SimpleAdapter(getBaseContext(), countries, R.layout.grid_view_content, from, to);
return adapter;
// lv.setAdapter(new ListAdapter(getApplicationContext()));
}
/** Invoked by the Android on "doInBackground" is executed */
@Override
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
lv.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
//}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
@Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
String imgUrl = (String) hm[0].get("flag_path");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("image",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("image");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
adapter = (SimpleAdapter ) lv.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("image",path);
//lv.invalidateViews();
adapter.notifyDataSetChanged();
}
}
}
}
我是新手。我不知道在我的应用程序中使用lazyloader代码的位置。
我想在我使用lazyloader的应用程序中使用GridView。我想在gridview中显示加载所有项目的项目。
答案 0 :(得分：0)
使用以下代码为我工作。
Main.java
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.GridView;
public class Main extends Activity {
String mImagesPath;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mImagesPath = this.getFilesDir().getParent() + "/images/";
createImagesDir(mImagesPath);
copyImagesToStorage();
loadGridView();
}
/**
* Method handles the logic for setting the adapter for the gridview
*/
private void loadGridView(){
GridView lLazyGrid = (GridView) this.findViewById(R.id.gridview);
try {
LazyImageAdapter lLazyAdapter = new LazyImageAdapter(this.getApplicationContext(),
null,
mImagesPath);
lLazyGrid.setAdapter(lLazyAdapter);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Copy images from assets to storage
*/
private void copyImagesToStorage(){
AssetManager lAssetManager = getAssets();
String[] lFiles = null;
String lTag = "copyImageFail";
try {
// get all of the files in the assets directory
lFiles = lAssetManager.list("");
} catch (IOException e) {
Log.e(lTag, e.getMessage());
}
for(int i=0; i<lFiles.length; i++) {
// We have a file to copy
try {
// copy the file
copyFile(lFiles[i], mImagesPath + lFiles[i]);
} catch(Exception e) {
Log.e(lTag, e.getMessage());
}
}
}
/**
* Method copies the contents of one stream to another
* @param aIn stream to copy from
* @param aOut stream to copy to
* @throws IOException
*/
private void copyFile(String aIn, String aOut) throws IOException {
byte[] lBuffer = new byte[1024];
int lRead;
final int lOffset = 0;
// create an in and out stream
InputStream lIn = getAssets().open(aIn);
OutputStream lOut = new FileOutputStream(aOut);
// Copy contents while there is data
while((lRead = lIn.read(lBuffer)) != -1){
lOut.write(lBuffer, lOffset, lRead);
}
// clean up after our streams
lIn.close();
lIn = null;
lOut.flush();
lOut.close();
lOut = null;
}
/**
* Create the directory specified at aPath if it does not exist
* @param aPath directory to check for and create
*/
private void createImagesDir(String aPath){
File lDir = new File(aPath);
if(!lDir.exists()){
lDir.mkdir();
}
}
}
LazyImageAdapter.java
import java.io.File;
import android.content.Context;
import android.graphics.Bitmap;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.ViewSwitcher;
import com.bacaj.lazygridview.ImageLoader.ImageLoadListener;
public class LazyImageAdapter extends BaseAdapter implements ImageLoadListener {
private static final int PROGRESSBARINDEX = 0;
private static final int IMAGEVIEWINDEX = 1;
private Context mContext = null;
private OnClickListener mItemClickListener;
private Handler mHandler;
private ImageLoader mImageLoader = null;
private File mDirectory;
/**
* Lazy loading image adapter
* @param aContext
* @param lClickListener click listener to attach to each item
* @param lPath the path where the images are located
* @throws Exception when path can't be read from or is not a valid directory
*/
public LazyImageAdapter(
Context aContext,
OnClickListener lClickListener,
String lPath
) throws Exception {
mContext = aContext;
mItemClickListener = lClickListener;
mDirectory = new File(lPath);
// Do some error checking
if(!mDirectory.canRead()){
throw new Exception("Can't read this path");
}
else if(!mDirectory.isDirectory()){
throw new Exception("Path is a not a directory");
}
mImageLoader = new ImageLoader(this);
mImageLoader.start();
mHandler = new Handler();
}
@Override
protected void finalize() throws Throwable {
// TODO Auto-generated method stub
super.finalize();
// stop the thread we started
mImageLoader.stopThread();
}
public int getCount() {
return mDirectory.listFiles().length;
}
public Object getItem(int aPosition) {
String lPath = null;
File []lFiles = mDirectory.listFiles();
if(aPosition < lFiles.length){
lPath = mDirectory.listFiles()[aPosition].getAbsolutePath();
}
return lPath;
}
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return 0;
}
public View getView(final int aPosition, View aConvertView, ViewGroup parent) {
final ViewSwitcher lViewSwitcher;
String lPath = (String)getItem(aPosition);
// logic for conserving resources see google video on making your ui fast
// and responsive
if (null == aConvertView) {
lViewSwitcher = new ViewSwitcher(mContext);
lViewSwitcher.setPadding(8, 8, 8, 8);
ProgressBar lProgress = new ProgressBar(mContext);
lProgress.setLayoutParams(new ViewSwitcher.LayoutParams(80, 80));
lViewSwitcher.addView(lProgress);
ImageView lImage = new ImageView(mContext);
lImage.setLayoutParams(new ViewSwitcher.LayoutParams(100, 100));
lViewSwitcher.addView(lImage);
// attach the onclick listener
lViewSwitcher.setOnClickListener(mItemClickListener);
} else {
lViewSwitcher = (ViewSwitcher) aConvertView;
}
ViewTagInformation lTagHolder = (ViewTagInformation) lViewSwitcher
.getTag();
if (lTagHolder == null ||
!lTagHolder.aImagePath.equals(lPath)) {
// The Tagholder is null meaning this is a first time load
// or this view is being recycled with a different image
// Create a ViewTag to store information for later
ViewTagInformation lNewTag = new ViewTagInformation();
lNewTag.aImagePath = lPath;
lViewSwitcher.setTag(lNewTag);
// Grab the image view
// Have the progress bar display
// Then queue the image loading
ImageView lImageView = (ImageView) lViewSwitcher.getChildAt(1);
lViewSwitcher.setDisplayedChild(PROGRESSBARINDEX);
mImageLoader.queueImageLoad(lPath, lImageView, lViewSwitcher);
}
return lViewSwitcher;
}
public void handleImageLoaded(
final ViewSwitcher aViewSwitcher,
final ImageView aImageView,
final Bitmap aBitmap) {
// The enqueue the following in the UI thread
mHandler.post(new Runnable() {
public void run() {
// set the bitmap in the ImageView
aImageView.setImageBitmap(aBitmap);
// explicitly tell the view switcher to show the second view
aViewSwitcher.setDisplayedChild(IMAGEVIEWINDEX);
}
});
}
}
/**
* View holder pattern as described in google sample code
* we may want to add more attributes to this if the path was
* say being stored in a sqlite database
* @author bacaj
*/
class ViewTagInformation {
String aImagePath;
}
ImageLoader.java
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Looper;
import android.util.Log;
import android.widget.ImageView;
import android.widget.ViewSwitcher;
public class ImageLoader extends Thread {
public interface ImageLoadListener {
void handleImageLoaded(ViewSwitcher aViewSwitcher, ImageView aImageView, Bitmap aBitmap);
}
private static final String TAG = ImageLoader.class.getSimpleName();
ImageLoadListener mListener = null;
private Handler handler;
/**
* Image loader takes an object that extends ImageLoadListener
* @param lListener
*/
ImageLoader(ImageLoadListener lListener){
mListener = lListener;
}
@Override
public void run() {
try {
// preparing a looper on current thread
// the current thread is being detected implicitly
Looper.prepare();
// Looper gets attached to the current thread by default
handler = new Handler();
Looper.loop();
// Thread will start
} catch (Throwable t) {
Log.e(TAG, "ImageLoader halted due to a error: ", t);
}
}
/**
* Method stops the looper and thus the thread
*/
public synchronized void stopThread() {
// Use the handler to schedule a quit on the looper
handler.post(new Runnable() {
public void run() {
// This runs on the ImageLoader thread
Log.i(TAG, "DownloadThread loop quitting by request");
Looper.myLooper().quit();
}
});
}
/**
* Method queues the image at path to load
* Note that the actual loading takes place in the UI thread
* the ImageView and ViewSwitcher are just references for the
* UI thread.
* @param aPath - Path where the bitmap is located to load
* @param aImageView - The ImageView the UI thread will load
* @param aViewSwitcher - The ViewSwitcher that needs to display the imageview
*/
public synchronized void queueImageLoad(
final String aPath,
final ImageView aImageView,
final ViewSwitcher aViewSwitcher) {
// Wrap DownloadTask into another Runnable to track the statistics
handler.post(new Runnable() {
public void run() {
try {
synchronized (aImageView){
// make sure this thread is the only one performing activities on
// this imageview
BitmapFactory.Options lOptions = new BitmapFactory.Options();
lOptions.inSampleSize = 1;
Bitmap lBitmap = BitmapFactory.decodeFile(aPath, lOptions);
//aImage.setImageBitmap(lBitmap);
// Load the image here
signalUI(aViewSwitcher, aImageView, lBitmap);
}
}
catch(Exception e){
e.printStackTrace();
}
}
});
}
/**
* Method is called when the bitmap is loaded. The UI thread adds the bitmap to the imageview.
* @param aViewSwitcher - The ViewSwitcher that needs to display the imageview
* @param aImageView - The ImageView the UI thread will load
* @param aImage - The Bitmap that gets loaded into the ImageView
*/
private void signalUI(
ViewSwitcher aViewSwitcher,
ImageView aImageView,
Bitmap aImage){
if(mListener != null){
// we have an object that implements ImageLoadListener
mListener.handleImageLoaded(aViewSwitcher, aImageView, aImage);
}
}
}
希望它可以帮助你。
答案 1 :(得分：0)
在这里你可以理解：
示例：
Google上的搜索结果：android lazy loading images in a listview tutorial
答案 2 :(得分：0)
// Setting adapter for the listview
lv.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
这个代码就是问题所在，你正在启动数百个AsynTasks（线程），这会导致你提到的问题。
我建议您使用自定义网格适配器和任何其他Lazy加载库进行图像加载。