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Android开发：史上最简单方便的viewpager加indicator的方法
开发Android应用的时候，每次给viewpager加indicator的时候，是不是感觉到很无力呢，看看JakeWharton大神的github，要么要应用library，要么把code加到自己的项目中，还要加attrs，加各种value，比如colors，strings，其实超过90%以上的时候，我们的需要其实很简单，只是在底部的中间加上指示圆点，而且JakeWharton大神的默认的是空心圆圈，还要在onDraw中改成实心的圆形，是不是厌烦啦，每次都要这么麻烦，好了，终极简单的解决方法出来了，想看效果：
当然，这个效果照搬别人的图，不过实现这个效果，我用了超级简单的方法，一劳永逸：
只要三个步骤，复制粘贴，再复制粘贴，然后在activity中写几行代码即可。
- 第一步，复制，粘贴
新建一个类，叫做CircleIndicatorHelper，然后复制如下的代码进去：
public class CircleIndicatorHelper {
private CirclePageIndicator mCircleIndicator;
private Context mContext;
public CircleIndicatorHelper(Context context) {
mCircleIndicator = new CirclePageIndicator(context);
mContext = context;
}
public void setViewpager(ViewPager viewPager) {
ViewGroup parentView = (ViewGroup) viewPager.getParent();
LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT, Gravity.BOTTOM);
lp.setMargins(0, 0, 0, dpToPx(8));
mCircleIndicator.setLayoutParams(lp);
parentView.addView(mCircleIndicator);
mCircleIndicator.setViewPager(viewPager);
}
public void setFillColor(String colorString) {
int color = Color.parseColor(colorString);
mCircleIndicator.setFillColor(color);
}
public void setDefaultColor(String colorString) {
int color = Color.parseColor(colorString);
mCircleIndicator.setDefaultColor(color);
}
public void setRadius(int radius) {
mCircleIndicator.setRadius(dpToPx(radius));
}
private int dpToPx(int dp) {
DisplayMetrics resourec = mContext.getResources().getDisplayMetrics();
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, resourec);
}
}
- 第二部，再新建一个类，名字叫复制，粘贴
public class CirclePageIndicator extends View{
private static final int INVALID_POINTER = -1;
private float mRadius;
// private final Paint mPaintPageFill = new Paint(ANTI_ALIAS_FLAG);
private final Paint mPaintStroke = new Paint(ANTI_ALIAS_FLAG);
private final Paint mPaintFill = new Paint(ANTI_ALIAS_FLAG);
private ViewPager mViewPager;
private ViewPager.OnPageChangeListener mListener;
private int mCurrentPage;
private int mSnapPage;
private float mPageOffset;
private int mScrollState;
private int mOrientation;
private boolean mCentered;
private boolean mSnap;
private float cicleSpace;
public CirclePageIndicator(Context context) {
this(context, null);
}
public CirclePageIndicator(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public CirclePageIndicator(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
if (isInEditMode()) return;
final Resources res = getResources();
final int defaultFillColor = Color.parseColor("#7F7F7F");
final int defaultStrokeColor = Color.parseColor("#D0D0D0");
final float defaultRadius = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 3, res.getDisplayMetrics());
mCentered = true;
mPaintStroke.setStyle(Style.FILL);
mPaintStroke.setColor(defaultStrokeColor);
mPaintFill.setStyle(Style.FILL);
mPaintFill.setColor(defaultFillColor);
mRadius = defaultRadius;
cicleSpace = mRadius*3;
}
public void setCentered(boolean centered) {
mCentered = centered;
invalidate();
}
public boolean isCentered() {
return mCentered;
}
public void setDefaultColor(int strokeColor) {
mPaintStroke.setColor(strokeColor);
invalidate();
}
public void setFillColor(int fillColor) {
mPaintFill.setColor(fillColor);
invalidate();
}
public void setRadius(float radius) {
mRadius = radius;
cicleSpace = radius*3;
invalidate();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mViewPager == null) {
return;
}
final int count = mViewPager.getAdapter().getCount();
if (count == 0) {
return;
}
if (mCurrentPage >= count) {
setCurrentItem(count - 1);
return;
}
int longSize;
int longPaddingBefore;
int longPaddingAfter;
int shortPaddingBefore;
if (mOrientation == HORIZONTAL) {
longSize = getWidth();
longPaddingBefore = getPaddingLeft();
longPaddingAfter = getPaddingRight();
shortPaddingBefore = getPaddingTop();
} else {
longSize = getHeight();
longPaddingBefore = getPaddingTop();
longPaddingAfter = getPaddingBottom();
shortPaddingBefore = getPaddingLeft();
}
final float shortOffset = shortPaddingBefore + mRadius;
float longOffset = longPaddingBefore + mRadius;
if (mCentered) {
longOffset += ((longSize - longPaddingBefore - longPaddingAfter) / 2.0f) - ((count * cicleSpace) / 2.0f);
}
float dX;
float dY;
float pageFillRadius = mRadius;
//Draw stroked circles
for (int iLoop = 0; iLoop < count; iLoop++) {
float drawLong = longOffset + (iLoop * cicleSpace);
if (mOrientation == HORIZONTAL) {
dX = drawLong;
dY = shortOffset;
} else {
dX = shortOffset;
dY = drawLong;
}
// Only paint fill if not completely transparent
canvas.drawCircle(dX, dY, mRadius, mPaintStroke);
}
//Draw the filled circle according to the current scroll
float cx = (mSnap ? mSnapPage : mCurrentPage) * cicleSpace;
if (!mSnap) {
cx += mPageOffset * cicleSpace;
}
if (mOrientation == HORIZONTAL) {
dX = longOffset + cx;
dY = shortOffset;
} else {
dX = shortOffset;
dY = longOffset + cx;
}
canvas.drawCircle(dX, dY, mRadius, mPaintFill);
}
public void setViewPager(ViewPager view) {
if (mViewPager == view) {
return;
}
if (mViewPager != null) {
mViewPager.setOnPageChangeListener(null);
}
if (view.getAdapter() == null) {
throw new IllegalStateException("ViewPager does not have adapter instance.");
}
mViewPager = view;
mViewPager.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
if (mSnap || mScrollState == ViewPager.SCROLL_STATE_IDLE) {
mCurrentPage = position;
mSnapPage = position;
invalidate();
}
if (mListener != null) {
mListener.onPageSelected(position);
}
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
mCurrentPage = position;
mPageOffset = positionOffset;
invalidate();
if (mListener != null) {
mListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
}
@Override
public void onPageScrollStateChanged(int state) {
mScrollState = state;
if (mListener != null) {
mListener.onPageScrollStateChanged(state);
}
}
});
invalidate();
}
public void setViewPager(ViewPager view, int initialPosition) {
setViewPager(view);
setCurrentItem(initialPosition);
}
public void setCurrentItem(int item) {
if (mViewPager == null) {
throw new IllegalStateException("ViewPager has not been bound.");
}
mViewPager.setCurrentItem(item);
mCurrentPage = item;
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
if (mOrientation == HORIZONTAL) {
setMeasuredDimension(measureLong(widthMeasureSpec), measureShort(heightMeasureSpec));
} else {
setMeasuredDimension(measureShort(widthMeasureSpec), measureLong(heightMeasureSpec));
}
}
/**
* Determines the width of this view
*
* @param measureSpec
* A measureSpec packed into an int
* @return The width of the view, honoring constraints from measureSpec
*/
private int measureLong(int measureSpec) {
int result;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if ((specMode == MeasureSpec.EXACTLY) || (mViewPager == null)) {
//We were told how big to be
result = specSize;
} else {
//Calculate the width according the views count
final int count = mViewPager.getAdapter().getCount();
result = (int)(getPaddingLeft() + getPaddingRight()
+ (count * 2 * mRadius) + (count - 1) * mRadius + 1);
//Respect AT_MOST value if that was what is called for by measureSpec
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
/**
* Determines the height of this view
*
* @param measureSpec
* A measureSpec packed into an int
* @return The height of the view, honoring constraints from measureSpec
*/
private int measureShort(int measureSpec) {
int result;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if (specMode == MeasureSpec.EXACTLY) {
//We were told how big to be
result = specSize;
} else {
//Measure the height
result = (int)(2 * mRadius + getPaddingTop() + getPaddingBottom() + 1);
//Respect AT_MOST value if that was what is called for by measureSpec
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
@Override
public void onRestoreInstanceState(Parcelable state) {
SavedState savedState = (SavedState)state;
super.onRestoreInstanceState(savedState.getSuperState());
mCurrentPage = savedState.currentPage;
mSnapPage = savedState.currentPage;
requestLayout();
}
@Override
public Parcelable onSaveInstanceState() {
Parcelable superState = super.onSaveInstanceState();
SavedState savedState = new SavedState(superState);
savedState.currentPage = mCurrentPage;
return savedState;
}
static class SavedState extends BaseSavedState {
int currentPage;
public SavedState(Parcelable superState) {
super(superState);
}
private SavedState(Parcel in) {
super(in);
currentPage = in.readInt();
}
@Override
public void writeToParcel(Parcel dest, int flags) {
super.writeToParcel(dest, flags);
dest.writeInt(currentPage);
}
@SuppressWarnings("UnusedDeclaration")
public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
@Override
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
@Override
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
}代码有点长啊，不过只是复制粘贴，应该没什么问题吧
- 第三部，在含有viewpager的activity，引用如下几句代码，即可加上viewpagerindicator了
private CircleIndicatorHelper mIndicatorHelper = new CircleIndicatorHelper(this); mIndicatorHelper.setViewpager(mViewPager);
好了，就是这么的简单，这么的任性，从此再也不用担心加小圆圈了，不过问题来了，怎么自定义呢，我要的圆圈的颜色，大小，间距，OK，这些都是一句代码搞定；
mIndicatorHelper.setFillColor("#651717");
mIndicatorHelper.setDefaultColor("#00A2E8");
mIndicatorHelper.setRadius(8);设置填充颜色，设置默认颜色，设置大小，简单便捷
好了，最后，别忘了，把viewpager的parent View设置成FrameLayout噢
Android开发：史上最简单方便的viewpager加indicator的方法
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