这是我的代码。它在数据不足时加载更多数据。我想在加载更多数据时将页脚ProgressBar添加到GridView 。怎么做？我在StackOverflow上看过很多问题，但没有答案。
public class MainActivity extends Activity {
private static final String TAG = "MainActivity";
private final List<Integer> commonImageList = new ArrayList<Integer>();
private int index = 0;
private boolean isLoading = false;
private static final int NUM = 18;
private ImageAdapter adapter;
@Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Task task = new Task(mThumbIds, index);
task.setOnPostExecuteListener(new OnPostExecuteListener<List<Integer>>() {
@Override
public void onPostExecute(final List<Integer> result) {
System.out.println("RESULT: " + result);
if(result.isEmpty()) {
return;
}
// Store it.
commonImageList.addAll(result);
// Prepare gridView.
final GridView gridview = (GridView) findViewById(R.id.gridview);
adapter = new ImageAdapter(MainActivity.this, commonImageList);
gridview.setAdapter(adapter);
gridview.setOnScrollListener(new OnScrollListener() {
@Override
public void onScrollStateChanged(final AbsListView view, final int scrollState) {
}
@Override
public void onScroll(final AbsListView view, final int firstVisibleItem,
final int visibleItemCount, final int totalItemCount) {
System.out.println("firstVisibleItem: " + firstVisibleItem);
System.out.println("visibleItemCount: " + visibleItemCount);
System.out.println("totalItemCount: " + totalItemCount);
final boolean loadMore = (firstVisibleItem + visibleItemCount >= totalItemCount);
System.out.println("loadMore: " + loadMore);
System.out.println("isLoading: " + isLoading);
if(loadMore && !isLoading) {
// TODO Show footer here.
ShowLog.showLogInfo(TAG, "============= LOAD MORE =============");
// Get more images.
index = index + NUM;
final Task task = new Task(mThumbIds, index);
task.setOnPreExecuteListener(new OnPreExecuteListener() {
@Override
public void onPreExecute() {
isLoading = true;
}
});
task.setOnPostExecuteListener(new OnPostExecuteListener<List<Integer>>() {
@Override
public void onPostExecute(final List<Integer> result) {
System.out.println("RESULT222: " + result);
if(result.isEmpty()) {
return;
}
System.out.println("HIEU THONG MINH");
// Update common list.
commonImageList.addAll(result);
// Update adapter.
adapter.notifyDataSetChanged();
isLoading = false;
}
});
task.execute();
}
}
});
}
});
task.execute();
}
private class Task extends AbstractWorkerTask<Void, Void, List<Integer>> {
private final Integer []thumbs;
private final int index;
public Task(final Integer []thumbs, final int index) {
this.thumbs = thumbs;
this.index = index;
}
@Override
protected List<Integer> doInBackground(final Void... params) {
final List<Integer> list = new ArrayList<Integer>();
for(int i = index; i < index + NUM && i < thumbs.length; ++i) {
list.add(thumbs[i]);
}
return list;
}
}
public static class ImageAdapter extends BaseAdapter {
private final Context context;
private final List<Integer> imageList;
public ImageAdapter(final Context c, final List<Integer> imageList) {
context = c;
this.imageList = imageList;
}
@Override
public int getCount() {
return imageList.size();
}
@Override
public Object getItem(final int position) {
return null;
}
@Override
public long getItemId(final int position) {
return 0;
}
// create a new ImageView for each item referenced by the Adapter
@Override
public View getView(final int position, final View convertView, final ViewGroup parent) {
ImageView imageView;
if (convertView == null) { // if it's not recycled, initialize some attributes
imageView = new ImageView(context);
imageView.setLayoutParams(new GridView.LayoutParams(150, 150));
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setPadding(8, 8, 8, 8);
} else {
imageView = (ImageView) convertView;
}
imageView.setImageResource(imageList.get(position));
return imageView;
}
}
// references to our images
private static final Integer[] mThumbIds = {
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
};
}
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/gridview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:columnWidth="150dp"
android:numColumns="3"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp"
android:stretchMode="columnWidth"
android:gravity="center"
/>
答案 0 :(得分：3)
这里我添加了GridView中加载更多项目的逻辑
的 1。在Adapter的最后输入数据
public class MediaGridAdapter extends BaseAdapter {
private ArrayList<Media> list;
private final Media special = new Media("-1", "", "", "", "");
public MediaGridAdapter(Context context, int imageID, ArrayList<Media> array, int type) {
list = array;
if(list != null) {
list.add(special);
}
}
public void appendDataList(ArrayList<Media> appendedList, boolean isEnd) { //called in postExecute to append new data
//remove special element in original list
list.remove(list.size() - 1);
//append collection of media to list
list.addAll(appendedList);
//check to add special element
if(!isEnd) {
list.add(special);
}
}
}
<强> 2。在getView方法中：检查它是否是最后一个位置（是我们的假项目）为此返回特殊布局（进度条...）。
if(position == (list.size() - 1)) {
Context context = parent.getContext();
item = (RelativeLayout) LayoutInflater.from(context).inflate(R.layout.item_special_more, null);
item.setTag(MORE_BUTTON);
return item;
}
onItemClick检查标记中的最后一个标记，以启动getMoreAsyncTask
if (v.getTag().equals(MediaGridAdapter.MORE_BUTTON)) {
GetMoreItems task = new GetMoreItems();
task.execute(url);
return;
}
答案 1 :(得分：0)
通过在制作项目可见/消失时利用动态布局更改，我发现了一种更少侵入性的方法。为此，我使用了相对布局，但也可以使用其他东西。 这是xml布局：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ProgressBar
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/loader_view"
android:visibility="visible"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true"
android:layout_centerHorizontal="true"
android:padding="32dp" />
<GridView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/grid_view"
android:layout_toStartOf="@id/loader_view"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="false"
android:layout_above="@+id/loader_view"
android:numColumns="@integer/grid_view_column_count"
android:scrollbarStyle="insideOverlay"
android:scrollbars="none"
android:listSelector="@null"
android:smoothScrollbar="false"></GridView>
</RelativeLayout>
关于此的一些注释：
进度条显示在gridview下面，但您必须先在xml中定义它，因为GridView中有：android:layout_toStartOf="@id/loader_view"引用。
您可以增加进度条上的填充以使加载区域更大，例如与网格的行高匹配。
网格视图android:numColumns="@integer/grid_view_column_count"是来自资源的动态值，随时可以更改它。您可以在那里使用一个数字，但外部效果更好，因为您可以根据屏幕宽度设置值。
以下代码将转到Fragment的onCreateView：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.grid_and_loader_view, container, false);
GridView gridView = (GridView) view.findViewById(R.id.grid_view);
//store a class reference to the loader:
_loader = (ProgressBar) view.findViewById(R.id.loader_view);
//set up your grid adapter e.g.:
//_adapter = new GridImageAdapter(this.getActivity());
//gridView.setAdapter(_adapter);
return view;
}
您可以通过以下方式开始/停止片段加载：
public void startLoading() {
if(_loader != null) {
_loader.setVisibility(View.VISIBLE);
}
}
public void stopLoading() {
if(_loader != null) {
_loader.setVisibility(View.GONE);
}
}
我发现，更好的解决方案是控制适配器的加载行为， 所以我将片段作为可加载接口（可选）形式的参考传递给适配器，并从那里调用上面的start / stopLoading函数。