[Android]最省記憶體的ViewPager添加小圓點指標

[Android]最省記憶體的ViewPager添加小圓點指標
原理：

這個你可以用View疊加來實現，但是這個效果不太理想，1占記憶體，而移植起來不方便，需要找各種資源，所以採用自己繪製更好，方便，而且效率高。

解決方案：

package com.youtu.view;import java.util.ArrayList;import java.util.List;import java.util.Map;import android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Paint.Style;import android.support.v4.view.ViewPager;import android.util.AttributeSet;import android.view.View;public class ADView extends ViewPager {AdAdapter mAdAdapter;Context context;Paint paint;List> urls;public ADView(Context context, AttributeSet attrs) {super(context, attrs);this.context = context;paint = new Paint();InitAdapter();}private void InitAdapter() {urls = new ArrayList>();mAdAdapter = new AdAdapter(context, urls);this.setAdapter(mAdAdapter);}public void setData(List> data) {urls.clear();for (int i = 0; i < data.size(); i++) {urls.add(data.get(i));}if(urls.size()>0){this.setVisibility(View.VISIBLE);}else{this.setVisibility(View.GONE);}mAdAdapter.notifyDataSetChanged();}@Overridepublic void draw(Canvas canvas) {super.draw(canvas);drawCycle(canvas);}private void drawCycle(Canvas canvas) {canvas.save();canvas.translate(getScrollX(), getScrollY());int count = 0;if (this.getAdapter() != null) {count = this.getAdapter().getCount();}int select = getCurrentItem();float density = getContext().getResources().getDisplayMetrics().density;int itemWidth = (int) (11 * density);int itemHeight = itemWidth / 2;int x = (getWidth() - count * itemWidth)/2;int y = getHeight() - itemWidth;int minItemHeight = (int) ((float) itemHeight * 0.8F);paint.setAntiAlias(true);paint.setStyle(Style.FILL);for (int i = 0; i < count; i++) {if (select == i) {paint.setColor(0xFFbdbdbd);canvas.drawCircle(x + itemWidth * i + itemWidth / 2, y, minItemHeight, paint);} else {paint.setColor(0xFFe6e6e6);canvas.drawCircle(x + itemWidth * i + itemWidth / 2, y, minItemHeight, paint);}}canvas.restore();}}