Question

我在主要活动中创建了一个名为DrawView的自定义视图。我在onDraw()类中实现了DrawView方法，它最初绘制了一个圆圈。然后我添加了一个触摸监听器，这样当用户点击时，它就会绘制一个正方形。我到达了用户点击的部分并绘制了一个正方形。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
        }
    }
}

非常感谢帮助。

Answer 1

这里是用户向下，触摸侦听器触发时移动和向上绘制矩形的简单片段，只是在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;

}

这是onDraw（）

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

Answer 2

您可以创建一个绘图监听器：

public interface OnDrawListener {
    void onDraw(Canvas c);
}

...

private class DrawView extends View {
    private OnDrawListener onDrawListener;

    public void setOnDrawListener(OnDrawListener onDrawListener) {
        this.onDrawListener=onDrawListener;
    }

    @Override
    protected void onDraw(Canvas c) {
        onDrawListener.onDraw(c);
    }
}

然后编辑覆盖侦听器：

// onCreate
drawing.setOnDrawListener(new OnDrawListener() {
    @Override
    public void onDraw(Canvas c) {
        // draw circle
    }
});

然后再次触摸事件并覆盖它以绘制正方形。

Answer 3

你必须覆盖原始的类函数：

@Override
public void onDraw(Canvas canvas

要强制绘图，请使用viewObject.invalidate（）

Answer 4

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.GREEN);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(5);   


   protected void onDraw(Canvas canvas) {   
        canvas.drawColor(Color.TRANSPARENT);
        canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
        canvas.drawPath(mPath, mPaint);
    }

Android，从主要活动中提取

4 个答案: