一个简单的Android自定义View的demo,画弧形,文字,开启一个多线程更新ui界面,在子线程更新ui是不允许的,但是View提供了方法,让我们来了解下吧。
1.封装一个抽象的View类 BaseView.java
- /**
- * 封装基本View
- * @author ansen
- * @create time 2015-08-07
- */
- public abstract class BaseView extends View{
- private MyThread myThread;
- public BaseView(Context context, AttributeSet attrs) {
- super(context, attrs);
- }
- public BaseView(Context context) {
- super(context);
- }
- protected abstract void onDrawSub(Canvas canvas);//绘制图像
- protected abstract void logic();//逻辑方法 子类实现
- @Override
- protected void onDraw(Canvas canvas) {
- if(null==myThread){
- myThread=new MyThread();
- myThread.start();
- }else{
- onDrawSub(canvas);
- }
- }
- private boolean running=true;//控制循环
- @Override
- protected void onDetachedFromWindow() {
- running=false;//销毁View的时候设置成false,退出无限循环
- super.onDetachedFromWindow();
- }
- //开启一个子线程绘制ui
- private class MyThread extends Thread{
- @Override
- public void run() {
- while(running){
- logic();
- postInvalidate();//重新绘制,会调用onDraw
- try {
- Thread.sleep(200);
- } catch (InterruptedException e) {
- e.printStackTrace();
- }
- }
- }
- }
- }
2.在逻辑View类中实现自己想要绘制的内容 LogicView.java
1).集成BaseView,实现onDrawSub()跟logic()抽象方法
2).在onDraw()方法中绘制图形 例如:画弧形 画文字
3).onDrawSub()方法中实现绘制的逻辑
- /**
- * Android自定义View 画弧形,文字,并增加动画效果
- * @author ansen
- * @create time 2015-08-07
- */
- public class LogicView extends BaseView{
- private Paint paint;//画笔
- private int x=0;
- private RectF rectF=new RectF(150,150,380,380);
- private int sweepAngle=0;//弧的结束度数
- private Random random=new Random();
- public LogicView(Context context, AttributeSet attrs) {
- super(context, attrs);
- init();
- }
- public LogicView(Context context) {
- super(context);
- init();
- }
- //初始化画笔
- private void init(){
- paint=new Paint();
- paint.setTextSize(60);
- }
- @Override
- protected final void onDrawSub(Canvas canvas) {
- canvas.drawText("Hello World", x, 100, paint);
- //第一个参数是RectF 左上的x y坐标 右下的x y坐标
- //第二个参数是 弧形的开始角度
- //第三个参数是 弧形的结束角度
- //第四个参数是 true:画扇形 false:画弧线
- //第五个参数是 画笔
- canvas.drawArc(rectF, 0, sweepAngle, true, paint);
- }
- @Override
- protected void logic() {
- x+=20;
- sweepAngle+=3;//每次弧度加3
- //随机设置画笔的颜色
- int r=random.nextInt(255);
- int g=random.nextInt(255);
- int b=random.nextInt(255);
- paint.setARGB(255, r, g, b);
- if(sweepAngle>=360){//如果弧度大于360° 从头开始
- sweepAngle=0;
- }
- if(x>getWidth()){//如果移动到屏幕外,从头开始
- int textWidth=(int) paint.measureText("Hello World");//测量文字宽度
- x=0-textWidth;
- }
- }
- }
3.显示View的Activity MainActivity.java
- public class MainActivity extends Activity {
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(new LogicView(this));
- }
- }
4.效果图如下:
