Android 使ListAdapter成为可循环使用的可调整大小的视图
我正在创建一个自定义视图，它将有一个扩展和压缩状态——在压缩状态下，它将只显示一个标签和一个图标，在扩展状态下，它将在下面显示一条消息。以下是迄今为止它的工作原理的屏幕截图：Android 使ListAdapter成为可循环使用的可调整大小的视图,android,android-listview,layoutparams,Android,Android Listview,Layoutparams,我正在创建一个自定义视图，它将有一个扩展和压缩状态——在压缩状态下，它将只显示一个标签和一个图标，在扩展状态下，它将在下面显示一条消息。以下是迄今为止它的工作原理的屏幕截图： 视图本身在测量后保留压缩和扩展状态的大小值，因此很容易在两种状态之间设置动画，并且在正常实践中使用视图时（例如在线性布局中），一切都按预期工作。通过调用getLayoutParams（），可以更改视图大小。height=newHeight；requestLayout（） 但是，在列表视图中使用该视图时，该视图将被回收并保
视图线性布局getLayoutParams（），可以更改视图大小。height=newHeight；requestLayout（）
但是，在列表视图中使用该视图时，该视图将被回收并保持其以前的高度。因此，如果视图在隐藏时展开，则在为下一个列表项回收视图时，它将显示为展开。即使我在ListAdapter
中请求布局，它似乎也不会收到另一个布局传递。我考虑过使用具有两种不同视图类型（扩展视图和压缩视图）的回收器，但是大小会根据消息的大小而有所不同。在列表视图
中重新连接视图时，是否有我可以侦听的事件？或者你对如何处理这个问题还有其他建议吗
编辑：这是我确定视图的展开高度和压缩高度的方式：
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if(r - l > 0 && b - t > 0 && dimensionsDirty) {
int widthSpec = MeasureSpec.makeMeasureSpec(r - l, MeasureSpec.EXACTLY);
messageView.setVisibility(GONE);
measure(widthSpec, MeasureSpec.UNSPECIFIED);
condensedHeight = getMeasuredHeight();
messageView.setVisibility(VISIBLE);
measure(widthSpec, MeasureSpec.UNSPECIFIED);
expandedHeight = getMeasuredHeight();
dimensionsDirty = false;
}
}
您是否可以重写适配器的getView方法，并检查convertView变量（它是第二个参数，至少在我正在查看的ArrayAdapter中是这样）。您应该能够对其调用GetLayoutParameters以获取其高度，并根据位置变量相应地调整它。编辑：makeMeasureSpec的两个调用的参数顺序固定。奇怪的是，它的工作方式不正确，所以我几乎想知道我是否在做一些多余的事情。不管怎样，我只是想指出一点——下面要下载的项目没有这些更正
好吧，我真的很困扰，我没能弄明白这一点，所以我决定更加熟悉布局和测量系统，这是我想出的解决方案
一个自定义的ViewGroup
扩展FrameLayout
，它承载一个直接子对象（如ScrollView
）
自定义ListAdapter
，用于跟踪每个列表项的展开/折叠状态
一个自定义的OnItemClickListener
，用于处理在折叠和展开状态之间设置动画的请求
我想分享这段代码，以防其他人发现它有用。它应该是相当灵活的，但我毫不怀疑有缺陷和可以改进的地方。例如，我在编程上滚动列表视图时遇到问题（似乎没有一种方法可以真正滚动内容，而不仅仅是视图），因此每次更改视图大小时，我都使用smoothScrollToPosition（int）
。这有一个硬编码的400毫秒的持续时间，这是不必要的，因此在将来我可能会尝试编写自己的版本，持续时间为0（即scrollToPosition（int）
）
一般用途如下：
列表项XML应该将您的ResizeLayout
作为层次结构的根，从那里您可以构建任何想要的布局结构。基本上，只需将常规列表项布局包装在ResizeLayout
标记中即可
在布局中，应该有一个id为collapse\u to
的视图。这是布局将环绕到的视图（即确定折叠高度的视图）
如果要通过列表适配器进行回收，请执行以下重要操作：
- 检索回收视图时，始终调用
reuse（）
（例如convertView
）
- 在返回回收视图之前，始终调用
setIsExpanded（boolean）
；否则，它将保持在回收前的状态
我可能最终会将其投入git回购，但目前代码如下：
ResizeLayout.java
这是大部分代码。我还将包括我用于进一步测试的活动
和适配器
。它们非常通用，但它们有效地说明了用途
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.*;
import android.widget.FrameLayout;
/*
* ResizeLayout
*
* Custom ViewGroup that allows you to specify a view in the child hierarchy to wrap to, and
* allows for the view to be expanded to the full size of the content.
*
* Author: Kevin Coppock
* Date: 2013/03/02
*/
public class ResizeLayout extends FrameLayout {
private static final int PX_PER_SEC = 900; //Pixels per Second to animate layout changes
private final LayoutAnimation animation = new LayoutAnimation();
private final int wrapSpec = MeasureSpec.makeMeasureSpec(LayoutParams.WRAP_CONTENT, MeasureSpec.UNSPECIFIED);
private int collapsedHeight = 0;
private int expandedHeight = 0;
private boolean contentsChanged = true;
private State state = State.COLLAPSED;
private OnLayoutChangedListener listener;
public ResizeLayout(Context context) { super(context); }
public ResizeLayout(Context context, AttributeSet attrs) { super(context, attrs); }
public ResizeLayout(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); }
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
if(getChildCount() > 0) {
View child = getChildAt(0);
child.layout(0, 0, child.getMeasuredWidth(), child.getMeasuredHeight());
}
//If the layout parameters have changed and the view is animating, notify listeners
if(changed && animation.isAnimating()) {
switch(state) {
case COLLAPSED: fireOnLayoutCollapsing(left, top, right, bottom); break;
case EXPANDED: fireOnLayoutExpanding(left, top, right, bottom); break;
}
}
}
/**
* Reset the internal state of the view to defaults. This should be called any time you change the contents
* of this ResizeLayout (e.g. recycling through a ListAdapter)
*/
public void reuse() {
collapsedHeight = expandedHeight = 0;
contentsChanged = true;
state = State.COLLAPSED;
requestLayout();
}
/**
* Set the state of the view. This should ONLY be called after a call to reuse() as it does not animate
* the view; it simply sets the internal state. An example of usage is in a ListAdapter -- if the view is
* recycled, it may be in the incorrect state, so it should be set here to the correct state before layout.
* @param isExpanded whether or not the view should be in the expanded state
*/
public void setIsExpanded(boolean isExpanded) {
state = isExpanded ? State.EXPANDED : State.COLLAPSED;
}
/**
* Animates the ResizeLayout between COLLAPSED and EXPANDED states, only if it is not currently animating.
*/
public void animateToNextState() {
if(!animation.isAnimating()) {
animation.reuse(state.getStartHeight(this), state.getEndHeight(this));
state = state.next();
startAnimation(animation);
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = MeasureSpec.getSize(widthMeasureSpec);
int height = MeasureSpec.getSize(heightMeasureSpec);
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if(getChildCount() < 1) { //ResizeLayout has no child; default to spec, or padding if unspecified
setMeasuredDimension(
widthMode == MeasureSpec.UNSPECIFIED ? getPaddingLeft() + getPaddingRight() : width,
heightMode == MeasureSpec.UNSPECIFIED ? getPaddingTop() + getPaddingBottom() : height
);
return;
}
View child = getChildAt(0); //Get the only child of the ResizeLayout
if(contentsChanged) { //If the contents of the view have changed (first run, or after reset from reuse())
contentsChanged = false;
updateMeasurementsForChild(child, widthMeasureSpec, heightMeasureSpec);
return;
}
//This state occurs on the second run. The child might be wrap_content, so the MeasureSpec will be unspecified.
//Skip measuring the child and just accept the measurements from the first run.
if(heightMode == MeasureSpec.UNSPECIFIED) {
setMeasuredDimension(getWidth(), getHeight());
} else {
//Likely in mid-animation; we have a fixed-height from the MeasureSpec so use it
child.measure(widthMeasureSpec, heightMeasureSpec);
setMeasuredDimension(child.getMeasuredWidth(), child.getMeasuredHeight());
}
}
/**
* Sets the measured dimension for this ResizeLayout, getting the initial measurements
* for the condensed and expanded heights from the child view.
* @param child the child view of this ResizeLayout
* @param widthSpec the width MeasureSpec from onMeasure()
* @param heightSpec the height MeasureSpec from onMeasure()
*/
private void updateMeasurementsForChild(View child, int widthSpec, int heightSpec) {
child.measure(widthSpec, wrapSpec); //Measure the child using WRAP_CONTENT for the height
//Get the View that has been selected as the "collapse to" view (ID = R.id.collapse_to)
View viewToCollapseTo = child.findViewById(R.id.collapse_to);
if(viewToCollapseTo != null) {
//The collapsed height should be the height of the collapseTo view + any top or bottom padding
collapsedHeight = viewToCollapseTo.getMeasuredHeight() + child.getPaddingTop() + child.getPaddingBottom();
//The expanded height is simply the full height of the child (measured with WRAP_CONTENT)
expandedHeight = child.getMeasuredHeight();
//Re-Measure the child to reflect the state of the view (COLLAPSED or EXPANDED)
int newHeightMeasureSpec = MeasureSpec.makeMeasureSpec(state.getStartHeight(this), MeasureSpec.EXACTLY);
child.measure(widthSpec, newHeightMeasureSpec);
}
setMeasuredDimension(child.getMeasuredWidth(), child.getMeasuredHeight());
}
@Override
public void addView(View child) {
if(getChildCount() > 0) {
throw new IllegalArgumentException("ResizeLayout can host only one direct child.");
} else {
super.addView(child);
}
}
@Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
if(getChildCount() > 0) {
throw new IllegalArgumentException("ResizeLayout can host only one direct child.");
} else {
super.addView(child, index, params);
}
}
@Override
public void addView(View child, ViewGroup.LayoutParams params) {
if(getChildCount() > 0) {
throw new IllegalArgumentException("ResizeLayout can host only one direct child.");
} else {
super.addView(child, params);
}
}
@Override
public void addView(View child, int width, int height) {
if(getChildCount() > 0) {
throw new IllegalArgumentException("ResizeLayout can host only one direct child.");
} else {
super.addView(child, width, height);
}
}
/**
* Handles animating the view between its expanded and collapsed states by adjusting the
* layout parameters of the containing object and requesting a layout pass.
*/
private class LayoutAnimation extends Animation implements Animation.AnimationListener {
private int startHeight = 0, deltaHeight = 0;
private boolean isAnimating = false;
/**
* Just a default interpolator and friction I think feels nice; can be changed.
*/
public LayoutAnimation() {
setInterpolator(new DecelerateInterpolator(2.2f));
setAnimationListener(this);
}
/**
* Sets the duration of the animation to a duration matching the specified value in
* Pixels per Second (PPS). For example, if the view animation is 60 pixels, then a PPS of 60
* would set a duration of 1000ms (i.e. duration = (delta / pps) * 1000). PPS is used rather
* than a fixed time so that the animation speed is consistent regardless of the contents
* of the view.
* @param pps the number of pixels per second to resize the layout by
*/
private void setDurationPixelsPerSecond(int pps) {
setDuration((int) (((float) Math.abs(deltaHeight) / pps) * 1000));
}
/**
* Allows reuse of a single LayoutAnimation object. Call this before starting the animation
* to restart the animation and set the new parameters
* @param startHeight the height from which the animation should begin
* @param endHeight the height at which the animation should end
*/
public void reuse(int startHeight, int endHeight) {
reset();
setStartTime(0);
this.startHeight = startHeight;
this.deltaHeight = endHeight - startHeight;
setDurationPixelsPerSecond(PX_PER_SEC);
}
/**
* Applies the height transformation to this containing ResizeLayout
* @param interpolatedTime the time (0.0 - 1.0) interpolated based on the set interpolator
* @param t the transformation associated with the animation -- not used here
*/
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
getLayoutParams().height = startHeight + (int)(deltaHeight * interpolatedTime);
requestLayout();
}
public boolean isAnimating() {
return isAnimating;
}
@Override
public void onAnimationStart(Animation animation) {
isAnimating = true;
}
@Override
public void onAnimationEnd(Animation animation) {
isAnimating = false;
}
@Override
public void onAnimationRepeat(Animation animation) {
/*Not implemented*/
}
}
/**
* Interface to listen for layout changes during an animation
*/
public interface OnLayoutChangedListener {
public void onLayoutExpanding(int l, int t, int r, int b);
public void onLayoutCollapsing(int l, int t, int r, int b);
}
/**
* Sets a listener for changes to this view's layout
* @param listener the listener for layout changes
*/
public void setOnBoundsChangedListener(OnLayoutChangedListener listener) {
this.listener = listener;
}
private void fireOnLayoutExpanding(int l, int t, int r, int b) {
if(listener != null) listener.onLayoutExpanding(l, t, r, b);
}
private void fireOnLayoutCollapsing(int l, int t, int r, int b) {
if(listener != null) listener.onLayoutCollapsing(l, t, r, b);
}
protected enum State {
COLLAPSED{
@Override
public State next() {
return EXPANDED;
}
@Override
public int getEndHeight(ResizeLayout view) {
return view.expandedHeight;
}
@Override
public int getStartHeight(ResizeLayout view) {
return view.collapsedHeight;
}
},
EXPANDED{
@Override
public State next() {
return COLLAPSED;
}
@Override
public int getEndHeight(ResizeLayout view) {
return view.collapsedHeight;
}
@Override
public int getStartHeight(ResizeLayout view) {
return view.expandedHeight;
}
};
public abstract State next();
public abstract int getStartHeight(ResizeLayout view);
public abstract int getEndHeight(ResizeLayout view);
}
}
list_item.xml
基本列表项布局示例。只在顶部有一个图标和一个标题（图标被设置为collapse\u to
视图）和一个下面对齐的消息视图
<?xml version="1.0" encoding="utf-8"?>
<com.example.resize.ResizeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp">
<ImageView
android:id="@+id/collapse_to"
android:src="@drawable/holoku"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scaleType="centerInside"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:contentDescription="@string/icon_desc"
tools:ignore="UseCompoundDrawables"
/>
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_alignTop="@id/collapse_to"
android:layout_alignBottom="@id/collapse_to"
android:layout_toRightOf="@id/collapse_to"
android:gravity="center_vertical"
android:paddingLeft="20dp"
android:textSize="20dp"
android:textColor="#198EBC"
/>
<TextView
android:id="@+id/text"
android:layout_marginTop="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="12dp"
android:textColor="#444444"
android:layout_below="@id/collapse_to"
android:text="@string/message"
/>
</RelativeLayout>
</com.example.resize.ResizeLayout>
现在我还没有在API 17之前的任何东西上测试过它，但是运行lint检查来发现新的API问题，这应该可以追溯到2.2（API 8）
如果您想下载示例项目并自己玩，您可以下载。您可能应该始终在Adapter.getView（…）
方法中的行中设置高度（顺便问一下，newHeight
从何而来？），并跟踪其他位置的状态。也就是说，如果要将POJO馈送到适配器
，则向其添加一个简单的布尔值，指示折叠/扩展状态就足够了。或者，您可以使用类似于散列集的内容，并添加处于“扩展”状态的索引。@MH。嗯，视图的高度取决于其内容，因此新高度是在视图的重写onLayout
方法中测量的。我计划稍后在ListAdapter中跟踪扩展/压缩状态，并相应地设置视图的状态。我已经为你的问题添加了这个，如果它有意义的话。我现在正在尝试使用onAttachedToWindow（）
和OnAttachedFromWindow（）
执行某些操作。“在ListView中重新附加视图时，是否有我可以侦听的事件？”您是否忽略了明显的问题？当convertView！=null
该视图来自废料堆。正如您所知，RecycleBin只有一个侦听器
<?xml version="1.0" encoding="utf-8"?>
<com.example.resize.ResizeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp">
<ImageView
android:id="@+id/collapse_to"
android:src="@drawable/holoku"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scaleType="centerInside"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:contentDescription="@string/icon_desc"
tools:ignore="UseCompoundDrawables"
/>
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_alignTop="@id/collapse_to"
android:layout_alignBottom="@id/collapse_to"
android:layout_toRightOf="@id/collapse_to"
android:gravity="center_vertical"
android:paddingLeft="20dp"
android:textSize="20dp"
android:textColor="#198EBC"
/>
<TextView
android:id="@+id/text"
android:layout_marginTop="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="12dp"
android:textColor="#444444"
android:layout_below="@id/collapse_to"
android:text="@string/message"
/>
</RelativeLayout>
</com.example.resize.ResizeLayout>