我在listview中水平添加项目，但如果我有单项，我希望它在水平方向中心。
我尝试了很多来自堆栈溢出的解决方案，但仍然有所帮助。
请帮忙。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:weightSum="10"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/noUser_layout"
android:orientation="vertical"
android:layout_weight="10"
android:visibility="gone"
android:gravity="center">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/noMessageLogo"
android:src="@mipmap/eapp_icon"/>
<TextView android:text="@string/loading_Message" android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:layout_marginLeft="25dp"
android:layout_marginRight="25dp"
android:id="@+id/noMessage"
android:gravity="center"
android:fontFamily="sans-serif"
android:textSize="16sp"
android:textStyle="bold"
android:textColor="@android:color/black" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:id="@+id/parentLayout"
android:orientation="vertical"
android:layout_weight="3.8"
android:gravity="center|center_horizontal">
<TextView android:text="Parent" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:id="@+id/parentText"
android:gravity="center"
android:fontFamily="sans-serif"
android:textSize="16sp"
android:textStyle="bold"
android:textColor="@android:color/holo_blue_dark" />
<android.support.v7.widget.RecyclerView
android:id="@+id/parentList"
android:layout_width="wrap_content"
android:layout_centerHorizontal="true"
android:layout_height="wrap_content"
/>
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content" android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2.5"
android:paddingTop="10dp"
android:paddingBottom="10dp"
android:id="@+id/contactLayout"
android:layout_centerHorizontal="true"
android:orientation="vertical">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="8dp"
android:id="@+id/userImage"
android:layout_gravity="center"
android:src="@drawable/user_icon" />
<TextView android:text="Contact Name" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:id="@+id/name"
android:fontFamily="sans-serif"
android:textSize="15sp"
android:textStyle="bold"
android:layout_gravity="left"
android:textColor="@android:color/black"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:id="@+id/childrenLayout"
android:layout_centerHorizontal="true"
android:layout_weight="3.8"
android:orientation="vertical"
android:gravity="center|center_horizontal">
<TextView android:text="Child" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/childText"
android:gravity="center"
android:layout_margin="10dp"
android:fontFamily="sans-serif"
android:textSize="16sp"
android:textStyle="bold"
android:textColor="@android:color/holo_blue_dark" />
<android.support.v7.widget.RecyclerView
android:id="@+id/childList"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center|center_horizontal" />
</LinearLayout>
</LinearLayout>
答案 0 :(得分：1)
我使用了窗口管理器来获取屏幕的总宽度，并用于设置回收视图。
以下布局管理器用于水平循环视图，即LinearLayoutManager
public class WrapHeightLinearLayoutManager extends LinearLayoutManager {
Context mContext;
public WrapHeightLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
mContext = context;
}
private int[] mMeasuredDimension = new int[2];
@Override
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state,
int widthSpec, int heightSpec) {
final int widthMode = View.MeasureSpec.getMode(widthSpec);
final int heightMode = View.MeasureSpec.getMode(heightSpec);
final int widthSize = View.MeasureSpec.getSize(widthSpec);
final int heightSize = View.MeasureSpec.getSize(heightSpec);
int width = 0;
int height = 0;
for (int i = 0; i < getItemCount(); i++) {
measureScrapChild(recycler, i,
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
mMeasuredDimension);
if (getOrientation() == HORIZONTAL) {
//width = width + mMeasuredDimension[0];
if (i == 0) {
WindowManager wm = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int widthWin = size.x;
int heightWin = size.y;
width = widthWin;
height = mMeasuredDimension[1];
}
} else {
height = height + mMeasuredDimension[1];
if (i == 0) {
width = mMeasuredDimension[0];
}
}
}
switch (widthMode) {
case View.MeasureSpec.EXACTLY:
width = widthSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
switch (heightMode) {
case View.MeasureSpec.EXACTLY:
height = heightSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
Logger.getInstanceLogger().printVerbose("WrapHeightLinearLayoutManager","width ==>"+width+" height==>"+height);
setMeasuredDimension(width, height);
}
private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
int heightSpec, int[] measuredDimension) {
View view = recycler.getViewForPosition(position);
if (view != null) {
RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
getPaddingLeft() + getPaddingRight(), p.width);
int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
getPaddingTop() + getPaddingBottom(), p.height);
view.measure(childWidthSpec, childHeightSpec);
measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
recycler.recycleView(view);
}
}
}
答案 1 :(得分：-1)
这个简单的example解决了我的问题：）
汇总代码在这里：
public class SpinnerWheelActivity extends Activity {
private static final int NUM_ITEMS = 3;
private static final String BUNDLE_LIST_PIXELS = "allPixels";
private float itemWidth;
private float padding;
private float firstItemWidth;
private float allPixels;
private int mLastPosition;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_spinner_wheel);
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
itemWidth = getResources().getDimension(R.dimen.item_width);
padding = (size.x - itemWidth) / 2;
firstItemWidth = getResources().getDimension(R.dimen.padding_item_width);
allPixels = 0;
final RecyclerView items = (RecyclerView) findViewById(R.id.item_list);
LinearLayoutManager shopItemslayoutManager = new LinearLayoutManager(getApplicationContext());
shopItemslayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
items.setLayoutManager(shopItemslayoutManager);
// to center item
items.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
synchronized (this) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
calculatePositionAndScroll(recyclerView);
}
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
allPixels += dx;
}
});
ExtraItemsAdapter adapter = new ExtraItemsAdapter(NUM_ITEMS);
items.setAdapter(adapter);
if (NUM_ITEMS > 0) // init position
scrollListToPosition(items, 0);
}
@Override
protected void onResume() {
super.onResume();
//final RecyclerView items = (RecyclerView) findViewById(R.id.item_list);
//ViewTreeObserver vto = items.getViewTreeObserver();
//vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
// @Override
// public void onGlobalLayout() {
// items.getViewTreeObserver().removeOnGlobalLayoutListener(this);
// calculatePositionAndScroll(items);
// }
//});
}
private void calculatePositionAndScroll(RecyclerView recyclerView) {
int expectedPosition = Math.round((allPixels + padding - firstItemWidth) / itemWidth);
// Special cases for the padding items
if (expectedPosition == -1) {
expectedPosition = 0;
} else if (expectedPosition >= recyclerView.getAdapter().getItemCount() - 2) {
expectedPosition--;
}
scrollListToPosition(recyclerView, expectedPosition);
}
private void scrollListToPosition(RecyclerView recyclerView, int expectedPosition) {
float targetScrollPos = expectedPosition * itemWidth + firstItemWidth - padding;
float missingPx = targetScrollPos - allPixels;
if (missingPx != 0) {
recyclerView.smoothScrollBy((int) missingPx, 0);
}
}
@Override
protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
allPixels = savedInstanceState.getFloat(BUNDLE_LIST_PIXELS);
}
@Override
protected void onSaveInstanceState(@NonNull Bundle outState) {
super.onSaveInstanceState(outState);
outState.putFloat(BUNDLE_LIST_PIXELS, allPixels);
}
/*---------- Adapters ----------*/
public class ExtraItemsAdapter extends RecyclerView.Adapter<ViewHolder> {
private static final int VIEW_TYPE_PADDING = 1;
private static final int VIEW_TYPE_ITEM = 2;
private final int mNumItems;
public ExtraItemsAdapter(int numItems) {
mNumItems = numItems;
}
@Override
public int getItemCount() {
return mNumItems + 2; // We have to add 2 paddings
}
@Override
public int getItemViewType(int position) {
if (position == 0 || position == getItemCount() - 1) {
return VIEW_TYPE_PADDING;
}
return VIEW_TYPE_ITEM;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
// create a new view
if (viewType == VIEW_TYPE_ITEM) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item, parent, false);
return new ViewHolder(v);
} else {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_padding, parent, false);
return new ViewHolder(v);
}
}
@Override
public void onBindViewHolder(ViewHolder holder, final int position) {
if (getItemViewType(position) == VIEW_TYPE_ITEM) {
// We bind the item to the view
holder.text.setText(String.valueOf(position));
}
}
}
/*---------- ViewHolders ----------*/
public class ViewHolder extends RecyclerView.ViewHolder {
TextView text;
public ViewHolder(View itemView) {
super(itemView);
text = (TextView) itemView.findViewById(R.id.item_text);
}
}
}