本文共 5985 字，大约阅读时间需要 19 分钟。

上篇已经实现了条件换行的自定义VIew，最后也说到onLayout来设置换行显示，这里用ViewGroup来实现，无非canvas.drawText控制文字换行换成onLayout来控制textview的换行。

既然是ViewGroup，那里面装的就是View了，这里使用上篇自定义的textview，因为系统的Textview是有行距的。

首先，onMeasure还是会首先执行，你可以使用自定义View时候的方法来计算宽高(文字大小+padding)+viewgroup的padding，也可以直接得到子View的宽高，然后加上padding。 得到子view的个数： int hadChildCount = getChildCount(); 得到子view的实例：   View child = getChildAt(i); 计算子view的宽高等： measureChild(child, widthMeasureSpec, heightMeasureSpec); 得到子view的宽高：int childMeasuredHeight = child.getMeasuredHeight(); onMeasure已经得到了当前viewgroup的所有view，现在需要对子view的位置进行排布 使用View.layout(left,top,right,bottom)设置位置即可:四个点确定一个矩形范围  

效果图：

 

实例代码如下：

public class MyTextview_Viewgroup extends ViewGroup {    public MyTextview_Viewgroup(Context context) {        super(context);    }    public MyTextview_Viewgroup(Context context, AttributeSet attrs) {        super(context, attrs);        initAtters(context, attrs);    }    public MyTextview_Viewgroup(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initAtters(context, attrs);    }    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)    public MyTextview_Viewgroup(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {        super(context, attrs, defStyleAttr, defStyleRes);        initAtters(context, attrs);    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        int startLeft = getPaddingLeft();        int startTop = getPaddingTop();        int startRight = getPaddingLeft();        int startBottom = getPaddingTop();        for (int i = 0; i < childs.size(); i++) {            View child = childs.get(i);            startRight = startRight + child.getMeasuredWidth();            startBottom = startBottom + child.getMeasuredHeight();            //left top right bottom            child.layout(startLeft, startTop, startRight, startBottom);            startTop = startTop + child.getMeasuredHeight();        }    }    String text = "需要显示的文字";    private void initAtters(Context context, @Nullable AttributeSet attrs) {        TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.MyTextview);        text = array.getString(R.styleable.MyTextview_texcontent);    }    private void initView(int widthSize) {        //因为onmeasure会执行多次        this.removeAllViews();        //首先还是判断能不能一行放下        Paint paint = null;        Rect rect = null;        if (paint == null) {            paint = new Paint();            paint.setTextSize(SizeUtil.sp2px(getContext(), 20.0f));            paint.setColor(Color.parseColor("#000000"));            paint.setAntiAlias(true);            paint.setFilterBitmap(true);//位图过滤            ;        }        if (rect == null) {            rect = new Rect();        }        paint.getTextBounds(text, 0, text.length(), rect);        //        if (widthSize - getPaddingLeft() - getPaddingRight() >= rect.width()) {            //一行容纳            MyTextview textView = new MyTextview(getContext());            textView.setPadding(0, 0, 0, 0);            ViewGroup.LayoutParams layoutParams = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);            textView.setLayoutParams(layoutParams);            textView.setText(text);            this.addView(textView);            return;        }        List
   
     rowStrings = new ArrayList<>();        double rows = text.length() / 7.0;        int lineNum = (int) Math.ceil(rows);        //一行文字所包含的文字数        //0开始，依次加然后判断        for (int i = 0; i < lineNum; i++) {            String rowText = "";            if (i == lineNum - 1) {                rowStrings.add(text.substring(i * 7, text.length()));                rowText = text.substring(i * 7, text.length());            } else {                rowStrings.add(text.substring(i * 7, (i + 1) * 7));                rowText = text.substring(i * 7, (i + 1) * 7);            }            MyTextview textView = new MyTextview(getContext());            textView.setPadding(0, 0, 0, 0);            ViewGroup.LayoutParams layoutParams = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);            textView.setLayoutParams(layoutParams);            textView.setText(rowText);            this.addView(textView);        }    }    List
    
      childs;    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        childs = new ArrayList<>();        //       Log.e("MyViewgroup+onMeasure", "现在有多少个子view" + getChildCount());        int widthMode = MeasureSpec.getMode(widthMeasureSpec);   //获取宽的模式        int heightMode = MeasureSpec.getMode(heightMeasureSpec); //获取高的模式        int widthSize = MeasureSpec.getSize(widthMeasureSpec);   //获取宽的尺寸        int heightSize = MeasureSpec.getSize(heightMeasureSpec); //获取高的尺寸        initView(widthSize);        //测量子view的宽高，然后得到整个的宽高        int width = 0;        int height = 0;        int hadChildCount = getChildCount();        for (int i = 0; i < hadChildCount; i++) {            View child = getChildAt(i);            childs.add(child);            //测量下子view的大小            measureChild(child, widthMeasureSpec, heightMeasureSpec);            int childMeasuredHeight = child.getMeasuredHeight();            int childMeasuredWidth = child.getMeasuredWidth();            // Log.e("当前child的宽和高是", childMeasuredWidth + "-" + childMeasuredHeight);            if (childMeasuredWidth > width) {                width = childMeasuredWidth + getPaddingLeft() + getPaddingRight();            }            height = height + childMeasuredHeight;        }        if (widthMode == MeasureSpec.EXACTLY) {            width = widthSize;        } else {        }        if (heightMode == MeasureSpec.EXACTLY) {            height = heightSize;        }        //保存测量宽度和测量高度        setMeasuredDimension(width, height + getPaddingBottom() + getPaddingTop());        Log.e("计算出来viewgroup的高度是", height + getPaddingTop() + getPaddingBottom() + "");    }}
    
   

 

 

转载地址：http://scrci.baihongyu.com/