本文主要是介绍Android自定义View-仿华为手机管家病毒查杀类似于雷达扫描动画效果，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
最近在使用华为手机管家病毒查杀时有一个类似雷达扫描的动画，发现该动画旋转轴未对准圆心，如下图：
这样不仔细看，看不出来，咱们放大看一下，放大后如下：
现在我们可以清楚看到这个问题，于是想自己实现一把，好了，为了便于理解，这里就按照动画所见内容依次展开来说。
先简单的分析一下这里的元素，主要有3个园，三条直线，一个渐变扇形，一个渐变圆弧，知道这些以后，我们就可以开始进行代码编写了，那么首先定义一下所需要的画笔，画布及一些数据
//初始化画笔
private void initPaint() {mPaintCircleOrLine = new Paint();mPaintCircleOrLine.setStrokeWidth(2);mPaintCircleOrLine.setAntiAlias(true);mPaintCircleOrLine.setStyle(Paint.Style.STROKE);mPaintCircleOrLine.setColor(getResources().getColor(R.color.colorCircleOrLine));mPaintArc1 = new Paint();mPaintArc1.setStyle(Paint.Style.FILL);mPaintArc1.setAntiAlias(true);mPaintArc2 = new Paint();mPaintArc2.setStrokeWidth(4);mPaintArc2.setStyle(Paint.Style.STROKE);mPaintArc2.setAntiAlias(true);mPaintArc2.setColor(getResources().getColor(R.color.colorArcBorder));mPaintLine = new Paint();mPaintLine.setStrokeWidth(4);mPaintLine.setStyle(Paint.Style.STROKE);mPaintLine.setAntiAlias(true);mPaintLine.setColor(getResources().getColor(R.color.colorLine));}
注意这里画园和十字直线使用的同一个画笔的样式，如果你需要不同的样式，可以分开定义。初始化操作完成了之后，就是给变量赋值，我选择在onSizeChange()方法里面对变量进行赋值，代码如下：
@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);mWidth = getWidth();mHeight = getHeight();mRectF = new RectF(getPaddingLeft(), getPaddingTop(), mWidth-getPaddingRight(), mHeight-getPaddingBottom());SweepGradient sweepGradient1 = new SweepGradient(mWidth / 2, mHeight / 2,new int[]{Color.TRANSPARENT, getResources().getColor(R.color.colorArc)}, new float[]{0.8f, 1f});mPaintArc1.setShader(sweepGradient1);SweepGradient sweepGradient2 = new SweepGradient(mWidth / 2, mHeight / 2,Color.TRANSPARENT, getResources().getColor(R.color.colorArcBorder));mPaintArc2.setShader(sweepGradient2);Log.i("wang", String.format("width:%s, height:%s", mWidth, mHeight));}到这里我们的准备工作都做完了，接下来就进行绘制了，我重写了onDraw方法，我们看一下onDraw方法里面的操作：
@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);Log.i("ScanView", "onDraw()");canvasCircle(canvas);canvasLine(canvas);//根据matrix中设定角度，不断绘制shader,呈现出一种扇形扫描效果if(threadRunning) {canvas.concat(matrix);canvasArc(canvas);}}private void canvasCircle(Canvas canvas) {canvas.drawCircle(mWidth / 2, mHeight / 2, (mWidth - getPaddingLeft() - getPaddingRight()) / 6, mPaintCircleOrLine);canvas.drawCircle(mWidth / 2, mHeight / 2, (mWidth - getPaddingLeft() - getPaddingRight()) / 3, mPaintCircleOrLine);canvas.drawCircle(mWidth / 2, mHeight / 2, (mWidth - getPaddingLeft() - getPaddingRight()) / 2, mPaintCircleOrLine);}private void canvasLine(Canvas canvas) {canvas.drawLine(getPaddingLeft(), mHeight/2, mWidth - getPaddingRight(), mHeight/2, mPaintCircleOrLine);canvas.drawLine(mWidth/2, getPaddingTop(), mWidth/2, mHeight - getPaddingBottom(), mPaintCircleOrLine);}private void canvasArc(Canvas canvas) {canvas.drawArc(mRectF, 0, 180, true, mPaintArc1);canvas.drawArc(mRectF, 0, 180, false, mPaintArc2);canvas.drawLine(getPaddingLeft()-2, mHeight/2, mWidth/2, mHeight/2, mPaintLine);}
这样就绘制了整个UI，接下来实现动画效果，就可以实现整体的效果。
这里实现动画的时候，用到了Matrix这个东西，使用Matrix可以实现强大的图形动画，包位移、旋转、缩放、透明等效果，定义一线程，通过Matrix旋转操作实现动画，代码如下：protected class ScanThread extends Thread {private ScanView view;public ScanThread(ScanView view) {// TODO Auto-generated constructor stubthis.view = view;}@Overridepublic void run() {Log.i("ScanView", "run()");// TODO Auto-generated method stubwhile (threadRunning) {view.post(new Runnable() {public void run() {start = start + 1;matrix = new Matrix();matrix.preRotate(start, mWidth/2, mWidth/2);view.invalidate();}});try {Thread.sleep(5);} catch (InterruptedException e) {e.printStackTrace();}}}}好了，最终整体代码如下：
package com.wwj.custom.scan.view;import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;/*** Created by Administrator on 2017/4/25.*/public class ScanView extends View {private Paint mPaintCircleOrLine, mPaintArc1, mPaintArc2, mPaintLine;private float mWidth, mHeight;private RectF mRectF;private Matrix matrix;//旋转效果起始角度private int start = 0;private boolean threadRunning = false;private ScanThread mThread;public ScanView(Context context) {super(context);initPaint();}public ScanView(Context context, AttributeSet attrs) {super(context, attrs);initPaint();}private void initPaint() {mPaintCircleOrLine = new Paint();mPaintCircleOrLine.setStrokeWidth(2);mPaintCircleOrLine.setAntiAlias(true);mPaintCircleOrLine.setStyle(Paint.Style.STROKE);mPaintCircleOrLine.setColor(getResources().getColor(R.color.colorCircleOrLine));mPaintArc1 = new Paint();mPaintArc1.setStyle(Paint.Style.FILL);mPaintArc1.setAntiAlias(true);mPaintArc2 = new Paint();mPaintArc2.setStrokeWidth(4);mPaintArc2.setStyle(Paint.Style.STROKE);mPaintArc2.setAntiAlias(true);mPaintArc2.setColor(getResources().getColor(R.color.colorArcBorder));mPaintLine = new Paint();mPaintLine.setStrokeWidth(4);mPaintLine.setStyle(Paint.Style.STROKE);mPaintLine.setAntiAlias(true);mPaintLine.setColor(getResources().getColor(R.color.colorLine));}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);mWidth = getWidth();mHeight = getHeight();mRectF = new RectF(getPaddingLeft(), getPaddingTop(), mWidth-getPaddingRight(), mHeight-getPaddingBottom());SweepGradient sweepGradient1 = new SweepGradient(mWidth / 2, mHeight / 2,new int[]{Color.TRANSPARENT, getResources().getColor(R.color.colorArc)}, new float[]{0.8f, 1f});mPaintArc1.setShader(sweepGradient1);SweepGradient sweepGradient2 = new SweepGradient(mWidth / 2, mHeight / 2,Color.TRANSPARENT, getResources().getColor(R.color.colorArcBorder));mPaintArc2.setShader(sweepGradient2);Log.i("wang", String.format("width:%s, height:%s", mWidth, mHeight));}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);Log.i("ScanView", "onDraw()");canvasCircle(canvas);canvasLine(canvas);//根据matrix中设定角度，不断绘制shader,呈现出一种扇形扫描效果if(threadRunning) {canvas.concat(matrix);canvasArc(canvas);}}private void canvasCircle(Canvas canvas) {canvas.drawCircle(mWidth / 2, mHeight / 2, (mWidth - getPaddingLeft() - getPaddingRight()) / 6, mPaintCircleOrLine);canvas.drawCircle(mWidth / 2, mHeight / 2, (mWidth - getPaddingLeft() - getPaddingRight()) / 3, mPaintCircleOrLine);canvas.drawCircle(mWidth / 2, mHeight / 2, (mWidth - getPaddingLeft() - getPaddingRight()) / 2, mPaintCircleOrLine);}private void canvasLine(Canvas canvas) {canvas.drawLine(getPaddingLeft(), mHeight/2, mWidth - getPaddingRight(), mHeight/2, mPaintCircleOrLine);canvas.drawLine(mWidth/2, getPaddingTop(), mWidth/2, mHeight - getPaddingBottom(), mPaintCircleOrLine);}private void canvasArc(Canvas canvas) {canvas.drawArc(mRectF, 0, 180, true, mPaintArc1);canvas.drawArc(mRectF, 0, 180, false, mPaintArc2);canvas.drawLine(getPaddingLeft()-2, mHeight/2, mWidth/2, mHeight/2, mPaintLine);}public void start() {mThread = new ScanThread(this);mThread.start();threadRunning = true;}public void stop() {threadRunning = false;invalidate();}protected class ScanThread extends Thread {private ScanView view;public ScanThread(ScanView view) {// TODO Auto-generated constructor stubthis.view = view;}@Overridepublic void run() {Log.i("ScanView", "run()");// TODO Auto-generated method stubwhile (threadRunning) {view.post(new Runnable() {public void run() {start = start + 1;matrix = new Matrix();matrix.preRotate(start, mWidth/2, mWidth/2);view.invalidate();}});try {Thread.sleep(5);} catch (InterruptedException e) {e.printStackTrace();}}}}
}github地址：https://github.com/wjwang0914/CustomScanView
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