android-自定义伸缩Textview

自定义伸缩TextView效果图 如下：

test2.gif

伸缩效果的思路

1.设置初始的高度 2.设置展开的高度 3.伸缩的动画效果

创建R.layout.cookdetail_item_desc布局

image.png

创建一个FoldingTextView 继承 LinearLayout 做一次初始化

public class FoldingTextView extends LinearLayout implements View.OnClickListener {

    private TextView tv_content;
    private ImageView folding_imageview;
 

    public FoldingTextView(Context context) {
        this(context, null);
    }

    public FoldingTextView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public FoldingTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initView(context);
    }

    private void initView(Context context) {
        setOrientation(VERTICAL);
        View view = View.inflate(context, R.layout.cookdetail_item_desc, null);
        tv_content = view.findViewById(R.id.tv_content);
        folding_imageview = view.findViewById(R.id.detail_desc_folding_imageview);
        folding_imageview.setOnClickListener(this);
        addView(view);
    }

按照刚刚的思路 第一步先设置开始的高度

 public int initHeight() {
        int measuredWidth = tv_content.getMeasuredWidth();
        TextView textView = new TextView(getContext());
        textView.setTextSize(TypedValue.COMPLEX_UNIT_DIP, 15);
        int width = MeasureSpec.makeMeasureSpec(measuredWidth, MeasureSpec.EXACTLY);
        textView.setMaxLines(3);
        textView.setLines(3);
        int height = MeasureSpec.makeMeasureSpec(2000, MeasureSpec.AT_MOST);
        textView.measure(width, height);
        return textView.getMeasuredHeight();
    }

通过new TextView，得到textView,设置setMaxLines(3)，setLines(3),
设置初始的高度,获取textview的高度要先通过测量textView.measure(width, height);才能获取textView.getMeasuredHeight()的值，不然为空

第二步 设置伸开的高度

   public int maxHeight() {
        int measuredWidth = tv_content.getMeasuredWidth();
        int width = MeasureSpec.makeMeasureSpec(measuredWidth, MeasureSpec.EXACTLY);
        int height = MeasureSpec.makeMeasureSpec(2000, MeasureSpec.AT_MOST);
        tv_content.measure(width, height);
        return tv_content.getMeasuredHeight();
    }

为什么不使用tv_content，而要创建一个TextView来设置开始的高度？

如果使用tv_content设置开始的高度，设置的最大行数。到展开的时候也要再次设置一次setMaxline，还有一个可能伸缩的效果产生影响

第三步 通过动画ValueAnimator来完成伸缩效果

 public void expand() {
        int startHeight = 0;
        int endHeight = 0;
        if (!isExpand) {
            startHeight = initHeight();
            endHeight = maxHeight();
            isExpand = true;
        } else {
            startHeight = maxHeight();
            endHeight = initHeight();
            isExpand = false;
        }

        final ViewGroup.LayoutParams params = tv_content.getLayoutParams();

        ValueAnimator animator = ValueAnimator.ofInt(startHeight, endHeight);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                int value = (int) animation.getAnimatedValue();
                params.height = value;
                tv_content.setLayoutParams(params);
            }
        });

        animator.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {

            }

            @Override
            public void onAnimationEnd(Animator animation) {
                if (isExpand) {
                    folding_imageview.setBackgroundResource(R.drawable.ic_public_arrow_up);
                } else {
                    folding_imageview.setBackgroundResource(R.drawable.ic_public_arrow_down);
                }
            }

            @Override
            public void onAnimationCancel(Animator animation) {

            }

            @Override
            public void onAnimationRepeat(Animator animation) {

            }
        });

        animator.setDuration(300);
        animator.start();

    }

完成，收工！！！