Android，从主要 Activity 中绘制

Question

我在主 Activity 中创建了一个名为 DrawView 的自定义 View 。我在 DrawView 类中实现了 onDraw() 方法，它最初绘制了一个圆。然后我添加了一个触摸监听器，这样当用户单击时，它就会绘制一个正方形。我负责用户点击并绘制正方形的部分。我不确定该怎么做。

public class TestActivity extends Activity {
    DrawView drawing;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ViewGroup myLayout = (ViewGroup) findViewById(R.id.mainLayout);

        drawing = new DrawView(this);
        myLayout.addView(drawing);  

        drawing.setOnTouchListener(new View.OnTouchListener() {

            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    // draw a square
                }
                return true;
            }
        });
    }

    private class DrawView extends View {

        public DrawView(Context context) {
            super(context);
        }

        protected void onDraw(Canvas canvas) {
            Paint myPaint = new Paint();
            myPaint.setColor(Color.BLACK);
            // draw a circle
        }
    }
}

非常感谢您的帮助。

Answer 1

这里是当用户向下、移动和向上触发触摸监听器时绘制矩形的简单 fragment ，只需在 DrawView 类中覆盖而不是通过 setOnTouchListener()

在 DrawView 类中定义 Rect r = new Rect() 然后在 DrawView 类中实现此代码

public boolean onTouch(View v, MotionEvent event) {
   if (event.getAction() == MotionEvent.ACTION_DOWN) {
      sx = event.getX();
      sy = event.getY();
      r.set(sx,sy,sx,sy);
   }else if(event.getAction==MotionEvent.ACTION_UP){
      r.set(sx,sy,event.getX(),event.getY());
   }else if(event.getAction==MotionEvent.ACTION_MOVE){
      r.set(sx,sy,event.getX(),event.getY());
   }
   invalidate();
   return true;

这里是onDraw()

public void onDraw(Canvas canvas){
    super.onDraw(canvas);
    canvas.drawRect(r, new Paint());
}