接上篇,
android自定义View&自定义ViewGroup(上)
上篇主要是自定义View，本篇来看看自定义ViewGroup。
先来复习一下一般自定义ViewGroup中需要复写的方法：
void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
void onSizeChanged(int w, int h, int oldw, int oldh)
void onLayout(boolean changed, int left, int top, int right, int bottom)
void onDraw(Canvas canvas)注：ViewGroup的onLayout方法是必须重写的，而onDraw方法默认是不会调用的，如果想执行onDraw方法，可以通过下面两种方法：
1.设置透明背景：
在构造函数中：setBackgroundColor(Color.TRANSPARENT);
或者在xml中：android:background="@color/transparent"
2.或者可以在构造函数中添加setWillNotDraw(false);
自定义ViewGroup中如果需要获得自定义属性，方法和上篇自定义View中获取方法是一样的，请参照上篇。
ViewGroup常用重写方法:
- onMeasure
measureChildren方法触发所有子View的onMeasure方法测量自己并把测量结果回传给ViewGroup(ViewGroup传递给子View建议宽高和测量模式，如果子View的宽高是wrap_content，那么只有子View测量出自己的宽和高)，当所有子View测量完毕后，再调用setMeasuredDimension将ViewGroup自身的宽和高传给它的父View。 - 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。
- onDraw
上面已经提到，自定义ViewGroup默认不会触发onDraw方法，需要设置背景色或者setWillNotDraw(false)来手动触发。
自定义ViewGroup例子，先上图：
代码已上传到github：自定义ViewGroup（五环图）
思路：首先是5个自定义圆环，在自定义ViewGroup的onLayout中排列他们，在onDraw中写文字。
核心代码：
public class CustomFiveRings extends ViewGroup {
private Context mContext;
private TextPaint mPaint;
private int startX;//圆环起始X轴
private int startY;//圆环起始Y轴
private int mWidth;//ViewGroup的宽
private int mHeight;//ViewGroup的高
public CustomFiveRings(Context context) {
this(context, null);
}
public CustomFiveRings(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public CustomFiveRings(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
setBackgroundColor(Color.TRANSPARENT);
mContext = context;
mPaint = new TextPaint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setTextSize(50);
mPaint.setColor(Color.BLACK);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//触发所有子View的onMeasure函数去测量宽高
measureChildren(widthMeasureSpec, heightMeasureSpec);
//MeasureSpec封装了父View传递给子View的布局要求
int wMode = MeasureSpec.getMode(widthMeasureSpec);
int wSize = MeasureSpec.getSize(widthMeasureSpec);
int hMode = MeasureSpec.getMode(heightMeasureSpec);
int hSize = MeasureSpec.getSize(heightMeasureSpec);
switch (wMode) {
case MeasureSpec.EXACTLY:
mWidth = wSize;
break;
case MeasureSpec.AT_MOST:
//这里应该先计算所有子view的宽度，暂时先写死
mWidth = wSize;
break;
case MeasureSpec.UNSPECIFIED:
break;
}
switch (hMode) {
case MeasureSpec.EXACTLY:
mHeight = hSize;
break;
case MeasureSpec.AT_MOST:
//这里应该先计算所有子view的高度，暂时先写死
mHeight = hSize;
// mHeight = getCircleHeight() / 2 * 3;
break;
case MeasureSpec.UNSPECIFIED:
break;
}
setMeasuredDimension(mWidth, mHeight);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int childNum = getChildCount();
startX = startY = 0;
int gap = 10;//同一行圆圈之间的间隔
int screenWidth = DpUtil.getScreenSizeWidth(mContext);
int firstTotalWidth = 0;//第一行子View的总宽度
int secondTotalWidth = 0;//第二行子View的总宽度
for (int i = 0; i < childNum; i++) {
View childView = getChildAt(i);
int childWidth = childView.getMeasuredWidth();
if (i <= 2) {
//前三个总宽度
firstTotalWidth += childWidth;
} else {
//后两个总宽度
secondTotalWidth += childWidth;
}
}
int leftFMargin = (screenWidth - firstTotalWidth - gap * 2) / 2;
int leftSMargin = (screenWidth - secondTotalWidth - gap) / 2;
for (int i = 0; i < childNum; i++) {
View childView = getChildAt(i);
int childWidth = childView.getMeasuredWidth();
int childHeight = childView.getMeasuredHeight();
if (i <= 2) {
//排列前三个圆圈
if (i == 0) {
childView.layout(leftFMargin + startX, startY, leftFMargin + startX + childWidth, startY + childHeight);
startX += childWidth;
} else {
childView.layout(leftFMargin + startX + gap, startY, leftFMargin + startX + gap + childWidth, startY + childHeight); startX += (childWidth + gap);
}
if (i == 2) {
startX = 0;
startY += childHeight / 2;
}
} else {
//排列后两个圆圈
if (i == 3) {
childView.layout(leftSMargin + startX, startY, leftSMargin + startX + childWidth, startY + childHeight);
startX += childWidth;
} else {
childView.layout(leftSMargin + startX + gap, startY, leftSMargin + startX + gap + childWidth, startY + childHeight); startX += (childWidth + gap);
}
}
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int screenWidth = DpUtil.getScreenSizeWidth(mContext);
String upStr = "同一个世界，同一个梦想";
String downStr = "One World,One Dream";
canvas.drawText(upStr, (screenWidth - mPaint.measureText(upStr)) / 2, getCircleHeight() / 2 * 3 + 60, mPaint);
canvas.drawText(downStr, (screenWidth - mPaint.measureText(downStr)) / 2, getCircleHeight() / 2 * 3 + 120, mPaint);
}
/**
* 获得圆环高度
*
* @return 圆环高度
*/
private int getCircleHeight() {
//5个圆环大小是一样的，这里就直接取第一个了
View childView = getChildAt(0);
return childView.getMeasuredHeight();
}}
