android - グリッドビューにレイジーローダーを追加するにはどうすればよいですか?

Question

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(); 

            }
        }

    }
}

私はこれが初めてです。lazyloaderアプリケーションでコードを使用する場所がわかりません。

lazyloaderを使用しているアプリケーションで使用したいGridView。グリッドビューにすべてのアイテムを読み込んでアイテムを表示したい。

Answer 1

ここで理解できます：

スレッド プール スレッドでのコードの実行

ThreadPoolExecutor

AsyncTask の仕組み

例：

例 1

例 2

例 3

Google での結果:リストビュー チュートリアルでの android 遅延読み込み画像

Answer 2

            // 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);

        }

このコードが問題です。あなたが言及した問題を引き起こしている何百もの AsynTasks (スレッド) を開始しています。

画像の読み込みにはカスタム グリッド アダプターとその他の遅延読み込みライブラリを使用することをお勧めします。

カスタム グリッド アダプタ

ListView での画像の遅延読み込み

Answer 3

次のコードを使用してください。

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);
        }
    }

}

お役に立てば幸いです。