ViewPager 详解（四）——自主实现滑动指示条X

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这篇文章中单纯讲述划动指示条的实现方法，而对于交互Tab的实现，就不再讲解，最后给出网上的一段源码，大家可以去研究一下，有关交互Tab的实现原理是一样的，难度不大

效果图

xml布局

<?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"               >    <ImageView        android:id="@+id/cursor"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:scaleType="matrix"        android:src="@mipmap/a" />    <android.support.v4.view.ViewPager        android:id="@+id/viewpager"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center"/></LinearLayout>

java代码

public class MainActivity extends AppCompatActivity {    private View view1, view2, view3;    private List<View> viewList;// view数组    private ViewPager viewPager; // 对应的viewPager    private ImageView cursor;    private int bmpw = 0; // 游标宽度    private int offset = 0;// // 动画图片偏移量    private int currIndex = 0;// 当前页卡编号    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        viewPager = (ViewPager) findViewById(R.id.viewpager);        LayoutInflater inflater = getLayoutInflater();        view1 = inflater.inflate(R.layout.layout1, null);        view2 = inflater.inflate(R.layout.layout2, null);        view3 = inflater.inflate(R.layout.layout3, null);        viewList = new ArrayList<View>();// 将要分页显示的View装入数组中        viewList.add(view1);        viewList.add(view2);        viewList.add(view3);        //初始化指示器位置        initCursorPos();        viewPager.setAdapter(new MyPagerAdapter(viewList));        viewPager.setOnPageChangeListener(new MyPageChangeListener());    }    //初始化指示器位置    public void initCursorPos() {        // 初始化动画        cursor = (ImageView) findViewById(R.id.cursor);        bmpw = BitmapFactory.decodeResource(getResources(), R.mipmap.a)                .getWidth();// 获取图片宽度        DisplayMetrics dm = new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(dm);        int screenW = dm.widthPixels;// 获取分辨率宽度        offset = (screenW / viewList.size() - bmpw) / 2;// 计算偏移量        Matrix matrix = new Matrix();        matrix.postTranslate(offset, 0);        cursor.setImageMatrix(matrix);// 设置动画初始位置    }    //页面改变监听器    public class MyPageChangeListener implements ViewPager.OnPageChangeListener {        int one = offset * 2 + bmpw;// 页卡1 -> 页卡2 偏移量        int two = one * 2;// 页卡1 -> 页卡3 偏移量        @Override        public void onPageSelected(int arg0) {            Animation animation = null;            switch (arg0) {                case 0:                    if (currIndex == 1) {                        animation = new TranslateAnimation(one, 0, 0, 0);                    } else if (currIndex == 2) {                        animation = new TranslateAnimation(two, 0, 0, 0);                    }                    break;                case 1:                    if (currIndex == 0) {                        animation = new TranslateAnimation(offset, one, 0, 0);                    } else if (currIndex == 2) {                        animation = new TranslateAnimation(two, one, 0, 0);                    }                    break;                case 2:                    if (currIndex == 0) {                        animation = new TranslateAnimation(offset, two, 0, 0);                    } else if (currIndex == 1) {                        animation = new TranslateAnimation(one, two, 0, 0);                    }                    break;            }            currIndex = arg0;            animation.setFillAfter(true);// True:图片停在动画结束位置            animation.setDuration(300);            cursor.startAnimation(animation);        }        @Override        public void onPageScrolled(int arg0, float arg1, int arg2) {        }        @Override        public void onPageScrollStateChanged(int arg0) {        }    }    /**     * ViewPager适配器     */    public class MyPagerAdapter extends PagerAdapter {        public List<View> mListViews;        public MyPagerAdapter(List<View> mListViews) {            this.mListViews = mListViews;        }        @Override        public boolean isViewFromObject(View arg0, Object arg1) {            // TODO Auto-generated method stub            return arg0 == arg1;        }        @Override        public int getCount() {            // TODO Auto-generated method stub            return mListViews.size();        }        @Override        public void destroyItem(ViewGroup container, int position, Object object) {            // TODO Auto-generated method stub            container.removeView(mListViews.get(position));        }        @Override        public Object instantiateItem(ViewGroup container, int position) {            // TODO Auto-generated method stub            container.addView(mListViews.get(position));            return mListViews.get(position);        }    }}

分步讲解：

1、initCursorPos（）—初始化指示器位置
游标在初始化显示时，我们要根据屏幕宽度来显示游标位置

//初始化指示器位置  public void initCursorPos() {      // 初始化动画      cursor = (ImageView) findViewById(R.id.cursor);      bmpw = BitmapFactory.decodeResource(getResources(), R.drawable.a)              .getWidth();// 获取图片宽度      DisplayMetrics dm = new DisplayMetrics();      getWindowManager().getDefaultDisplay().getMetrics(dm);      int screenW = dm.widthPixels;// 获取分辨率宽度      offset = (screenW / viewList.size() - bmpw) / 2;// 计算偏移量      Matrix matrix = new Matrix();      matrix.postTranslate(offset, 0);      cursor.setImageMatrix(matrix);// 设置动画初始位置  }

偏移量计算图示：

偏移量计算

2、MyPageChangeListener（）—页面改变监听器

根据滑动到的页面，把游标滑动找指定位置

public class MyPageChangeListener implements OnPageChangeListener {      int one = offset * 2 + bmpw;// 页卡1 -> 页卡2 偏移量      int two = one * 2;// 页卡1 -> 页卡3 偏移量      @Override      public void onPageSelected(int arg0) {          Animation animation = null;          switch (arg0) {          case 0:              if (currIndex == 1) {                  animation = new TranslateAnimation(one, 0, 0, 0);              } else if (currIndex == 2) {                  animation = new TranslateAnimation(two, 0, 0, 0);              }              break;          case 1:              if (currIndex == 0) {                  animation = new TranslateAnimation(offset, one, 0, 0);              } else if (currIndex == 2) {                  animation = new TranslateAnimation(two, one, 0, 0);              }              break;          case 2:              if (currIndex == 0) {                  animation = new TranslateAnimation(offset, two, 0, 0);              } else if (currIndex == 1) {                  animation = new TranslateAnimation(one, two, 0, 0);              }              break;          }          currIndex = arg0;          animation.setFillAfter(true);// True:图片停在动画结束位置          animation.setDuration(300);          cursor.startAnimation(animation);      }

偏移量计算图示：

偏移量计算图示

有交互式的DEMO

效果图

activity_main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"              android:layout_width="fill_parent"              android:layout_height="fill_parent"              android:orientation="vertical" >    <LinearLayout        android:id="@+id/linearLayout1"        android:layout_width="fill_parent"        android:layout_height="100.0dip"        android:background="#FFFFFF" >        <TextView            android:id="@+id/text1"            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:layout_weight="1.0"            android:gravity="center"            android:text="页卡1"            android:textColor="#000000"            android:textSize="22.0dip" />        <TextView            android:id="@+id/text2"            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:layout_weight="1.0"            android:gravity="center"            android:text="页卡2"            android:textColor="#000000"            android:textSize="22.0dip" />        <TextView            android:id="@+id/text3"            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:layout_weight="1.0"            android:gravity="center"            android:text="页卡3"            android:textColor="#000000"            android:textSize="22.0dip" />    </LinearLayout>    <ImageView        android:id="@+id/cursor"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:scaleType="matrix"        android:src="@mipmap/a" />    <android.support.v4.view.ViewPager        android:id="@+id/vPager"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center"        android:layout_weight="1.0"        android:background="#000000"        android:flipInterval="30"        android:persistentDrawingCache="animation" /></LinearLayout>

MainActiviy

import android.app.Activity;import android.graphics.BitmapFactory;import android.graphics.Matrix;import android.os.Bundle;import android.os.Parcelable;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.OnPageChangeListener;import android.util.DisplayMetrics;import android.view.LayoutInflater;import android.view.View;import android.view.animation.Animation;import android.view.animation.TranslateAnimation;import android.widget.ImageView;import android.widget.TextView;import java.util.ArrayList;import java.util.List;/** * Tab页面手势滑动切换以及动画效果 * * @author D.Winter * */public class MainActivity extends Activity {    // ViewPager是google SDk中自带的一个附加包的一个类，可以用来实现屏幕间的切换。    // android-support-v4.jar    private ViewPager mPager;//页卡内容    private List<View> listViews; // Tab页面列表    private ImageView cursor;// 动画图片    private TextView t1, t2, t3;// 页卡头标    private int offset = 0;// 动画图片偏移量    private int currIndex = 0;// 当前页卡编号    private int bmpW;// 动画图片宽度    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        InitImageView();        InitTextView();        InitViewPager();    }    /**     * 初始化头标     */    private void InitTextView() {        t1 = (TextView) findViewById(R.id.text1);        t2 = (TextView) findViewById(R.id.text2);        t3 = (TextView) findViewById(R.id.text3);        t1.setOnClickListener(new MyOnClickListener(0));        t2.setOnClickListener(new MyOnClickListener(1));        t3.setOnClickListener(new MyOnClickListener(2));    }    /**     * 初始化ViewPager     */    private void InitViewPager() {        mPager = (ViewPager) findViewById(R.id.vPager);        listViews = new ArrayList<View>();        LayoutInflater mInflater = getLayoutInflater();        listViews.add(mInflater.inflate(R.layout.layout1, null));        listViews.add(mInflater.inflate(R.layout.layout2, null));        listViews.add(mInflater.inflate(R.layout.layout3, null));        mPager.setAdapter(new MyPagerAdapter(listViews));        mPager.setCurrentItem(0);        mPager.setOnPageChangeListener(new MyOnPageChangeListener());    }    /**     * 初始化动画     */    private void InitImageView() {        cursor = (ImageView) findViewById(R.id.cursor);        bmpW = BitmapFactory.decodeResource(getResources(), R.mipmap.a)                .getWidth();// 获取图片宽度        DisplayMetrics dm = new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(dm);        int screenW = dm.widthPixels;// 获取分辨率宽度        offset = (screenW / 3 - bmpW) / 2;// 计算偏移量        Matrix matrix = new Matrix();        matrix.postTranslate(offset, 0);        cursor.setImageMatrix(matrix);// 设置动画初始位置    }    /**     * ViewPager适配器     */    public class MyPagerAdapter extends PagerAdapter {        public List<View> mListViews;        public MyPagerAdapter(List<View> mListViews) {            this.mListViews = mListViews;        }        @Override        public void destroyItem(View arg0, int arg1, Object arg2) {            ((ViewPager) arg0).removeView(mListViews.get(arg1));        }        @Override        public void finishUpdate(View arg0) {        }        @Override        public int getCount() {            return mListViews.size();        }        @Override        public Object instantiateItem(View arg0, int arg1) {            ((ViewPager) arg0).addView(mListViews.get(arg1), 0);            return mListViews.get(arg1);        }        @Override        public boolean isViewFromObject(View arg0, Object arg1) {            return arg0 == (arg1);        }        @Override        public void restoreState(Parcelable arg0, ClassLoader arg1) {        }        @Override        public Parcelable saveState() {            return null;        }        @Override        public void startUpdate(View arg0) {        }    }    /**     * 头标点击监听     */    public class MyOnClickListener implements View.OnClickListener {        private int index = 0;        public MyOnClickListener(int i) {            index = i;        }        @Override        public void onClick(View v) {            mPager.setCurrentItem(index);        }    };    /**     * 页卡切换监听     */    public class MyOnPageChangeListener implements OnPageChangeListener {        int one = offset * 2 + bmpW;// 页卡1 -> 页卡2 偏移量        int two = one * 2;// 页卡1 -> 页卡3 偏移量        @Override        public void onPageSelected(int arg0) {            Animation animation = null;            switch (arg0) {                case 0:                    if (currIndex == 1) {                        animation = new TranslateAnimation(one, 0, 0, 0);                    } else if (currIndex == 2) {                        animation = new TranslateAnimation(two, 0, 0, 0);                    }                    break;                case 1:                    if (currIndex == 0) {                        animation = new TranslateAnimation(offset, one, 0, 0);                    } else if (currIndex == 2) {                        animation = new TranslateAnimation(two, one, 0, 0);                    }                    break;                case 2:                    if (currIndex == 0) {                        animation = new TranslateAnimation(offset, two, 0, 0);                    } else if (currIndex == 1) {                        animation = new TranslateAnimation(one, two, 0, 0);                    }                    break;            }            currIndex = arg0;            animation.setFillAfter(true);// True:图片停在动画结束位置            animation.setDuration(300);            cursor.startAnimation(animation);        }        @Override        public void onPageScrolled(int arg0, float arg1, int arg2) {        }        @Override        public void onPageScrollStateChanged(int arg0) {        }    }}

总结自：启航大神的博客http://blog.csdn.net/harvic880925/article/details/38557517

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