android-由于视图测量而导致的版面设计性能不佳？
作者：互联网
我遇到了性能问题,我认为这是由于对我的观点进行衡量所致.
我的布局是通过编程方式构建的,因此无法显示我的布局的xml.但是,这里有一些可能导致此问题的观点：
>一个用于包装所有内容的ScrollView(宽度：MATCH_PARENT,高度：MATCH_PARENT)
>包含所有不同内容部分的LinearLayout(宽度：MATCH_PARENT,高度：MATCH_PARENT,前一个视图的子级)
>两个异步填充的LinearListViews(LinearLayout)(宽度：MATCH_PARENT,高度：WRAP_CONTENT,上一个视图的子代)
当我填充LinearListView时,似乎只会出现此问题.添加视图似乎会触发View.measure被多次调用：
为什么多次调用View.measure？ LinearLayout的大小为MATH_PARENT,这意味着在添加子项时不必再次对其进行测量,对吗？
我不太确定如何防止这种情况的发生或如何调试问题.我尝试将LinearListView的可见性设置为GONE,直到添加了所有项目,但这并没有改变.
我希望我能提供足够的信息,以便有人指出正确的方向.
编辑#1(07/01)：
这是用于LinearListViews的适配器基类的某些部分：
public abstract class DataProviderAdapter<T> extends BaseAdapter
{
...
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
View row = convertView;
T item = getItem(position);
Log.d(TAG, "getView(): Position: " + position + ", ConvertView: "
+ (convertView == null ? "null" : convertView) + ", TotalCount: " + getCount());
if (row == null) {
row = buildRow(position);
markRowAsLoading(row);
}
if (item == null) {
if (convertView != null) {
markRowAsLoading(row);
}
int skip;
if (itemsRequestParams != null) {
int pageSize = itemsRequestParams.getTake();
// determine how many items to skip
skip = position - (position % pageSize);
}
else {
skip = 0;
}
// if the page isn't already being fetched
if (!pagesReceiving.contains(skip)) {
pagesReceiving.add(skip);
AsyncTaskUtil.executeMultiThreaded(new ReceiveItemsTask(), skip);
}
}
else {
Log.d(TAG, getClass().getSimpleName() + " - PrepareRow: " + getItemId(position)
+ ", Pos: " + position);
prepareRow(row, item, position);
}
return row;
}
protected void processDataResult(int skip, DataResult<T> result)
{
if (result instanceof GroupedDataResult<?>) {
GroupedDataResult<T> groupedResult = (GroupedDataResult<T>)result;
totalItemCount = groupedResult.getTotalGroupCount() + groupedResult.getTotalItemCount();
}
else {
totalItemCount = result.getTotalItemCount();
}
for (int i = 0; i < result.getItems().size(); i++) {
itemList.put(skip + i, result.getItems().get(i));
}
Log.d(TAG, "processDataResult(" + skip + ")");
notifyDataSetChanged();
}
static protected class CellHolder
{
public ProgressBar ProgressSpinner;
public List<android.widget.ImageView> Images;
public List<TextView> Labels;
private final HashMap<String, Object> _extras = new HashMap<String, Object>();
public void putExtra(String key, Object value)
{
_extras.put(key, value);
}
@SuppressWarnings("unchecked")
public <T> T getExtra(String key)
{
return _extras.containsKey(key) ? (T)_extras.get(key) : null;
}
}
...
private class ReceiveItemsTask extends AsyncTask<Integer, Void, DataResult<T>>
{
private int skip;
@Override
protected DataResult<T> doInBackground(Integer... params)
{
skip = params[0];
DataResult<T> items = getItems(skip);
Log.d(TAG, "doInBackground(" + skip + ")");
return items;
}
@Override
protected void onPostExecute(DataResult<T> result)
{
Log.d(TAG,
"onPostExecute("
+ (result == null ? "null" : result.getItems().size() + "/"
+ result.getTotalItemCount()) + ")");
if (result == null) {
return;
}
processDataResult(skip, result);
Log.d(TAG, "onPostExecute end");
}
}
}
编辑#2(07/01)：
我将RelativeLayout子类化,并覆盖了onMeasure,以便我可以记录正在测量哪些视图以及以什么顺序进行记录.
结果如下：
07-01 15:37:37.434: V/DefaultLayout(8172): DefaultLayout.onMeasure
07-01 15:37:37.434: V/DefaultLayout(8172): TabView.onMeasure
07-01 15:37:37.434: V/DefaultLayout(8172): ItemDetailsContainerView.onMeasure
07-01 15:37:37.438: V/DefaultLayout(8172): HeaderView.onMeasure
07-01 15:37:37.438: V/DefaultLayout(8172): ItemDetailsInfoFieldsLayout.onMeasure
07-01 15:37:37.438: V/DefaultLayout(8172): ItemReviewTableView.onMeasure
07-01 15:37:37.438: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.438: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.442: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.442: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.442: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.442: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.442: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.442: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.446: V/DefaultLayout(8172): ItemReviewTableView.onMeasure
07-01 15:37:37.446: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.446: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.446: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.446: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.450: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.450: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.450: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.450: V/DefaultLayout(8172): InfoFieldsLayout.onMeasure
07-01 15:37:37.450: V/DefaultLayout(8172): RelatedItemsTableView.onMeasure
07-01 15:37:37.454: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.458: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.462: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.466: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.470: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.474: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.478: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.478: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.482: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.482: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.486: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.486: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.490: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.490: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.494: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.494: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.498: V/DefaultLayout(8172): RelatedItemsTableView.onMeasure
07-01 15:37:37.498: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.498: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.502: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.502: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.506: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.506: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.510: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.510: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.514: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.514: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.518: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.518: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.522: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.522: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.526: V/DefaultLayout(8172): RatingView.onMeasure
07-01 15:37:37.526: V/DefaultLayout(8172): RatingView.onMeasure
...
此列表会持续一段时间.但是对我来说似乎很奇怪,它始于测量顶视图(DefaultLayout.onMeasure),然后还测量所有子视图(因此所有视图).它多次这样做！
是什么导致onMeasure在顶视图上被调用？
编辑#3(07/02)：
可能是notifyDataSetChanged()触发了顶视图的测量？
编辑#4(07/03)：
是的,似乎notifyDataSetChanged()触发了要测量的顶级视图(我能够在新的测试项目中重现此视图).并且由于我的适配器的工作方式,notifyDataSetChanged()被多次调用.
当我调用notifyDataSetChanged()时,测量所有视图的原因是什么？有什么方法可以防止这种情况发生吗？
解决方法:
您没有说相对布局的位置,这是列表的包装器吗？
根据罗曼·盖伊(Romain Guy)的说法,相对布局始终执行两次度量传递,因此这可能会导致某些速度降低.您是否甚至有嵌套的相对布局？显然,这可能具有指数的时间复杂度.
请参阅以下答案以供参考(以及指向他实际说过的Google io视频的链接)：
https://stackoverflow.com/a/17496262/1281144
标签：android-layout,android-view,android 来源： https://codeday.me/bug/20191030/1969997.html