Android自定义ViewGroup控件

一、简单实现自定义ViewGroup四个顶点放置View
重写generateLayoutParams方法指定ViewGroup的LayoutParams为MarginLayoutParams。重写onMeasure方法，计算childView的测量模式及值，设置ViewGroup的宽和高。重写onLayout方法，设置所有childView的位置。

public class NewlineViewGroup extends ViewGroup {

    private MarginLayoutParams params = null;
    private int count;
    private int cWidth = 0;
    private int cHeight = 0;

    public NewlineViewGroup(Context context) {
        super(context);
    }

    public NewlineViewGroup(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

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

    /**
     * 重写父类的该方法，返回MarginLayoutParams的实例
     *
     * @param attrs
     * @return
     */
    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new MarginLayoutParams(getContext(), attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //计算出所有的childView的宽高
        measureChildren(widthMeasureSpec, heightMeasureSpec);
        //获取childView数量
        count = getChildCount();
        setMeasuredDimension(measureWidth(widthMeasureSpec), measureHeight(heightMeasureSpec));
    }

    /**
     * 测量宽度
     *
     * @param measureSpec
     * @return
     */
    private int measureWidth(int measureSpec) {
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);
        if (specMode == MeasureSpec.AT_MOST) {//设置为wrap_content
            int t = 0, b = 0;
            for (int i = 0; i < count; i++) {
                View childView = getChildAt(i);
                //获取子view的宽
                cWidth = childView.getMeasuredWidth();
                params = (MarginLayoutParams) childView.getLayoutParams();
                if (i == 0 || i == 1) {
                    t += cWidth + params.leftMargin + params.rightMargin;
                }
                if (i == 2 || i == 3) {
                    b += cWidth + params.leftMargin + params.rightMargin;
                }
            }
            specSize = Math.max(t, b);
            return specSize;
        }
        return specSize;
    }

    /**
     * 测量高度
     *
     * @param measureSpec
     * @return
     */
    private int measureHeight(int measureSpec) {
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);
        if (specMode == MeasureSpec.AT_MOST) {//设置为wrap_content
            int l = 0, r = 0;
            for (int i = 0; i < count; i++) {
                View childView = getChildAt(i);
                //获取子view的高
                cHeight = childView.getMeasuredHeight();
                params = (MarginLayoutParams) childView.getLayoutParams();
                if (i == 0 || i == 2) {
                    l += cHeight + params.topMargin + params.bottomMargin;
                }
                if (i == 1 || i == 3) {
                    r += cHeight + params.topMargin + params.bottomMargin;
                }
            }
            specSize = Math.max(l, r);
            return specSize;
        }
        return specSize;
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        for (int i = 0; i < count; i++) {
            View childView = getChildAt(i);
            cWidth = childView.getMeasuredWidth();
            cHeight = childView.getMeasuredHeight();
            params = (MarginLayoutParams) childView.getLayoutParams();
            int cl = 0, cr = 0, ct = 0, cb = 0;
            switch (i) {
                case 0:
                    cl = params.leftMargin;
                    ct = params.topMargin;
                    break;
                case 1:
                    cl = getWidth() - cWidth - params.leftMargin;
                    ct = params.topMargin;
                    break;
                case 2:
                    cl = params.leftMargin;
                    ct = getHeight() - cHeight - params.bottomMargin;
                    break;
                case 3:
                    cl = getWidth() - cWidth - params.leftMargin - params.rightMargin;
                    ct = getHeight() - cHeight - params.bottomMargin;
                    break;
            }
            cr = cl + cWidth;
            cb = cHeight + ct;
            childView.layout(cl, ct, cr, cb);
        }
    }
}

xml文件中的实现

    <com.example.yinyuetai.myapplication.newline.NewlineViewGroup
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp">

        <TextView
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:background="#FF4444"
            android:gravity="center"
            android:text="0"
            android:textColor="#FFFFFF"
            android:textSize="22sp"
            android:textStyle="bold" />

        <TextView
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:background="#00ff00"
            android:gravity="center"
            android:text="1"
            android:textColor="#FFFFFF"
            android:textSize="22sp"
            android:textStyle="bold" />

        <TextView
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:background="#ff0000"
            android:gravity="center"
            android:text="2"
            android:textColor="#FFFFFF"
            android:textSize="22sp"
            android:textStyle="bold" />

        <TextView
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:background="#0000ff"
            android:gravity="center"
            android:text="3"
            android:textColor="#FFFFFF"
            android:textSize="22sp"
            android:textStyle="bold" />
    </com.example.yinyuetai.myapplication.newline.NewlineViewGroup>

二、实现ViewGroup自动换行
代码中邮详细注解不在赘述

private int childCount;
    private static final int PADDING_HOR = 20;
    private static final int PADDING_VER = 20;
    private static final int SIDE_MARGIN = 40;
    private static final int TEXT_MARGIN = 40;

    public WordWrapViewGroup(Context context) {
        super(context);
    }

    public WordWrapViewGroup(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

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

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new MarginLayoutParams(getContext(), attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //横纵坐标
        int x = 0;
        int y = 0;
        //行数
        int rows = 1;
        //获取view的数量
        childCount = getChildCount();
        //获取父控件宽度
        int specWidth = MeasureSpec.getSize(widthMeasureSpec);
        //实际宽度
        int actualWidth = specWidth - SIDE_MARGIN * 2;
        for (int i = 0; i < childCount; i++) {
            View view = getChildAt(i);
            //设置边框距离
            view.setPadding(PADDING_HOR, PADDING_VER, PADDING_HOR, PADDING_VER);
            //设置父控件ViewGroup大小
            view.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
            //获得当前控件的宽高
            int width = view.getMeasuredWidth();
            int height = view.getMeasuredHeight();
            //计算总宽度
            x += width + TEXT_MARGIN;
            //判断是否超出实际宽度
            if (x > actualWidth) {
                x = width;
                rows++;
            }
            y = rows * (height + TEXT_MARGIN);
        }
        setMeasuredDimension(actualWidth, y);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int actualWidth = r - l;
        //横纵坐标开始
        int x = 0;
        int y = 0;
        //行数
        int rows = 1;
        for (int i = 0; i < childCount; i++) {
            View view = getChildAt(i);
            int width = view.getMeasuredWidth();
            int height = view.getMeasuredHeight();
            x += width + TEXT_MARGIN;
            if (x > actualWidth) {
                x = width + TEXT_MARGIN;
                rows++;
            }
            y = rows * (height + TEXT_MARGIN);
            view.layout(x - width, y - height, x, y);
        }
    }
}