我正在使用 GridView 来显示许多图像的缩略图，因此用户可以选择其中任何一个，我将全屏显示该图像。 网格的每个项目仅由一个 ImageView 组成，图像是从远程服务器检索的。
当触摸某个项目时，将启动另一个 Activity 以全屏显示图像。
这里我用了Universal Image Loader 。在这里，我对 Gridview 使用相同的方式，如 this类是通用图像加载器的一部分。
我以为一切都很顺利，直到我注意到当我滚动屏幕时，某些项目正在重复并再次加载。
所以我将显示图像逻辑放在 convertview== null 部分中，所以现在每当我在网格中向下滚动然后返回时，项目都会更改其位置并被复制。项目 ImageView (缩略图)在很多项目中重复，但其实际内容不同，当我单击该项目时，我可以看到这一点。现在滚动速度比第一个代码太慢。
所以我的主要问题是
如果我使用第一个代码:
1)如果我使用第一个代码，那么当我向下或向上滚动时，图像(项目)会一次又一次地加载。
如果我使用第二个代码:
2)如果我使用第二个代码，则项目(图像缩略图)将显示重复并显示为其他图像的缩略图。 3)Gridview滚动太慢。
代码:1
public class ImageAdapter extends BaseAdapter {
ArrayList<GallaryImage> imageList = null;
private Context context;
private class ViewHolder {
public ImageView image;
public ProgressBar pb;
}
public ImageAdapter(final Context context,
final ArrayList<GallaryImage> imageAttributesList) {
this.imageList = imageAttributesList;
this.context = context;
}
@Override
public int getCount() {
return imageList.size();
}
@Override
public GallaryImage getItem(final int position) {
return imageList.get(position);
}
@Override
public long getItemId(final int position) {
return position;
}
@Override
public View getView(final int position, final View convertView,
final ViewGroup parent) {
View view = convertView;
ViewHolder holder = null;
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater
.inflate(R.layout.item_grid_image, parent, false);
holder = new ViewHolder();
holder.pb = (ProgressBar) view.findViewById(R.id.pb_grid_image);
holder.image = (ImageView) view.findViewById(R.id.grid_image);
view.setTag(holder);
} else {
holder = (ViewHolder) view.getTag();
}
display(holder.image, imageList.get(position).mImageUrl, holder.pb);
return view;
}
/**
* @param img
* @param url
* @param spinner
*/
public void display(ImageView img, String url, final ProgressBar spinner) {
imageLoader.displayImage(url, img, options,
new ImageLoadingListener() {
@Override
public void onLoadingStarted(String imageUri, View view) {
spinner.setVisibility(View.VISIBLE);
}
@Override
public void onLoadingFailed(String imageUri, View view,
FailReason failReason) {
spinner.setVisibility(View.GONE);
}
@Override
public void onLoadingComplete(String imageUri,
View view, Bitmap loadedImage) {
spinner.setVisibility(View.GONE);
}
@Override
public void onLoadingCancelled(String imageUri,
View view) {
}
});
}
/**
* @param updateData
*/
public void updatedData(ArrayList<GallaryImage> imgList) {
this.imageList = imgList;
notifyDataSetChanged();
}
}
代码:2
private static final String TAG = "[Photography: ImageGridActivity]";
private DisplayImageOptions options;
private GridView mGridView = null;
ArrayList<GallaryImage> mGridViewImagesList;
private ImageAdapter mImageAdapter = null;
private String mImageUrl = null;
private String mGallaryTitle = null;
@Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_grid);
options = new DisplayImageOptions.Builder()
.showImageOnFail(R.drawable.ic_error)
.showStubImage(R.drawable.photo_default).cacheOnDisc()
.bitmapConfig(Bitmap.Config.RGB_565).build();
final Bundle bundle = getIntent().getExtras();
if (bundle != null) {
mImageUrl = bundle.getString(Constants.GALLARY_FETCH_URL);
mGallaryTitle = bundle.getString(Constants.GALLARY_TYPE);
if (mGallaryTitle != null) {
Locale loc = Locale.getDefault();
TextView tvTitleText = (TextView) findViewById(R.id.tv_title_bar_text);
tvTitleText.setText(mGallaryTitle.toUpperCase(loc));
}
mGridView = (GridView) findViewById(R.id.gridview);
mGridViewImagesList = Utility.getImagesList(mImageUrl,
ImageGridActivity.this);
if (mGridViewImagesList != null && !mGridViewImagesList.isEmpty()) {
mImageAdapter = new ImageAdapter(ImageGridActivity.this,
mGridViewImagesList);
((GridView) mGridView).setAdapter(mImageAdapter);
} else {
// did refresh after the previous images are loaded in the
// gridview.
if (Utility.checkConnection(ImageGridActivity.this)) {
Log.i(TAG,
"Wifi/Internet Connection found , have to parse the xml");
final FetchImagesAsyncTaskFeed asyncTask = new FetchImagesAsyncTaskFeed(
true);
asyncTask.execute(mImageUrl);
}
}
mGridView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(final AdapterView<?> parent,
final View view, final int position, final long id) {
if (mGridViewImagesList != null
&& !mGridViewImagesList.isEmpty()) {
startImagePagerActivity(mGridViewImagesList, position);
} else {
Log.d(TAG, "There is no image about this grid image");
}
}
});
}
}
/**
* back button key event
*/
private void goBack() {
finish();
// overridePendingTransition(R.anim.slide_in_right,
// R.anim.slide_out_right);
}
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
goBack();
return true;
}
return super.onKeyUp(keyCode, event);
}
/**
* @param position
*/
private void startImagePagerActivity(
final ArrayList<GallaryImage> mImageAttributesList,
final int position) {
String[] urls = new String[mImageAttributesList.size()];
final Intent intent = new Intent(this, ImagePagerActivity.class);
intent.putExtra(Constants.GALLARY_IMAGE_POSITION_BUNDLE_KEY, position);
for (int i = 0; i < mImageAttributesList.size(); i++) {
urls[i] = mImageAttributesList.get(i).mImageUrl;
}
intent.putExtra(Constants.GALLARY_IMAGES_IMAGE_BUNDLE_KEY, urls);
startActivity(intent);
}
public class ImageAdapter extends BaseAdapter {
ArrayList<GallaryImage> imageList = null;
private class ViewHolder {
public ImageView image;
public ProgressBar pb;
}
public ImageAdapter(final Context context,
final ArrayList<GallaryImage> imageAttributesList) {
this.imageList = imageAttributesList;
}
@Override
public int getCount() {
return imageList.size();
}
@Override
public GallaryImage getItem(final int position) {
return imageList.get(position);
}
@Override
public long getItemId(final int position) {
return position;
}
@Override
public View getView(final int position, final View convertView,
final ViewGroup parent) {
View view = convertView;
final ViewHolder holder;
if (convertView == null) {
view = getLayoutInflater().inflate(R.layout.item_grid_image,
parent, false);
holder = new ViewHolder();
holder.pb = (ProgressBar) view.findViewById(R.id.pb_grid_image);
holder.image = (ImageView) view.findViewById(R.id.grid_image);
view.setTag(holder);
display(holder.image, imageList.get(position).mImageUrl, holder.pb);
} else {
holder = (ViewHolder) view.getTag();
}
return view;
}
/**
* @param img
* @param url
* @param spinner
*/
public void display(ImageView img, String url, final ProgressBar spinner) {
imageLoader.displayImage(url, img, options,
new ImageLoadingListener() {
@Override
public void onLoadingStarted(String imageUri, View view) {
spinner.setVisibility(View.VISIBLE);
}
@Override
public void onLoadingFailed(String imageUri, View view,
FailReason failReason) {
spinner.setVisibility(View.GONE);
}
@Override
public void onLoadingComplete(String imageUri,
View view, Bitmap loadedImage) {
spinner.setVisibility(View.GONE);
}
@Override
public void onLoadingCancelled(String imageUri,
View view) {
}
});
}
/**
* @param updateData
*/
public void updatedData(ArrayList<GallaryImage> imgList) {
this.imageList = imgList;
notifyDataSetChanged();
}
}
/**
* @author
*
*/
private class FetchImagesAsyncTaskFeed extends
AsyncTask<String, Void, String> {
ProgressBar progressbar = null;
boolean showProgress = false;
public FetchImagesAsyncTaskFeed(boolean showProgress) {
this.showProgress = showProgress;
}
@Override
protected void onPreExecute() {
if (showProgress) {
progressbar = (ProgressBar) ImageGridActivity.this
.findViewById(R.id.gv_progressBar);
progressbar.setVisibility(View.VISIBLE);
}
}
@Override
protected String doInBackground(final String... urls) {
try {
final String imageUrl = urls[0];
final GridViewImagesXMLHandler mGallaryXMLHandler = new GridViewImagesXMLHandler();
mGridViewImagesList = mGallaryXMLHandler.getImages(imageUrl);
if (mGridViewImagesList != null
&& !mGridViewImagesList.isEmpty()) {
Utility.setImagesInfromation(imageUrl, mGridViewImagesList,
ImageGridActivity.this);
}
} catch (final Exception e) {
Log.e(TAG, "Exception in fetch images from the url", e);
}
return null;
}
@Override
protected void onPostExecute(final String result) {
if (mGridViewImagesList != null && !mGridViewImagesList.isEmpty()) {
if (mImageAdapter != null) {
mImageAdapter.updatedData(mGridViewImagesList);
// mPullRefreshGridView.onRefreshComplete();
} else {
mImageAdapter = new ImageAdapter(ImageGridActivity.this,
mGridViewImagesList);
((GridView) mGridView).setAdapter(mImageAdapter);
}
}
// mPullRefreshGridView.onRefreshComplete();
if (progressbar != null) {
progressbar.setVisibility(View.GONE);
}
}
}
GridView XML 文件
<GridView
android:id="@+id/gridview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="@id/title_bar"
android:alwaysDrawnWithCache="true"
android:gravity="center"
android:horizontalSpacing="4dip"
android:numColumns="4"
android:scrollingCache="true"
android:smoothScrollbar="true"
android:stretchMode="columnWidth"
android:verticalSpacing="4dip" />
请帮我解决这个问题。感谢您的帮助。
谢谢
最佳答案
因为我们每次进入getView()时都会设置ImageView的背景。每次当一个项目对用户可见时(当您滚动时发生)，getView() 都会调用。 由于 BaseAdapter 回收 View ，因此我们被迫在 if 和 else 条件之后设置数据。将所有图像保存在一个 DiskLruCache中 更快地加载它们并检查它是否存在，然后从那里显示，否则下载它并将其添加到 DiskLruCache
关于android - GridView 内的项目在上下滚动时再次加载，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16556242/