Draw multiple rectangles android canvas

问题

I'm trying to draw 4 rectangles on the canvas so that the canvas is divided in 4 equal rectangles. With the code I now have, only the last rectangle in my code is drawn.

This is the code in my Activity:

 protected void onCreate(Bundle savedInstanceState) {
     ...
setContentView(new MyView(this));
 }

public class MyView extends View {

    public MyView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        setFocusableInTouchMode(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
        int x = getWidth();
        int y = getHeight();


        Paint paintTopLeft = new Paint();
        paintTopLeft.setStyle(Paint.Style.FILL);
        paintTopLeft.setColor(Color.WHITE);
        canvas.drawPaint(paintTopLeft);
        // Use Color.parseColor to define HTML colors
        paintTopLeft.setColor(Color.parseColor("#F44336"));
        canvas.drawRect(0,0,x / 2,y / 2,paintTopLeft);

        Paint paintTopRight = new Paint();
        paintTopRight.setStyle(Paint.Style.FILL);
        paintTopRight.setColor(Color.WHITE);
        canvas.drawPaint(paintTopRight);
        // Use Color.parseColor to define HTML colors
        paintTopRight.setColor(Color.parseColor("#2196F3"));
        canvas.drawRect(x / 2, 0, x, y / 2, paintTopRight);

    }
}

What am I doing wrong?

回答1:

Actually I see only two rectangles that are drawn with your code. But anyway, the problem is that you are calling canvas.drawPaint which clears/fills the complete canvas with that color. So you are erasing all rectangles that have been drawn already just before you draw the last one.

This code should work:

protected void onCreate(Bundle savedInstanceState) {
     ...
setContentView(new MyView(this));
 }

public class MyView extends View {

    public MyView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        setFocusableInTouchMode(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
        int x = getWidth();
        int y = getHeight();    

        Paint paintTopLeft = new Paint();
        paintTopLeft.setStyle(Paint.Style.FILL);
        paintTopLeft.setColor(Color.WHITE);
        //canvas.drawPaint(paintTopLeft);  // don't do that
        // Use Color.parseColor to define HTML colors
        paintTopLeft.setColor(Color.parseColor("#F44336"));
        canvas.drawRect(0,0,x / 2,y / 2,paintTopLeft);

        Paint paintTopRight = new Paint();
        paintTopRight.setStyle(Paint.Style.FILL);
        paintTopRight.setColor(Color.WHITE);
        // canvas.drawPaint(paintTopRight);  // don't do that
        // Use Color.parseColor to define HTML colors
        paintTopRight.setColor(Color.parseColor("#2196F3"));
        canvas.drawRect(x / 2, 0, x, y / 2, paintTopRight);    
    }
}

来源：https://stackoverflow.com/questions/31163898/draw-multiple-rectangles-android-canvas

标签

android

android-canvas