我遇到了一个问题，需要通过编程的方式向ConstraintLayout中添加视图，并设置布局所需的所有约束条件。
目前我的代码无法正常工作：
ConstraintLayout layout = (ConstraintLayout) findViewById(R.id.mainConstraint);
ConstraintSet set = new ConstraintSet();
set.clone(layout);
ImageView view = new ImageView(this);
layout.addView(view,0);
set.connect(view.getId(), ConstraintSet.TOP, layout.getId(), ConstraintSet.TOP, 60);
set.applyTo(layout);
ImageView 在布局上甚至都没有出现。当添加到 RelativeLayout 时，它就能正常工作。我认为在添加ImageView后，你应该克隆布局。
ConstraintLayout layout = (ConstraintLayout)findViewById(R.id.mainConstraint);
ConstraintSet set = new ConstraintSet();
ImageView view = new ImageView(this);
view.setId(View.generateViewId()); // cannot set id after add
layout.addView(view,0);
set.clone(layout);
set.connect(view.getId(), ConstraintSet.TOP, layout.getId(), ConstraintSet.TOP, 60);
set.applyTo(layout); // apply to layout
将如何动态向使用XML创建的视图添加元素与https://dev59.com/d1kS5IYBdhLWcg3wKzqq#40527407合并。
我发现了一个“更简单”的解决方案，这对于添加多个一致的视图非常有效，它使用 Viewbinding 和 ViewModel。
在这种情况下，我正在创建一个标题文本视图和一个RecyclerView [有适用于此的库，但是我发现通过这样做能够获得更多的控制权]。
步骤1,2
<?xml version="1.0" encoding="utf-8"?>
<androidx.core.widget.NestedScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.hometab.HomeFragment">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="@+id/constraint_parent"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- otherviews here -->
<LinearLayout
android:id="@+id/dynamic_linear_layout"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginTop="@dimen/margin_large"
android:orientation="vertical"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/curated_recycler" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.core.widget.NestedScrollView>
第三步
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/dynamic_constraint"
xmlns:app="http://schemas.android.com/apk/res-auto">
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="@dimen/margin_large"
app:layout_constraintStart_toStartOf="parent" />
<View
android:id="@+id/title_view"
android:layout_width="0dp"
android:layout_height="40dp"
android:layout_gravity="center"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/shop_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/diary"
android:textAppearance="@style/TextAppearance.AppCompat.Medium"
android:textColor="@android:color/black"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/title_view"
app:layout_constraintStart_toStartOf="@id/guideline"
app:layout_constraintTop_toTopOf="@+id/title_view" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/shop_recycler"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:clipToPadding="false"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="@id/guideline"
app:layout_constraintTop_toBottomOf="@+id/title_view" />
</androidx.constraintlayout.widget.ConstraintLayout>
步骤四、五
binding = FragmentHomeBinding.inflate(getLayoutInflater());
ShopViewModel shopViewModel = new ViewModelProvider(this).get(ShopViewModel.class);
shopViewModel.getAllShops(false).observe(getViewLifecycleOwner(), shopEntities -> {
List<ConstraintLayout> shopConstraints = new ArrayList<>();
for (ShopEntity shopEntity : shopEntities) {
// get an instance of the dynamic_view.xml
DynamicViewBinding dynamicViewBinding = DynamicViewBinding.inflate(getLayoutInflater());
// add text view content
dynamicViewBinding.shopName.setText(shopEntity.getName());
// initialize the recycler layout adapter
dynamicViewBinding.shopRecycler.setLayoutManager(new ProductCardLayoutManager(getContext(), 1,
GridLayoutManager.HORIZONTAL, false, 80));
// get all products and add them to recycler view
productViewModel.getAllProductsByShop(shopEntity.getShopId(), 10).observe(getViewLifecycleOwner(), productEntities ->
dynamicViewBinding.shopRecycler.setAdapter(new ProductAdapter(getActivity(), productEntities)));
// attach dynamic view to list of dynamic constraint layouts
shopConstraints.add(dynamicViewBinding.getRoot());
}
// remove all previous views from the linear layout
binding.dynamicLinearLayout.removeAllViews();
// add the new views
for (ConstraintLayout shopConstraint : shopConstraints) {
binding.dynamicLinearLayout.addView(shopConstraint);
}
});
MotionLayout比较棘手，因为它具有多个ConstraintSets，所以需要特殊处理。如果您使用针对ConstraintLayout的解决方案，由于某种原因，它会将您的视图定位在右下角的某个位置。在MotionLayout中添加视图的正确方法是使用updateState而不是applyTo：
/* ...up until this point the steps are the same: create constraint set,
set view's id, clone, connect, etc. */
layout.updateState(R.id.start, set)
end ConstraintSet，即R.id.end），请使用专用的cloneConstraintSet方法并设置视图的大小：// Clone the constraint set using MotionLayout's `cloneConstraintSet`
val setEnd = layout.cloneConstraintSet(R.id.end)
// Set the view's width and height
setEnd.constrainWidth(view.id, ConstraintLayout.LayoutParams.WRAP_CONTENT)
setEnd.constrainHeight(view.id, ConstraintLayout.LayoutParams.WRAP_CONTENT)
// Update state
layout.updateState(R.id.end, setEnd)
val view = ImageView(this)
view.layoutParams = ConstraintLayout.LayoutParams(
ConstraintLayout.LayoutParams.WRAP_CONTENT,
ConstraintLayout.LayoutParams.WRAP_CONTENT
).apply {
topToTop = R.id.mainConstraint
topMargin = 60
}
val layout = findViewById<ConstraintLayout>(R.id.mainConstraint)
layout.addView(view)
ConstraintLayout.LayoutParams layoutParams = new ConstraintLayout.LayoutParams(
ConstraintLayout.LayoutParams.WRAP_CONTENT,
ConstraintLayout.LayoutParams.WRAP_CONTENT
);
layoutParams.topToTop = R.id.mainConstraint;
layoutParams.topMargin = 60;
ImageView view = new ImageView(this);
view.setLayoutParams(layoutParams);
ConstraintLayout layout = findViewById(R.id.mainConstraint);
layout.addView(view);
view.layoutParams = (tv.layoutParams as ConstraintLayout.LayoutParams).apply {
topMargin = 120
}
ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) view.getLayoutParams();
layoutParams.topMargin = 120;
view.setLayoutParams(layoutParams);