自定义简易的viewpager指示器

package com.example.dxy.myapplication.view;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.os.Build;import android.os.Bundle;import android.os.Parcelable;import android.support.annotation.RequiresApi;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentActivity;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentPagerAdapter;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.util.AttributeSet;import android.view.View;import android.view.ViewGroup;import com.example.dxy.myapplication.R;import java.util.ArrayList;public class IndicatorView extends View implements ViewPager.OnPageChangeListener {    //节点间距    private float mNodeGap;    //节点个数    private int mNodeCount;    //节点圆形半径    private float mNodeRadius;    //节点默认填充颜色    private int mNodeColor;    //移动节点填充颜色    private int mSelectedNodeColor;    //当前选中节点的索引    private int mCurrentIndex = 0;    //viewpager偏移量[0,1)    private float mCurrentPositionOffset = 0;    private ViewPager mViewPager;    private Paint mNodePaint = new Paint(Paint.ANTI_ALIAS_FLAG);    private Paint mSelectedNodePaint = new Paint(Paint.ANTI_ALIAS_FLAG);    private Context mContext;    public IndicatorView(Context context) {        this(context, null);    }    public IndicatorView(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public IndicatorView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        this.mContext = context;        obtainAttributes(context, attrs);    }    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)    public IndicatorView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {        super(context, attrs, defStyleAttr, defStyleRes);        this.mContext = context;        obtainAttributes(context, attrs);    }    private void obtainAttributes(Context context, AttributeSet attrs) {        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.IndicatorView);        mNodeGap = ta.getDimension(R.styleable.IndicatorView_node_gap, dp2px(10));        mNodeColor = ta.getColor(R.styleable.IndicatorView_node_default_color, Color.parseColor("#FFFF00"));        mSelectedNodeColor = ta.getColor(R.styleable.IndicatorView_node_select_color, Color.parseColor("#FF0000"));        mNodeRadius = ta.getDimension(R.styleable.IndicatorView_node_radius, dp2px(5));        mNodePaint.setColor(mNodeColor);        mNodePaint.setStyle(Paint.Style.FILL);        mSelectedNodePaint.setColor(mSelectedNodeColor);        mSelectedNodePaint.setStyle(Paint.Style.FILL);        ta.recycle();    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        if (mNodeCount <= 0) {            super.onMeasure(widthMeasureSpec, heightMeasureSpec);        } else {            final int measureWidth = (int) ((mNodeCount - 1) * mNodeGap + mNodeCount * 2 * mNodeRadius);            final int measureHeight = (int) (2 * mNodeRadius);            setMeasuredDimension(measureWidth, measureHeight);        }    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        for (int i = 0; i < mNodeCount; i++) {            canvas.drawCircle(mNodeRadius + i * mNodeGap + 2 * i * mNodeRadius, mNodeRadius, mNodeRadius, mNodePaint);        }        canvas.drawCircle(mNodeRadius + mCurrentIndex * mNodeGap + 2 * mCurrentIndex * mNodeRadius + (2 * mNodeRadius + mNodeGap) * mCurrentPositionOffset                , mNodeRadius, mNodeRadius, mSelectedNodePaint);    }    @Override    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {        /**         * position:当前View的位置         * mCurrentPositionOffset:当前View的偏移量比例.[0,1)         */        this.mCurrentIndex = position;        this.mCurrentPositionOffset = positionOffset;        invalidate();    }    @Override    public void onPageSelected(int i) {        //会出现mCurrentPositionOffset!=0,这个方法调用        //加if判断防颤抖        if (mCurrentPositionOffset == 0) {            mCurrentIndex = i;            invalidate();        }           }    @Override    public void onPageScrollStateChanged(int i) {    }    @Override    protected Parcelable onSaveInstanceState() {        Bundle bundle = new Bundle();        bundle.putParcelable("instanceState", super.onSaveInstanceState());        bundle.putInt("mCurrentTab", mCurrentIndex);        bundle.putInt("mNodeCount", mNodeCount);        return bundle;    }    @Override    protected void onRestoreInstanceState(Parcelable state) {        if (state instanceof Bundle) {            Bundle bundle = (Bundle) state;            mCurrentIndex = bundle.getInt("mCurrentTab");            mNodeCount = bundle.getInt("mNodeCount");            if (mCurrentIndex >= 0 && mCurrentIndex < mNodeCount) {                requestLayout();            }            state = bundle.getParcelable("instanceState");        }        super.onRestoreInstanceState(state);    }    /**     * 关联ViewPager,用于连适配器都不想自己实例化的情况     */    public void setViewPager(ViewPager vp, FragmentActivity fa, ArrayList fragments) {        setViewPager(vp, fa.getSupportFragmentManager(), fragments);    }    /**     * 关联ViewPager,用于连适配器都不想自己实例化的情况     */    public void setViewPager(ViewPager vp, FragmentManager fm, ArrayList fragments) {        if (vp == null) {            throw new IllegalStateException("ViewPager can not be NULL !");        }        this.mViewPager = vp;        this.mViewPager.setAdapter(new InnerPagerAdapter(fm, fragments));        this.mViewPager.removeOnPageChangeListener(this);        this.mViewPager.addOnPageChangeListener(this);        mNodeCount = fragments.size();        requestLayout();    }    static class InnerPagerAdapter extends FragmentPagerAdapter {        private ArrayList fragments = new ArrayList<>();        public InnerPagerAdapter(FragmentManager fm, ArrayList fragments) {            super(fm);            this.fragments = fragments;        }        @Override        public int getCount() {            return fragments.size();        }        @Override        public Fragment getItem(int position) {            return fragments.get(position);        }        @Override        public void destroyItem(ViewGroup container, int position, Object object) {            // 覆写destroyItem并且空实现,这样每个Fragment中的视图就不会被销毁            // super.destroyItem(container, position, object);        }        @Override        public int getItemPosition(Object object) {            return PagerAdapter.POSITION_NONE;        }    }    protected int dp2px(float dp) {        final float scale = mContext.getResources().getDisplayMetrics().density;        return (int) (dp * scale + 0.5f);    }    protected int sp2px(float sp) {        final float scale = this.mContext.getResources().getDisplayMetrics().scaledDensity;        return (int) (sp * scale + 0.5f);    }}
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