我有一个TextView，它首先显示一小部分长文本。
用户可以按下“查看更多”按钮来展开 TextView 并查看该文本的其余部分。
进行测试，我可以通过简单地将 TextView.setMaxLines 的值在 4 用于折叠和 Integer.MAX_VALUE 用于展开来实现。
现在，我希望这种行为伴随着动画。我知道在this question 中几乎完成了一个解决方案，但我尝试实施它并没有成功。
有人可以帮我解决这个问题吗？
【问题讨论】：
标签： android android-animation textview
你可以查看我在 ExpandableTexTView 上的博文：
这个想法是，最初 TextView 将显示一小部分长文本，当单击它时，它将显示其余文本。
所以这是我如何解决它的代码。
package com.rokonoid.widget;
import android.content.Context;
import android.content.res.TypedArray;
import android.text.SpannableStringBuilder;
import android.util.AttributeSet;
import android.view.View;
import android.widget.TextView;
/**
* User: Bazlur Rahman Rokon
* Date: 9/7/13 - 3:33 AM
*/
public class ExpandableTextView extends TextView {
private static final int DEFAULT_TRIM_LENGTH = 200;
private static final String ELLIPSIS = ".....";
private CharSequence originalText;
private CharSequence trimmedText;
private BufferType bufferType;
private boolean trim = true;
private int trimLength;
public ExpandableTextView(Context context) {
this(context, null);
}
public ExpandableTextView(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView);
this.trimLength = typedArray.getInt(R.styleable.ExpandableTextView_trimLength, DEFAULT_TRIM_LENGTH);
typedArray.recycle();
setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
trim = !trim;
setText();
requestFocusFromTouch();
}
});
}
private void setText() {
super.setText(getDisplayableText(), bufferType);
}
private CharSequence getDisplayableText() {
return trim ? trimmedText : originalText;
}
@Override
public void setText(CharSequence text, BufferType type) {
originalText = text;
trimmedText = getTrimmedText(text);
bufferType = type;
setText();
}
private CharSequence getTrimmedText(CharSequence text) {
if (originalText != null && originalText.length() > trimLength) {
return new SpannableStringBuilder(originalText, 0, trimLength + 1).append(ELLIPSIS);
} else {
return originalText;
}
}
public CharSequence getOriginalText() {
return originalText;
}
public void setTrimLength(int trimLength) {
this.trimLength = trimLength;
trimmedText = getTrimmedText(originalText);
setText();
}
public int getTrimLength() {
return trimLength;
}
}
并在 attr.xml 中添加以下行
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="ExpandableTextView">
<attr name="trimLength" format="integer"/>
</declare-styleable>
</resources>
将以下内容放入您的 main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<com.rokonoid.widget.ExpandableTextView
android:id="@+id/lorem_ipsum"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
并测试您的活动
package com.rokonoid.widget;
import android.app.Activity;
import android.os.Bundle;
public class MyActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
String yourText = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. " +
"Ut volutpat interdum interdum. Nulla laoreet lacus diam, vitae " +
"sodales sapien commodo faucibus. Vestibulum et feugiat enim. Donec " +
"semper mi et euismod tempor. Sed sodales eleifend mi id varius. Nam " +
"et ornare enim, sit amet gravida sapien. Quisque gravida et enim vel " +
"volutpat. Vivamus egestas ut felis a blandit. Vivamus fringilla " +
"dignissim mollis. Maecenas imperdiet interdum hendrerit. Aliquam" +
" dictum hendrerit ultrices. Ut vitae vestibulum dolor. Donec auctor ante" +
" eget libero molestie porta. Nam tempor fringilla ultricies. Nam sem " +
"lectus, feugiat eget ullamcorper vitae, ornare et sem. Fusce dapibus ipsum" +
" sed laoreet suscipit. ";
ExpandableTextView expandableTextView = (ExpandableTextView) findViewById(R.id.lorem_ipsum);
expandableTextView.setText(yourText);
}
}
【讨论】：
ObjectAnimator animation = ObjectAnimator.ofInt(yourTextView, "maxLines", tv.getLineCount());
animation.setDuration(200).start();
这将在 200 毫秒内完全扩展您的 TextView。您可以将tv.getLineCount() 替换为您希望将其折叠回的任意多行文本。
----更新----
以下是一些您可以使用的便捷方法：
private void expandTextView(TextView tv){
ObjectAnimator animation = ObjectAnimator.ofInt(tv, "maxLines", tv.getLineCount());
animation.setDuration(200).start();
}
private void collapseTextView(TextView tv, int numLines){
ObjectAnimator animation = ObjectAnimator.ofInt(tv, "maxLines", numLines);
animation.setDuration(200).start();
}
如果您使用的是 API 16+，则可以使用 textView.getMaxLines() 轻松确定您的 textView 是否已展开。
private void cycleTextViewExpansion(TextView tv){
int collapsedMaxLines = 3;
ObjectAnimator animation = ObjectAnimator.ofInt(tv, "maxLines",
tv.getMaxLines() == collapsedMaxLines? tv.getLineCount() : collapsedMaxLines);
animation.setDuration(200).start();
}
注意事项：
如果 maxLines 尚未设置，或者您已设置 set the height of your textView in pixels，您可能会得到 ArrayIndexOutOfBounds 异常。
上面的例子总是需要 200ms，无论是扩展 3 行还是 400 行。如果你想要一个一致的扩展率，你可以这样做：
int duration = (textView.getLineCount() - collapsedMaxLines) * 10;
【讨论】：
ellipsize 属性（设置为“结束”）时，TextView 不再可点击，您也无法再展开它。
我为此创建了一个开源库，因为我对在互联网上找到的其他解决方案不满意。我已经把它放在了 GitHub 上，任何人都可以免费使用。
public class ExpandableTextView extends TextView
{
// copy off TextView.LINES
private static final int MAXMODE_LINES = 1;
private OnExpandListener onExpandListener;
private TimeInterpolator expandInterpolator;
private TimeInterpolator collapseInterpolator;
private final int maxLines;
private long animationDuration;
private boolean animating;
private boolean expanded;
private int originalHeight;
public ExpandableTextView(final Context context)
{
this(context, null);
}
public ExpandableTextView(final Context context, final AttributeSet attrs)
{
this(context, attrs, 0);
}
public ExpandableTextView(final Context context, final AttributeSet attrs, final int defStyle)
{
super(context, attrs, defStyle);
// read attributes
final TypedArray attributes = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView, defStyle, 0);
this.animationDuration = attributes.getInt(R.styleable.ExpandableTextView_animation_duration, BuildConfig.DEFAULT_ANIMATION_DURATION);
attributes.recycle();
// keep the original value of maxLines
this.maxLines = this.getMaxLines();
// create default interpolators
this.expandInterpolator = new AccelerateDecelerateInterpolator();
this.collapseInterpolator = new AccelerateDecelerateInterpolator();
}
@Override
public int getMaxLines()
{
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN)
{
return super.getMaxLines();
}
try
{
final Field mMaxMode = TextView.class.getField("mMaxMode");
mMaxMode.setAccessible(true);
final Field mMaximum = TextView.class.getField("mMaximum");
mMaximum.setAccessible(true);
final int mMaxModeValue = (int) mMaxMode.get(this);
final int mMaximumValue = (int) mMaximum.get(this);
return mMaxModeValue == MAXMODE_LINES ? mMaximumValue : -1;
}
catch (final Exception e)
{
return -1;
}
}
/**
* Toggle the expanded state of this {@link ExpandableTextView}.
* @return true if toggled, false otherwise.
*/
public boolean toggle()
{
if (this.expanded)
{
return this.collapse();
}
return this.expand();
}
/**
* Expand this {@link ExpandableTextView}.
* @return true if expanded, false otherwise.
*/
public boolean expand()
{
if (!this.expanded && !this.animating && this.maxLines >= 0)
{
this.animating = true;
// notify listener
if (this.onExpandListener != null)
{
this.onExpandListener.onExpand(this);
}
// get original height
this.measure
(
MeasureSpec.makeMeasureSpec(this.getMeasuredWidth(), MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)
);
this.originalHeight = this.getMeasuredHeight();
// set maxLines to MAX Integer
this.setMaxLines(Integer.MAX_VALUE);
// get new height
this.measure
(
MeasureSpec.makeMeasureSpec(this.getMeasuredWidth(), MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)
);
final int fullHeight = this.getMeasuredHeight();
final ValueAnimator valueAnimator = ValueAnimator.ofInt(this.originalHeight, fullHeight);
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener()
{
@Override
public void onAnimationUpdate(final ValueAnimator animation)
{
final ViewGroup.LayoutParams layoutParams = ExpandableTextView.this.getLayoutParams();
layoutParams.height = (int) animation.getAnimatedValue();
ExpandableTextView.this.setLayoutParams(layoutParams);
}
});
valueAnimator.addListener(new AnimatorListenerAdapter()
{
@Override
public void onAnimationEnd(final Animator animation)
{
ExpandableTextView.this.expanded = true;
ExpandableTextView.this.animating = false;
}
});
// set interpolator
valueAnimator.setInterpolator(this.expandInterpolator);
// start the animation
valueAnimator
.setDuration(this.animationDuration)
.start();
return true;
}
return false;
}
/**
* Collapse this {@link TextView}.
* @return true if collapsed, false otherwise.
*/
public boolean collapse()
{
if (this.expanded && !this.animating && this.maxLines >= 0)
{
this.animating = true;
// notify listener
if (this.onExpandListener != null)
{
this.onExpandListener.onCollapse(this);
}
// get new height
final int fullHeight = this.getMeasuredHeight();
final ValueAnimator valueAnimator = ValueAnimator.ofInt(fullHeight, this.originalHeight);
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener()
{
@Override
public void onAnimationUpdate(final ValueAnimator animation)
{
final ViewGroup.LayoutParams layoutParams = ExpandableTextView.this.getLayoutParams();
layoutParams.height = (int) animation.getAnimatedValue();
ExpandableTextView.this.setLayoutParams(layoutParams);
}
});
valueAnimator.addListener(new AnimatorListenerAdapter()
{
@Override
public void onAnimationEnd(final Animator animation)
{
// set maxLines to original value
ExpandableTextView.this.setMaxLines(ExpandableTextView.this.maxLines);
ExpandableTextView.this.expanded = false;
ExpandableTextView.this.animating = false;
}
});
// set interpolator
valueAnimator.setInterpolator(this.collapseInterpolator);
// start the animation
valueAnimator
.setDuration(this.animationDuration)
.start();
return true;
}
return false;
}
/**
* Sets the duration of the expand / collapse animation.
* @param animationDuration duration in milliseconds.
*/
public void setAnimationDuration(final long animationDuration)
{
this.animationDuration = animationDuration;
}
/**
* Sets a listener which receives updates about this {@link ExpandableTextView}.
* @param onExpandListener the listener.
*/
public void setOnExpandListener(final OnExpandListener onExpandListener)
{
this.onExpandListener = onExpandListener;
}
/**
* Returns the {@link OnExpandListener}.
* @return the listener.
*/
public OnExpandListener getOnExpandListener()
{
return onExpandListener;
}
/**
* Sets a {@link TimeInterpolator} for expanding and collapsing.
* @param interpolator the interpolator
*/
public void setInterpolator(final TimeInterpolator interpolator)
{
this.expandInterpolator = interpolator;
this.collapseInterpolator = interpolator;
}
/**
* Sets a {@link TimeInterpolator} for expanding.
* @param expandInterpolator the interpolator
*/
public void setExpandInterpolator(final TimeInterpolator expandInterpolator)
{
this.expandInterpolator = expandInterpolator;
}
/**
* Returns the current {@link TimeInterpolator} for expanding.
* @return the current interpolator, null by default.
*/
public TimeInterpolator getExpandInterpolator()
{
return this.expandInterpolator;
}
/**
* Sets a {@link TimeInterpolator} for collpasing.
* @param collapseInterpolator the interpolator
*/
public void setCollapseInterpolator(final TimeInterpolator collapseInterpolator)
{
this.collapseInterpolator = collapseInterpolator;
}
/**
* Returns the current {@link TimeInterpolator} for collapsing.
* @return the current interpolator, null by default.
*/
public TimeInterpolator getCollapseInterpolator()
{
return this.collapseInterpolator;
}
/**
* Is this {@link ExpandableTextView} expanded or not?
* @return true if expanded, false if collapsed.
*/
public boolean isExpanded()
{
return this.expanded;
}
public interface OnExpandListener
{
void onExpand(ExpandableTextView view);
void onCollapse(ExpandableTextView view);
}
}
使用 ExpandableTextView 非常简单，它只是一个添加了一些额外功能的常规 TextView。通过定义android:maxLines属性，可以设置TextView折叠状态的默认行数。
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<at.blogc.android.views.ExpandableTextView
android:id="@+id/expandableTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/lorem_ipsum"
android:maxLines="5"
android:ellipsize="end"
app:animation_duration="1000"/>
<!-- Optional parameter animation_duration: sets the duration of the expand animation -->
<Button
android:id="@+id/button_toggle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/expand"/>
</LinearLayout>
在您的 Activity 或 Fragment 中：
final ExpandableTextView expandableTextView = (ExpandableTextView) this.findViewById(R.id.expandableTextView);
final Button buttonToggle = (Button) this.findViewById(R.id.button_toggle);
// set animation duration via code, but preferable in your layout files by using the animation_duration attribute
expandableTextView.setAnimationDuration(1000L);
// set interpolators for both expanding and collapsing animations
expandableTextView.setInterpolator(new OvershootInterpolator());
// or set them separately
expandableTextView.setExpandInterpolator(new OvershootInterpolator());
expandableTextView.setCollapseInterpolator(new OvershootInterpolator());
// toggle the ExpandableTextView
buttonToggle.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(final View v)
{
expandableTextView.toggle();
buttonToggle.setText(expandableTextView.isExpanded() ? R.string.collapse : R.string.expand);
}
});
// but, you can also do the checks yourself
buttonToggle.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(final View v)
{
if (expandableTextView.isExpanded())
{
expandableTextView.collapse();
buttonToggle.setText(R.string.expand);
}
else
{
expandableTextView.expand();
buttonToggle.setText(R.string.collapse);
}
}
});
// listen for expand / collapse events
expandableTextView.setOnExpandListener(new ExpandableTextView.OnExpandListener()
{
@Override
public void onExpand(final ExpandableTextView view)
{
Log.d(TAG, "ExpandableTextView expanded");
}
@Override
public void onCollapse(final ExpandableTextView view)
{
Log.d(TAG, "ExpandableTextView collapsed");
}
});
您可以轻松地将这个库作为 gradle 依赖项添加到您的 Android 项目中。查看 Github 上的项目以获取更多说明：
【讨论】：
expandText.setInterpolator(new OvershootInterpolator()); expandText.setMaxLines(4); expandText.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { if(expandText.isExpanded()){ expandText.collapse(); } else{ expandText.expand(); } } });
平滑扩展（使用高度和ObjectAnimator）
仅供参考：需要 API 11
public static void expandCollapsedByMaxLines(@NonNull final TextView text) {
final int height = text.getMeasuredHeight();
text.setHeight(height);
text.setMaxLines(Integer.MAX_VALUE); //expand fully
text.measure(View.MeasureSpec.makeMeasureSpec(text.getMeasuredWidth(), View.MeasureSpec.EXACTLY), View.MeasureSpec.makeMeasureSpec(ViewGroup.LayoutParams.WRAP_CONTENT, View.MeasureSpec.UNSPECIFIED));
final int newHeight = text.getMeasuredHeight();
ObjectAnimator animation = ObjectAnimator.ofInt(text, "height", height, newHeight);
animation.setDuration(250).start();
}
附：我假设 TextView 受 maxLines 限制。
P.S.S.感谢 Amagi82 ObjectAnimator 示例
【讨论】：
如果你想根据行数来做，这里有一个方法：
（完整代码的Gist）
/**
* Ellipsize the text when the lines of text exceeds the value provided by {@link #makeExpandable} methods.
* Appends {@link #MORE} or {@link #LESS} as needed.
* TODO: add animation
* Created by vedant on 3/10/15.
*/
public class ExpandableTextView extends TextView {
private static final String TAG = "ExpandableTextView";
private static final String ELLIPSIZE = "... ";
private static final String MORE = "more";
private static final String LESS = "less";
private String mFullText;
private int mMaxLines;
//...constructors...
public void makeExpandable(String fullText, int maxLines) {
mFullText =fullText;
mMaxLines = maxLines;
ViewTreeObserver vto = getViewTreeObserver();
vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
ViewTreeObserver obs = getViewTreeObserver();
obs.removeOnGlobalLayoutListener(this);
if (getLineCount() <= maxLines) {
setText(mFullText);
} else {
setMovementMethod(LinkMovementMethod.getInstance());
showLess();
}
}
});
}
/**
* truncate text and append a clickable {@link #MORE}
*/
private void showLess() {
int lineEndIndex = getLayout().getLineEnd(mMaxLines - 1);
String newText = mFullText.substring(0, lineEndIndex - (ELLIPSIZE.length() + MORE.length() + 1))
+ ELLIPSIZE + MORE;
SpannableStringBuilder builder = new SpannableStringBuilder(newText);
builder.setSpan(new ClickableSpan() {
@Override
public void onClick(View widget) {
showMore();
}
}, newText.length() - MORE.length(), newText.length(), 0);
setText(builder, BufferType.SPANNABLE);
}
/**
* show full text and append a clickable {@link #LESS}
*/
private void showMore() {
// create a text like subText + ELLIPSIZE + MORE
SpannableStringBuilder builder = new SpannableStringBuilder(mFullText + LESS);
builder.setSpan(new ClickableSpan() {
@Override
public void onClick(View widget) {
showLess();
}
}, builder.length() - LESS.length(), builder.length(), 0);
setText(builder, BufferType.SPANNABLE);
}
}
【讨论】：
以下是使用上述一些响应对我有用的方法（我在示例中使用的是 ButterKnife）：
private static final MAX_LINE_COUNT = 3;
@Bind(R.id.description)
TextView mDescription;
@Override
protected void onCreate(Bundle savedInstanceState) {
if(!TextUtils.isEmpty(mDescription)) {
mDescription.setText(mItem.description);
mDescription.setMaxLines(MAX_LINE_COUNT);
mDescription.setEllipsize(TextUtils.TruncateAt.END);
} else {
mDescription.setVisibility(View.GONE);
}
}
@OnClick(R.id.description)
void collapseExpandTextView(TextView tv) {
if (tv.getMaxLines() == MAX_LINE_COUNT) {
// collapsed - expand it
tv.setEllipsize(null);
tv.setMaxLines(Integer.MAX_VALUE);
} else {
// expanded - collapse it
tv.setEllipsize(TextUtils.TruncateAt.END);
tv.setMaxLines(MAX_LINE_COUNT);
}
ObjectAnimator animation = ObjectAnimator.ofInt(tv, "maxLines", tv.getMaxLines());
animation.setDuration(200).start();
}
当用户点击描述时，它会根据最大行数折叠或展开。 这仅适用于 API 16+。
我遇到的问题是行数在某些点返回零，而行数和最大计数在某些点是相同的值。
【讨论】：
你可以做这样的事情。它适用于任何类型的视图，无论是普通视图，还是 ListView 或 RecyclerView 中的视图：
在onCreate() 或类似的地方，添加：
// initialize integers
int collapsedHeight, expandedHeight;
// get collapsed height after TextView is drawn
textView.post(new Runnable() {
@Override
public void run() {
collapsedHeight = textView.getMeasuredHeight();
}
});
// view that will expand/collapse your TextView
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// number of max lines when collapsed
if (textView.getMaxLines() == 2) {
// expand
textView.setMaxLines(Integer.MAX_VALUE);
textView.measure(View.MeasureSpec.makeMeasureSpec(notifMessage.getMeasuredWidth(), View.MeasureSpec.EXACTLY), View.MeasureSpec.makeMeasureSpec(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED));
expandedHeight = textView.getMeasuredHeight();
ObjectAnimator animation = ObjectAnimator.ofInt(textView, "height", collapsedHeight, expandedHeight);
animation.setDuration(250).start();
} else {
// collapse
ObjectAnimator animation = ObjectAnimator.ofInt(textView, "height", expandedHeight, collapsedHeight);
animation.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animator) {
}
@Override
public void onAnimationEnd(Animator animator) {
// number of max lines when collapsed
textView.setMaxLines(2);
}
@Override
public void onAnimationCancel(Animator animator) {
}
@Override
public void onAnimationRepeat(Animator animator) {
}
});
animation.setDuration(250).start();
}
}
});
这将使您可以通过单击所需的任何视图来展开/折叠 TextView。 （你当然也可以选择 TextView 本身）
【讨论】：
RecyclerView 内展开TextView，新的TextViews 将在滚动期间展开。要重置TextView，请在RecyclerView 中使用textView.setLines(2)。
动画可以使用新的TransitionManager，调用maxLines属性设置数量
fun toggleReadMoreTextView(linesWhenCollapsed: Float) {
if (viewDataBinding.textView.maxLines != Integer.MAX_VALUE) {
// exapand
viewDataBinding.textView.maxLines = Integer.MAX_VALUE
} else {
// collapse
viewDataBinding.textView.maxLines = linesWhenCollapsed
}
// start animation
TransitionManager.beginDelayedTransition(viewDataBinding.constraintLayout)
}
【讨论】：
TextView 大约 200-500 毫秒。如果您在RecyclerView 内展开TextView，新的TextViews 将在滚动期间展开。要重置TextView，请在RecyclerView 中使用textView.setLines(2)。
请参阅下面的链接以获取可扩展的 TextView，其中包含多行和更多文本的选项。
Resizeable Text View(View More and View Less)
在 TextView 中设置文本后，在 Java 类中添加以下行。
// YourCustomeClass.class [your customized class]
// yourTextView [ TextView yourTextView = findViewById(R.id.yourTextView) ];
YourCustomeClass.doResizeTextView(yourTextView, 3, "More", true);
// 3 - No of lines after user wants to expand it.
// "More" : text want to see end of your TextView after shrink
// True : flag for viewMore
【讨论】：
Cliffus' answer 与我所寻找的很接近，但它不支持使用 setMaxLines() 方法，当您无法通过 XML 设置最大行数时会导致问题。
我已经 forked their library 并做到了，因此使用 setMaxLines() 不会破坏展开/折叠操作。我还更新了 Gradle 配置并将其迁移到 AndroidX。否则，用法和以前一样。
您可以使用 Jitpack 将其包含在您的项目中：
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
dependencies {
implementation 'com.github.zacharee:Android-ExpandableTextView:Tag'
}
Tag 是最新的提交标签 (https://jitpack.io/#zacharee/Android-ExpandableTextView/)。
用法与原库完全相同。在您的 XML 中包含 ExpandableTextView：
<at.blogc.android.views.ExpandableTextView
...
android:maxLines="10"
/>
并在代码中展开/折叠：
if (expandable.isExpanded) {
expandable.collapse()
else {
expandable.expand()
}
【讨论】：
RecylerView。
在 ListView 或 RecyclerView 中，我们总是使用 OnPreDrawListener 而不是使用 OnGlobalLayoutListener。在开始时也会为不可见的行触发此回调。来自官方文档：
private void makeTextViewResizable(final TextView tv, final int maxLine, final String expandText, final boolean viewMore){
try {
if (tv.getTag() == null) {
tv.setTag(tv.getText());
}
//OnGlobalLayoutListener
ViewTreeObserver vto = tv.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
ViewTreeObserver obs = tv.getViewTreeObserver();
// obs.removeGlobalOnLayoutListener((ViewTreeObserver.OnGlobalLayoutListener) mActivity);
obs.removeOnPreDrawListener(this);
if (maxLine == 0) {
int lineEndIndex = tv.getLayout().getLineEnd(0);
String text = tv.getText().subSequence(0, lineEndIndex - expandText.length() + 1) + " " + expandText;
tv.setText(text);
tv.setMovementMethod(LinkMovementMethod.getInstance());
tv.setText(
addClickablePartTextViewResizable(Html.fromHtml(tv.getText().toString()), tv, expandText,
viewMore), TextView.BufferType.SPANNABLE);
} else if (maxLine > 0 && tv.getLineCount() >= maxLine) {
int lineEndIndex = tv.getLayout().getLineEnd(maxLine - 1);
String text = tv.getText().subSequence(0, lineEndIndex - expandText.length() + 1) + " " + expandText;
tv.setText(text);
tv.setMovementMethod(LinkMovementMethod.getInstance());
tv.setText(
addClickablePartTextViewResizable(Html.fromHtml(tv.getText().toString()), tv, expandText,
viewMore), TextView.BufferType.SPANNABLE);
} else {
int lineEndIndex = tv.getLayout().getLineEnd(tv.getLayout().getLineCount() - 1);
String text = tv.getText().subSequence(0, lineEndIndex) + " " + expandText;
tv.setText(text);
tv.setMovementMethod(LinkMovementMethod.getInstance());
tv.setText(
addClickablePartTextViewResizable(Html.fromHtml(tv.getText().toString()), tv, expandText,
viewMore), TextView.BufferType.SPANNABLE);
}
return true;
}
});
} catch (Exception e) {
e.printStackTrace();
}
}
【讨论】：
主要是为了在文本末尾添加“查看更多”的情况，我向您展示我的截断文本视图。经过大量实验后，在 RecyclerView 项目视图中加载这些文本视图时，它似乎可以无缝工作。
package com.example.android.widgets;
import android.content.Context;
import android.support.annotation.Nullable;
import android.support.v7.widget.AppCompatTextView;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.TextUtils;
import android.text.style.ForegroundColorSpan;
import android.text.style.RelativeSizeSpan;
import android.util.AttributeSet;
import com.example.android.R;
public class TruncatingTextView extends AppCompatTextView {
public static final String TWO_SPACES = " ";
private int truncateAfter = Integer.MAX_VALUE;
private String suffix;
private RelativeSizeSpan truncateTextSpan = new RelativeSizeSpan(0.75f);
private ForegroundColorSpan viewMoreTextSpan = new ForegroundColorSpan(Color.BLUE);
private static final String MORE_STRING = getContext().getString(R.string.more);
private static final String ELLIPSIS = getContext().getString(R.string.ellipsis);
public TruncatingTextView(Context context) {
super(context);
}
public TruncatingTextView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public TruncatingTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public void setText(CharSequence fullText, @Nullable CharSequence afterTruncation, int truncateAfterLineCount) {
this.suffix = TWO_SPACES + MORE_STRING;
if (!TextUtils.isEmpty(afterTruncation)) {
suffix += TWO_SPACES + afterTruncation;
}
// Don't call setMaxLines() unless we have to, since it does a redraw.
if (this.truncateAfter != truncateAfterLineCount) {
this.truncateAfter = truncateAfterLineCount;
setMaxLines(truncateAfter);
}
setText(fullText);
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (getLayout() != null && getLayout().getLineCount() > truncateAfter) {
int lastCharToShowOfFullTextAfterTruncation = getLayout().getLineVisibleEnd(truncateAfter - 1) - suffix.length() - ELLIPSIS.length();
if (getText().length() <= lastCharToShowOfFullTextAfterTruncation) {
// No idea why this would be the case, but to prevent a crash, here it is. Besides, if this is true, we should be less than our maximum lines and thus good to go.
return;
}
int startIndexOfMoreString = lastCharToShowOfFullTextAfterTruncation + TWO_SPACES.length() + 1;
SpannableString truncatedSpannableString = new SpannableString(getText().subSequence(0, lastCharToShowOfFullTextAfterTruncation) + ELLIPSIS + suffix);
truncatedSpannableString.setSpan(truncateTextSpan, startIndexOfMoreString, truncatedSpannableString.length(), Spannable.SPAN_EXCLUSIVE_INCLUSIVE);
truncatedSpannableString.setSpan(viewMoreTextSpan, startIndexOfMoreString, startIndexOfMoreString + MORE_STRING.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
setText(truncatedSpannableString);
}
}
}
您始终可以选择为 truncateAfter 添加自己的属性，并使用上述任何答案来添加展开/折叠动画（我没有处理展开/折叠的代码，但使用上述动画之一很容易完成答案）。
我把这个放在这里更多是为了那些试图为他们的文本视图找到“查看更多”功能的人。
【讨论】：
现在，使用这个很棒的库 ExpandableTextView 为请求的 TextView 提供动画和所有必需的控件变得更加容易，在这个库中，您只需将其添加到您的 gradle 中，然后在您的xml：
<com.ms.square.android.expandabletextview.ExpandableTextView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:expandableTextView="http://schemas.android.com/apk/res-auto"
android:id="@+id/expand_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
expandableTextView:maxCollapsedLines="4"
expandableTextView:animDuration="200">
<TextView
android:id="@id/expandable_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:textSize="16sp"
android:textColor="#666666" />
<ImageButton
android:id="@id/expand_collapse"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="16dp"
android:layout_gravity="right|bottom"
android:background="@android:color/transparent"/>
</com.ms.square.android.expandabletextview.ExpandableTextView>
然后在您的代码中使用它，例如：
TextView expandableTextView = (ExpandableTextView) findViewById(R.id.expand_text_view);
如您所见，您可以控制所需的最大行数、动画持续时间以及 TextView 扩展技术所需的所有设置。
【讨论】：
这是一个类似方法的仓库： https://github.com/CorradiSebastian/ExpandableTextView
从这个问题中得出：
【讨论】：
第 1 步
<?xml version="1.0" encoding="utf-8"?>
<shape
xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient
android:startColor="#11FFFFFF"
android:centerColor="#33FFFFFF"
android:endColor="#99FFFFFF"
android:angle="270" />
</shape>
第 2 步
<TextView
android:id="@+id/overviewText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:maxLines="3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="@+id/textView8"
app:layout_constraintTop_toBottomOf="@+id/textView8" />
<ImageView
android:id="@+id/seeMoreImage"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="@drawable/background_white"
android:visibility="invisible"
app:layout_constraintBottom_toBottomOf="@+id/overviewText"
app:layout_constraintEnd_toEndOf="@+id/overviewText"
app:layout_constraintStart_toStartOf="@+id/overviewText"
app:srcCompat="@drawable/ic_arrow_down"
tools:ignore="VectorDrawableCompat" />
第 3 步
var isTextViewClicked = true
if (binding.overviewText.lineCount > 3)
binding.seeMoreImage.visibility = View.VISIBLE
binding.seeMoreImage.setOnClickListener {
isTextViewClicked = if(isTextViewClicked){
binding.overviewText.maxLines = Integer.MAX_VALUE
binding.seeMoreImage.setImageResource(R.drawable.ic_arrow_up)
false
} else {
binding.overviewText.maxLines = 3
binding.seeMoreImage.setImageResource(R.drawable.ic_arrow_down)
true
}
}
【讨论】：
创建没有库和自定义类的简单解决方案。
首先使用（例如）两个TextView 创建item.xml。一个用于显示文本，它将被展开，另一个用于按钮 - “显示更多”。
...
<TextView
android:id="@+id/item_info_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="16sp"
tools:text="Test long text info\nTest long text info\nTest long text info\nTest long text info | Test long text info | Test long text info"
android:maxLines="@integer/info_collected_lines"
android:fontFamily="@string/font_roboto_regular"
android:textColor="@color/text_second"
android:layout_marginTop="8dp"
android:ellipsize="end"/>
<TextView
android:id="@+id/item_more_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="12sp"
android:text="@string/see_more"
android:singleLine="true"
android:fontFamily="@string/font_roboto_regular"
android:textColor="@color/text_accent"
android:ellipsize="marquee"/>
...
其他资源：
<color name="text_accent">#0070AA</color>
<color name="text_second">#616161</color>
<string name="font_roboto_regular" translatable="false">sans-serif</string>
<string name="font_roboto_medium" translatable="false">sans-serif-medium</string>
<string name="see_more">Show more</string>
<integer name="club_info_collected_lines">4</integer>
<integer name="club_info_expanded_lines">10</integer>
它看起来像这样：
下一步是为展开文本添加逻辑。我们在RecyclerView.ViewHolder 里面做：
class ItemHolder(view: View) : RecyclerView.ViewHolder(view) {
...
private val infoText = view.findViewById<TextView>(R.id.item_info_text)
private val moreText = view.findViewById<TextView>(R.id.item_more_text)
fun bind(item: Item, callback: Callback) {
infoText.text = item.info
// This is extension (show code later) need for getting correct [TextView.getLineCount]. Because before draw view it always == 0.
infoText.afterLayoutConfiguration {
val hasEllipsize = infoText.layout.getEllipsisCount(infoText.lineCount - 1) > 0
moreText.visibility = if (hasEllipsize) View.VISIBLE else View.GONE
if (hasEllipsize) {
val maxLines = itemView.context.resources.getInteger(R.integer.club_info_expanded_lines)
moreText.setOnClickListener {
infoText.maxLines = maxLines
it.visibility = View.GONE
}
}
}
...
}
// Call this inside [RecyclerView.Adapter.onViewRecycled] for prevent memory leaks.
fun unbind() {
moreText.setOnClickListener(null)
}
}
扩展名：
/**
* Function for detect when layout completely configure.
*/
fun View.afterLayoutConfiguration(func: () -> Unit) {
viewTreeObserver?.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
override fun onGlobalLayout() {
viewTreeObserver?.removeOnGlobalLayoutListener(this)
func()
}
})
}
我尝试在TransitionManager.beginDelayedTransition 中使用动画，但在RecyclerView 内部看起来很难看。就像没有任何动画的样子。
【讨论】：
在你的应用模块gradle中添加依赖
dependencies {
implementation 'com.github.arshadbinhamza:ViewMore:1.0.9'
}
// ViewMoreHolder.load(textView_description,text, Typeface of end Text,UnderLine,number_of_lines,click_for_end_text_only);
// ViewMoreHolder.load(tv_description,description, Typeface.DEFAULT,true,3,false);
请查看我添加的示例（这是从以前的答案中提取的针对我的应用程序要求的解决方案）。我们可以根据要求更新/增强库
【讨论】：