在ConstraintLayout中填充一个ViewStub时，似乎导致生成的视图失去了所有约束。我猜我们可以使用ConstraintSet为填充的视图定义约束，但这有点违背了ViewStub的初衷。
有什么好的方法解决这个问题吗？
如何在ConstraintLayout中使用ViewStub？
25
- joharei
3个回答
64
有一个简单的解决方案：
在您的ViewStub中，让inflatedId属性与id保持相同，就像这样：
如下所示：
<ViewStub
android:id="@+id/pocket_view"
android:inflatedId="@+id/pocket_view"
android:layout="@layout/game_pocket_view"
android:layout_width="@dimen/game_pocket_max_width"
android:layout_height="@dimen/game_pocket_max_height"
app:layout_constraintLeft_toLeftOf="@id/avatar_view"
app:layout_constraintRight_toRightOf="@id/avatar_view"
app:layout_constraintTop_toTopOf="@id/avatar_view"
app:layout_constraintBottom_toBottomOf="@id/avatar_view"
/>
- banxi1988
2
1
我遇到了同样的问题，并找到了一个代码解决方法。只需迭代ConstraintLayout（ViewStub的父级）的每个子项，并将引用从存根id更改为已填充id。
我实现了自己的ViewStub，因为否则IDE预览无法正常工作。这是我正在使用的类。我从android项目中复制了代码，并更改了它以使IDE预览正确显示。
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.ViewStub;
import androidx.annotation.LayoutRes;
import androidx.annotation.Nullable;
import androidx.constraintlayout.widget.ConstraintHelper;
import androidx.constraintlayout.widget.ConstraintLayout;
import java.lang.ref.WeakReference;
import rocks.tbog.tblauncher.R;
/**
* Copy of {@link android.view.ViewStub} so that we can see something in the preview
*/
public final class ViewStubPreview extends View {
private int mLayoutResource;
private int mInflatedId;
private WeakReference<View> mInflatedViewRef = null;
private LayoutInflater mInflater = null;
private OnInflateListener mInflateListener = null;
public ViewStubPreview(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public ViewStubPreview(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ViewStubPreview,
defStyle, 0);
mInflatedId = a.getResourceId(R.styleable.ViewStubPreview_inflatedId, NO_ID);
mLayoutResource = a.getResourceId(R.styleable.ViewStubPreview_layout, 0);
setId(a.getResourceId(R.styleable.ViewStubPreview_id, NO_ID));
a.recycle();
if (!isInEditMode()) {
setVisibility(GONE);
setWillNotDraw(true);
}
}
/**
* Returns the id taken by the inflated view. If the inflated id is
* {@link View#NO_ID}, the inflated view keeps its original id.
*
* @return A positive integer used to identify the inflated view or
* {@link #NO_ID} if the inflated view should keep its id.
* @attr name android:inflatedId
* @see #setInflatedId(int)
*/
public int getInflatedId() {
return mInflatedId;
}
/**
* Defines the id taken by the inflated view. If the inflated id is
* {@link View#NO_ID}, the inflated view keeps its original id.
*
* @param inflatedId A positive integer used to identify the inflated view or
* {@link #NO_ID} if the inflated view should keep its id.
* @attr name android:inflatedId
* @see #getInflatedId()
*/
public void setInflatedId(int inflatedId) {
mInflatedId = inflatedId;
}
/**
* Returns the layout resource that will be used by {@link #setVisibility(int)} or
* {@link #inflate()} to replace this StubbedView
* in its parent by another view.
*
* @return The layout resource identifier used to inflate the new View.
* @attr name android:layout
* @see #setLayoutResource(int)
* @see #setVisibility(int)
* @see #inflate()
*/
public int getLayoutResource() {
return mLayoutResource;
}
/**
* Specifies the layout resource to inflate when this StubbedView becomes visible or invisible
* or when {@link #inflate()} is invoked. The View created by inflating the layout resource is
* used to replace this StubbedView in its parent.
*
* @param layoutResource A valid layout resource identifier (different from 0.)
* @attr name android:layout
* @see #getLayoutResource()
* @see #setVisibility(int)
* @see #inflate()
*/
public void setLayoutResource(int layoutResource) {
mLayoutResource = layoutResource;
}
/**
* Set {@link LayoutInflater} to use in {@link #inflate()}, or {@code null}
* to use the default.
*/
public void setLayoutInflater(LayoutInflater inflater) {
mInflater = inflater;
}
/**
* Get current {@link LayoutInflater} used in {@link #inflate()}.
*/
public LayoutInflater getLayoutInflater() {
return mInflater;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
if (isInEditMode()) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
return;
}
setMeasuredDimension(0, 0);
}
@Override
public void draw(Canvas canvas) {
if (isInEditMode())
super.draw(canvas);
}
@Override
protected void dispatchDraw(Canvas canvas) {
}
/**
* When visibility is set to {@link #VISIBLE} or {@link #INVISIBLE},
* {@link #inflate()} is invoked and this StubbedView is replaced in its parent
* by the inflated layout resource. After that calls to this function are passed
* through to the inflated view.
*
* @param visibility One of {@link #VISIBLE}, {@link #INVISIBLE}, or {@link #GONE}.
* @see #inflate()
*/
@Override
public void setVisibility(int visibility) {
if (mInflatedViewRef != null) {
View view = mInflatedViewRef.get();
if (view != null) {
view.setVisibility(visibility);
} else {
throw new IllegalStateException("setVisibility called on un-referenced view");
}
} else {
super.setVisibility(visibility);
if (visibility == VISIBLE || visibility == INVISIBLE) {
inflate();
}
}
}
/**
* Inflates the layout resource identified by {@link #getLayoutResource()}
* and replaces this StubbedView in its parent by the inflated layout resource.
*
* @return The inflated layout resource.
*/
public View inflate() {
final ViewParent viewParent = getParent();
if (viewParent instanceof ViewGroup) {
if (mLayoutResource != 0) {
final ViewGroup parent = (ViewGroup) viewParent;
final LayoutInflater factory;
if (mInflater != null) {
factory = mInflater;
} else {
factory = LayoutInflater.from(getContext());
}
final View view = factory.inflate(mLayoutResource, parent, false);
if (mInflatedId != NO_ID) {
view.setId(mInflatedId);
}
final int index = parent.indexOfChild(this);
parent.removeViewInLayout(this);
final ViewGroup.LayoutParams layoutParams = getLayoutParams();
if (layoutParams != null) {
parent.addView(view, index, layoutParams);
} else {
parent.addView(view, index);
}
// update parent ConstraintLayout constraints
if (parent instanceof ConstraintLayout)
updateConstraintsAfterStubInflate((ConstraintLayout) parent, getId(), view.getId());
mInflatedViewRef = new WeakReference<>(view);
if (mInflateListener != null) {
mInflateListener.onInflate(this, view);
}
return view;
} else {
throw new IllegalArgumentException("ViewStub must have a valid layoutResource");
}
} else {
throw new IllegalStateException("ViewStub must have a non-null ViewGroup viewParent");
}
}
/**
* Specifies the inflate listener to be notified after this ViewStub successfully
* inflated its layout resource.
*
* @param inflateListener The OnInflateListener to notify of successful inflation.
* @see android.view.ViewStub.OnInflateListener
*/
public void setOnInflateListener(OnInflateListener inflateListener) {
mInflateListener = inflateListener;
}
@Nullable
public static View inflateStub(@Nullable View view) {
return inflateStub(view, 0);
}
@Nullable
public static View inflateStub(@Nullable View view, @LayoutRes int layoutRes) {
if (view instanceof ViewStubPreview) {
if (layoutRes != 0)
((ViewStubPreview) view).setLayoutResource(layoutRes);
// ViewStubPreview already calls updateConstraintsAfterStubInflate
return ((ViewStubPreview) view).inflate();
}
if (!(view instanceof ViewStub))
return view;
ViewStub stub = (ViewStub) view;
int stubId = stub.getId();
// get parent before the call to inflate
ConstraintLayout constraintLayout = stub.getParent() instanceof ConstraintLayout ? (ConstraintLayout) stub.getParent() : null;
if (layoutRes != 0)
stub.setLayoutResource(layoutRes);
View inflatedView = stub.inflate();
int inflatedId = inflatedView.getId();
updateConstraintsAfterStubInflate(constraintLayout, stubId, inflatedId);
return inflatedView;
}
private static void updateConstraintsAfterStubInflate(@Nullable ConstraintLayout constraintLayout, int stubId, int inflatedId) {
if (inflatedId == View.NO_ID)
return;
// change parent ConstraintLayout constraints
if (constraintLayout != null && stubId != inflatedId) {
int childCount = constraintLayout.getChildCount();
for (int childIdx = 0; childIdx < childCount; childIdx += 1) {
View child = constraintLayout.getChildAt(childIdx);
if (child instanceof ConstraintHelper) {
// get a copy of the id list
int[] refIds = ((ConstraintHelper) child).getReferencedIds();
boolean changed = false;
// change constraint reference IDs
for (int idx = 0; idx < refIds.length; idx += 1) {
if (refIds[idx] == stubId) {
refIds[idx] = inflatedId;
changed = true;
}
}
if (changed)
((ConstraintHelper) child).setReferencedIds(refIds);
}
ConstraintLayout.LayoutParams params = (ConstraintLayout.LayoutParams) child.getLayoutParams();
if (changeConstraintLayoutParamsTarget(params, stubId, inflatedId))
child.setLayoutParams(params);
}
}
}
private static boolean changeConstraintLayoutParamsTarget(ConstraintLayout.LayoutParams params, int fromId, int toId) {
boolean changed = false;
if (params.leftToLeft == fromId) {
params.leftToLeft = toId;
changed = true;
}
if (params.leftToRight == fromId) {
params.leftToRight = toId;
changed = true;
}
if (params.rightToLeft == fromId) {
params.rightToLeft = toId;
changed = true;
}
if (params.rightToRight == fromId) {
params.rightToRight = toId;
changed = true;
}
if (params.topToTop == fromId) {
params.topToTop = toId;
changed = true;
}
if (params.topToBottom == fromId) {
params.topToBottom = toId;
changed = true;
}
if (params.bottomToTop == fromId) {
params.bottomToTop = toId;
changed = true;
}
if (params.bottomToBottom == fromId) {
params.bottomToBottom = toId;
changed = true;
}
if (params.baselineToBaseline == fromId) {
params.baselineToBaseline = toId;
changed = true;
}
if (params.baselineToTop == fromId) {
params.baselineToTop = toId;
changed = true;
}
if (params.circleConstraint == fromId) {
params.circleConstraint = toId;
changed = true;
}
if (params.startToEnd == fromId) {
params.startToEnd = toId;
changed = true;
}
if (params.startToStart == fromId) {
params.startToStart = toId;
changed = true;
}
if (params.endToStart == fromId) {
params.endToStart = toId;
changed = true;
}
if (params.endToEnd == fromId) {
params.endToEnd = toId;
changed = true;
}
return changed;
}
/**
* Listener used to receive a notification after a ViewStub has successfully
* inflated its layout resource.
*
* @see android.view.ViewStub#setOnInflateListener(android.view.ViewStub.OnInflateListener)
*/
public interface OnInflateListener {
/**
* Invoked after a ViewStub successfully inflated its layout resource.
* This method is invoked after the inflated view was added to the
* hierarchy but before the layout pass.
*
* @param stub The ViewStub that initiated the inflation.
* @param inflated The inflated View.
*/
void onInflate(ViewStubPreview stub, View inflated);
}
}
注意：静态方法inflateStub也适用于android.view.ViewStub。
- TBog
0
考虑不要使用相同的id和inflatedId，因为这可能导致未定义的行为和崩溃，例如：
java.lang.IllegalArgumentException: Wrong state class... This usually happens when two views of different type have the same id in the same hierarchy.（这种情况可能发生在旋转或从后台返回后恢复状态时，具体取决于您的膨胀位置。）
如果您不希望修改父ConstraintLayout的ConstraintSet，则有一种替代方案 - {{link1：androidx.costraintlayout.widget.Barrier}}
例如，假设您的视图是：
<ScrollView
android:id="@+id/some_scroll_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toTopOf="@+id/some_view_stub">
<ViewStub
android:id="@+id/some_view_stub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inflatedId="@+id/some_view"
android:layout="@layout/some_view_layout"
app:layout_constraintBottom_toBottomOf="parent" />
当视图存根被填充时，
some_scroll_view的约束将不再有效。我们可以这样引入一个
Barrier： <ScrollView
android:id="@+id/some_scroll_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toTopOf="@+id/some_barrier">
<androidx.constraintlayout.widget.Barrier
android:id="@+id/some_barrier"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:barrierDirection="top"
app:constraint_referenced_ids="some_view_stub,some_view" />
<ViewStub
android:id="@+id/some_view_stub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inflatedId="@+id/some_view"
android:layout="@layout/some_view_layout"
app:layout_constraintBottom_toBottomOf="parent" />
请注意，
app:constraint_referenced_ids 包括 ViewStub 的 id 和其 inflatedId。- BVB
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id是ViewSub的句柄，而inflatedId是代替它的结果布局的句柄。 - Shazbot