我们首先看一下效果图，有个整体的印象
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
准备
这里决定采用canvas（画布）和paint（画笔）实现了这个简单动画控件。
由图片可以看到有两条交叉的十字线、几个圆圈和一些白点，那么首先定义一下所需的画笔，画布及一些数据
setBackgroundColor(Color.TRANSPARENT); //宽度=5，抗锯齿，描边效果的白色画笔 mPaintLine = new Paint(); mPaintLine.setStrokeWidth(5); mPaintLine.setAntiAlias(true); mPaintLine.setStyle(Style.STROKE); mPaintLine.setColor(Color.WHITE); //宽度=5，抗锯齿，描边效果的浅绿色画笔 mPaintCircle = new Paint(); mPaintCircle.setStrokeWidth(5); mPaintCircle.setAntiAlias(true); mPaintCircle.setStyle(Style.FILL); mPaintCircle.setColor(0x99000000); //暗绿色的画笔 mPaintSector = new Paint(); mPaintSector.setColor(0x9D00ff00); mPaintSector.setAntiAlias(true); //定义一个暗绿色的梯度渲染 mShader = new SweepGradient(viewSize / 2, viewSize / 2, Color.TRANSPARENT, Color.GREEN); mPaintSector.setShader(mShader); //白色实心画笔 mPaintPoint=new Paint(); mPaintPoint.setColor(Color.WHITE); mPaintPoint.setStyle(Style.FILL); //随机生成一些数组点，模拟雷达扫描结果 point_x = UtilTools.Getrandomarray(15, 300); point_y = UtilTools.Getrandomarray(15, 300);
这里说一下这个SweepGradient
SweepGradient的构造函数：
public SweepGradient(float cx, float cy, int[] colors, float[] positions)
public SweepGradient(float cx, float cy, int color0, int color1)
其中cx,cy 指定圆心, color1,color0 或 colors 指定渐变的颜色 ，对于使用多于两种颜色时，还可以通过positions 指定每种颜色的相对位置，positions 设为NULL时表示颜色均匀分布。
绘制基本图形
canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintCircle); canvas.drawCircle(viewSize / 2, viewSize / 2, 255, mPaintLine); canvas.drawCircle(viewSize / 2, viewSize / 2, 125, mPaintLine); canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintLine); //绘制两条十字线 canvas.drawLine(viewSize / 2, 0, viewSize / 2, viewSize, mPaintLine); canvas.drawLine(0, viewSize / 2, viewSize, viewSize / 2, mPaintLine);
这样就绘制除了整个UI,接下来加上动画，就可以实现整体的效果。
动画实现
这里实现动画的时候，用到了Matrix这个东西，也就是矩阵。上学的时候，线性代数老师讲各种线性变换时，脑子里在想，这玩意是干嘛使得，现在总算是遇上了，现在看起来也是云里雾里。总的来说就是可以使用Matrix实现强大的图形动画，包括位移、旋转、缩放及透明变化等效果，matrix有着一系列的setTranslate,setRotate,setScale等方法。很方便的实现图形各种变换，主要还是需要理解各种变换。
动画实现线程
protected class ScanThread extends Thread { private RadarView view; public ScanThread(RadarView view) { // TODO Auto-generated constructor stub this.view = view; } @Override public void run() { // TODO Auto-generated method stub while (threadRunning) { if (isstart) { view.post(new Runnable() { public void run() { start = start + 1; matrix = new Matrix(); //设定旋转角度,制定进行转转操作的圆心// matrix.postRotate(start, viewSize / 2, viewSize / 2);// matrix.setRotate(start,viewSize/2,viewSize/2); matrix.preRotate(direction*start,viewSize/2,viewSize/2); view.invalidate(); } }); try { Thread.sleep(5); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } }
首先，这里在一个独立线程中不断的对start做累加，作为旋转角度。然后将其和matrix关联。这里尝试使用了matrix的三个方法，暂时没有发现区别。
动画绘制
接下来在onDraw方法中不断绘制图形即可
//根据matrix中设定角度，不断绘制shader,呈现出一种扇形扫描效果 canvas.concat(matrix); canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintSector);
最终实现
好了，最终整体的代码如下：
public class RadarView extends FrameLayout { private Context mContext; private int viewSize = 800; private Paint mPaintLine; private Paint mPaintCircle; private Paint mPaintSector; public boolean isstart = false; private ScanThread mThread; private Paint mPaintPoint; //旋转效果起始角度 private int start = 0; private int[] point_x; private int[] point_y; private Shader mShader; private Matrix matrix; public final static int CLOCK_WISE=1; public final static int ANTI_CLOCK_WISE=-1; @IntDef({ CLOCK_WISE, ANTI_CLOCK_WISE }) public @interface RADAR_DIRECTION { } //默认为顺时针呢 private final static int DEFAULT_DIERCTION=CLOCK_WISE; //设定雷达扫描方向 private int direction=DEFAULT_DIERCTION; private boolean threadRunning = true; public RadarView(Context context, AttributeSet attrs) { super(context, attrs); // TODO Auto-generated constructor stub mContext = context; initPaint(); } public RadarView(Context context) { super(context); // TODO Auto-generated constructor stub mContext = context; initPaint(); } private void initPaint() { // TODO Auto-generated method stub setBackgroundColor(Color.TRANSPARENT); //宽度=5，抗锯齿，描边效果的白色画笔 mPaintLine = new Paint(); mPaintLine.setStrokeWidth(5); mPaintLine.setAntiAlias(true); mPaintLine.setStyle(Style.STROKE); mPaintLine.setColor(Color.WHITE); //宽度=5，抗锯齿，描边效果的浅绿色画笔 mPaintCircle = new Paint(); mPaintCircle.setStrokeWidth(5); mPaintCircle.setAntiAlias(true); mPaintCircle.setStyle(Style.FILL); mPaintCircle.setColor(0x99000000); //暗绿色的画笔 mPaintSector = new Paint(); mPaintSector.setColor(0x9D00ff00); mPaintSector.setAntiAlias(true); mShader = new SweepGradient(viewSize / 2, viewSize / 2, Color.TRANSPARENT, Color.GREEN); mPaintSector.setShader(mShader); //白色实心画笔 mPaintPoint=new Paint(); mPaintPoint.setColor(Color.WHITE); mPaintPoint.setStyle(Style.FILL); //随机生成的点，模拟雷达扫描结果 point_x = UtilTools.Getrandomarray(15, 300); point_y = UtilTools.Getrandomarray(15, 300); } public void setViewSize(int size) { this.viewSize = size; setMeasuredDimension(viewSize, viewSize); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // TODO Auto-generated method stub setMeasuredDimension(viewSize, viewSize); } public void start() { mThread = new ScanThread(this); mThread.setName("radar"); mThread.start(); threadRunning = true; isstart = true; } public void stop() { if (isstart) { threadRunning = false; isstart = false; } } @Override protected void onDraw(Canvas canvas) { // TODO Auto-generated method stub canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintCircle); canvas.drawCircle(viewSize / 2, viewSize / 2, 255, mPaintLine); canvas.drawCircle(viewSize / 2, viewSize / 2, 125, mPaintLine); canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintLine); //绘制两条十字线 canvas.drawLine(viewSize / 2, 0, viewSize / 2, viewSize, mPaintLine); canvas.drawLine(0, viewSize / 2, viewSize, viewSize / 2, mPaintLine); //这里在雷达扫描过制定圆周度数后，将随机绘制一些白点，模拟搜索结果 if (start > 100) { for (int i = 0; i < 2; i++) { canvas.drawCircle(viewSize / 2 + point_x[i], viewSize / 2 + point_y[i], 10, mPaintPoint); } } if (start > 200) { for (int i = 2; i < 5; i++) { canvas.drawCircle(viewSize / 2 + point_x[i], viewSize / 2 + point_y[i], 10, mPaintPoint); } } if (start > 300) { for (int i = 5; i < 9; i++) { canvas.drawCircle(viewSize / 2 + point_x[i], viewSize / 2 + point_y[i], 10, mPaintPoint); } } if (start > 500) { for (int i = 9; i < 11; i++) { canvas.drawCircle(viewSize / 2 + point_x[i], viewSize / 2 + point_y[i], 10, mPaintPoint); } } if (start > 800) { for (int i = 11; i < point_x.length; i++) { canvas.drawCircle(viewSize / 2 + point_x[i], viewSize / 2 + point_y[i], 10, mPaintPoint); } } //根据matrix中设定角度，不断绘制shader,呈现出一种扇形扫描效果 canvas.concat(matrix); canvas.drawCircle(viewSize / 2, viewSize / 2, 350, mPaintSector); super.onDraw(canvas); } public void setDirection(@RADAR_DIRECTION int direction) { if (direction != CLOCK_WISE && direction != ANTI_CLOCK_WISE) { throw new IllegalArgumentException("Use @RADAR_DIRECTION constants only!"); } this.direction = direction; } protected class ScanThread extends Thread { private RadarView view; public ScanThread(RadarView view) { // TODO Auto-generated constructor stub this.view = view; } @Override public void run() { // TODO Auto-generated method stub while (threadRunning) { if (isstart) { view.post(new Runnable() { public void run() { start = start + 1; matrix = new Matrix(); //设定旋转角度,制定进行转转操作的圆心// matrix.postRotate(start, viewSize / 2, viewSize / 2);// matrix.setRotate(start,viewSize/2,viewSize/2); matrix.preRotate(direction*start,viewSize/2,viewSize/2); view.invalidate(); } }); try { Thread.sleep(5); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } }}
说明
多余的部分就不再解释，代码里已经注释的很清楚。这个RadarView的使用也是很简单，需要停止时，调用其stop方法即可。
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); RadarView radarView = (RadarView) findViewById(R.id.radar); //设置雷达扫描方向 radarView.setDirection(RadarView.ANTI_CLOCK_WISE); radarView.start(); }
这里雷达ViewSize设置为800，所以在布局文件中设定大小时将不起作用，正常使用时，需根据实际需求调整viewsize大小和几个Circle的半径，从而达到更有好的UI展示效果。
总结
以上就是Android中雷达扫描效果实现的全部内容，希望本文对大家Android开发有所帮助。
就是对虚怀若谷谦虚谨慎八个字真正理解的人，
