做一個自定義View的小練習，效果如下
只需要畫一個圓、一個圓弧、一個百分比文本，添加一個點擊事件，傳入百分比重繪
1、在res/values文件夾下新建attrs.xml文件，編寫自定義屬性：
<?xml version="1.0" encoding="utf-8"?><resources> <declare-styleable name="CirclePercentView" > <attr name="circleBg" format="color"/> <attr name="arcColor" format="color"/> <attr name="arcWidth" format="dimension"/> <attr name="percentTextColor" format="color"/> <attr name="percentTextSize" format="dimension"/> <attr name="radius" format="dimension"/> </declare-styleable></resources>
2、新建CirclePercentView繼承View，重寫構造方法：
public CirclePercentView(Context context) { this(context, null); } public CirclePercentView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public CirclePercentView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); }3、在第三個構造方法中獲取自定義屬性的值：
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.CirclePercentView, defStyleAttr, 0); mCircleColor = ta.getColor(R.styleable.CirclePercentView_circleBg, 0xff8e29fa); mArcColor = ta.getColor(R.styleable.CirclePercentView_arcColor, 0xffffee00); mArcWidth = ta.getDimensionPixelSize(R.styleable.CirclePercentView_arcWidth, DensityUtils.dp2px(context, 16)); mPercentTextColor = ta.getColor(R.styleable.CirclePercentView_arcColor, 0xffffee00); mPercentTextSize = ta.getDimensionPixelSize(R.styleable.CirclePercentView_percentTextSize, DensityUtils.sp2px(context, 16)); mRadius = ta.getDimensionPixelSize(R.styleable.CirclePercentView_radius, DensityUtils.dp2px(context, 100)); ta.recycle();
4、創建畫圖所使用的對象，如Paint、Rect、RectF：
mCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG); mCirclePaint.setStyle(Paint.Style.FILL); mCirclePaint.setColor(mCircleColor); mArcPaint = new Paint(Paint.ANTI_ALIAS_FLAG); mArcPaint.setStyle(Paint.Style.STROKE); mArcPaint.setStrokeWidth(mArcWidth); mArcPaint.setColor(mArcColor); mArcPaint.setStrokeCap(Paint.Cap.ROUND);//使圓弧兩頭圓滑 mPercentTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG); mPercentTextPaint.setStyle(Paint.Style.STROKE); mPercentTextPaint.setColor(mPercentTextColor); mPercentTextPaint.setTextSize(mPercentTextSize); mArcRectF = new RectF();//圓弧的外接矩形 mTextBound = new Rect();//文本的范圍矩形
5、重寫onMeasure()方法，計算自定義View的寬高：
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { setMeasuredDimension(measureDimension(widthMeasureSpec), measureDimension(heightMeasureSpec)); } private int measureDimension(int measureSpec) { int result; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec); if (specMode == MeasureSpec.EXACTLY) {//精確地，代表寬高為定值或者match_parent時 result = specSize; } else { result = 2 * mRadius; if (specMode == MeasureSpec.AT_MOST) {//最大地，代表寬高為wrap_content時 result = Math.min(result, specSize); } } return result; }6、重寫onDraw()方法，繪制圓、圓弧和百分比文本，注意坐標的計算：
@Override protected void onDraw(Canvas canvas) { //畫圓 canvas.drawCircle(getWidth() / 2, getHeight() / 2, mRadius, mCirclePaint); //畫圓弧 mArcRectF.set(getWidth() / 2 - mRadius + mArcWidth / 2, getHeight() / 2 - mRadius + mArcWidth / 2 , getWidth() / 2 + mRadius - mArcWidth / 2, getHeight() / 2 + mRadius - mArcWidth / 2); canvas.drawArc(mArcRectF, 270, 360 * mCurPercent / 100, false, mArcPaint); String text = mCurPercent + "%"; //計算文本寬高 mPercentTextPaint.getTextBounds(text, 0, String.valueOf(text).length(), mTextBound); //畫百分比文本 canvas.drawText(text, getWidth() / 2 - mTextBound.width() / 2 , getHeight() / 2 + mTextBound.height() / 2, mPercentTextPaint); }7、給這個view設置點擊事件，暴露一個動態設置百分比的方法：
public void setCurPercent(float curPercent) { ValueAnimator anim = ValueAnimator.ofFloat(mCurPercent, curPercent); //動畫時長由百分比大小決定 anim.setDuration((long) (Math.abs(mCurPercent - curPercent) * 20)); anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { float value = (float) animation.getAnimatedValue(); mCurPercent = (float) (Math.round(value * 10)) / 10;//四舍五入保留到小數點后兩位 invalidate();//重繪，重走onDraw()方法，這也是不能再onDraw()中創建對象的原因 } }); anim.start(); } public void setOnCircleClickListener(OnClickListener onClickListener) { this.mOnClickListener = onClickListener; } //在構造方法中 setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if (mOnClickListener != null) { mOnClickListener.onClick(CirclePercentView.this); } } });8、在activity_main.xml布局文件中使用該View：
<!-- 使用自定義命名空間namespace，cpv是該控件名的首字母縮寫，可以隨意取 --><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:cpv="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent"> <!-- cpv后面的屬性名對應attrs.xml文件中的自定義屬性名 --> <com.monkey.customviewdemo.view.CirclePercentView android:id="@+id/circlePercentView" android:layout_width="match_parent" android:layout_height="match_parent" cpv:arcColor="#ffee00" cpv:arcWidth="@dimen/activity_horizontal_margin" cpv:circleBg="#8e29fa" cpv:percentTextColor="#ffee00" cpv:percentTextSize="16sp" cpv:radius="100dp" /></RelativeLayout>
9、在MainActivity.java中設置監聽，傳入百分比：
mCirclePercentView = (CirclePercentView) findViewById(R.id.circlePercentView); mCirclePercentView.setOnCircleClickListener(new View.OnClickListener() { @Override public void onClick(View v) { float percent = (float) (Math.random() * 99 + 1); mCirclePercentView.setCurPercent(percent); } });代碼下載地址：
https://github.com/MonkeyMushroom/CirclePercentView/tree/master
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。
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