解决ViewStub约束布局 约束失效的问题
1.背景
在项目中进行性能优化或包体积控制的时候，就要进行xml或布局优化。
通常我们进行布局优化或xml加载优化的时候，就不得不提到到的几个标签merge、include、ViewStub，这几个标签作用不做赘述，重点讲一下本期的ViewStub；
ViewStub使用场景是，需要复用layout但第一时间用不到，使用ViewStub做延迟加载。其原理特性就是：将目标layout引入后，替换自己，并将自己的属性LayoutParams设置给目标View/layout
ViewStub在使用的时候，有两种方式：
- 在在xml中通过
layout属性引入目标layout； - 或者在代码中动态使用
setLayoutResource注入；
最后在代码调用ViewStub.inflate()或ViewStub.setVisibility(View.VISIBLE)使引入的布局替换ViewStub。
2.问题
上面使用方式没有任何问题，使用起来也非常快捷方便，但问题也随之而来。
-
一定要有一个layout
ViewStub引入布局，一定要有一个额外的Layout，即使是Layout里面只有一个View，也需要单独为它提供一个Layout； -
它只能引入Layout
有时候我们在代码中，需要动态的添加一个View，如果ViewGroup比较简单例如线性布局或者FrameLayout还好收，但是复杂的View，相对布局就需要动态设置Rule，而约束布局就相对来说比较复杂了，不是太了解约束布局动态更改约束规则的朋友就头疼了（我是自己研究了一下午才完全搞明白的），需要动态的加好几行代码控制约束，碰到View动态变换位置的场景更是要写好多代码。
于是，我就在想，如何解决这两个问题呢？为什么不能让ViewStub 把这两者结合呢
为什么ViewStub不能用在动态添加View，结合自己的特性，把ViewStub本身的layoutParams设置给动态添加的View呢？
3.寻找可行性
带着上面的问题，我重新看了一下它的源码。
@RemoteView
public final class ViewStub extends View {
private int mInflatedId;
private int mLayoutResource;
private WeakReference<View> mInflatedViewRef;
private LayoutInflater mInflater;
private OnInflateListener mInflateListener;
public ViewStub(Context context) {
this(context, 0);
}
/**
* Creates a new ViewStub with the specified layout resource.
*
* @param context The application's environment.
* @param layoutResource The reference to a layout resource that will be inflated.
*/
public ViewStub(Context context, @LayoutRes int layoutResource) {
this(context, null);
mLayoutResource = layoutResource;
}
public ViewStub(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public ViewStub(Context context, AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}
public ViewStub(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context);
final TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.ViewStub, defStyleAttr, defStyleRes);
saveAttributeDataForStyleable(context, R.styleable.ViewStub, attrs, a, defStyleAttr,
defStyleRes);
mInflatedId = a.getResourceId(R.styleable.ViewStub_inflatedId, NO_ID);
mLayoutResource = a.getResourceId(R.styleable.ViewStub_layout, 0);
mID = a.getResourceId(R.styleable.ViewStub_id, NO_ID);
a.recycle();
setVisibility(GONE);
setWillNotDraw(true);
}
@IdRes
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.
* 为引入的layout设置一个id
*/
@android.view.RemotableViewMethod(asyncImpl = "setInflatedIdAsync")
public void setInflatedId(@IdRes int inflatedId) {
mInflatedId = inflatedId;
}
/** @hide **/
public Runnable setInflatedIdAsync(@IdRes int inflatedId) {
mInflatedId = inflatedId;
return null;
}
@LayoutRes
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.
* 注入需要引入的layoutId
*/
@android.view.RemotableViewMethod(asyncImpl = "setLayoutResourceAsync")
public void setLayoutResource(@LayoutRes int layoutResource) {
mLayoutResource = layoutResource;
}
/** @hide **/
public Runnable setLayoutResourceAsync(@LayoutRes int layoutResource) {
mLayoutResource = layoutResource;
return null;
}
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) {
setMeasuredDimension(0, 0);
}
@Override
public void draw(Canvas 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.
* 设置visibility 为VISIBLE 或者INVISIBLE时，会直接引入布局
*/
@Override
@android.view.RemotableViewMethod(asyncImpl = "setVisibilityAsync")
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();
}
}
}
/** @hide **/
public Runnable setVisibilityAsync(int visibility) {
if (visibility == VISIBLE || visibility == INVISIBLE) {
ViewGroup parent = (ViewGroup) getParent();
return new ViewReplaceRunnable(inflateViewNoAdd(parent));
} else {
return null;
}
}
private View inflateViewNoAdd(ViewGroup parent) {
final LayoutInflater factory;
if (mInflater != null) {
factory = mInflater;
} else {
factory = LayoutInflater.from(mContext);
}
final View view = factory.inflate(mLayoutResource, parent, false);
if (mInflatedId != NO_ID) {
view.setId(mInflatedId);
}
return view;
}
private void replaceSelfWithView(View view, ViewGroup parent) {
final int index = parent.indexOfChild(this);
//移除自身。
parent.removeViewInLayout(this);
final ViewGroup.LayoutParams layoutParams = getLayoutParams();
if (layoutParams != null) {
//把目标view按照自身index添加到parent中，并把自身的layoutParams设置到目标View。
parent.addView(view, index, layoutParams);
} else {
parent.addView(view, index);
}
}
/**
* 引入布局。核心代码
*/
public View inflate() {
final ViewParent viewParent = getParent();
if (viewParent != null && viewParent instanceof ViewGroup) {
if (mLayoutResource != 0) {
final ViewGroup parent = (ViewGroup) viewParent;
//通过LayoutInflater 引入目标布局，inAttachToParent 为false。
final View view = inflateViewNoAdd(parent);
//移除ViewStub自身，并添加目标view到同样的位置，将自身的layoutParams设置给目标View
replaceSelfWithView(view, parent);
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");
}
}
public void setOnInflateListener(OnInflateListener inflateListener) {
mInflateListener = inflateListener;
}
/**
* 布局引入监听
*/
public static interface OnInflateListener {
void onInflate(ViewStub stub, View inflated);
}
/** @hide **/
public class ViewReplaceRunnable implements Runnable {
public final View view;
ViewReplaceRunnable(View view) {
this.view = view;
}
@Override
public void run() {
replaceSelfWithView(view, (ViewGroup) getParent());
}
}
}
ViewStub代码非常简单，相信各位大佬都能看懂；
- 构造函数里
setVisibility(GONE)和setWillNotDraw(true)方法还有draw和dispatchDraw()方法重写后是空实现我们可知，ViewStub没有被绘制出来，所以不会消耗过多性能。 inflate()作用就是引入目标布局但不直接加入parant，而是将自身从parent中移除，然后按照同样的viewIndex把目标View加入到parent中，并把自身的LayoutParams设置给目标View；
原理就是这么简单。
那么，如何解决我们的痛点呢？
4.解决只能引入layout不能动态添加View的问题
重新看一下inflate()方法：
public View inflate() {
final ViewParent viewParent = getParent();
if (viewParent != null && viewParent instanceof ViewGroup) {
if (mLayoutResource != 0) {
final ViewGroup parent = (ViewGroup) viewParent;
//通过LayoutInflater 引入目标布局，inAttachToParent 为false。
final View view = inflateViewNoAdd(parent);
//移除ViewStub自身，并添加目标view到同样的位置，将自身的layoutParams设置给目标View
replaceSelfWithView(view, parent);
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");
}
}
这里替换分为两步：
- 1.使用LayoutInflate把layout引入；
- 2.第一步引入的View替换自身；
是不是思路就来了，我完全可以多态出来一个inflate(View view)方法，把我们动态构造的View传进去啊！！
那我是不是可以自定义一个View继承ViewStub呢？😏😏😏
说干就干！
但当我兴致勃勃的去继承ViewStub时候，编译器却报错了，才发现ViewStub有一个注解@RemoteView，它不可以被继承。
那软的不行，来硬的，我直接自己实现一份（其实是就是ctrl+c，ctrl+v😏😏）可以了吧！
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 androidx.annotation.IdRes;
import androidx.annotation.LayoutRes;
import androidx.annotation.Nullable;
import androidx.constraintlayout.widget.ConstraintLayout;
import com.avatr.ivi.enoch.R;
import com.avatr.ivi.enochsdk.base.tools.L;
import java.lang.ref.WeakReference;
public class ViewRocket extends View {
private static final L.Tag TAG = new L.Tag("ViewRocket");
private Context mContext;
private WeakReference<View> mInflatedViewRef;
@LayoutRes
private int mLayoutResource;
@IdRes
private int mInflatedId = NO_ID;
private boolean mIsLaunched = false;
public ViewRocket(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
mContext = context;
}
public ViewRocket(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ViewRocket);
mLayoutResource = a.getResourceId(R.styleable.ViewRocket_layout, 0);
mInflatedId = a.getResourceId(R.styleable.ViewRocket_inflatedId, NO_ID);
setVisibility(GONE);
setWillNotDraw(true);
}
//省略不必要代码
public View launch() {
if (mLayoutResource == 0) {
L.e(TAG, "launch: ");
return null;
}
return launch(mLayoutResource);
}
public View launch(@LayoutRes int layoutRes) {
final View view = inflateViewNoAdd((ViewGroup) getParent(), layoutRes);
launch(view);
return view;
}
public void launch(View view) {
if (mIsLaunched) {
L.e(TAG, "sendView: The rocket is disposable and cannot be fired repeatedly");
return;
}
final ViewGroup parent = (ViewGroup) getParent();
final int index = parent.indexOfChild(this);
parent.removeViewInLayout(this);
//如果View没有id,就给view生成一个id
if (view.getId() == View.NO_ID) {
mInflatedId = View.generateViewId();
view.setId(mInflatedId);
}
final ViewGroup.LayoutParams layoutParams = getLayoutParams();
if (layoutParams != null) {
parent.addView(view, index, layoutParams);
} else {
parent.addView(view, index);
}
mIsLaunched = true;
mInflatedViewRef = new WeakReference<>(view);
}
private View inflateViewNoAdd(ViewGroup parent, int layoutRes) {
final LayoutInflater factory = LayoutInflater.from(mContext);
final View view = factory.inflate(layoutRes, parent, false);
if (layoutRes != NO_ID) {
view.setId(layoutRes);
}
return view;
}
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) {
launch();
}
}
}
public boolean isLaunched() {
return mIsLaunched;
}
}
attr属性，兼容ViewStub本身的属性：
<declare-styleable name="ViewRocket">
<attr name="inflatedId" format="reference" />
<attr name="layout" format="reference" />
</declare-styleable>
方法几乎和ViewStub一模一样，但是我扩展了几个方法：
/**
* 在布局中设置了layout，或通过调用setLayoutResource后调用。
*/
public View launch() {
if (mLayoutResource == 0) {
L.e(TAG, "launch: ");
return null;
}
return launch(mLayoutResource);
}
/**
* 直接引入布局，不需要在xml或调用setLayoutResource设置layoutId
*/
public View launch(@LayoutRes int layoutRes) {
final View view = inflateViewNoAdd((ViewGroup) getParent(), layoutRes);
launch(view);
return view;
}
/**
* 核心方法，可以在内部或外部，直接传入目标View
*/
public void launch(View view) {
if (mIsLaunched) {
L.e(TAG, "sendView: The rocket is disposable and cannot be fired repeatedly");
return;
}
final ViewGroup parent = (ViewGroup) getParent();
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);
}
mIsLaunched = true;
mInflatedViewRef = new WeakReference<>(view);
}
可以看到，关键方法我加了参数，这样不管在内部或外部都可以直接调用传入目标View，这样我们在实际使用就变成这样：
- 1.在布局中使用
ViewRocket和ViewStub同样的方式占位； - 2.在代码中：
View view = new CustomComplicateView(context);
viewRocket.launch(view);
怎么样，是不是如此的丝滑柔顺！这样就解决了我们的第一个痛点，动态添加构造出来的View，不需要额外添加一个xml！
如此解决了这个问题，我开心的大喊，我真是个小聪明！
5. 随之而来的问题！
当我开开心心的在项目中使用时候，突然发现出问题了。
我的场景是，约束布局中有两个自定义View A,B使用ViewRocket引入,A、B有依赖关系。正常操作就是B的ViewRocket依赖A的ViewRocket，但是我这么用的时候，launch之后发现出问题了。两个View位置根本不对！
吓我一跳，有问题？我赶紧替换了ViewStub重试，发现ViewStub和我一样的问题。
什么原理呢？
正好我前两天研究过约束布局，知道动态建立约束需要connect目标View的Id；另外我们在launch时候，如果不主动设置inflateId或之前给目标View设置过id，目标View是没有id的！
也就是说，我的ViewRocket在引入目标view之后，和ViewRocket的约束关系，没有转移到新添加的VIew上！所以导致布局出现错乱。
那么，我是不是可以把ViewRocket的id设置给新的View呢？
6.解决约束布局约束失效
public void launch(View view) {
if (mIsLaunched) {
L.e(TAG, "sendView: The rocket is disposable and cannot be fired repeatedly");
return;
}
final ViewGroup parent = (ViewGroup) getParent();
final int index = parent.indexOfChild(this);
parent.removeViewInLayout(this);
//如果parentView是约束布局，把自身id设置给运送的View
if (parent instanceof ConstraintLayout) {
mInflatedId = this.getId();
view.setId(mInflatedId);
}
//如果View没有id,就给view生成一个id
if (view.getId() == View.NO_ID) {
mInflatedId = View.generateViewId();
view.setId(mInflatedId);
}
final ViewGroup.LayoutParams layoutParams = getLayoutParams();
if (layoutParams != null) {
parent.addView(view, index, layoutParams);
} else {
parent.addView(view, index);
}
mIsLaunched = true;
mInflatedViewRef = new WeakReference<>(view);
}
在项目里重新尝试，可以了！！！完美，哈哈哈哈
7.总结
一顿操作，就解决了ViewStub的两个问题：
- 只能引入layout而不能动态添加new出来的View的问题；
- 解决约束布局约束失效的问题。
其实这个这个问题比较简单，相信各位大佬轻松可以想到解决方案。不过不管问题是复杂还是简单，作为一个小趴菜，最重要的还是要有发现问题是，自己去努力探索去尝试的态度。每天都去靠自己的努力和思考解决问题，这样就能不断进步，不断提高，直到有一天能和各位大佬一样，嘿嘿嘿😏😏😏
完整代码：
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 androidx.annotation.IdRes;
import androidx.annotation.LayoutRes;
import androidx.annotation.Nullable;
import androidx.constraintlayout.widget.ConstraintLayout;
import com.avatr.ivi.enoch.R;
import com.avatr.ivi.enochsdk.base.tools.L;
import java.lang.ref.WeakReference;
/**
* Created By : Wilson.lu
* Created At : 2022/12/2 at 22:16
* Name : View火箭.因为像一次性火箭把人送到空间站，所以命名
* Abilities : ViewStub的Pro版本;
* <p>
* 支持ViewStub本身的功能;
* 可以动态添加单个View，不用再为单个View写一个xml布局
* 修复约束布局使用ViewStub 约束失效的问题；
* <p>
* <p>
* 用法eg:
*
* <p>
* viewRocket.setLayoutResource(R.layout.layout_any_layout);
* viewRocket.launch();
* <p>
* View customView = new CustomView(context);
* viewRocket.launch(customView)
* <p>
* viewRocket.launch(R.layout.layout_any_layout);
* <p>
* 注意：暂时不支持<merge>标签
*/
public class ViewRocket extends View {
private static final L.Tag TAG = new L.Tag("ViewRocket");
private Context mContext;
private WeakReference<View> mInflatedViewRef;
@LayoutRes
private int mLayoutResource;
@IdRes
private int mInflatedId = NO_ID;
public ViewRocket(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
mContext = context;
}
public ViewRocket(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ViewRocket);
mLayoutResource = a.getResourceId(R.styleable.ViewRocket_layout, 0);
mInflatedId = a.getResourceId(R.styleable.ViewRocket_inflatedId, NO_ID);
setVisibility(GONE);
setWillNotDraw(true);
}
public void setInflatedId(@IdRes int inflatedId) {
mInflatedId = inflatedId;
}
/**
* 获取要运送的View的id，没有launch之前获取不到真正的值
*
* @return
*/
public int getInflatedId() {
return mInflatedId;
}
public void setLayoutResource(@LayoutRes int layoutResource) {
mLayoutResource = layoutResource;
}
public View launch() {
if (mLayoutResource == 0) {
L.e(TAG, "launch: ");
return null;
}
return launch(mLayoutResource);
}
public View launch(@LayoutRes int layoutRes) {
final View view = inflateViewNoAdd((ViewGroup) getParent(), layoutRes);
launch(view);
return view;
}
public void launch(View view) {
if (mIsLaunched) {
L.e(TAG, "sendView: The rocket is disposable and cannot be fired repeatedly");
return;
}
final ViewGroup parent = (ViewGroup) getParent();
final int index = parent.indexOfChild(this);
parent.removeViewInLayout(this);
if (parent instanceof ConstraintLayout) {
//如果parentView是约束布局，把自身id设置给运送的View
mInflatedId = this.getId();
view.setId(mInflatedId);
}
//如果View没有id,就给view生成一个id
if (view.getId() == View.NO_ID) {
mInflatedId = View.generateViewId();
view.setId(mInflatedId);
}
final ViewGroup.LayoutParams layoutParams = getLayoutParams();
if (layoutParams != null) {
parent.addView(view, index, layoutParams);
} else {
parent.addView(view, index);
}
mIsLaunched = true;
mInflatedViewRef = new WeakReference<>(view);
}
private View inflateViewNoAdd(ViewGroup parent, int layoutRes) {
final LayoutInflater factory = LayoutInflater.from(mContext);
final View view = factory.inflate(layoutRes, parent, false);
if (layoutRes != NO_ID) {
view.setId(layoutRes);
}
return view;
}
public void setVisibility(int visibility) {
// 当真正的布局文件被加载之后
if (mInflatedViewRef != null) {
// 获取到当前的View
View view = mInflatedViewRef.get();
if (view != null) {
//操纵当前View的可见行
view.setVisibility(visibility);
} else {
throw new IllegalStateException("setVisibility called on un-referenced view");
}
} else {
//没有调用inflate的话，会设置可见性
super.setVisibility(visibility);
//当 当前设置可见性为 VISIBLE或者INVISIBLE的时候，会调用inflate方法。
if (visibility == VISIBLE || visibility == INVISIBLE) {
launch();
}
}
}
@Override
public void draw(Canvas canvas) {
super.draw(null);
}
private boolean mIsLaunched = false;
public boolean isLaunched() {
return mIsLaunched;
}
}
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