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這篇文章主要講解了“Android如何自定義圓點指示器”，文中的講解內容簡單清晰，易于學習與理解，下面請大家跟著小編的思路慢慢深入，一起來研究和學習“Android如何自定義圓點指示器”吧！
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，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置不同的大小 所以分別設置每個圓點的坐標 然后用for循環繪制圓點
這里有一點要注意 new RectF() 的四個參數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的時候設置的
接下來是設置總的圓點個數的方法
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.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 然后設置指示器的圓點個數，最后在ViewPager的OnPageChangeListener中設置當前的 頁面的圓點。
感謝各位的閱讀，以上就是“Android如何自定義圓點指示器”的內容了，經過本文的學習后，相信大家對Android如何自定義圓點指示器這一問題有了更深刻的體會，具體使用情況還需要大家實踐驗證。這里是億速云，小編將為大家推送更多相關知識點的文章，歡迎關注！
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