自定义View+Handle 实现模拟时钟效果

利用自定义View 绘画时钟，实现时针，分针，秒针

package com.example.liyang.customview;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Shader;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.View;

import java.util.Calendar;

/**
 * paint a clock
 * Created by liyang on 2016/3/28.
 */
public class ClockView extends View implements  Handler.Callback{
    private Paint paint;
    private Handler handler = new Handler(this);
    private Bitmap bitmap;
    private BitmapShader bitmapShader;

    public ClockView(Context context) {
        this(context,null);

    }

    public ClockView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        paint = new Paint();
        handler.sendEmptyMessage(0);
        bitmap = BitmapFactory.decodeResource(context.getResources(), R.mipmap.img1);
        bitmapShader = new BitmapShader(bitmap,BitmapShader.TileMode.CLAMP,BitmapShader.TileMode.CLAMP);
    }

    public ClockView(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        //draw a clock
        // between 200px
        // we can translate  canvas to clock'center
        canvas.save();

        // make clock in center
        canvas.translate(getWidth()/2,getHeight()/2);
        float min = Math.min(getWidth()/200.0f,getHeight()/200.f);
        canvas.scale(min,min);// let clock bigger
        canvas.drawColor(Color.WHITE);


        // draw backGround-----------------------------------
        canvas.save();
        Paint temp = new Paint();
        temp.setShader(bitmapShader);
        canvas.translate(-100, -100);
        canvas.drawCircle(100, 100, 100,temp);
        canvas.restore();
//----------------------------------------------------------------


       // canvas.translate(100,100);
        //canvas.drawColor(Color.WHITE);
        paint.setStrokeWidth(5);
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.BLACK);
        paint.setAntiAlias(true);
        canvas.drawCircle(0,0,100,paint);

        // draw 1 2 ..
        canvas.save();
        for (int i =0; i<12;i++){
            if (i%3==0){
                paint.setStrokeWidth(7);
                canvas.drawLine(0,-100,0,-85,paint);

            }else
                paint.setStrokeWidth(5);
            canvas.drawLine(0,-100,0,-90,paint);

            canvas.rotate(30,0,0);//默认的锚点就是 00 写不写都行
        }

        // only after translate
        canvas.restore();
        Calendar calendar = Calendar.getInstance();

        //draw miao
        canvas.save();

        paint.setStrokeWidth(3);
        paint.setColor(Color.RED);

        //draw


        // calculate rotate one circle is 360  so  * 360
        canvas.rotate(calendar.get(Calendar.SECOND)*6,0,0);
        // draw miao
        canvas.drawLine(0,10,0,-90,paint);
        canvas.restore();


        //  ------------------minutes
        canvas.save();
        // move to init
        canvas.rotate(calendar.get(Calendar.MINUTE)*6+calendar.get(Calendar.SECOND)*6f/60,0,0);

        //draw line
        canvas.drawLine(0,10,0,-80,paint);
        canvas.restore();


        //  ------------------hour
        canvas.save();
        canvas.rotate(calendar.get(Calendar.HOUR)*30+calendar.get(Calendar.SECOND)*6f/3600,0,0);
        canvas.drawLine(0,10,0,-50,paint);
        canvas.restore();

        // as same start
        canvas.restore();


    }

    @Override
    public boolean handleMessage(Message msg) {

        switch (msg.what){
            case 0:


                // 通知画布去 刷新
                //同步刷新 通知 快 缺点是 只能在主线程 中有用
                invalidate();
                handler.sendEmptyMessage(0);
                //异步通知  优点是 ： 可以在子线程中 使用 缺点是慢
              //  postInvalidate();
                break;
        }

        return true;
    }
}