Android动画之雷达扫描效果

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。

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