效果

演示

說明

為了實現 ViewPager 切換 Fragment 時的標籤效果（類似新聞客戶端導航的效果）

程式碼

package com.demo.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.Gravity;
import android.view.View;
import android.view.WindowManager;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.demo.R;
import com.demo.factory.Axis;

import java.util.List;



public class ViewPagerBelowIndicator extends LinearLayout {
    /**
     * view的寬度
     */
    private int mWidth=-1;
    public void setmWidth(int mWidth) {
        this.mWidth = mWidth;
    }

    /**
     * 預設字型大小
     */
    private final float DEFAULT_TEXTSIZE=Axis.scaleTextSize(30);
    private float textSize=-1f;//字型大小
    public void setTextSize(float textSize) {
        this.textSize = textSize;
    }

    /**
     * 指示器文字位置
     */

    private int IndicatePosition = 1;

    /**
     * 繪製矩形的畫筆
     */
    private Paint mPaint;
    /**
     * path構成一個矩形
     */
    private Path mPath;
    /**

     * 矩形的寬度
     */
    private int mTriangleWidth;

    /**
     * 畫筆顏色
     */
    private int IndicatorColor = 0xFFFFFFFF;

    /**
     * 矩形的高度
     */
    private int mTriangleHeight = 50; //指示條的高度
    private int mTriangleH;

    private static final float MAGNIFICATION_DEFAULT_TAB = (float) 3.0;
    /**
     * 矩形的寬度為單個Tab的1/3
     */
    private static final double RADIO_TRIANGEL = 1.0f / 3;
    /**
     * 矩形的最大寬度
     */
    private int dimension_triangel_width = (int) (getScreenWidth() / 3 * RADIO_TRIANGEL);

    /**
     * 初始時，矩形指示器的偏移量
     */
    private int mInitTranslationX;
    /**
     * 手指滑動時的偏移量
     */
    private float mTranslationX;

    /**
     * 預設的Tab數量
     */
    private  final int COUNT_DEFAULT_TAB = 3;
    /**
     * tab數量
     */
    private int mTabVisibleCount = COUNT_DEFAULT_TAB;

    /**
     * tab上的內容
     */
    private List<String> mTabTitles;
    /**
     * 與之繫結的ViewPager
     */
    public ViewPager mViewPager;


    /**
     * 標題正常時的顏色
     */
    private   int COLOR_TEXT_NORMAL = 0xFF999999;

    /**
     * 標題選中時的顏色
     */
    private   int COLOR_TEXT_HIGHLIGHTCOLOR = 0xFFFFFFFF;

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

    public ViewPagerBelowIndicator(Context context, AttributeSet attrs) {
        super(context, attrs);

        // 獲得自定義屬性，tab的數量
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ViewPagerIndicator);
        mTabVisibleCount = 6;
        //設定指示條寬度的放大係數
        float magnification = 1.0f / 4;
        dimension_triangel_width = (int) (getScreenWidth() / 3 * magnification);

        if (mTabVisibleCount < 0)
            mTabVisibleCount = COUNT_DEFAULT_TAB;
        a.recycle();

        // 初始化畫筆
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setColor(IndicatorColor);
        mPaint.setStyle(Style.FILL);
        //mPaint.setPathEffect(new CornerPathEffect(4));
    }



    /**
     * 繪製指示器
     */
    @Override
    protected void dispatchDraw(Canvas canvas) {
        canvas.drawColor(0x00FFFFFF);
        canvas.save();
        // 畫筆平移到正確的位置
        canvas.translate(mInitTranslationX + mTranslationX,  getHeight());
        canvas.drawPath(mPath, mPaint);
        canvas.restore();

        super.dispatchDraw(canvas);
    }

    /**
     * 初始化矩形的寬度
     */
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mTriangleH = (int) (w / mTabVisibleCount * RADIO_TRIANGEL);
        // width
        mTriangleWidth = Math.min(dimension_triangel_width, dimension_triangel_width);

        //初始化矩形指示器
        iniTrectangle();

        // 初始時的偏移量
        mInitTranslationX = getWidth() / mTabVisibleCount / 2 - mTriangleWidth
                / 2;
    }

    /**
     * 設定可見的tab的數量
     *
     * @param count
     */
    public void setVisibleTabCount(int count) {
        this.mTabVisibleCount = count;
    }

    public void setIndicatePosition(int IndicatePosition){
        this.IndicatePosition = getHeight();
        invalidate();
    }

    /**
     * 設定tab的標題內容 可選，可以自己在佈局檔案中寫死
     *
     * @param datas
     */
    public void setTabItemTitles(List<String> datas) {
        // 如果傳入的list有值，則移除佈局檔案中設定的view
        if (datas != null && datas.size() > 0) {
            this.removeAllViews();
            this.mTabTitles = datas;

            for (String title : mTabTitles) {
                // 新增view
                addView(generateTextView(title));
            }
            // 設定item的click事件
            setItemClickEvent();
        }

    }

    /**
     * 對外的ViewPager的回撥介面
     */
    public interface PageChangeListener {
        public void onPageScrolled(int position, float positionOffset,
                                   int positionOffsetPixels);

        public void onPageSelected(int position);

        public void onPageScrollStateChanged(int state);
    }

    // 對外的ViewPager的回撥介面
    private PageChangeListener onPageChangeListener;

    // 對外的ViewPager的回撥介面的設定
    public void setOnPageChangeListener(PageChangeListener pageChangeListener) {
        this.onPageChangeListener = pageChangeListener;
    }

    // 設定關聯的ViewPager
    public void setViewPager(ViewPager mViewPager, int pos) {
        this.mViewPager = mViewPager;

        mViewPager.addOnPageChangeListener(new OnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                // 設定字型顏色高亮
                resetTextViewColor();
                highLightTextView(position);

                // 回撥
                if (onPageChangeListener != null) {
                    onPageChangeListener.onPageSelected(position);
                }
            }

            @Override
            public void onPageScrolled(int position, float positionOffset,
                                       int positionOffsetPixels) {
                // 滾動
                scroll(position, positionOffset);

                // 回撥
                if (onPageChangeListener != null) {
                    onPageChangeListener.onPageScrolled(position,
                            positionOffset, positionOffsetPixels);
                }

            }

            @Override
            public void onPageScrollStateChanged(int state) {
                // 回撥
                if (onPageChangeListener != null) {
                    onPageChangeListener.onPageScrollStateChanged(state);
                }

            }
        });
        // 設定當前頁
        mViewPager.setCurrentItem(pos);
        // 高亮
        highLightTextView(pos);
    }

    /**
     * 設定指示器顏色
     */
    public  void setIndicatorColor(int IndicatorColor){
        this.IndicatorColor = IndicatorColor;
        mPaint.setColor(IndicatorColor);
        invalidate();

    }

    /**
     * 設定正常標題顏色
     * @param COLOR_TEXT_NORMAL
     */
    public void setCOLOR_TEXT_NORMAL(int COLOR_TEXT_NORMAL) {
        this.COLOR_TEXT_NORMAL = COLOR_TEXT_NORMAL;
    }
    /**
     * 設定選中標題顏色
     * @param COLOR_TEXT_HIGHLIGHTCOLOR
     */
    public void setCOLOR_TEXT_HIGHLIGHTCOLOR(int COLOR_TEXT_HIGHLIGHTCOLOR) {
        this.COLOR_TEXT_HIGHLIGHTCOLOR = COLOR_TEXT_HIGHLIGHTCOLOR;
    }

    /**
     * 高亮文字
     *
     * @param position
     */
    protected void highLightTextView(int position) {
        View view = getChildAt(position);
        if (view instanceof TextView) {
            ((TextView) view).setTextColor(COLOR_TEXT_HIGHLIGHTCOLOR);
        }

    }

    /**
     * 重置文字顏色
     */
    private void resetTextViewColor() {
        for (int i = 0; i < getChildCount(); i++) {
            View view = getChildAt(i);
            if (view instanceof TextView) {
                ((TextView) view).setTextColor(COLOR_TEXT_NORMAL);
            }
        }
    }

    /**
     * 設定點選事件
     */
    public void setItemClickEvent() {
        int cCount = getChildCount();
        for (int i = 0; i < cCount; i++) {
            final int j = i;
            View view = getChildAt(i);
            view.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    mViewPager.setCurrentItem(j);
                }
            });
        }
    }

    /**
     * 根據標題生成我們的TextView
     *
     * @param text
     * @return
     */
    private TextView generateTextView(String text)
    {
        TextView tv = new TextView(getContext());
        LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
        lp.width =(mWidth!=-1?mWidth:getScreenWidth())/ mTabVisibleCount;
        tv.setGravity(Gravity.CENTER);
        tv.setTextColor(COLOR_TEXT_NORMAL);
        tv.setText(text);
        tv.setTextSize(textSize!=-1f?textSize:DEFAULT_TEXTSIZE);
        tv.setLayoutParams(lp);
        return tv;
    }

    /**
     * 初始化矩形指示器
     */
    private void iniTrectangle() {
        mPath = new Path();
        mPath.rewind();
        mTriangleHeight = 50;//指示條的高度

        mPath.moveTo(mTriangleWidth, mTriangleHeight / 5);
        mPath.lineTo(-mTriangleWidth / 100, mTriangleHeight / 5);
        mPath.lineTo(-mTriangleWidth / 100, -mTriangleHeight / 5);
        mPath.lineTo(mTriangleWidth, -mTriangleHeight / 5);
        mPath.close();
    }

    /**
     * 指示器跟隨手指滾動，以及容器滾動
     *
     * @param position
     * @param offset
     */
    public void scroll(int position, float offset) {
        /**
         * <pre>
         *  0-1:position=0 ;1-0:postion=0;
         * </pre>
         */
        // 不斷改變偏移量，invalidate
        mTranslationX = getWidth() / mTabVisibleCount * (position + offset);

        int tabWidth = getScreenWidth() / mTabVisibleCount;

        // 容器滾動，當移動到倒數最後一個的時候，開始滾動
        if (offset > 0 && position >= (mTabVisibleCount - 2)
                && getChildCount() > mTabVisibleCount) {
            if (mTabVisibleCount != 1) {
                this.scrollTo((position - (mTabVisibleCount - 2)) * tabWidth
                        + (int) (tabWidth * offset), 0);
            } else
            // 為count為1時 的特殊處理
            {
                this.scrollTo(
                        position * tabWidth + (int) (tabWidth * offset), 0);
            }
        }

        invalidate();
    }

    /**
     * 設定佈局中view的一些必要屬性；如果設定了setTabTitles，佈局中view則無效
     */
    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();

        int cCount = getChildCount();

        if (cCount == 0)
            return;

        for (int i = 0; i < cCount; i++) {
            View view = getChildAt(i);
            LayoutParams lp = (LayoutParams) view
                    .getLayoutParams();
            lp.weight = 0;
            lp.width = getScreenWidth() / mTabVisibleCount;
            view.setLayoutParams(lp);
        }
        // 設定點選事件
        setItemClickEvent();

    }

    /**
     * 獲得螢幕的寬度
     *
     * @return
     */
    public int getScreenWidth() {
        WindowManager wm = (WindowManager) getContext().getSystemService(
                Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(outMetrics);
        return outMetrics.widthPixels;
    }

}

使用方式

1 . Activity中初始化設定

        indicator=new ViewPagerBelowIndicator(this);
        int mWidth= Axis.getWidth()-Axis.scaleX(300)*2;
        indicator.setmWidth(mWidth);
        indicator.setVisibleTabCount(3);
        indicator.setCOLOR_TEXT_NORMAL(Color.BLACK);
        indicator.setTextSize(Axis.scaleTextSize(32));
        indicator.setCOLOR_TEXT_HIGHLIGHTCOLOR(ContextCompat.getColor(this,R.color.color3973FF));
        indicator.setIndicatorColor(Color.TRANSPARENT);
        RelativeLayout.LayoutParams indicator_lp=new RelativeLayout.LayoutParams(mWidth,HEAD_WIDTH);
        indicator_lp.addRule(RelativeLayout.CENTER_IN_PARENT);
        headView.addView(indicator,indicator_lp);

2 . 和 ViewPager 物件關聯

        List<String> mTitles = Arrays.asList("雲端", "車機", "手機");
        //給tab加上標題
        indicator.setTabItemTitles(mTitles);
        //設定關聯的ViewPager，預設顯示第一個
        indicator.setViewPager(mViewPager,1);//mViewPager為ViewPager子類