Android動畫之雷達掃描效果

我們先看一下效果圖，有個整體的印象

好了，為了便於理解，這裡就按照動畫所見內容依次展開來說

準備

這裡決定採用canvas（

準備

這裡決定採用canvas（紙）和畫布paint（畫筆）實作了這個簡單動畫控制。

由圖片可以看到有兩條交叉的十字線、幾個圓圈和一些白點，那麼首先定義一下所需的畫筆，畫布及一些數據

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);

這裡說一下這個SweepGradient

SweepGradient的構造函數：

public SweepGradient(float cx, float cy, int[] colors, float[] positions)

public SweepGradient(float cx, float cy, int color0, int color1)

其中cx,cy 指定圓心, color1,color0 或colors 指定漸變的顏色，對於使用多於兩種顏色時，還可以透過positions 指定每種顏色的相對位置，positions 設為NULL時表示顏色均勻分佈。

繪製基本圖形

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);

這樣就繪製除了整個UI,接下來加上動畫，就可以實現整體的效果。

動畫實作

這裡實現動畫的時候，用到了Matrix這個東西，也就是矩陣。上學的時候，線性代數老師講各種線性變換時，腦子裡在想，這玩意是乾嘛使得，現在總算是遇上了，現在看起來也是雲裡霧裡。總的來說就是可以使用Matrix實現強大的圖形動畫，包括位移、旋轉、縮放及透明變化等效果，matrix有著一系列的setTranslate,setRotate,setScale等方法。很方便的實作圖形各種變換，主要還是需要理解各種變換。

動畫實作線程

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，這裡在一個獨立線程中不斷的對start做累加，作為旋轉角度。然後將其和matrix關聯。這裡嘗試使用了matrix的三種方法，暫時沒有發現差異。

動畫繪製

接下來在onDraw方法中不斷繪製圖形即可

//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);

最終實現

好了，最終整體的代碼如下：

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();
     }
    }
   }
  }
 }
}

就說明

好了，最終整體的代碼如下：

@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();
 }

就說明

程式碼裡已經註解的很清楚。這個RadarView的使用也很簡單，需要停止時，呼叫其stop方法即可。

rrreee

這裡雷達ViewSize設定為800，所以在佈局文件中設定大小時將不起作用，正常使用時，需根據實際需求調整viewsize大小和幾個Circle的半徑，從而達到更有好的UI展示效果。

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