自定義ViewGroup

title: 自定義ViewGroup
tags: ViewGroup,Android,自定義View

初始化

  1. 重寫構(gòu)造函數(shù)——三個(gè)
  2. 通過this調(diào)用
  3. init來獲取自定義的屬性

    public SwipeLayout(Context context) {
    this(context,null);
    }
    
    public SwipeLayout(Context context, AttributeSet attrs) {
    this(context, attrs,0);
    }
    
    public SwipeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs, defStyleAttr);
    }

獲取自定義屬性

布局文件 attr.xml

    <declare-styleable name="SwipeLayout">
        <attr name="leftView" format="reference"/>
        <attr name="rightView" format="reference"/>
        <attr name="contentView1" format="reference"/>
        <attr name="canRightSwipe1" format="boolean" />
        <attr name="canLeftSwipe1" format="boolean" />
        <attr name="fraction1" format="float" />
    </declare-styleable>

獲取屬性

        TypedArray typedArray = context.obtainStyledAttributes(attrs,R.styleable.SwipeLayout);
        leftViewId = typedArray.getResourceId(R.styleable.SwipeLayout_leftView,-1);
        rightViewId = typedArray.getResourceId(R.styleable.SwipeLayout_rightView,-1);
        contentViewId = typedArray.getResourceId(R.styleable.SwipeLayout_contentView1,-1);
        canLeftSwipe = typedArray.getBoolean(R.styleable.SwipeLayout_canLeftSwipe1,true);
        canRightSwipe = typedArray.getBoolean(R.styleable.SwipeLayout_canRightSwipe1,true);
        mFraction = typedArray.getFloat(R.styleable.SwipeLayout_fraction1,0.5f);
       
        typedArray.recycle();

onMeasure

思路

  1. View是match_parent 的特殊處理，其他的正常處理
  2. 正常的最終需要調(diào)用 setMeasuredDimension 方法，需要的參數(shù) 寬高、寬高的spec以及state
  3. match_parent 的最終需要調(diào)用 measure方法，需要參數(shù)widthMeasureSpec, heightMeasureSpec
  4. onMeasure前面所做的事情都是來獲取這些參數(shù)
setMeasuredDimension(resolveSizeAndState(maxWidth,widthMeasureSpec,childState)
                ,resolveSizeAndState(maxHeight,heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));
                
                
view.measure(childWidthMeasureSpec,childHeightMeasureSpec);

步驟

  1. 獲取子View的數(shù)量

代碼

 @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //1. 獲取childView的個(gè)數(shù)
        setClickable(true);
        int count = getChildCount();
        //參考frameLayout測量代碼
        final boolean measureMatchParentChildren =
                MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY ||
                        MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY;
        mMatchParentChildren.clear();
        int maxHeight = 0;
        int maxWidth = 0;
        int childState = 0;
        //遍歷childViews
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                measureChildWithMargins(child,widthMeasureSpec,0,heightMeasureSpec,0);
                final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
                maxHeight = Math.max(maxHeight,child.getMeasuredHeight()+lp.leftMargin+lp.rightMargin);
                maxWidth = Math.max(maxWidth,child.getMeasuredWidth()+lp.topMargin+lp.bottomMargin);
                childState = combineMeasuredStates(childState, child.getMeasuredState());

                if (measureMatchParentChildren){
                    if ( lp.width == LayoutParams.MATCH_PARENT || lp.height == LayoutParams.MATCH_PARENT) {
                        mMatchParentChildren.add(child);
                    }
                }
            }
        }

        //寬度和高度還要考慮背景的大小
        maxHeight = Math.max(maxHeight,getSuggestedMinimumHeight());
        maxWidth = Math.max(maxWidth,getSuggestedMinimumWidth());

//        設(shè)置具體寬高
        setMeasuredDimension(resolveSizeAndState(maxWidth,widthMeasureSpec,childState)
                ,resolveSizeAndState(maxHeight,heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));

        count = mMatchParentChildren.size();
        if (count > 1) {
            for (int i = 0; i < count; i++) {
                View view = mMatchParentChildren.get(i);
                MarginLayoutParams lp = (MarginLayoutParams) view.getLayoutParams();

                final int childWidthMeasureSpec;
                if ( lp.width == LayoutParams.MATCH_PARENT) {
                    int width = Math.max(0,getMeasuredWidth()
                            - lp.leftMargin - lp.rightMargin);
                    childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width,MeasureSpec.EXACTLY);
                }else {
                    childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,lp.leftMargin+lp.rightMargin
                            ,lp.width);
                }

                final int childHeightMeasureSpec;
                if ( lp.height == LayoutParams.MATCH_PARENT) {
                    int height = Math.max(0,getMeasuredHeight()
                            - lp.topMargin - lp.bottomMargin);
                    childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height,MeasureSpec.EXACTLY);
                }else{
                    childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,lp.topMargin+lp.bottomMargin
                            ,lp.height);
                }

                view.measure(childWidthMeasureSpec,childHeightMeasureSpec);
            }
        }
    }

onLayout

思路

  1. 調(diào)用layout方法，需要四個(gè)參數(shù)
view.layout(rLeft,rTop,rRight,rBottom)

padding——內(nèi)邊距
margin——外邊距

代碼

 @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {

        // 1. 先找到布局中的View
        int count = getChildCount();
        int left = 0 + getPaddingLeft();
        int right = 0 + getPaddingLeft();
        int top = 0 + getPaddingTop();
        int bottom = 0 + getPaddingTop();

        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            if (mLeftView == null && child.getId() == leftViewId) {
                mLeftView = child;
                mLeftView.setClickable(true);
            }else if (mRightView == null && child.getId() == rightViewId){
                mRightView = child;
                mRightView.setClickable(true);
            }else if (mContentView == null && child.getId() == contentViewId){
                mContentView = child;
                mContentView.setClickable(true);
            }
        }

        //2. 設(shè)置放置的位置

        if (mContentView != null) {
            mContentViewLp = (MarginLayoutParams) mContentView.getLayoutParams();
            int cTop = mContentViewLp.topMargin + top;
            int cLeft = mContentViewLp.leftMargin + left;
            int cRight = cLeft + mContentView.getMeasuredWidth();

            //TODO  此處能不能使用 ??? mContentViewLp.height
            int cBottom = cTop + mContentView.getMeasuredHeight();

            mContentView.layout(cLeft, cTop, cRight, cBottom);
        }

        if (mLeftView != null) {
            MarginLayoutParams leftViewLp = (MarginLayoutParams) mLeftView.getLayoutParams();
            int cTop = leftViewLp.topMargin + top;
            int cRight = 0 - leftViewLp.rightMargin ;
            int cLeft = 0 - mLeftView.getMeasuredWidth() + leftViewLp.rightMargin + leftViewLp.leftMargin;
            int cBottom = top + mLeftView.getMeasuredHeight() + leftViewLp.bottomMargin;

            mLeftView.layout(cLeft,cTop,cRight,cBottom);
        }

        if (mRightView != null) {
            MarginLayoutParams rightViewLp = (MarginLayoutParams) mRightView.getLayoutParams();
            int rTop = rightViewLp.topMargin + top;
            int rLeft = rightViewLp.leftMargin + mContentView.getRight() + mContentViewLp.rightMargin;
            int rRight = rLeft + mRightView.getMeasuredWidth();
            int rBottom = rTop + mRightView.getMeasuredHeight();;

            mRightView.layout(rLeft,rTop,rRight,rBottom);
        }

    }

幾個(gè)常用函數(shù)

getX() 是表示W(wǎng)idget相對于自身左上角的x坐標(biāo)

getRawX() 是表示相對于屏幕左上角的x坐標(biāo)值

理解 getScrollX()

image

1是手機(jī)屏幕，在此區(qū)域內(nèi)的人眼可以看見
2是幕布
3是內(nèi)容

getScrollX 其實(shí)獲取的值，就是這塊幕布在窗口左邊界時(shí)候的值了，而幕布上面哪個(gè)點(diǎn)是原點(diǎn)（0，0）呢？就是初始化時(shí)內(nèi)容顯示的位置。

  • 將幕布往右推動(dòng)的時(shí)候，幕布在窗口左邊界的值就會(huì)在0的左邊（-100）
  • 向左推動(dòng)，則其值會(huì)是在0的右邊（100）

scrollTo()和scrollBy(x,y)

scrollTo(int x, int y) 是將View中內(nèi)容滑動(dòng)到相應(yīng)的位置，參考的坐標(biāo)系原點(diǎn)為parent View的左上角。

  • 參數(shù)為正的，右移
  • 參數(shù)為負(fù)值，左移

scrollTo()指的是移動(dòng)到指定的(x,y)位置
而scrollBy(x,y)指的是，在當(dāng)前位置在移動(dòng)(x,y)個(gè)位置

阻止父層的View截獲touch事件

調(diào)用getParent().requestDisallowInterceptTouchEvent(true);方法。一旦底層View收到touch的action后調(diào)用這個(gè)方法那么父層View就不會(huì)再調(diào)用onInterceptTouchEvent了，也無法截獲以后的action

ViewGroup generateLayoutParams() 方法的作用

父容器生成 子view 的布局LayoutParams;

如果一個(gè)View想要被添加到這個(gè)容器中，這個(gè)view可以調(diào)用此方法生成和容器類匹配的布局LayoutParams，

這個(gè)方法主要是用于父容器添加子View時(shí)調(diào)用。

用于生成和此容器類型相匹配的布局參數(shù)類

startScroll方法

第一個(gè)參數(shù)是起始移動(dòng)的x坐標(biāo)值，第二個(gè)是起始移動(dòng)的y坐標(biāo)值，第三個(gè)第四個(gè)參數(shù)都是移到某點(diǎn)的坐標(biāo)值，而duration 當(dāng)然就是執(zhí)行移動(dòng)的時(shí)間

computeScroll方法

當(dāng)startScroll執(zhí)行過程中即在duration時(shí)間內(nèi)，computeScrollOffset 方法會(huì)一直返回false，但當(dāng)動(dòng)畫執(zhí)行完成后會(huì)返回返加true.

@Override
    public void computeScroll() {
        //判斷Scroller是否執(zhí)行完畢：
        if (mScroller.computeScrollOffset()) {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            //通知View重繪-invalidate()->onDraw()->computeScroll()
            invalidate();
        }
    }

onDetachedFromWindow()

銷毀View的時(shí)候調(diào)用這個(gè)方法，我們可以在里面做一些清理工作（做一些收尾工作）如：取消廣播注冊等等

最后編輯于 ：
?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時(shí)請結(jié)合常識與多方信息審慎甄別。
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點(diǎn)，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容