Android 引导界面，导航圆点的实现

大神略过，如有不足，请轻喷！！！最后附上下载地址。

在开始本篇文章前，咱们先来聊聊实现的思路。引导界面，ViewPager这是毋庸置疑的。然后就是圆点的实现，咱们可以自己画出来相应的圆点以及相邻圆点之间的距离。利用ViewPager图片移动百分比(屏幕宽度)动态算出圆点要移动的距离。

ViewPager的实现相信来到这篇文章的童鞋都是会的，就直接贴代码了

 @Override
    public int getCount() {
        return arrayImages.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view==object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        ImageView iv = arrayImages.get(position);
        container.addView(iv);
        return iv;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View)object);
    }

接下来的就是圆点的实现了：

• 首先需要在布局上画出咱们的圆点个数：

// 动态得出圆点的个数，距离，并添加到线性布局中
for (int i = 0;i<mImages.length;i++){
            ImageView iv = new ImageView(this);
            iv.setBackgroundResource(mImages[i]);
            mImageViewArrayList.add(iv);
            
            ImageView circleView = new ImageView(this);
            circleView.setBackgroundResource(R.drawable.guide_circle_shape_select);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.WRAP_CONTENT,LinearLayout.LayoutParams.WRAP_CONTENT);
            if (i>0){
                params.leftMargin = 8;
            }
            circleView.setLayoutParams(params)；
            mLlContainear.addView(circleView);//在添加到布局文件中是的时需要注意一点：要添加的父布局是什么布局，这里添加的就是什么布局。
        }

• 得到两个点之间的距离：(必须要页面绘制完成，否者得到的距离为0)

mGuide_red_point.getViewTreeObserver().addOnGlobalLayoutListener(
                new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                mGuide_red_point.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                mPointWidth = mLlContainear.getChildAt(1).getLeft()-
                        mLlContainear.getChildAt(0).getLeft();
            }
        });

• 利用百分比得到移动的距离并赋值：

 @Override
            public void onPageScrolled(int position,
                                       float positionOffset, int positionOffsetPixels) {

                int leftMargin = (int) (position * mPointWidth + mPointWidth * positionOffset);
                RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)
                        mGuide_red_point.getLayoutParams();
                params.leftMargin = leftMargin;
                mGuide_red_point.setLayoutParams(params);
            }

最后附上完整的代码：

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_guide);

        mGuide_viewpager =  (ViewPager) findViewById(R.id.guide_viewpager);
        mGuide_begin = (Button) findViewById(R.id.guide_begin);
        mLlContainear = (LinearLayout)findViewById(R.id.llContainer);
        mGuide_red_point = (ImageView)findViewById(R.id.guide_red_point);
        mImages = new int[]{R.drawable.guide_1,
                R.drawable.guide_3,
                R.drawable.guide_4,
                R.drawable.guide_5};

        mImageViewArrayList =  new ArrayList<ImageView>();

        // 动态得出圆点的个数，距离，并添加到线性布局中
        for (int i = 0;i<mImages.length;i++){
            ImageView iv = new ImageView(this);
            iv.setBackgroundResource(mImages[i]);
            mImageViewArrayList.add(iv);

            ImageView circleView = new ImageView(this);
            circleView.setBackgroundResource(R.drawable.guide_circle_shape_select);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.WRAP_CONTENT,LinearLayout.LayoutParams.WRAP_CONTENT);
            if (i>0){
                params.leftMargin = 8;
            }
            circleView.setLayoutParams(params);
            mLlContainear.addView(circleView);
        }

        mGuide_red_point.getViewTreeObserver().addOnGlobalLayoutListener(
                new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                mGuide_red_point.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                mPointWidth = mLlContainear.getChildAt(1).getLeft()-
                        mLlContainear.getChildAt(0).getLeft();
            }
        });

        Guide_Adapter ga = new Guide_Adapter(mImageViewArrayList,this);
        mGuide_viewpager.setAdapter(ga);

        mGuide_viewpager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position,
                                       float positionOffset, int positionOffsetPixels) {

                int leftMargin = (int) (position * mPointWidth + mPointWidth * positionOffset);
                RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)
                        mGuide_red_point.getLayoutParams();
                params.leftMargin = leftMargin;
                mGuide_red_point.setLayoutParams(params);
            }

            @Override
            public void onPageSelected(int position) {
               
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

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