之前在面试的时候被问到过一个问题，如何实现一个圆沿着一条线由大到小
当时回答的含糊不清，现在已经明白怎么去实现
关键点：Paint，path，canvas
一种方法
在activity中去控制圆的x,y坐标点 还有圆的直径。
在activity中写一个Timer 定时器，定时去绘制这个圆view。
圆view继承自view ，将变化接口暴露出去即可，重写onDrow函数，根据x y 轴重绘
上代码吧
public class ChangedCirclerView extends View {
private Paint mPaint;
private int BALL_SIZE;
//圆的坐标
private int ballX;
private int ballY;
public ChangedCirclerView(Context context){
super(context);
initView();
}
public ChangedCirclerView (Context context,int mballX, int mballY){
super(context);
initView();
ballX = mballX;
ballY = mballY;
}
public ChangedCirclerView(Context context, AttributeSet attributeSet){
super(context,attributeSet);
initView();
}
private void initView(){
mPaint = new Paint();
}
public void invalidateBall(int mBallX,int mBallY,int mBallRadiu) {
ballX = mBallX;
ballY = mBallY;
BALL_SIZE = mBallRadiu;
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mPaint.setColor(Color.rgb(255,215,0));
mPaint.setAntiAlias(true);
canvas.drawCircle(ballX,ballY,BALL_SIZE,mPaint);
}
}
然后是acitivity timer 控制代码
public class BallMoveActivity extends AppCompatActivity {
private Context context;
//小球初始的 X Y坐标点
private int baseX = 20;
private int baseY = 20;
private int baseRadiu = 10;
//定义球的两个方位速度
private int xSpeed = 10;
private int ySpeed = 30;
private int radiuSpeed = 5;
private int windowWidth ;
private int windowHight ;
private int ON_DRAW = 0;
private ChangedCirclerView circlerView;
private FrameLayout frameLayout;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
frameLayout = (FrameLayout) findViewById(R.id.activity_main);getWindowXY();
getWindowXY();
initTimer();
}
public void getWindowXY(){
WindowManager windowManager = (WindowManager)getSystemService(Context.WINDOW_SERVICE);
windowWidth = windowManager.getDefaultDisplay().getWidth();
windowHight = windowManager.getDefaultDisplay().getHeight();
}
private void initTimer(){
final Timer timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
baseX += xSpeed;
baseY += ySpeed;
baseRadiu += radiuSpeed;
Log.v("xy==",String.valueOf(baseX)+"...."+baseY);
Message message = new Message();
message.what = ON_DRAW;
handler.sendMessage(message);
}
},0,100);
}
public Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
if(msg.what == ON_DRAW){
if(circlerView == null){
circlerView = new ChangedCirclerView(context,baseX,baseY);
frameLayout.addView(circlerView);
}
if(baseX > windowWidth || baseY >windowHight){
baseX = 20;
baseY = 20;
baseRadiu = 10;
}
circlerView.invalidateBall(baseX,baseY,baseRadiu);
}
}
};
}
这样就能根据x y 轴控制圆的位置，还有直径控制圆的大小了
方法二
还有一种方法就是动画的方式
需要一个圆的图形，可以是自己的Drawable图片，也可以是自己绘制的
然后编写动画代码，translate动画，scale动画，这样就能定义一个圆从哪里到哪里，然后圆的大小怎么变化这样的需求