我正在尝试对弹力球实现减速。我可以上下移动球,但我想添加声明,因此当我从高处掉落球时,它会跳跃,然后再次撞击地面弹跳,慢慢地,它的速度会降低并在最后停止。
这是我的代码
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.os.Handler;
import android.util.AttributeSet;
import android.widget.ImageView;
public class AnimatedView extends ImageView{
private Context mContext;
int x = -1;
int y = -1;
private int xVelocity = 0;
private int yVelocity = 25;
private Handler h;
private final int FRAME_RATE = 20;
public AnimatedView(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
h = new Handler();
}
private Runnable r = new Runnable() {
@Override
public void run() {
invalidate();
}
};
protected void onDraw(Canvas c) {
BitmapDrawable ball = (BitmapDrawable) mContext.getResources().getDrawable(R.drawable.ball);
if (x<0 && y <0) {
x = this.getWidth()/2;
y = this.getHeight()/2;
} else {
x += xVelocity;
y += yVelocity;
if ((x > this.getWidth() - ball.getBitmap().getWidth()) || (x < 0)) {
xVelocity = xVelocity*-1;
}
if ((y > this.getHeight() - ball.getBitmap().getHeight()) || (y < 0)) {
yVelocity = yVelocity*-1;
}
}
c.drawBitmap(ball.getBitmap(), x, y, null);
h.postDelayed(r, FRAME_RATE);
}
希望任何人都可以帮助我。
提前致谢
最佳答案
加速度与速度的关系就像速度与位置的关系一样。你只需要根据你的位置和速度做你正在做的事情。
最简单的解决方案是添加
yVelocity += yAccel;
到 onDraw 的顶部,其中 yAccel 是一个整数,您希望每个刻度添加到 yVelocity。基于您的速度值
private int yAccel = -2;
可能是合适的。
编辑:您还应该添加检查以确保球不会落入地面。我将这些添加到反转速度的 block 中,以下代码对我有用。如果它不适合您,则项目的其他部分可能有问题。
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.os.Handler;
import android.util.AttributeSet;
import android.widget.ImageView;
public class AnimatedView extends ImageView {
private Context mContext;
int x = -1;
int y = -1;
private int xVelocity = 0;
private int yVelocity = 25;
private int yAccel = 2;
private Handler h;
private final int FRAME_RATE = 20;
public AnimatedView(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
h = new Handler();
}
private Runnable r = new Runnable() {
@Override
public void run() {
invalidate();
}
};
protected void onDraw(Canvas c) {
yVelocity += yAccel;
BitmapDrawable ball = (BitmapDrawable) mContext.getResources()
.getDrawable(R.drawable.cakes);
if (x < 0 && y < 0) {
x = this.getWidth() / 2;
y = this.getHeight() / 2;
} else {
x += xVelocity;
y += yVelocity;
if ((x > this.getWidth() - ball.getBitmap().getWidth()) || (x < 0)) {
xVelocity = xVelocity * -1;
x = Math.min(this.getWidth() - ball.getBitmap().getWidth(), x);
x = Math.max(0, x);
}
if ((y > this.getHeight() - ball.getBitmap().getHeight())
|| (y < 0)) {
yVelocity = (int)(yVelocity * -0.8f);
y = Math.min(this.getHeight() - ball.getBitmap().getHeight(), y);
y = Math.max(0, y);
}
}
c.drawBitmap(ball.getBitmap(), x, y, null);
h.postDelayed(r, FRAME_RATE);
}
}
关于java - 如何对弹力球实现声明?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20471531/