UI-Canvas

Posted on | In

Bitmap围绕一个点进行旋转

在项目中需要使用定位功能，也就是一个点围绕一个圆心进行旋转，查看了canvas的函数也就只有一个 canvas.drawBitmap(bitmap, matrix, paint)通过使用Matrix来实现旋转，这里实现一个demo，功能就是小原点顺时针绘制一个原然后逆时针撤销这个圆，通过Timer来实现。代码如下:

Surface.java实现绘制图形的类

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import java.util.Timer;
import java.util.TimerTask;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuff.Mode;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;
@SuppressLint("HandlerLeak")
class Surface extends SurfaceView implements Callback{
    Bitmap bmp;
    private Paint mPaint;
    private SurfaceHolder mHolder;
    public Surface(Context context) {
        super(context);
        mHolder = getHolder();
        mHolder.addCallback(this);
        mPaint = new Paint();
        mPaint.setColor(Color.GREEN);
        mPaint.setAntiAlias(true);//抗锯齿
        setFocusable(true);
        setFocusableInTouchMode(true);
        //        setZOrderOnTop(true);
        //        mHolder.setFormat(PixelFormat.TRANSPARENT);//设置背景透明
        bmp = BitmapFactory.decodeResource(getResources(), R.drawable.camera_r_local);
        bmp = Bitmap.createScaledBitmap(bmp, 15, 15, false);
    }
    public Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 0:
                    canvas_ok();
                    break;
            }
            super.handleMessage(msg);
        }
    };
    public void canvas_ok(){
        Canvas canvas = null;
        try {
            canvas = mHolder.lockCanvas();
            canvas.drawColor(Color.TRANSPARENT, Mode.CLEAR);//清除屏幕
            //          canvas.save();
            Matrix matrix = new Matrix();
            matrix.postTranslate(130, 0);
            matrix.postRotate(degree, 130 ,130);
            canvas.drawBitmap(bmp, matrix, mPaint);
            //          canvas.restore();
        } catch (Exception e) {
        } finally {
            if(canvas != null) {
                mHolder.unlockCanvasAndPost(canvas);
            }
        }
    }
    int degree = 0;
    Timer timer = new Timer();
    boolean flag = true;
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        canvas_ok();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                if (flag) {
                    degree++;
                    if (degree == 360) {
                        flag = false;
                    }
                }else {
                    degree--;
                    if(degree == -360 || degree == 0){
                        flag = true;
                    }
                }
                Log.e("flag", degree+"  : "+flag);
                handler.sendEmptyMessage(0);
            }
        }, 50, 50);
    }
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
                               int height) {
    }
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        if (timer != null) {
            timer.cancel();
            timer = null;
        }
    }
}

Main7.java是主类

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import android.app.Activity;
import android.os.Bundle;
import android.widget.RelativeLayout;
public class Main7 extends Activity{
    Surface surface;
    RelativeLayout.LayoutParams laParams;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        surface = new Surface(this);
        laParams = new RelativeLayout.LayoutParams(260,  260);
        setContentView(surface, laParams);
    }
}