Android 多點觸控 (Multi-Touch)

Android 的多點觸控 (multi-touch),

在 onTouchEvent 事件中, 可透過 MotionEvent 實現之,

範例, 如下 :

Java 程式 :

 程式碼

public class helloWorld extends Activity
{
    private int gCenterX = 160;
    private int gCenterY = 240;
    private int gRadius = 100;
   
    private int gTouchX1, gTouchY1, gTouchX2, gTouchY2;
   
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       
        setContentView( new View(this){
           
            Paint vPaint = new Paint();  // 繪製樣式物件
            private int i = 0;           // 弧形角度
           
            @Override
            protected void onDraw(Canvas canvas)
            {
                // TODO Auto-generated method stub
                super.onDraw(canvas);
               
                // 設定繪圖樣式
                vPaint.setColor( 0xff00ffff ); // 畫筆顏色
                vPaint.setAntiAlias( true );   // 反鋸齒
                vPaint.setStyle( Paint.Style.STROKE );
               
                // 繪製一個圓形
                canvas.drawCircle( gCenterX, gCenterY, gRadius, vPaint );
            }
           
            @Override
            public boolean onTouchEvent(MotionEvent event)
            {
                int pointerCount = event.getPointerCount();  // 幾個觸控點
               
                switch( event.getAction() )
                {
                    case MotionEvent.ACTION_DOWN:  // 按下
                        break;
                   
                    case MotionEvent.ACTION_MOVE:  // 拖曳移動
                       
                        if( pointerCount == 1 )  // 單點觸控
                        {
                            gCenterX = (int) event.getX();
                            gCenterY = (int) event.getY();
                        }
                        else if( pointerCount == 2 )  // 多點觸控
                        {
                            gTouchX1 = (int) event.getX(0);  // 第一個觸控點
                            gTouchY1 = (int) event.getY(0);
                            gTouchX2 = (int) event.getX(1);  // 第二個觸控點
                            gTouchY2 = (int) event.getY(1);
                           
                            gCenterX = (int)((gTouchX1 + gTouchX2)/2);
                            gCenterY = (int)((gTouchY1 + gTouchY2)/2);
                            gRadius = (int)(Math.sqrt( Math.pow(gTouchX2-gTouchX1, 2)
                                                     + Math.pow(gTouchY2-gTouchY1, 2)
                                                     )/2);
                        }
                       
                        // 重繪, 再一次執行 onDraw 程序
                        invalidate();
                        break;
                       
                    case MotionEvent.ACTION_UP:    // 放開
                        break;
                }
               
                // TODO Auto-generated method stub
                return true;
            }
        });
    }
}

範例結果 :

昭佑.天翔