这篇文章主要讲解了“Android如何自定义圆点指示器”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“Android如何自定义圆点指示器”吧！
先上效果图
大概思路就是自定义View 从左至右绘制圆点 然后在ViewPager的OnPageChangeListener中设置当前页面的圆点
下面是代码
先定义属性
<resources> <attr name="selectedColor" format="color"/> <attr name="unselectedColor" format="color"/> <declare-styleable name="Indicator"> <attr name="selectedColor"/> <attr name="unselectedColor"/> </declare-styleable> </resources>
接下来是自定义的View
public class Indicator extends View{ private static final int DEFAULT_TOTAL_INDEX = 5; private static final int DEFAULT_CURRENT_INDEX = 0; private static final int DEFAULT_CIRCLE_DISTANCE = 40; private static final int DEFAULT_CIRCLE_RADIUS = 8; private static final int DEFAULT_CIRCLE_SELECTED_RADIUS = 11; private int selectedColor; private int unselectedColor; private int currentIndex; private int totalIndex; private Paint paint; private int startX; private int startSelectedY; private int startY; private int centreX; public Indicator(Context context) { this(context,null); } public Indicator(Context context, AttributeSet attrs) { this(context, attrs,0); } public Indicator(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs,R.styleable.Indicator,defStyleAttr,0); selectedColor = typedArray.getColor(R.styleable.Indicator_selectedColor, Color.LTGRAY); unselectedColor = typedArray.getColor(R.styleable.Indicator_unselectedColor,Color.WHITE); typedArray.recycle(); totalIndex = DEFAULT_TOTAL_INDEX; currentIndex = DEFAULT_CURRENT_INDEX; paint = new Paint(); }从TypedArray中获取自定义的属性，totalIndex是总的圆点个数，currentIndex是当前页面的圆点
接下来是重写的OnDraw()方法
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); centreX = getWidth() / 2; startSelectedY = getHeight() / 2 - DEFAULT_CIRCLE_SELECTED_RADIUS; startY = getHeight() / 2 - DEFAULT_CIRCLE_RADIUS; if (totalIndex % 2 == 0){ startX = centreX - (int)(1.0 * (totalIndex - 1)/2 * DEFAULT_CIRCLE_DISTANCE); }else{ startX = centreX - totalIndex / 2 * DEFAULT_CIRCLE_DISTANCE; } paint.setAntiAlias(true); paint.setColor(unselectedColor); int tempX = startX; for(int i = 0 ; i < totalIndex ; i++ ){ RectF rectF = new RectF(tempX - DEFAULT_CIRCLE_RADIUS,startY, tempX + DEFAULT_CIRCLE_RADIUS,startY + 2 * DEFAULT_CIRCLE_RADIUS); if (i == currentIndex) { paint.setColor(selectedColor); rectF = new RectF(tempX - DEFAULT_CIRCLE_SELECTED_RADIUS,startSelectedY, tempX + DEFAULT_CIRCLE_SELECTED_RADIUS,startSelectedY + 2 * DEFAULT_CIRCLE_SELECTED_RADIUS); } canvas.drawOval(rectF,paint); if (paint.getColor() == selectedColor) paint.setColor(unselectedColor); tempX += DEFAULT_CIRCLE_DISTANCE; } }因为当前页面的圆点和未选中页面的圆点要设置不同的大小 所以分别设置每个圆点的坐标 然后用for循环绘制圆点
这里有一点要注意 new RectF() 的四个参数分别是圆点外面的矩形的左上角的X,Y和右下角的X,Y
接下来是设置当前页面的圆点的方法
public void setCurrentIndex(int currentIndex){ //if (currentIndex < 0) // currentIndex += totalIndex ; //if (currentIndex > totalIndex - 1) // currentIndex %= totalIndex; this.currentIndex = currentIndex; invalidate(); }注释里的代码是当页面可以循环的时候设置的
接下来是设置总的圆点个数的方法
public void setTotalIndex(int totalIndex){ int oldTotalIndex = this.totalIndex; if (totalIndex < 1) return; if (totalIndex < oldTotalIndex){ if (currentIndex == totalIndex ) currentIndex = totalIndex - 1; } this.totalIndex = totalIndex; invalidate(); }当删除圆点的时候 如果currentIndex是最后一个 让currentIndex向前移动
接下来是重写的OnMeasure()方法
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(measureWidth(widthMeasureSpec),measureHeight(heightMeasureSpec)); } private int measureHeight(int measureSpec){ int result; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); int desired = DEFAULT_CIRCLE_SELECTED_RADIUS * 2 + getPaddingBottom() + getPaddingTop(); if(specMode == MeasureSpec.EXACTLY) { result = Math.max(desired,specSize); }else{ if(specMode == MeasureSpec.AT_MOST){ result = Math.min(desired,specSize); } else result = desired; } return result; } private int measureWidth(int measureSpec){ int result; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); int desired = (totalIndex - 1) * DEFAULT_CIRCLE_DISTANCE + DEFAULT_CIRCLE_SELECTED_RADIUS * 2 + getPaddingLeft() + getPaddingRight(); if(specMode == MeasureSpec.EXACTLY) { result = Math.max(desired,specSize); }else{ if(specMode == MeasureSpec.AT_MOST){ result = Math.min(desired,specSize); }else result = desired; } return result; }下面是MainActivity的布局代码，很简单
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.lzh223.learnviewpager.MainActivity"> <android.support.v4.view.ViewPager android:id="@+id/viewPager" android:layout_width="match_parent" android:layout_height="match_parent"/> <com.example.lzh223.learnviewpager.Indicator app:selectedColor="#FFFFFF" app:unselectedColor="#C7C7C7" android:id="@+id/indicator" android:layout_centerInParent="true" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </RelativeLayout>
下面是MainActivity的代码
public class MainActivity extends AppCompatActivity { View layout1,layout2,layout3; ViewPager viewPager; Indicator indicator; List<View> viewList; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); viewPager = (ViewPager) findViewById(R.id.viewPager); LayoutInflater inflater = getLayoutInflater(); layout1 = inflater.inflate(R.layout.layout1,null); layout2 = inflater.inflate(R.layout.layout2,null); layout3 = inflater.inflate(R.layout.layout3,null); viewList = new ArrayList<>(); viewList.add(layout1); viewList.add(layout2); viewList.add(layout3); indicator = (Indicator) findViewById(R.id.indicator); indicator.setTotalIndex(viewList.size()); PagerAdapter pagerAdapter = new PagerAdapter() { @Override public int getCount() { return viewList.size(); } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView(viewList.get(position)); } @Override public Object instantiateItem(ViewGroup container, int position) { container.addView(viewList.get(position)); return position; } @Override public boolean isViewFromObject(View view, Object object) { return view == viewList.get(Integer.parseInt(object.toString())); } }; viewPager.setAdapter(pagerAdapter); viewPager.setOnPageChangeListener(new PageChangeListener()); } public class PageChangeListener implements ViewPager.OnPageChangeListener{ @Override public void onPageSelected(int position) { indicator.setCurrentIndex(position); } @Override public void onPageScrollStateChanged(int state) { } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } }ViewPager里添加了三个空页面 然后设置指示器的圆点个数，最后在ViewPager的OnPageChangeListener中设置当前的 页面的圆点。
感谢各位的阅读，以上就是“Android如何自定义圆点指示器”的内容了，经过本文的学习后，相信大家对Android如何自定义圆点指示器这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是亿速云，小编将为大家推送更多相关知识点的文章，欢迎关注！
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