image.png

自定義view

 @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int mode = MeasureSpec.getMode(widthMeasureSpec);
        int size = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        if(mode == MeasureSpec.AT_MOST){
            setMeasuredDimension(500,heightSize);
        }

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        int width = getWidth();
        int height = getHeight();

        int paddingLeft = getPaddingLeft();
       int paddingRight = getPaddingRight();
        int paddingBottom = getPaddingBottom();
        int paddingTop = getPaddingTop();

        canvas.drawCircle((width+paddingLeft-paddingRight)/2,(height-paddingBottom+paddingTop)/2,Math.min((width-paddingLeft-paddingRight)/2,(height-paddingBottom-paddingTop)/2),paint);

    }

自定義viewgroup，對onMeasure和onLayout的處理

 @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //假設(shè)這是一個linearlayout vertical 具體情況具體討論
        //
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        
        measureChildren(widthMeasureSpec,heightMeasureSpec);
        //調(diào)用了measureChild 里面合成了view的MeasureSpec髓涯，然后view調(diào)用了measure
        //如果mode 是EXACTLY  按照自己的size去設(shè)置 這里不寫了
        //如果是AL_MOST 遍歷子元素袒啼，寬度是最大子元素寬度，高度是所有子元素加起來的高度。

        //1.判斷子元素?cái)?shù)量 //2.遍歷子元素 獲取寬高 //3.給viewgroup設(shè)置寬高
        int childCount = getChildCount();
        //如果是0 直接寬高設(shè)為0
        //如果不是
        int viewMeasurHeight = 0;
        int viewMeasuredWidth = 0;
        for (int i =0;i<childCount;i++){
            View childAt = getChildAt(i);
             viewMeasurHeight = childAt.getMeasuredHeight();
            viewMeasuredWidth  = childAt.getMeasuredWidth();
            //假設(shè)每個view的寬高固定
            break;
        }
        setMeasuredDimension(viewMeasuredWidth,viewMeasurHeight*childCount);
        //實(shí)際情況中還要考慮view的margin,和自己的padding
    }

   @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        //還是以onMeasure做假設(shè)的 線性布局蚓再，Vertical
        //每一個view 從上到下排列滑肉。x坐標(biāo)不變，y坐標(biāo)一直變大摘仅。

        int childCount = getChildCount();
        for (int i = 0;i<childCount;i++){
            View view = getChildAt(i);
            int measuredHeight = view.getMeasuredHeight();
            int measuredWidth = view.getMeasuredWidth();
            //四個坐標(biāo)
            view.layout(0,measuredHeight*i,measuredWidth,measuredHeight*(i+1));
            //如果把viewgroup的padding 和view的margin考慮進(jìn)去
            int paddingLeft = getPaddingLeft();
            int paddingRight = getPaddingRight();
            //top 和bottom不寫了 一樣的情況靶庙。
            MarginLayoutParams layoutParams = (MarginLayoutParams) view.getLayoutParams();
            int leftMargin = layoutParams.leftMargin;
            int rightMargin = layoutParams.rightMargin;
            
            view.layout(leftMargin+paddingLeft,measuredHeight*i,measuredWidth+paddingRight+rightMargin,measuredHeight*(i+1));
        }

    }

public MyVIewCircle(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.MyVIewCircle);
        int color = typedArray.getColor(R.styleable.MyVIewCircle_color, Color.RED);
        typedArray.recycle();
        init();
    }