畫板

• 程式碼

public class PaintView extends View {

    private Paint mPaint;//畫筆工具
    private Path mPath;//路徑

    public PaintView(Context context) {
        super(context);
        init();
    }

    public PaintView(Context context,  AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public PaintView(Context context,  AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init(){
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.STROKE);//設定畫筆為邊線樣式，另外還有FILL全填充
        mPaint.setColor(Color.BLACK);//設定畫筆顏色
        mPaint.setStrokeWidth(5);//設定邊線寬度

        mPath = new Path();//新建路徑
    }

    /**
     * @author dingtao
     * @date 2018/11/29 4:44 PM
     *
     * 觸控方法
     */
    @Override
    public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()){
            case MotionEvent.ACTION_UP://手指擡起
                break;
            case MotionEvent.ACTION_DOWN://手指按下，路徑移動到觸控點
                mPath.moveTo(event.getX(),event.getY());//路徑移動到觸控點
                break;
            case MotionEvent.ACTION_MOVE://手指移動
                mPath.lineTo(event.getX(),event.getY());//路徑連線到移動的點
                break;
        }
        invalidate();//重新整理控制元件，回撥onDraw方法
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.drawPath(mPath,mPaint);//畫路徑
    }
 

• 佈局

  直接託自定義控制元件就可以

• 效果
  可以拓展 + 一個圓形放在畫板中
  實現觸控圓形,拖動圓形的效果
  

修改方法中的值就可以

public boolean onTouchEvent(MotionEvent event) {
        x = event.getX();
        y = event.getY();
       /* switch (event.getAction()){
            case MotionEvent.ACTION_UP:
                break;
            case MotionEvent.ACTION_MOVE:
                mPath.moveTo(event.getX(),event.getY());
                break;
             case MotionEvent.ACTION_DOWN:
                 mPath.lineTo(event.getX(), event.getY());
                 x = event.getX();
                 y = event.getY();
                 break;
        }*/
        //*****************
        invalidate();
        return true;
    }
@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //canvas畫布****
    canvas.drawCircle(x,y,100,myPaint);
    //canvas.drawPath(mPath,myPaint);
}