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前言
最近项目中需要加一个圆点指示器，在切换页面的时候使用，网上有开源的项目viewflow和viewpageIndicator,这两者都有很好的效果，但遗憾的是都有局限性，一个是只能用于viewflow，另一个只能用在viewpage上面，而我项目中的页面切换用的是自定义View，上面两个项目中的圆点指示器都不能拿来直接用，于是就借鉴viewflow做了一个简单易用的通用圆点指示器。
效果图
用法介绍
简单用法
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
......
gridview.setOnPageChangedListener(new OnPageChangedListener() {
@Override
public void onPageChanged(PagedDragDropGrid sender, int newPageNumber) {
//当页面切换的时候调用此方法改变被选中的圆点
indicator.setCurrentPage(newPageNumber);
}
});
//设置总共的页数
indicator.initData(adapter.pageCount(), 0);
//设置当前的页面
indicator.setCurrentPage(0);
//注：如果需要在切换页面时同时改变pagecount，initData和setCurrentPage可以同时使用。
}
按照上面做了以后就能正常使用了，如果你想定制圆点的大小，圆点间的间距，选中圆点和未选中圆点的颜色，那么请继续往下看吧。
详细用法
可配置的属性：
属性在xml中的用法：
android:id="@+id/xCircleIndicator"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="@dimen/indicator_bottom_margin"
indicator:circleInterval="@dimen/circleInterval"
indicator:fillColor="#F96A0E"
indicator:radius="@dimen/radius"
indicator:strokeColor="#cecece" />
当然设置参数不会局限于xml配置，也可以在java代码中动态设置
/**
* Sets the fill color
*
*@param color
* ARGB value for the text
*/
public void setFillColor(int color) {
mPaintFill.setColor(color);
invalidate();
}
/**
* Sets the stroke color
*
*@param color
* ARGB value for the text
*/
public void setStrokeColor(int color) {
mPaintStroke.setColor(color);
invalidate();
}
/**
* Sets the circle interval
*
*@param circleInterval
* unit px
*/
public void setCircleInterval(int circleInterval) {
this.circleInterval = circleInterval;
invalidate();
}
/**
* Sets the circle radius
*
*@param circleInterval
* unit px
*/
public void setRadius(int radius) {
this.radius = radius;
invalidate();
}
可以看到，在改变参数以后都调用了view.invalidate()方法，invalidate()函数的主要作用是请求View树进行重绘，然后在我们自定义view中会依次回调onMeasure(),onLayout()和onDraw()。在我们需要在onMeasure中完成测量，并在onDraw中完成了最终的绘制。
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(measureWidth(widthMeasureSpec),
measureHeight(heightMeasureSpec));
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// Draw stroked circles
for (int iLoop = 0; iLoop < pageTotalCount; iLoop++) {
canvas.drawCircle(getPaddingLeft() + radius
+ (iLoop * (2 * radius + circleInterval)), getPaddingTop()
+ radius, radius, mPaintStroke);
}
int cx = 0;
// if (flowWidth != 0) {
// // Draw the filled circle according to the current scroll
// cx = (currentScroll * (2 * radius + radius)) / flowWidth;
// }
cx = (2 * radius + circleInterval) * currentPage;
// The flow width has been upadated yet. Draw the default position
canvas.drawCircle(getPaddingLeft() + radius + cx, getPaddingTop()
+ radius, radius, mPaintFill);
}
/**
* 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 measureWidth(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
// We were told how big to be
if (specMode == MeasureSpec.EXACTLY) {
result = specSize;
} else { // Calculate the width according the views count
result = getPaddingLeft() + getPaddingRight()
+ (pageTotalCount * 2 * radius) + (pageTotalCount - 1)
* circleInterval;
// 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 measureHeight(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
// We were told how big to be
if (specMode == MeasureSpec.EXACTLY) {
result = specSize;
}
// Measure the height
else {
result = 2 * radius + getPaddingTop() + getPaddingBottom();
// 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;
}
以上就全部介绍完了，如果你对android-Universal-CircleIndicator感兴趣，可以在github上关注android-Universal-CircleIndicator
当然你也可以点此直接下载
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