自定義ViewPager指示器（仿MIUI）

效果圖

代碼示例
MainActivity.java

package com.example.viewpagerindicator;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;

import com.example.viewpagerindicator.view.ViewPagerIndicator;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MainActivity extends FragmentActivity {
    private ViewPager viewPager;
    private ViewPagerIndicator vpi_indicator;
    private List<String> mTitles = Arrays.asList("短信", "收藏", "推薦");
    private List<VpSimpleFragment> mContent = new ArrayList<>();
    private FragmentPagerAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initViews();
        initData();
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                // 總的偏移量 = tabWidth(一個控件的寬度) * positionOffset + position * tabWidth
                vpi_indicator.scroll(position, positionOffset);
            }

            @Override
            public void onPageSelected(int position) {

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

    private void initData() {
        for (String title : mTitles) {
            VpSimpleFragment fragment = VpSimpleFragment.newInstance(title);
            mContent.add(fragment);
        }
        adapter = new FragmentPagerAdapter(getSupportFragmentManager()) {
            @Override
            public Fragment getItem(int position) {
                return mContent.get(position);
            }

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

    private void initViews() {
        viewPager = findViewById(R.id.viewPager);
        vpi_indicator = findViewById(R.id.vpi_indicator);
    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#fff"
    tools:context="com.example.viewpagerindicator.MainActivity">

    <com.example.viewpagerindicator.view.ViewPagerIndicator
        android:id="@+id/vpi_indicator"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="#000"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_message"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="@string/message"
            android:textColor="#CCFFFFFF"
            android:textSize="16sp" />

        <TextView
            android:id="@+id/tv_collect"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="@string/collect"
            android:textColor="#CCFFFFFF"
            android:textSize="16sp" />

        <TextView
            android:id="@+id/tv_recommend"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="@string/recommend"
            android:textColor="#CCFFFFFF"
            android:textSize="16sp" />

    </com.example.viewpagerindicator.view.ViewPagerIndicator>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </android.support.v4.view.ViewPager>


</LinearLayout>

VpSimpleFragment.java

package com.example.viewpagerindicator;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class VpSimpleFragment extends Fragment {
    private String mTitle;
    public static final String BUNDLE_TITLE = "title";

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        Bundle bundle = getArguments();
        if (bundle!=null){
            mTitle = bundle.getString("BUNDLE_TITLE");
        }
        TextView tv_content = new TextView(getActivity());
        tv_content.setGravity(Gravity.CENTER);
        tv_content.setText(mTitle);
        return tv_content;
    }

    public static VpSimpleFragment newInstance(String title) {
        Bundle bundle = new Bundle();
        bundle.putString("BUNDLE_TITLE", title);
        VpSimpleFragment fragment = new VpSimpleFragment();
        fragment.setArguments(bundle);
        return fragment;
    }
}

ViewPagerIndicator,java

package com.example.viewpagerindicator.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.CornerPathEffect;
import android.graphics.Paint;
import android.graphics.Path;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.widget.LinearLayout;


public class ViewPagerIndicator extends LinearLayout {
    private Paint mPaint;
    private Path mPath;
    // 三角形的寬
    private int triangleWidth;
    // 三角形的高
    private int triangleHeight;
    // 三角形底邊長度與標題欄的高度的比例(作用是適應於不同的屏幕)
    private static final float RADIO_TRIANGLE_WIDTH = 1 / 6F;
    // 三角形初始化的偏移位置
    private int initTranslationX;
    // 三角形移動時的偏移位置
    private int translationX;

    public ViewPagerIndicator(Context context) {
        // 把super改成this，默認調用下面的2個參數的構造方法
        this(context, null);
    }

    public ViewPagerIndicator(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        // 初始化畫筆
        initPaint();

    }

    private void initPaint() {
        mPaint = new Paint();
        // 設置畫筆抗鋸齒
        mPaint.setAntiAlias(true);
        // 設置畫筆的顏色
        mPaint.setColor(Color.WHITE);
        mPaint.setStyle(Paint.Style.FILL);
        // 設置三角形三個角連接處的弧度（不至於太尖）
        mPaint.setPathEffect(new CornerPathEffect(3));
    }

    // 設置三角形的大小(控件的寬高發生變化時都會回調這個方法)
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        // 三角形底邊的寬度(3是3個TextView控件)
        triangleWidth = (int) (w / 3 * RADIO_TRIANGLE_WIDTH);
        triangleHeight = triangleWidth / 2;
        // 標題欄的總寬度/3（3個控件）/2  得到每個控件寬度的一半，再減去三角形底邊寬度的一半
        initTranslationX = w / 3 / 2 - triangleWidth / 2;
        // 初始化三角形
        initTriangle();
    }

    private void initTriangle() {
        mPath = new Path();
        mPath.moveTo(0, 0);
        mPath.lineTo(triangleWidth, 0);
        mPath.lineTo(triangleWidth / 2, -triangleHeight);
        mPath.close();
    }

    // 三角形的繪製
    @Override
    protected void dispatchDraw(Canvas canvas) {
        canvas.save();
        // 平移位置
        canvas.translate(initTranslationX + translationX, getHeight() + 2);
        canvas.drawPath(mPath, mPaint);
        canvas.restore();

        super.dispatchDraw(canvas);

    }

    /**
     * 指示器跟隨手指進行滾動
     */
    public void scroll(int position, float offset) {
        // 獲取一個控件的寬度
        int tabWidth = getWidth() / 3;
        // 得到三角形偏移位置
        translationX = (int) (tabWidth * (position + offset));
        // 重繪三角形
        invalidate();
    }
}

3個以上tab上下聯動的效果圖

代碼示例
Mainactivity.java

package com.example.viewpagerindicator;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;

import com.example.viewpagerindicator.view.ViewPagerIndicator;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MainActivity extends FragmentActivity {
    private ViewPager viewPager;
    private ViewPagerIndicator vpi_indicator;
    private List<String> mTitles = Arrays.asList("短信", "收藏", "推薦","短信", "收藏", "推薦","短信", "收藏", "推薦");
    private List<VpSimpleFragment> mContent = new ArrayList<>();
    private FragmentPagerAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initViews();
        initData();
        vpi_indicator.setVisibleTabCounnt(4);
        vpi_indicator.setTabItemTitles(mTitles);
        viewPager.setAdapter(adapter);
        vpi_indicator.setViewPager(viewPager,0);
    }

    private void initData() {
        for (String title : mTitles) {
            VpSimpleFragment fragment = VpSimpleFragment.newInstance(title);
            mContent.add(fragment);
        }
        adapter = new FragmentPagerAdapter(getSupportFragmentManager()) {
            @Override
            public Fragment getItem(int position) {
                return mContent.get(position);
            }

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

    private void initViews() {
        viewPager = findViewById(R.id.viewPager);
        vpi_indicator = findViewById(R.id.vpi_indicator);
    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:hyman="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#fff"
    android:orientation="vertical"
    tools:context="com.example.viewpagerindicator.MainActivity">

    <com.example.viewpagerindicator.view.ViewPagerIndicator
        android:id="@+id/vpi_indicator"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="#000"
        android:orientation="horizontal"
        hyman:visible_tab_count="4">


    </com.example.viewpagerindicator.view.ViewPagerIndicator>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </android.support.v4.view.ViewPager>


</LinearLayout>

arrt.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!--自定義屬性，讓用戶指定tab的數量-->
    <attr name="visible_tab_count" format="integer" />
    <declare-styleable name="ViewPagerIndicator">
        <attr name="visible_tab_count"/>
    </declare-styleable>
</resources>

VpSimpleFragment.java

package com.example.viewpagerindicator;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class VpSimpleFragment extends Fragment {
    private String mTitle;
    public static final String BUNDLE_TITLE = "title";

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        Bundle bundle = getArguments();
        if (bundle!=null){
            mTitle = bundle.getString("BUNDLE_TITLE");
        }
        TextView tv_content = new TextView(getActivity());
        tv_content.setGravity(Gravity.CENTER);
        tv_content.setText(mTitle);
        return tv_content;
    }

    public static VpSimpleFragment newInstance(String title) {
        Bundle bundle = new Bundle();
        bundle.putString("BUNDLE_TITLE", title);
        VpSimpleFragment fragment = new VpSimpleFragment();
        fragment.setArguments(bundle);
        return fragment;
    }
}

ViewPagerIndicator.java

package com.example.viewpagerindicator.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.CornerPathEffect;
import android.graphics.Paint;
import android.graphics.Path;
import android.support.annotation.Nullable;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.example.viewpagerindicator.R;

import java.util.List;


public class ViewPagerIndicator extends LinearLayout {
    private Paint mPaint;
    private Path mPath;
    // 三角形的寬
    private int triangleWidth;
    // 三角形的高
    private int triangleHeight;
    // 三角形底邊長度與標題欄的高度的比例(作用是適應於不同的屏幕)
    private static final float RADIO_TRIANGLE_WIDTH = 1 / 6F;
    // 三角形底邊的最大寬度
    private final int DEMENTION_TRIANGLE_WIDTH_MAX = (int) (getScreenWidth() / 3 * RADIO_TRIANGLE_WIDTH);
    // 三角形初始化的偏移位置
    private int initTranslationX;
    // 三角形移動時的偏移位置
    private int translationX;
    private int tabVisibleCount;
    private static final int COUNT_DEFALUT_TAB = 4;
    private List<String> mTitles;
    // 字體顏色的常量
    private static final int COLOR_TEXT_NORMAL = 0x77FFFFFF;
    private static final int COLOR_TEXT_HIGHLIGHT = 0xFFFFFFFF;
    private ViewPager mViewPager;

    public ViewPagerIndicator(Context context) {
        // 把super改成this，默認調用下面的2個參數的構造方法
        this(context, null);
    }

    public ViewPagerIndicator(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        // 初始化畫筆
        initPaint();
        // 獲取可見tab的數量
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ViewPagerIndicator);
        tabVisibleCount = typedArray.getInt(R.styleable.ViewPagerIndicator_visible_tab_count, COUNT_DEFALUT_TAB);
        if (tabVisibleCount < 0) {
            tabVisibleCount = COUNT_DEFALUT_TAB;
        }
        typedArray.recycle();
    }

    /**
     * 當xml加載完成後回調該方法
     */
    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        // 獲取子元素的個數
        int mCount = getChildCount();
        if (mCount == 0) return;
        for (int i = 0; i < mCount; i++) {
            View view = getChildAt(i);
            LinearLayout.LayoutParams layoutParams = (LayoutParams) view.getLayoutParams();
            layoutParams.weight = 0;
            layoutParams.width = getScreenWidth() / tabVisibleCount;
            view.setLayoutParams(layoutParams);
        }
        setItemClickEvent();
    }

    /**
     * 獲取屏幕的寬度
     */
    private int getScreenWidth() {
        WindowManager windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        windowManager.getDefaultDisplay().getMetrics(outMetrics);
        return outMetrics.widthPixels;
    }

    private void initPaint() {
        mPaint = new Paint();
        // 設置畫筆抗鋸齒
        mPaint.setAntiAlias(true);
        // 設置畫筆的顏色
        mPaint.setColor(Color.WHITE);
        mPaint.setStyle(Paint.Style.FILL);
        // 設置三角形三個角連接處的弧度（不至於太尖）
        mPaint.setPathEffect(new CornerPathEffect(3));
    }

    // 設置三角形的大小(控件的寬高發生變化時都會回調這個方法)
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        // 三角形底邊的寬度(3是3個TextView控件)
        triangleWidth = (int) (w / tabVisibleCount * RADIO_TRIANGLE_WIDTH);
        triangleHeight = triangleWidth / 2;
        triangleWidth = Math.min(triangleWidth,DEMENTION_TRIANGLE_WIDTH_MAX);
        // 標題欄的總寬度/3（3個控件）/2  得到每個控件寬度的一半，再減去三角形底邊寬度的一半
        initTranslationX = w / tabVisibleCount / 2 - triangleWidth / 2;
        // 初始化三角形
        initTriangle();
    }

    private void initTriangle() {
        mPath = new Path();
        mPath.moveTo(0, 0);
        mPath.lineTo(triangleWidth, 0);
        mPath.lineTo(triangleWidth / 2, -triangleHeight);
        mPath.close();
    }

    // 三角形的繪製
    @Override
    protected void dispatchDraw(Canvas canvas) {
        canvas.save();
        // 平移位置
        canvas.translate(initTranslationX + translationX, getHeight() + 2);
        canvas.drawPath(mPath, mPaint);
        canvas.restore();

        super.dispatchDraw(canvas);

    }

    /**
     * 指示器跟隨手指進行滾動
     */
    public void scroll(int position, float offset) {
        // 獲取一個控件的寬度
        int tabWidth = getWidth() / tabVisibleCount;
        // 得到三角形偏移位置
        translationX = (int) (tabWidth * (position + offset));
        // 滿足下面的條件容器移動，在tab處於移動至最後一個時
        if (position >= (tabVisibleCount - 2) && offset > 0 && getChildCount() > tabVisibleCount) {
            if (tabVisibleCount != 1) {
                this.scrollTo((position - (tabVisibleCount - 2)) * tabWidth + (int) (tabWidth * offset), 0);
            } else {
                this.scrollTo(position * tabWidth + (int) (tabWidth * offset), 0);
            }
        }
        // 重繪三角形
        invalidate();
    }

    public void setTabItemTitles(List<String> titles) {
        if (titles != null && titles.size() > 0) {
            this.removeAllViews();
            mTitles = titles;
            for (String title : mTitles) {
                addView(generateTextView(title));
            }
            setItemClickEvent();
        }
    }

    /**
     * 動態設置可見tab數量的方法
     */
    public void setVisibleTabCounnt(int count) {
        tabVisibleCount = count;
    }

    /**
     * 根據title動態創建tab
     */


    private View generateTextView(String title) {
        TextView tv = new TextView(getContext());
        LinearLayout.LayoutParams layoutParams = new LayoutParams(LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
        layoutParams.width = getScreenWidth() / tabVisibleCount;
        tv.setText(title);
        tv.setGravity(Gravity.CENTER);
        // 設置字體的大小（單位sp，值）
        tv.setTextSize(TypedValue.COMPLEX_UNIT_SP, 16);
        tv.setTextColor(COLOR_TEXT_NORMAL);
        tv.setLayoutParams(layoutParams);
        return tv;
    }

    public interface PagerOnChangeListener {
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);

        public void onPageSelected(int position);

        public void onPageScrollStateChanged(int state);
    }

    private PagerOnChangeListener mListener;

    public void setOnPagerChangeListener(PagerOnChangeListener listener) {
        this.mListener = listener;
    }

    /**
     * 設置關聯的ViewPager
     */
    public void setViewPager(ViewPager viewPager, final int pos) {
        mViewPager = viewPager;
        mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                // 總的偏移量 = tabWidth(一個控件的寬度) * positionOffset + position * tabWidth
                scroll(position, positionOffset);
                if (mListener != null) {
                    mListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
                }
            }

            @Override
            public void onPageSelected(int position) {
                if (mListener != null) {
                    mListener.onPageSelected(position);
                }
                highLightTextView(position);
            }

            @Override
            public void onPageScrollStateChanged(int state) {
                if (mListener != null) {
                    mListener.onPageScrollStateChanged(state);
                }
            }
        });
        mViewPager.setCurrentItem(pos);
        highLightTextView(pos);
    }


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

    /**
     * 高亮選中tab的文本
     */
    private void highLightTextView(int pos) {
        resetTextViewColor();
        View view = getChildAt(pos);
        if (view instanceof TextView) {
            ((TextView) view).setTextColor(COLOR_TEXT_HIGHLIGHT);
        }
    }

    /**
     * 實現tab的點擊事件
     */
    private void setItemClickEvent() {
        int mCount = getChildCount();
        for (int i = 0; i < mCount; i++) {
            final int j = i;
            View view = getChildAt(i);
            view.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    mViewPager.setCurrentItem(j);
                }
            });
        }
    }
}

自定義ViewPager指示器（仿MIUI）

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