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