一个简单的Android轨迹动画

public class TestView extends View implements ViewTreeObserver.OnGlobalLayoutListener{
private Paint paint = new Paint();
private Bitmap bitmap;
private int[]local;
boolean enter = false;
int count;
ViewTreeObserver observer;
Canvas canvas;
float lastX = 0;
float lastY = 0;
public TestView(Context context) {
super(context);
}
public TestView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
observer = this.getViewTreeObserver();
observer.addOnGlobalLayoutListener(this);
getImageFromAssetsFile("target.png");//读取图片
}
public TestView(Context context, AttributeSet attrs) {
super(context, attrs);
observer = this.getViewTreeObserver();
observer.addOnGlobalLayoutListener(this);
getImageFromAssetsFile("target.png");
}
private void getImageFromAssetsFile(String fileName) {
AssetManager am = getResources().getAssets();
try {
InputStream is = am.open(fileName);
bitmap = BitmapFactory.decodeStream(is);
is.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
private void filterColor(){
int w = bitmap.getWidth();
int h = bitmap.getHeight();
int[]pixels = new int[w*h];
local = new int[w];//以原图宽为单位，保存点在原图Y轴上的位置
bitmap.getPixels(pixels,0,bitmap.getWidth(),0,0,bitmap.getWidth(),bitmap.getHeight());
for(int i = 0; i < w; i++){
int lenght = 0;
int total = 0;
for(int j = 0;j<h;j++){
if (bitmap.getPixel(i, j) !=0) {
lenght++;
total+=j;
}
}
System.out.println(lenght+"");
if(lenght<15||((float)i/(float) w)<0.85)
local[i] = total/lenght;
else
break;
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if(enter) {
paint.setAntiAlias(true);      //设置画笔为无锯齿
paint.setColor(Color.WHITE);     //设置画笔颜色
canvas.drawColor(Color.TRANSPARENT);     //透明背景
paint.setStrokeWidth((float) 6.0);    //线宽
paint.setStyle(Paint.Style.STROKE);
Path path = new Path();
path.moveTo(0, (((float) getMeasuredHeight()-25) / (float)bitmap.getHeight()) * (float) local[0]+7);
if (count <= bitmap.getWidth()) {
if(count<bitmap.getWidth())
count++;
for (int i = 1; i < count - 1; i++) {
if(local[i] 0) {
path.lineTo((getMeasuredWidth() / (float) bitmap.getWidth()) * (float) i, (((float) getMeasuredHeight()-25) / (float) bitmap.getHeight()) * (float) local[i]+7);
lastX = (getMeasuredWidth() / (float) bitmap.getWidth()) * (float) i;
lastY = (((float) getMeasuredHeight()-25 )/ (float) bitmap.getHeight()) * (float) local[i];
}
}
}
if(count<bitmap.getWidth())
postInvalidate();
else {
count = 0;
postInvalidate();
}
canvas.drawPath(path, paint);
paint.setStyle(Paint.Style.FILL);
canvas.drawCircle(lastX, lastY+7, 7, paint);
//   }
}else{
this.canvas = canvas;
}
}
@Override
public void onGlobalLayout() {
filterColor();
enter = true;
postInvalidate();
}
}