我刚刚开始学习Constraint Layout，它非常酷，我来讨论ConstraintSet并且卡住了。
我在开发人员文档中看到过ConstraintSet的一个例子，但是我无法理解，我已经实现了代码并且它正在工作但是我对这个概念并不清楚。
我想知道约束如何在不同的ConstraintSet中工作。
这就是我所做的：
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
android:id="@+id/act_main"
tools:context="com.reversebits.constraintanimdemo.MainActivity">
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:text="Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum"
app:layout_constraintEnd_toStartOf="@+id/guideline2"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginTop="8dp" />
<ImageView
android:id="@+id/imageView"
android:layout_width="0dp"
android:layout_height="160dp"
app:srcCompat="@mipmap/ic_launcher"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginEnd="8dp"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginTop="8dp"
app:layout_constraintStart_toStartOf="@+id/guideline2"
android:layout_marginStart="8dp" />
<android.support.constraint.Guideline
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/guideline"
android:orientation="vertical"
app:layout_constraintGuide_end="364dp" />
<android.support.constraint.Guideline
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/guideline2"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.5" />
<Button
android:onClick="foo"
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"/>
</android.support.constraint.ConstraintLayout>
clone.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="com.reversebits.constraintanimdemo.MainActivity">
<TextView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum"
app:layout_constraintStart_toStartOf="parent"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginStart="8dp"
android:id="@+id/textView"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginTop="8dp" />
<ImageView
android:id="@+id/imageView"
android:layout_width="0dp"
android:layout_height="160dp"
app:srcCompat="@mipmap/ic_launcher"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginEnd="8dp"
app:layout_constraintStart_toStartOf="parent"
android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="parent"
android:layout_marginBottom="8dp"
android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/textView" />
<Button
android:onClick="foo"
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"/>
</android.support.constraint.ConstraintLayout>
和MainActivity在这里：
import android.content.Context;
import android.os.Build;
import android.support.constraint.ConstraintLayout;
import android.support.constraint.ConstraintSet;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.transition.TransitionManager;
import android.view.View;
public class MainActivity extends AppCompatActivity {
ConstraintSet mConstraintSet1 = new ConstraintSet(); // create a Constraint Set
ConstraintSet mConstraintSet2 = new ConstraintSet(); // create a Constraint Set
ConstraintLayout mConstraintLayout; // cache the ConstraintLayout
boolean mOld = true;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Context context = this;
mConstraintSet2.clone(context, R.layout.clone); // get constraints from layout
setContentView(R.layout.activity_main);
mConstraintLayout = (ConstraintLayout) findViewById(R.id.act_main);
mConstraintSet1.clone(mConstraintLayout); // get constraints from ConstraintSet
}
public void foo(View view) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
TransitionManager.beginDelayedTransition(mConstraintLayout);
}
if (mOld = !mOld) {
mConstraintSet1.applyTo(mConstraintLayout); // set new constraints
} else {
mConstraintSet2.applyTo(mConstraintLayout); // set new constraints
}
}
}
答案 0 :(得分：0)
假设您想在单击按钮后移动某些视图。例如，您可以在activity_main.xml中定义布局，其中包含按钮。要获取主布局的ConstraintSet，请调用mConstraintSet1.clone(mConstraintLayout)。从辅助布局文件clone.xml克隆辅助布局（按钮单击后要显示的布局）。该布局包含具有相同ID的相同视图，但应用了其他约束。
用户点击按钮后，执行foo()。 foo()启动动画Transition，然后将所需的ConstraintSet应用于ConstraintLayout，从而导致视图移动。由于TransitionManager调用，动画会动画化。