JavaSwing基础之Layout布局相关知识详解

private void performLayout(WindowManager.LayoutParams lp, int desiredWindowWidth,
            int desiredWindowHeight) {
 
        final View host = mView;
        host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight());
    }

public void layout(int l, int t, int r, int b) {
 
        boolean changed = isLayoutModeOptical(mParent) ?
                setOpticalFrame(l, t, r, b) : setFrame(l, t, r, b);
 
        if (changed || (mPrivateFlags & PFLAG_LAYOUT_REQUIRED) == PFLAG_LAYOUT_REQUIRED) {
            onLayout(changed, l, t, r, b);
        }
    }
 
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    }

protected boolean setFrame(int left, int top, int right, int bottom) {
        boolean changed = false;
 
        if (mLeft != left || mRight != right || mTop != top || mBottom != bottom) {
            changed = true;
 
            // Remember our drawn bit
            int drawn = mPrivateFlags & PFLAG_DRAWN;
 
            int oldWidth = mRight - mLeft;
            int oldHeight = mBottom - mTop;
            int newWidth = right - left;
            int newHeight = bottom - top;
            boolean sizeChanged = (newWidth != oldWidth) || (newHeight != oldHeight);
 
            // Invalidate our old position
            invalidate(sizeChanged);
 
            mLeft = left;
            mTop = top;
            mRight = right;
            mBottom = bottom;
            mRendernode.setLeftTopRightBottom(mLeft, mTop, mRight, mBottom);
        }
        return changed;
    }

public final int getWidth() {
        return mRight - mLeft;
    }

@Override
    public final void layout(int l, int t, int r, int b) {
        if (!mSuppressLayout && (mTransition == null || !mTransition.isChangingLayout())) {
            if (mTransition != null) {
                mTransition.layoutChange(this);
            }
            super.layout(l, t, r, b);
        } else {
            mLayoutCalledWhileSuppressed = true;
        }
    }

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

public class VerticalLayout : ViewGroup {
 
    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int = 0) : super(
        context,
        attrs,
        defStyleAttr
    )
 
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {
    }
}

override fun generateLayoutParams(attrs: AttributeSet?): LayoutParams? {
        return MarginLayoutParams(context, attrs)
    }

protected final void setMeasuredDimension(int measuredWidth, int measuredHeight)

override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        //获取宽高的测量模式和测量大小
        val widthMode = MeasureSpec.getMode(widthMeasureSpec)
        val heightMode = MeasureSpec.getMode(heightMeasureSpec)
        val sizeWidth = MeasureSpec.getSize(widthMeasureSpec)
        val sizeHeight = MeasureSpec.getSize(heightMeasureSpec)
 
        var mHeight = 0
        var mWidth = 0
 
        //遍历子View，获取总高度
        for (i in 0 until childCount) {
            val childView = getChildAt(i)
            //测量子View的宽和高
            measureChild(childView, widthMeasureSpec, heightMeasureSpec)
            val lp = childView.layoutParams as MarginLayoutParams
            val childWidth = childView.measuredWidth + lp.leftMargin + lp.rightMargin
            val childHeight = childView.measuredHeight + lp.topMargin + lp.bottomMargin
 
            //计算得出最大宽度
            mWidth = Math.max(mWidth, childWidth)
            //累计计算高度
            mHeight += childHeight
        }
 
        //设置宽高
        setMeasuredDimension(
            if (widthMode == MeasureSpec.EXACTLY) sizeWidth else mWidth,
            if (heightMode == MeasureSpec.EXACTLY) sizeHeight else mHeight
        )
    }

override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
        var childWidth = 0
        var childHeight = 0
        var childTop = 0
        var lp: MarginLayoutParams
 
        //遍历子View，布局每个子View
        for (i in 0 until childCount) {
            val childView = getChildAt(i)
            childHeight = childView.measuredHeight
            childWidth = childView.measuredWidth
            lp = childView.layoutParams as MarginLayoutParams
 
            //累计计算top值
            childTop += lp.topMargin
 
            //布局子View
            childView.layout(
                lp.leftMargin,
                childTop,
                lp.leftMargin + childWidth,
                childTop + childHeight
            );
 
            childTop += childHeight + lp.bottomMargin
        }
    }

<com.panda.studynote3.VerticalLayout
        Android:layout_width="wrap_content"
        android:layout_height="wrap_content">
 
        <TextView
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:text="啦啦啦"
            android:textSize="20sp"
            android:textColor="@color/white"
            android:background="@color/design_default_color_primary"
            />
 
        <TextView
            android:layout_width="300dp"
            android:layout_height="200dp"
            android:layout_marginTop="20dp"
            android:background="@color/cardview_dark_background"
            android:textSize="20sp"
            android:textColor="@color/white"
            android:text="你好啊"
            />
 
        <TextView
            android:layout_width="140dp"
            android:layout_height="100dp"
            android:text="嘻嘻"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="10dp"
            android:textSize="20sp"
            android:gravity="center"
            android:textColor="@color/black"
            android:background="@color/teal_200"
            />
 
    </com.panda.studynote3.VerticalLayout>