Android实现花瓣飘落效果的步骤
作者：itfitness
这篇文章主要介绍了Android实现花瓣飘落效果的步骤，帮助大家更好的理解和学习使用Android开发，感兴趣的朋友可以了解下
效果展示
实现原理
- 首先需要生成绘制小花的坐标点，坐标点的横坐标是根据控件的宽度随机生成的，而纵坐标则设置为小花图片高度的负值（这样可以实现小花从屏幕外进入）。
- 将这些点存储到集合当中。
- 遍历集合根据点的位置绘制小花
- 绘制完后不断增加各个点的纵坐标
实现步骤
1.定义变量将变量初始化
private SurfaceHolder mHolder;
private boolean mFlag = true;//绘制小花线程的开关标志
private ArrayList<PointF> mFlowers;//小花点的坐标集合
private Random mRandom;//负责随机数生成
private Bitmap mBitmap;//小花的图案
public FlowerView(Context context) {
super(context);
init();
}
public FlowerView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public FlowerView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init(){
mHolder = getHolder();
mHolder.addCallback(this);
//设置背景透明
this.setZOrderOnTop(true);
mHolder.setFormat(PixelFormat.TRANSLUCENT);
mFlowers = new ArrayList<>();
mRandom = new Random();
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_hua);
}
2.实现添加花朵坐标点的方法
/**
* 添加花朵
*/
private void addFlower(){
PointF point = new PointF();
point.x=mRandom.nextInt(getWidth());//根据控件宽度随机生成X轴坐标
point.y=-mBitmap.getHeight();//纵坐标设置为小花图像的负值（产生从屏幕外进入的效果）
mFlowers.add(point);//将坐标点添加进集合
}
3.实现SurfaceHolder.Callback及Runnable接口
public class FlowerView extends SurfaceView implements SurfaceHolder.Callback,Runnable
4.在run方法中实现绘制逻辑
@Override
public void run() {
while (mFlag){
try {
Thread.sleep(80);//控制小花的下落速度
Canvas canvas = mHolder.lockCanvas();
PointF pointF = null;
//清屏操作（否则会残留一些无用图像）
if(canvas!=null){
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
}else {
continue;
}
for(PointF point: mFlowers){
pointF = point;
canvas.drawBitmap(mBitmap,pointF.x,pointF.y,null);
int i = mRandom.nextInt(getHeight()/50)+getHeight()/50;//修改雨滴线的纵坐标，使其看起来在下雨
pointF.y=pointF.y+i;
}
mHolder.unlockCanvasAndPost(canvas);
addFlower();
//当绘制点的纵坐标大于控件高度时，将该点移除
if(mFlowers.size()>0&&pointF!=null&&pointF.y>=getHeight()){
mFlowers.remove(pointF);
}
}catch (Exception e){}
}
}
5.在SurfaceHolder.Callback的回调方法中开启绘制线程
@Override
public void surfaceCreated(SurfaceHolder holder) {
mFlag = true;//surface创建时将线程开关打开
new Thread(this).start();//开启线程绘制
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
mFlowers.clear();//当控件发生改变时清除之前的绘制点
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
mFlag = false;//当surface销毁时关掉绘制线程
}
完整代码展示
public class FlowerView extends SurfaceView implements SurfaceHolder.Callback,Runnable{
private SurfaceHolder mHolder;
private boolean mFlag = true;//绘制小花线程的开关标志
private ArrayList<PointF> mFlowers;//小花点的坐标集合
private Random mRandom;//负责随机数生成
private Bitmap mBitmap;//小花的图案
public FlowerView(Context context) {
super(context);
init();
}
public FlowerView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public FlowerView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init(){
mHolder = getHolder();
mHolder.addCallback(this);
//设置背景透明
this.setZOrderOnTop(true);
mHolder.setFormat(PixelFormat.TRANSLUCENT);
mFlowers = new ArrayList<>();
mRandom = new Random();
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_hua);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
mFlag = true;
new Thread(this).start();
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
mFlowers.clear();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
mFlag = false;
}
@Override
public void run() {
while (mFlag){
try {
Thread.sleep(80);
Canvas canvas = mHolder.lockCanvas();
PointF pointF = null;
//清屏操作
if(canvas!=null){
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
}else {
continue;
}
for(PointF point: mFlowers){
pointF = point;
canvas.drawBitmap(mBitmap,pointF.x,pointF.y,null);
int i = mRandom.nextInt(getHeight()/50)+getHeight()/50;//修改雨滴线的纵坐标，使其看起来在下雨
pointF.y=pointF.y+i;
}
mHolder.unlockCanvasAndPost(canvas);
addFlower();
if(mFlowers.size()>0&&pointF!=null&&pointF.y>=getHeight()){
mFlowers.remove(pointF);
}
}catch (Exception e){}
}
}
/**
* 添加花朵
*/
private void addFlower(){
PointF point = new PointF();
point.x=mRandom.nextInt(getWidth());
point.y=-mBitmap.getHeight();
mFlowers.add(point);
}
}
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