Android粒子雨效果之音量条显示

Android粒子雨效果之音量条显示

学习自极客学院

* 主要的内容是关于自定义view的实现

* 线程的简单使用

首先要明白为什么要使用自定义view，自定义就是为了动态的获取view的宽高和view的样式。

我们可以如何实现自定义view呢？

自己定义一个class继承view

public abstract class BaseView extends View {

private MyThread thread;
private boolean running = true;
protected long sleepTime = 100;

public BaseView(Context context) {
super(context);
}

protected abstract void init();
protected abstract void drawSub(Canvas canvas);
protected abstract void logic();

public BaseView(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
protected void onDraw(Canvas canvas) {
if(thread == null){
thread = new MyThread();
thread.start();
}else{
drawSub(canvas);
}
}
@Override
protected void onDetachedFromWindow() {
running = false;
super.onDetachedFromWindow();
}
class MyThread extends Thread{
@Override
public void run() {
init();
long workTime;
while(running){
workTime = System.currentTimeMillis();
postInvalidate();
logic();
workTime = System.currentTimeMillis() - workTime;
try {
if(workTime < sleepTime){
Thread.sleep(sleepTime - workTime);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}

}

抽象了base类，且抽象了三个方法

线程绘制时间做个判断，停留的时间准确为等于绘制时间加上沉睡时间。

我这里定义了一个baseView，所以之后肯定会有自己要新建的classView来继承baseView，目的是为之后其他的view的创建更合适。

public class IrDisatanceView extends BaseView {

private ArrayList<IrDistanceItem> list = new ArrayList<IrDistanceItem>();
private IrDistanceItem irDistanceItem;
private final static int NUM = 8;
private int itemWidth = 20;

public IrDisatanceView(Context context) {
super(context);
}

public IrDisatanceView(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
protected void init() {

//  irDistanceItem = new IrDistanceItem(getHeight());
for (int i = 0; i < NUM; i++) {
list.add(new IrDistanceItem(i * getWidth() / NUM, itemWidth, getHeight()));
}
}

@Override
protected void drawSub(Canvas canvas) {

for (IrDistanceItem item:list) {
item.draw(canvas);
}
}

@Override
protected void logic() {
for (IrDistanceItem item:list) {
item.move();
}
}

}

这里主要是传参数到IrDistanceItem 类中去，获得IrDistanceItem 对象，再执行方法。

所以就涉及到了IrDistanceItem 这个类

public class IrDistanceItem implements IAnimation{

private int itemHeight;
private Paint paint = new Paint();
private int maxHeight;
private Random random = new Random();
private int itemWidth;
private int x;

private int maxRectNum;
private int rectNum;
private int distance = 3;

public IrDistanceItem(int itemHeight){
this.maxHeight = itemHeight;
init();
}
public IrDistanceItem(int x,int itemWidth,int itemHeight){
this.maxHeight = itemHeight;
this.x = x;
this.itemWidth = itemWidth;

init();
}
private void init(){
paint.setColor(Color.RED);

maxRectNum = maxHeight / (itemWidth + distance);
}

@Override
public void draw(Canvas canvas) {
//  canvas.drawRect(x,itemHeight,x+itemWidth,maxHeight,paint);
int num = maxRectNum - rectNum;
for (int i = 0; i < rectNum; i++) {
canvas.drawRect(x, (num + i) * (itemWidth + distance), x
+ itemWidth, (num + i + 1) * (itemWidth + distance)
- distance, paint);
}
}

@Override
public void move() {
//  itemHeight = random.nextInt(maxHeight);
rectNum = 1 + random.nextInt(maxRectNum);
}

}

关键就在于这个类，构造方法有很多个，看需求需要哪些参数，就对应增加或者减少相应的参数。

主要看draw这个方法，调用了canvas这个类，

canvas.drawRect(x, (num + i) * (itemWidth + distance), x

+ itemWidth, (num + i + 1) * (itemWidth + distance)

- distance, paint);

drawRect(X1,Y1,X2,Y2,paint);五个参数，分别是左上右下，和paint对象。可以参考这个:[]http://www.360doc.com/content/13/0703/16/8510389_297389451.shtml]

random是一个随机函数

maxRectNum 是通过计算得到的方块数

num 是实际小方块的数目

还有一个简单的接口IAnimation类

public interface IAnimation {

public void draw(Canvas canvas);
public void move();

}

不需要解释吧

IrDistanceAct

public class IrDistanceAct extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ir_distance);

}

}

不需要做任何修改

最后就是layout文件了