Android自定義圓點指示器

更新時間：2021年06月16日 15:00:54 作者：z11h

這篇文章主要為大家詳細介紹了Android自定義圓點指示器，文中示例代碼介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們可以參考一下

本文實例為大家分享了Android自定義圓點指示器的具體代碼，供大家參考，具體內(nèi)容如下

先上效果圖

大概思路就是自定義View 從左至右繪制圓點然后在ViewPager的OnPageChangeListener中設(shè)置當前頁面的圓點

下面是代碼

先定義屬性

<resources>
    <attr name="selectedColor" format="color"/>
    <attr name="unselectedColor" format="color"/>
    <declare-styleable name="Indicator">
        <attr name="selectedColor"/>
        <attr name="unselectedColor"/>
    </declare-styleable>
</resources>

接下來是自定義的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();
    }

從TypedArray中獲取自定義的屬性，totalIndex是總的圓點個數(shù)，currentIndex是當前頁面的圓點
接下來是重寫的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;
        }
    }

因為當前頁面的圓點和未選中頁面的圓點要設(shè)置不同的大小所以分別設(shè)置每個圓點的坐標然后用for循環(huán)繪制圓點
這里有一點要注意 new RectF() 的四個參數(shù)分別是圓點外面的矩形的左上角的X,Y和右下角的X,Y

接下來是設(shè)置當前頁面的圓點的方法

public void setCurrentIndex(int currentIndex){
        //if (currentIndex < 0)
        //    currentIndex += totalIndex ;
        //if (currentIndex > totalIndex - 1)
        //    currentIndex %= totalIndex;
        this.currentIndex = currentIndex;
        invalidate();
    }

注釋里的代碼是當頁面可以循環(huán)的時候設(shè)置的
接下來是設(shè)置總的圓點個數(shù)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();
    }

當刪除圓點的時候如果currentIndex是最后一個讓currentIndex向前移動
接下來是重寫的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的布局代碼，很簡單

<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.lzh123.learnviewpager.MainActivity">
 
    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
 
    <com.example.lzh123.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的代碼

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里添加了三個空頁面然后設(shè)置指示器的圓點個數(shù)，最后在ViewPager的OnPageChangeListener中設(shè)置當前的頁面的圓點。

以上就是本文的全部內(nèi)容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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