写一个最简单的Indicator

项目设计了很多这种指示器 image

虽然有很多Indicator 库，但是会引入没必要的资源，所以就自己写了一个最简单的指示器，记录一下。

public class MyIndictor extends LinearLayout {

    //绑定的 viewpager
    private ViewPager mViewPager;
    // viewpager 的适配器

    private PagerAdapter mPagerAdapter;

    // 添加到 视图中的 view 集合
    private List<ViewGroup> mViewGroups = new ArrayList<>();

    private ColorStateList mTextColor; //文字颜色
    private ColorStateList mIndictorColor; //指示器颜色

    private View lastSelectedIcon;  //上一次 选中的 指示器
    private View lastSelectedText;  //上一次 选中行的 文字

    public MyIndictor(Context context) {
        this(context, null);
    }


    public MyIndictor(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyIndictor(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs, defStyleAttr);
    }

    private void init(Context context, AttributeSet attrs, int defStyleAttr) {
        //读取 xml 中的配置
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.MyIndictor, defStyleAttr, 0);

        //解析属性
        mTextColor = a.getColorStateList(R.styleable.MyIndictor_Indictor_Text_Color);
        mIndictorColor = a.getColorStateList(R.styleable.MyIndictor_Indictor_Color);

        a.recycle();

        //设置 对齐方式
        this.setGravity(Gravity.CENTER_VERTICAL);
    }

    /**
     * 与 viewpager 进行绑定
     * @param viewPager
     */
    public void setUpWithViewPager(ViewPager viewPager) {

        this.mViewPager = viewPager;

        this.mPagerAdapter = viewPager.getAdapter();

        //设置 监听
        mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {

                //修改选中样式
                if (lastSelectedIcon != null) lastSelectedIcon.setSelected(false);
                if (lastSelectedText != null) lastSelectedText.setSelected(false);

                setSelect(position);

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

        int count = mPagerAdapter.getCount();

        //循环创建  指示器
        for (int i = 0; i < count; i++) {
            CharSequence title = mPagerAdapter.getPageTitle(i);
            LinearLayout linearlayout = createLinearlayout(i, title);
            addView(linearlayout);
        }

        setSelect(0);

    }

    /**
     * 根据 选中 index  设置样式
     * @param position
     */
    private void setSelect(int position) {
        View textView = mViewGroups.get(position).getChildAt(0);
        View view = mViewGroups.get(position).getChildAt(1);

        textView.setSelected(true);
        view.setSelected(true);

        lastSelectedIcon = textView;
        lastSelectedText = view;
    }

    /**
     * 创建指示器
     */
    private LinearLayout createLinearlayout(final int index, CharSequence text) {
        LinearLayout linearLayout = new LinearLayout(getContext());

        linearLayout.setOrientation(LinearLayout.VERTICAL);

        linearLayout.setGravity(Gravity.CENTER);


        //创建上方文本 控件
        TextView textView = new TextView(getContext());
        textView.setTextColor(mTextColor);
        textView.setTextSize(14);
        textView.setText(text);
        LinearLayout.LayoutParams textParams = new LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        textView.setLayoutParams(textParams);
        //触发主动 测量
        textView.measure(0,0);
        linearLayout.addView(textView);



        //创建下方指示器控件
        TextView view = new TextView(getContext());
        view.setBackground(getSelector(getDrawable(mIndictorColor.getDefaultColor()), getDrawable(mIndictorColor.getColorForState(new int[]{android.R.attr.state_selected}, Color.RED))));

        //宽度设置为 指示器的宽度
        int width = textView.getMeasuredWidth();
        LinearLayout.LayoutParams viewParams = new LayoutParams(width, UIUtils.dip2px(2));

        viewParams.topMargin = UIUtils.dip2px(6);

        view.setLayoutParams(viewParams);

        linearLayout.addView(view);


        //设置布局 属性
        LinearLayout.LayoutParams params = new LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT);

        params.weight = 1;

        linearLayout.setLayoutParams(params);

        //点击事件  修改 viewpager 的选中
        linearLayout.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                mViewPager.setCurrentItem(index);
            }
        });

        mViewGroups.add(linearLayout);

        return linearLayout;
    }

    /**
     * 创建 drawable
     * @param solid
     * @return
     */
    public static GradientDrawable getDrawable(int solid) {
        GradientDrawable gradientDrawable = new GradientDrawable();
        //设置填充颜色
        gradientDrawable.setColor(solid);
        //设置形状
        gradientDrawable.setShape(GradientDrawable.RECTANGLE);


        gradientDrawable.setCornerRadius(UIUtils.dip2px(2));

        return gradientDrawable;
    }

    /**
     * 代码创建Selector多状态图形
     * @param normalDrawable
     * @param pressDrawable
     * @return
     */
    public static StateListDrawable getSelector(Drawable normalDrawable, Drawable pressDrawable) {
        StateListDrawable stateListDrawable = new StateListDrawable();
        //给当前的颜色选择器添加选中图片的指向状态，未选中图片的指向状态
        stateListDrawable.addState(new int[]{android.R.attr.state_selected}, pressDrawable);
//        stateListDrawable.addState(new int[]{android.R.attr.state_enabled}, normalDrawable);
        //设置默认状态
        stateListDrawable.addState(new int[]{}, normalDrawable);
        return stateListDrawable;
    }
}