Android自定义控件：绘制ViewGroup控件

自定义布局ViewGroup：基本操作由四个函数完成：onMeasure()、onSizeChanged()、onLayout()、dispatchDraw()。
onMeasure
测量所有子控件的尺寸（触发所有子View的onMeasure方法测量自己并把测量结果回传给ViewGroup）和设置自己的尺寸。（所有子View测量完毕后，再调用setMeasuredDimension将ViewGroup自身的宽和高传给它的父View）getChildCount()方法，返回子View的数量，measureChild()方法，调用子View的测量方法。

onSizeChanged
在onMeasure()后执行，只有大小发生了变化才会执行onSizeChange

onLayout
排列所有子View的位置，通过getChildCount()获取所有子view，getChildAt获取childView调用各自的layout(int, int, int, int)方法来排列自己。

简单实现自动换行

public class CustomViewGroup extends ViewGroup {
    private final int PADDING_HOR = 10;
    private final int PADDING_VERTICAL = 20;
    //父控件的宽度
    private int parentWidth;
    private int coordinateX;
    private int coordinateY;
    //总行数
    private int number;

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

    public CustomViewGroup(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CustomViewGroup(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        coordinateX = 0;
        coordinateY = 0;
        number = 1;
        int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = getChildAt(i);
            if (child.getVisibility() != View.GONE) {
                child.setBackgroundColor(Color.RED);
                int width = child.getMeasuredWidth();
                int height = child.getMeasuredHeight();
                coordinateX += width;
                if (coordinateX > parentWidth) {
                    coordinateX = width;
                    number++;
                }
                coordinateY = number * height;
                child.layout(coordinateX - width, coordinateY - height, coordinateX, coordinateY);
            }
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        coordinateX = 0;
        coordinateY = 0;
        number = 1;
        parentWidth = measureSize(widthMeasureSpec, 240);
        int count = getChildCount();//子View数量
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            if (child.getVisibility() != View.GONE) {
                child.setPadding(PADDING_HOR, PADDING_VERTICAL, PADDING_HOR, PADDING_VERTICAL);
                child.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
                measureChild(child, widthMeasureSpec, heightMeasureSpec);
                int width = child.getMeasuredWidth();
                int height = child.getMeasuredHeight();
                coordinateX += width;
                if (coordinateX > parentWidth) {//换行
                    coordinateX = width;
                    number++;
                }
                coordinateY = number * (height);
            }
        }
        setMeasuredDimension(parentWidth, coordinateY);
    }

    /**
     * 计算父控件宽度
     *
     * @param measureSpec
     * @param defaultSize
     * @return
     */
    private int measureSize(int measureSpec, int defaultSize) {
        int mode = MeasureSpec.getMode(measureSpec);
        int size = MeasureSpec.getSize(measureSpec);
        int result = defaultSize;
        if (mode == MeasureSpec.EXACTLY) {
            result = size;
        } else if (mode == MeasureSpec.AT_MOST) {
            result = Math.max(size, result);
        }
        return result;
    }
}

        arrayList.add("张三");
        arrayList.add("测试测试测试测试测试测试");
        arrayList.add("李四");
        arrayList.add("测试测试测试测试测试测试测试测试测试测试测试测试");
        arrayList.add("王五");
        arrayList.add("测试测试测试测");
        arrayList.add("赵六");
        for (int i = 0; i < arrayList.size(); i++) {
            textView = new TextView(this);
            textView.setId(i);
            textView.setText(arrayList.get(i));
            customViewGroup.addView(textView);
        }