我正在为 android 实现一个应用程序,并且在使用来自 Internet 的数据填充列表视图时遇到了内存问题。发生的一个奇怪错误似乎是由于缺乏行回收造成的,因为它通常应该发生,如Google I/O 2009所述。
当我在http://android.amberfog.com/?p=296运行代码时,一切运行顺利,行视图被回收并且 listView 得到了最佳使用。
我现在想在另一个包含更多内容的活动中使用 listView,因此仅扩展 ListActivity 的类是不够的。所以,我有一个具有以下代码的活动:
public class MultipleItemsList extends Activity {
private Context mContext;
private MyCustomAdapter mAdapter;
private ListView listView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mContext = this;
listView = (ListView) findViewById(R.id.listView);
mAdapter = new MyCustomAdapter(mContext);
for (int i = 1; i < 50; i++) {
mAdapter.addItem("item " + i);
}
listView.setAdapter(mAdapter);
}
}
main.xml 也没什么特别的:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"/>
<ListView
android:id="@+id/listView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
上一个链接提出的 ListActivity 如下:
public class MultipleItemsList extends ListActivity {
private Context mContext;
private MyCustomAdapter mAdapter;
private ListView listView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mContext = this;
mAdapter = new MyCustomAdapter(mContext);
for (int i = 1; i < 50; i++) {
mAdapter.addItem("item " + i);
}
setListAdapter(mAdapter);
}
}
在这两种情况下,适配器如下:
public class MyCustomAdapter extends BaseAdapter {
private static final int TYPE_ITEM = 0;
private static final int TYPE_SEPARATOR = 1;
private static final int TYPE_MAX_COUNT = TYPE_SEPARATOR + 1;
private ArrayList<String> mData = new ArrayList<String>();
private LayoutInflater mInflater;
private TreeSet<Integer> mSeparatorsSet = new TreeSet<Integer>();
public static class ViewHolder {
public TextView textView;
}
public MyCustomAdapter(Context context) {
mInflater = LayoutInflater.from(context);
}
public void addItem(final String item) {
mData.add(item);
notifyDataSetChanged();
}
public void addSeparatorItem(final String item) {
mData.add(item);
// save separator position
mSeparatorsSet.add(mData.size() - 1);
notifyDataSetChanged();
}
@Override
public int getItemViewType(int position) {
return mSeparatorsSet.contains(position) ? TYPE_SEPARATOR : TYPE_ITEM;
}
@Override
public int getViewTypeCount() {
return TYPE_MAX_COUNT;
}
@Override
public int getCount() {
return mData.size();
}
@Override
public String getItem(int position) {
return mData.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
int type = getItemViewType(position);
Log.d("myCA", "getView " + position + " " + convertView + " type = " + type);
if (convertView == null) {
holder = new ViewHolder();
switch (type) {
case TYPE_ITEM:
convertView = mInflater.inflate(R.layout.item1, null);
holder.textView = (TextView)convertView.findViewById(R.id.text);
break;
case TYPE_SEPARATOR:
convertView = mInflater.inflate(R.layout.item2, null);
holder.textView = (TextView)convertView.findViewById(R.id.textSeparator);
break;
}
convertView.setTag(holder);
} else {
holder = (ViewHolder)convertView.getTag();
}
holder.textView.setText(mData.get(position));
return convertView;
}
}
所以,我的问题是,为什么在 ListActivity 的第二种情况下,视图回收没有问题,而在 Activity 的实施中,回收被搞砸了?
Log显示,使用ListActivity时,一切都被正确回收:
07-13 10:14:25.277: DEBUG/myCA(2336): getView 0 null type = 0
07-13 10:14:25.277: DEBUG/myCA(2336): getView 1 null type = 0
07-13 10:14:25.277: DEBUG/myCA(2336): getView 2 null type = 0
07-13 10:14:25.277: DEBUG/myCA(2336): getView 3 null type = 0
07-13 10:14:25.287: DEBUG/myCA(2336): getView 4 null type = 0
07-13 10:14:25.287: DEBUG/myCA(2336): getView 5 null type = 0
07-13 10:14:27.887: DEBUG/myCA(2336): getView 6 null type = 0
07-13 10:14:28.047: DEBUG/myCA(2336): getView 7 android.widget.LinearLayout@40522c30 type = 0
07-13 10:14:28.267: DEBUG/myCA(2336): getView 8 android.widget.LinearLayout@405236b8 type = 0
...
...
...
在我的 Activity 实现中,我看到以下内容:
07-13 10:11:47.517: DEBUG/myCA(2296): getView 0 null type = 0
07-13 10:11:47.517: DEBUG/myCA(2296): getView 1 android.widget.LinearLayout@405221e8 type = 0
07-13 10:11:47.517: DEBUG/myCA(2296): getView 2 android.widget.LinearLayout@405221e8 type = 0
07-13 10:11:47.517: DEBUG/myCA(2296): getView 3 android.widget.LinearLayout@405221e8 type = 0
07-13 10:11:47.527: DEBUG/myCA(2296): getView 4 android.widget.LinearLayout@405221e8 type = 0
07-13 10:11:47.527: DEBUG/myCA(2296): getView 5 android.widget.LinearLayout@405221e8 type = 0
07-13 10:11:47.547: DEBUG/myCA(2296): getView 0 android.widget.LinearLayout@405221e8 type = 0
07-13 10:11:47.547: DEBUG/myCA(2296): getView 1 null type = 0
07-13 10:11:47.547: DEBUG/myCA(2296): getView 2 null type = 0
07-13 10:11:47.557: DEBUG/myCA(2296): getView 3 null type = 0
...
...
...
回收明显存在问题的地方。
当父活动只是一个简单的活动而不是 ListActivity 时,我是否遗漏了一些能让 listView 正常运行的东西?过去有没有人遇到过类似的事情?
谢谢你的时间。