Android ListView小部件异步图像加载

Question

我想制作一个Android列表小部件，并且工作正常，但速度很慢，因为包含imgages并且图像加载非常慢。 我想要一个异步图像加载，但这不起作用。

图像异步加载类：

public class LoadBitmap extends AsyncTask<String, Void, Bitmap> {
    private RemoteViews mViews;
    public LoadBitmap(RemoteViews views){
        this.mViews = views;
    }

    @Override
    protected Bitmap doInBackground(String... params) {
        try {
            return decodeSampledBitmapFromResource(params[0], 1080, 1920);
            //NOTE:  it is not thread-safe to set the ImageView from inside this method.  It must be done in onPostExecute()
        } catch (Exception e) {
            Log.e("ImageDownload", "Download failed: " + e.getMessage());
        }
        return null;
    }
    @Override
    public void onPostExecute(Bitmap bitmap){
        super.onPostExecute(bitmap);
        if(bitmap != null) {
            mViews.setImageViewBitmap(R.id.widget_image, bitmap);
        }

    }
    private Bitmap decodeSampledBitmapFromResource(String path, int reqWidth, int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        options.inSampleSize = 4;
        BitmapFactory.decodeFile(path);
        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeFile(path, options);
    }

    private int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            final int halfHeight = height / 2;
            final int halfWidth = width / 2;
            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) >= reqHeight
                    && (halfWidth / inSampleSize) >= reqWidth) {
                inSampleSize *= 2;
            }
        }
        return inSampleSize;
    }
}

使用ListWidgetFactory类创建ListView项：

public class ListWidgetFactory implements RemoteViewsService.RemoteViewsFactory {
    private ArrayList<Note> mNotes;
    private Context mContext = null;
    private SimpleDateFormat mDateFormat;
    private Colors mColor;
    private int labelID;

    public ListWidgetFactory(Context context, Intent intent) {
        this.mContext = context;
        //int mAppWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID);
        labelID = intent.getIntExtra(ListAppWidget.LIST_WIDGET_LABEL_ID, -1);
        mNotes = new DatabaseManager(context).getSortedNotes(0, 0, labelID);
        mColor = new Colors(context);
        mDateFormat = new SimpleDateFormat(TIME_FORMAT, Locale.getDefault());
    }

    @Override
    public void onCreate() {
        // no-op
    }

    @Override
    public void onDestroy() {
        // no-op
    }

    @Override
    public int getCount() {
        return (mNotes.size());
    }

    @Override
    public RemoteViews getViewAt(int position) {
        RemoteViews card = new RemoteViews(mContext.getPackageName(), R.layout.item_widget_note);
        if(mNotes != null && position < mNotes.size()) {

            Note note = mNotes.get(position);

            card.setInt(R.id.widget_card, "setBackgroundColor", mColor.getCardBackgroundColor(note.getBgColor()));

            if (!note.getTitle().isEmpty()) {
                card.setViewVisibility(R.id.widget_title, VISIBLE);
                card.setTextViewText(R.id.widget_title, note.getTitle());
                card.setTextColor(R.id.widget_title, mColor.getPrimaryTextColor(note.getTextColor()));

            } else {
                card.setViewVisibility(R.id.widget_title, GONE);
            }

            if (!note.getText().getText().isEmpty()) {
                card.setViewVisibility(R.id.widget_content, VISIBLE);
                card.setTextViewText(R.id.widget_content, note.getText().getText());
                card.setTextColor(R.id.widget_content, mColor.getSecondaryTextColor(note.getTextColor()));

            } else {
                card.setViewVisibility(R.id.widget_content, GONE);
            }
            if (!note.getImagesList().getList().isEmpty()) {
                card.setViewVisibility(R.id.widget_image, VISIBLE);
                /*Bitmap bitmap= BitmapFactory.decodeFile(note.getImagesList().getElement(0).getSrc().split(":")[1]);
                if (bitmap != null){
                    card.setImageViewBitmap(R.id.widget_image, bitmap);
                }*/
                new LoadBitmap(card).execute(note.getImagesList().getElement(0).getSrc().split(":")[1]);

            } else {
                card.setViewVisibility(R.id.widget_image, GONE);
            }

            if (!note.getRecord().getText().isEmpty()) {
                card.setViewVisibility(R.id.widget_record, VISIBLE);
                String recDate = note.getRecord().getText().split("REC_")[1];
                card.setTextViewText(R.id.widget_record, recDate.substring(0, 4) + "." + recDate.substring(4, 6) + "." + recDate.substring(6, 8));
                card.setTextColor(R.id.widget_record, mColor.getSecondaryTextColor(note.getTextColor()));

            } else {
                card.setViewVisibility(R.id.widget_record, GONE);
            }


            if (note.getList() != null && !note.getList().getList().isEmpty()) {
                card.setViewVisibility(R.id.widget_list, VISIBLE);
                card.removeAllViews(R.id.widget_list);
                int db = 0;
                ArrayList<NoteChecked> chList = note.getList().getList();

                for (int i = 0; i < chList.size() && db < 6; ++i) {
                    if (!chList.get(i).getChecked()) {
                        RemoteViews listElement = new RemoteViews(mContext.getPackageName(), R.layout.list_group);
                        listElement.setTextViewText(R.id.list_title, chList.get(i).getLabel());
                        listElement.setTextColor(R.id.list_title, mColor.getSecondaryTextColor(note.getTextColor()));
                        listElement.setTextViewCompoundDrawablesRelative(R.id.list_title, R.drawable.ic_check_box_unchecked_grey_16dp, 0, 0, 0);
                        card.addView(R.id.widget_list, listElement);
                        ++db;
                    }
                }
                for (int i = 0; i < chList.size() && db < 6; ++i) {
                    if (chList.get(i).getChecked()) {
                        RemoteViews listElement = new RemoteViews(mContext.getPackageName(), R.layout.list_group);
                        listElement.setTextViewText(R.id.list_title, chList.get(i).getLabel());
                        listElement.setTextColor(R.id.list_title, mColor.getSecondaryTextColor(note.getTextColor()));
                        listElement.setTextViewCompoundDrawablesRelative(R.id.list_title, R.drawable.ic_check_box_grey_16dp, 0, 0, 0);
                        card.addView(R.id.widget_list, listElement);
                        ++db;
                    }
                }
            } else {
                card.setViewVisibility(R.id.widget_list, GONE);
            }
            if (note.getImagesList().getSize() > 0) {
                card.setViewVisibility(R.id.widget_image, VISIBLE);

            } else {
                card.setViewVisibility(R.id.widget_image, GONE);
            }
            try {
                if (note.getReminder().charAt(0) == 'T') {
                    card.setViewVisibility(R.id.widget_time, VISIBLE);
                    card.setTextViewText(R.id.widget_time, mDateFormat.format(DatabaseManager.mFormat.parse(note.getReminder().substring(1))));
                    card.setTextColor(R.id.widget_time, mColor.getSecondaryTextColor(note.getTextColor()));
                } else {
                    card.setViewVisibility(R.id.widget_time, GONE);
                }
            } catch (ParseException e) {
                e.printStackTrace();
            }

            Intent i = new Intent();
            i.putExtra(ListAppWidget.EXTRA_WORD, mNotes.get(position).getID());
            card.setOnClickFillInIntent(R.id.widget_card, i);
        }
        return (card);
    }

    @Override
    public RemoteViews getLoadingView() {
        return (null);
    }

    @Override
    public int getViewTypeCount() {
        return (1);
    }

    @Override
    public long getItemId(int position) {
        return (position);
    }

    @Override
    public boolean hasStableIds() {
        return (true);
    }

    @Override
    public void onDataSetChanged() {
        mNotes = new DatabaseManager(mContext).getSortedNotes(0, 0, labelID);
    }
}

Answer 1

您应该使用Picasso 。 这是一个功能强大的Android库。 您无需下载图像，只需将链接传递到lib，如下所示：

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);