Android自定义view渐变圆形动画

<resources 
  <declare-styleable name="ProgressRing" 
    <!--进度起始色-- 
    <attr name="pr_progress_start_color" format="color" / 
    <!--进度结束色-- 
    <attr name="pr_progress_end_color" format="color" / 
    <!--背景起始色-- 
    <attr name="pr_bg_start_color" format="color" / 
    <!--背景中间色-- 
    <attr name="pr_bg_mid_color" format="color" / 
    <!--背景结束色-- 
    <attr name="pr_bg_end_color" format="color" / 
    <!--进度值 介于0-100-- 
    <attr name="pr_progress" format="integer" / 
    <!--进度宽度-- 
    <attr name="pr_progress_width" format="dimension" / 
    <!--起始角度-- 
    <attr name="pr_start_angle" format="integer" / 
    <!--扫过的角度-- 
    <attr name="pr_sweep_angle" format="integer" / 
    <!--是否显示动画-- 
    <attr name="pr_show_anim" format="boolean" / 
  </declare-styleable 

</resources 

public class ProgressRing extends View {
private int progressStartColor;
private int progressEndColor;
private int bgStartColor;
private int bgMidColor;
private int bgEndColor;
private int progress;
private float progressWidth;
private int startAngle;
private int sweepAngle;
private boolean showAnim;
private int mMeasureHeight;
private int mMeasureWidth;
private Paint bgPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
private Paint progressPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
private RectF pRectF;
private float unitAngle;
private int curProgress = 0;
public ProgressRing(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ProgressRing);
progressStartColor = ta.getColor(R.styleable.ProgressRing_pr_progress_start_color, Color.YELLOW);
progressEndColor = ta.getColor(R.styleable.ProgressRing_pr_progress_end_color, progressStartColor);
bgStartColor = ta.getColor(R.styleable.ProgressRing_pr_bg_start_color, Color.LTGRAY);
bgMidColor = ta.getColor(R.styleable.ProgressRing_pr_bg_mid_color, bgStartColor);
bgEndColor = ta.getColor(R.styleable.ProgressRing_pr_bg_end_color, bgStartColor);
progress = ta.getInt(R.styleable.ProgressRing_pr_progress, 0);
progressWidth = ta.getDimension(R.styleable.ProgressRing_pr_progress_width, 8f);
startAngle = ta.getInt(R.styleable.ProgressRing_pr_start_angle, 150);
sweepAngle = ta.getInt(R.styleable.ProgressRing_pr_sweep_angle, 240);
showAnim = ta.getBoolean(R.styleable.ProgressRing_pr_show_anim, true);
ta.recycle();
unitAngle = (float) (sweepAngle / 100.0);
bgPaint.setStyle(Paint.Style.STROKE);
bgPaint.setStrokeCap(Paint.Cap.ROUND);
bgPaint.setStrokeWidth(progressWidth);
progressPaint.setStyle(Paint.Style.STROKE);
progressPaint.setStrokeCap(Paint.Cap.ROUND);
progressPaint.setStrokeWidth(progressWidth);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
/*for (int i = 0, end = (int) (progress * unitAngle); i <= end; i++) {
progressPaint.setColor(getGradient(i / (float) end, progressStartColor, progressEndColor));
canvas.drawArc(pRectF,
startAngle + i,
1,
false,
progressPaint);
}*/
if (!showAnim) {
curProgress = progress;
}
drawBg(canvas);
drawProgress(canvas);
if (curProgress < progress) {
curProgress++;
postInvalidate();
}
}
// 只需要画进度之外的背景即可
private void drawBg(Canvas canvas) {
float halfSweep = sweepAngle / 2;
for (int i = sweepAngle, st = (int) (curProgress * unitAngle); i   st; --i) {
if (i - halfSweep   0) {
bgPaint.setColor(getGradient((i - halfSweep) / halfSweep, bgMidColor, bgEndColor));
} else {
bgPaint.setColor(getGradient((halfSweep - i) / halfSweep, bgMidColor, bgStartColor));
}
canvas.drawArc(pRectF,
startAngle + i,
1,
false,
bgPaint);
}
}
private void drawProgress(Canvas canvas) {
for (int i = 0, end = (int) (curProgress * unitAngle); i <= end; i++) {
progressPaint.setColor(getGradient(i / (float) end, progressStartColor, progressEndColor));
canvas.drawArc(pRectF,
startAngle + i,
1,
false,
progressPaint);
}
}
public void setProgress(@IntRange(from = 0, to = 100) int progress) {
this.progress = progress;
invalidate();
}
public int getProgress() {
return progress;
}
public int getGradient(float fraction, int startColor, int endColor) {
if (fraction   1) fraction = 1;
int alphaStart = Color.alpha(startColor);
int redStart = Color.red(startColor);
int blueStart = Color.blue(startColor);
int greenStart = Color.green(startColor);
int alphaEnd = Color.alpha(endColor);
int redEnd = Color.red(endColor);
int blueEnd = Color.blue(endColor);
int greenEnd = Color.green(endColor);
int alphaDifference = alphaEnd - alphaStart;
int redDifference = redEnd - redStart;
int blueDifference = blueEnd - blueStart;
int greenDifference = greenEnd - greenStart;
int alphaCurrent = (int) (alphaStart + fraction * alphaDifference);
int redCurrent = (int) (redStart + fraction * redDifference);
int blueCurrent = (int) (blueStart + fraction * blueDifference);
int greenCurrent = (int) (greenStart + fraction * greenDifference);
return Color.argb(alphaCurrent, redCurrent, greenCurrent, blueCurrent);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mMeasureWidth = getMeasuredWidth();
mMeasureHeight = getMeasuredHeight();
if (pRectF == null) {
float halfProgressWidth = progressWidth / 2;
pRectF = new RectF(halfProgressWidth + getPaddingLeft(),
halfProgressWidth + getPaddingTop(),
mMeasureWidth - halfProgressWidth - getPaddingRight(),
mMeasureHeight - halfProgressWidth - getPaddingBottom());
}
}
}

<myCircle.ProgressRing
android:layout_width="320dp"
android:layout_height="320dp"
android:layout_gravity="center_horizontal"
app:pr_bg_end_color="#00ffffff"
app:pr_bg_mid_color="#CCCCCC"
app:pr_bg_start_color="#00ffffff"
app:pr_progress="70"
app:pr_progress_end_color="#F78930"
app:pr_progress_start_color="#00ffffff"
app:pr_progress_width="40dp" /