Question

我有TextView首先显示长文本的一小部分。

用户可以按＆＃34;查看更多＆＃34;按钮展开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之间用于折叠和Integer.MAX_VALUE进行扩展来实现。

现在，我希望这种行为伴随着一个动画。我知道在this question中，一个解决方案几乎已经完成，但我试图实现它并且我没有成功。

有人可以帮我这个吗？

提前致谢。

Answer 1

您可以在ExpandableTexTView上查看我的博文：

这个想法是，最初TextView将显示一小段长文本，当它被点击时，它将显示文本的其余部分。

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;
    }
}

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>

将以下内容放在main.xml

中

<?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>

测试你的活动

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);

    }
}

参考：Android – Expandable TextView

Answer 2

使用ObjectAnimator。

ObjectAnimator animation = ObjectAnimator.ofInt(yourTextView, "maxLines", tv.getLineCount());
animation.setDuration(200).start();

这将在200毫秒内完全展开TextView。您可以将tv.getLineCount()替换为要将其折叠回来的文本行数。

---- ----更新

以下是一些便捷方法：

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：

如果尚未设置maxLines，或者您set the height of your textView in pixels，则可以获得ArrayIndexOutOfBounds异常。

以上示例总是需要200毫秒，无论是扩展为3行还是400行。如果您想要一致的扩展速度，您可以执行以下操作：

int duration = (textView.getLineCount() - collapsedMaxLines) * 10;

Answer 3

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。我把它放在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，它只是一个常规的TextView，并添加了一些额外的功能。通过定义android：maxLines属性，您可以设置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>

在您的活动或片段中：

    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");
        }
    });

您可以轻松地将此库作为gradle依赖项添加到Android项目中。看一下Github上的项目以获得进一步的指示：

https://github.com/Blogcat/Android-ExpandableTextView

Answer 4

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();
}

P.S。我假设TextView受maxLines限制。
P.S.S.感谢ObjectAnimator示例的Amagi82

Answer 5

如果您想根据行数进行操作，可以采用以下方法：

（Gist完整代码）

/**
 * 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);
    }
}

Answer 6

以下是使用上述某些响应（我在示例中使用ButterKnife）对我有用的原因：

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，它将根据最大行折叠或展开。 这仅适用于API 16 +。

我遇到的问题是，行数在点处返回零，行数和最大计数在某些点上的值相同。

Answer 7

你可以这样做。它可以在任何类型的视图中工作，无论是普通视图，还是ListView或RecyclerView中的视图：

在onCreate()或类似内容中，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();
        }
    }
});

这将允许您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）

Answer 8

请参阅以下链接，了解可扩展的TextView，其中包含多行和更少文本的选项。

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

Answer 9

Cliffus' answer接近我的期望，但是它不支持使用setMaxLines()方法，当您无法通过XML设置最大行数时会导致问题。

我已经完成forked their library的使用，因此使用setMaxLines()不会破坏展开/折叠动作。我还更新了Gradle配置并将其迁移到AndroidX。否则，用法与以前相同。

您可以使用Jitpack将其包含在项目中：

allprojects {
    repositories {
        ...
        maven { url 'https://jitpack.io' }
    }
}

dependencies {
    implementation 'com.github.zacharee:Android-ExpandableTextView:Tag'
}

Tag是最新的提交标记（https://jitpack.io/#zacharee/Android-ExpandableTextView/）。

用法与原始库的用法完全相同。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()
}

Answer 10

在ListView或RecyclerView中，我们总是使用OnPreDrawListener，而不是使用OnGlobalLayoutListener。对于启动时的非可见行，也会触发此回调。从官方文档：

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();
        }

    }

Answer 11

主要针对添加＆＃34;查看更多＆＃34;到文本的最后，我向你呈现我的TruncatingTextView。经过大量实验后，在RecyclerView项目视图中加载这些文本视图时，它似乎无缝地工作。

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);
        }
    }
}

您总是可以选择为truncateAfter添加自己的属性，并使用上述任何答案添加动画以进行展开/折叠（我没有编码来处理展开/折叠，但可以通过使用上述动画之一轻松完成答复）。

我将此更多地放在那些试图找到＆＃34;查看更多＆＃34;文本视图的功能。

Answer 12

现在，使用这个真棒库ExpandableTextView提供动画和所有必需控件更加容易，在这个库中你只需将它添加到你的gradle然后定义它像你的xml中的以下内容：

  <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>

然后在你的代码中使用它，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以及动画持续时间和TextView扩展技术的所有必需设置。

Answer 13

这是具有类似方法的回购协议： https://github.com/CorradiSebastian/ExpandableTextView

是从这个问题出来的：

Custom Expandable TextView

Answer 14

您可以为动画使用新的TransitionManager并调用maxLines属性来设置数量

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)
}

Answer 15

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
        }
    }

Answer 16

创建没有库和自定义类的简单解决方案。

首先用（例如）两个 TextView 创建 item.xml。一个用于显示文本，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：

下一步是添加扩展文本的逻辑。我们在 RecyclerView.ViewHolder 内进行：

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：

/**
 * Function for detect when layout completely configure.
 */
fun View.afterLayoutConfiguration(func: () -> Unit) {
    viewTreeObserver?.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {
            viewTreeObserver?.removeOnGlobalLayoutListener(this)
            func()
        }
    })
}

我尝试将动画与 TransitionManager.beginDelayedTransition 一起使用，但它在 RecyclerView 中看起来很丑。就像没有任何动画的样子。

Android - 带动画的可扩展TextView

16 个答案: