自定义View——循环轮播View

来源：互联网发布：上饶招聘中年淘宝模特编辑：程序博客网时间：2024/06/04 19:52

通过scroller实现轮播View控件：

效果：

这里写图片描述

public class BannerLoopLayout extends ViewGroup {    private Scroller mScroller;    public BannerLoopLayout(Context context) {        this(context,null,0);    }    public BannerLoopLayout(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public BannerLoopLayout(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        mScroller = new Scroller(context);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        int w = MeasureSpec.getSize(widthMeasureSpec);        int h = MeasureSpec.getSize(heightMeasureSpec);        int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            View child = getChildAt(i);            LayoutParams lp = child.getLayoutParams();            lp.width = w;            lp.height = h;            child.setLayoutParams(lp);            measureChild(child,widthMeasureSpec,heightMeasureSpec);        }    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        int childCount = getChildCount();            for (int i = 0; i < childCount; i++) {                View child = getChildAt(i);                if (i == childCount - 1) {                    child.layout(-1 * getMeasuredWidth(), 0,                            -1 * getMeasuredWidth() + child.getMeasuredWidth(),                            child.getMeasuredHeight());                } else {                    child.layout(i * getMeasuredWidth(), 0,                            i * getMeasuredWidth() + child.getMeasuredWidth(),                            child.getMeasuredHeight());                }            }    }    private float startX;    private float lastX;    private int offX;    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        switch (ev.getAction()){            case MotionEvent.ACTION_DOWN:                startX = ev.getX();                lastX = startX;                break;            case MotionEvent.ACTION_MOVE:                offX = (int) Math.abs(ev.getX() - startX);                if (offX > 2){                    return true;                }                lastX = ev.getX();                break;        }        return super.onInterceptTouchEvent(ev);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        switch (event.getAction()){            case MotionEvent.ACTION_MOVE:                offX = (int) (event.getX() - startX);                scrollBy(-(int) (event.getX() - lastX), 0);                lastX = event.getX();                break;            case MotionEvent.ACTION_UP:                int scrollX;                if (getScrollX()>0){                    scrollX = (offX > 0)?getWidth()/4:getWidth()*3/4;                }else {                    scrollX = ((offX > 0)?getWidth()*3/4:getWidth()/4) * -1;                }                int targetIndex = (getScrollX() + scrollX) / getWidth();                int dx = targetIndex * getWidth() - getScrollX();                mScroller.startScroll(getScrollX(), 0, dx, 0);                invalidate();                checkChildLayout(targetIndex);                break;        }        return super.onTouchEvent(event);    }    private void checkChildLayout(int targetIndex){        int childCount = getChildCount();        int curIndex = (targetIndex+childCount*1000)%childCount;        View childLeft;        if (curIndex == 0) {            childLeft = getChildAt(childCount - 1);        }else {            childLeft = getChildAt(curIndex - 1);        }        childLeft.layout((targetIndex-1)*childLeft.getWidth()                ,0,targetIndex*childLeft.getWidth(),childLeft.getHeight());        View childRight;        if (curIndex == childCount-1) {            childRight = getChildAt(0);        }else {            childRight = getChildAt(curIndex + 1);        }        childRight.layout((targetIndex+1)*childRight.getWidth()                ,0,(targetIndex+2)*childRight.getWidth(),childRight.getHeight());    }    @Override    public void computeScroll() {        if (mScroller.computeScrollOffset()){            scrollTo(mScroller.getCurrX(),mScroller.getCurrY());            invalidate();        }    }}

布局文件：

 <com.rong.launchmode.view.BannerLoopLayout        android:layout_alignParentBottom="true"        android:layout_width="match_parent"        android:layout_height="100dp">        <Button            android:textSize="30sp"            android:text="btn1"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />        <Button            android:textSize="25sp"            android:text="btn2"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />        <Button            android:textSize="20sp"            android:text="btn3"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />        <Button            android:textSize="15sp"            android:text="btn4"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />    </com.rong.launchmode.view.BannerLoopLayout>

有点赶时间。。还没来得及注释，先发表再说。

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