12.18android绘图,橡皮擦

「爱情、让人受尽委屈。」 2022-08-06 03:25 237阅读 0赞

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package com.yunxunzh.wlyxh100.view;
    
    
    import android.content.Context;
    import android.graphics.Bitmap;
    import android.graphics.Bitmap.Config;
    import android.graphics.BitmapFactory;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.graphics.PorterDuff.Mode;
    import android.graphics.PorterDuffXfermode;
    import android.graphics.drawable.BitmapDrawable;
    import android.view.MotionEvent;
    import android.view.View;
    
    import com.yunxunzh.wlyxh100.R;
    
    public class DrawEraser extends View {
    	private final static String TAG = "DrawView";
    	private int x = 0;
    	private int y = 0;
    	private int r = 0;
    	private Paint mPaint = null;
    	Bitmap bitmap = null;
    	Canvas mcanvas = null;
    
    	public DrawEraser(Context context ) {
    		super(context);
    
    		//设置背景,如果不设置，擦掉后变白
    		setBackgroundDrawable(new BitmapDrawable(BitmapFactory.decodeResource(getResources(),
    				R.drawable.welcome_bg)));
    		
    		mPaint = new Paint();
    		mPaint.setAlpha(0);
    		mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
    		mPaint.setAntiAlias(true);
    		
    		Bitmap bm = BitmapFactory.decodeResource(getResources(),
    				R.drawable.welcome_bg);
    
    		bitmap = Bitmap.createBitmap(300, 400, Config.ARGB_8888);
    		mcanvas = new Canvas();
    		mcanvas.setBitmap(bitmap);
    		mcanvas.drawBitmap(bm, 0, 0, null);
    		this.setOnTouchListener(new OnTouchListener() {
    
    			@Override
    			public boolean onTouch(View v, MotionEvent event) {
    				x = (int) event.getX();
    				y = (int) event.getY();
    				r = (int) 20;
    				invalidate();
    				return true;
    			}
    		});
    	}
    
    	@Override
    	protected void onDraw(Canvas canvas) {
    		mcanvas.drawCircle(x, y, r, mPaint);
    		canvas.drawBitmap(bitmap, 0, 0, null);
    		super.onDraw(canvas);
    	}
    
    }