效果图：

代码：

import android.animation.Animator;import android.animation.AnimatorListenerAdapter;import android.animation.ValueAnimator;import android.content.Context;import android.text.TextUtils;import android.util.AttributeSet;import android.view.View;import android.view.animation.DecelerateInterpolator;import android.widget.LinearLayout;import android.widget.TextView;/** * Created by pengkv on 16/1/11. */public class ExpandTextView extends TextView implements View.OnClickListener {
          private int mMaxCount;//记录文本框的最大行数    private boolean isSinleLine = true;//是否是单行显示    private boolean isFitst = true;//是否是第一次測量    public ExpandTextView(Context context) {        super(context);        setOnClickListener(this);    }    public ExpandTextView(Context context, AttributeSet attrs) {        super(context, attrs);        setOnClickListener(this);    }    public ExpandTextView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        setOnClickListener(this);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        if (isFitst) {
     //假设是第一次測量，记录最大行数。測量后设置成单行            mMaxCount = getLineCount();            setEllipsize(TextUtils.TruncateAt.END);            setSingleLine();            isFitst = false;        }    }    @Override    public void onClick(View v) {        ValueAnimator animator;        final LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) getLayoutParams();        if (isSinleLine) {
     //设置展开动画的位移            setSingleLine(false);            animator = ValueAnimator.ofInt(getLineHeight(), mMaxCount * getLineHeight());        } else {
     //设置收缩动画的位移            animator = ValueAnimator.ofInt(mMaxCount * getLineHeight(), getLineHeight());        }        //属性动画的使用方法        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                params.height = (int) animation.getAnimatedValue();                setLayoutParams(params);            }        });        animator.setInterpolator(new DecelerateInterpolator());        animator.setDuration(300);        animator.setTarget(this);        animator.start();        animator.addListener(new AnimatorListenerAdapter() {            @Override            public void onAnimationEnd(Animator animation) {                super.onAnimationEnd(animation);                if (!isSinleLine) {
     //在动画结束后设置成单行，避免效果异常                    setSingleLine();                }                isSinleLine = !isSinleLine;            }        });    }}

XML使用：

//注意：不要在xml的view.ExpandTextView里面定义singleLine、ellipsize属性，否则会异常

Tip：

代码中涉及到的属性动画建议參考。

优化：

//点击事件的处理能够换成以下这样的更简洁的方式。

@Override    public void onClick(View v) {        final ObjectAnimator animator;        if (isSinleLine) {            setSingleLine(false);            animator = ObjectAnimator.ofInt(this, "height", getLineHeight(), mMaxCount * getLineHeight());        } else {            animator = ObjectAnimator.ofInt(this, "height", mMaxCount * getLineHeight(), getLineHeight());        }        animator.setDuration(300).start();        animator.addListener(new AnimatorListenerAdapter() {            @Override            public void onAnimationEnd(Animator animation) {                super.onAnimationEnd(animation);                if (!isSinleLine) {
     //在动画结束后设置成单行，避免效果异常                    setSingleLine();                }                isSinleLine = !isSinleLine;            }        });    }