進階四之Android UI介面之（Gallery仿圖像集浏覽）

兩個人共嘗一個痛苦只有半個痛苦，兩個人共享一個歡樂卻有兩個歡樂。

本講內容：Gallery仿圖像集浏覽

一、基本原理

在 Activity 中實現 OnGestureListener 的接口 onFling() 手勢事件，通過自定義的 View 繪制draw() 圖片

二、手勢坐標介紹

下面示例中，用到了OnGestureListener接口的onScroll()和OnFling()方法，涉及到了Android系統坐標及觸摸MotionEvent e1和e2、速度velocityX、velocityY等值

<喎?/kf/ware/vc/" target="_blank" class="keylink">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"/uploadfile/Collfiles/20150314/2015031408421070.png" alt="\">

下面是FlingView.java文件：

public class FlingView extends View {

	private Bitmap bitmap;
	private Bitmap nBitmap;
	private Bitmap fBitmap;

	public int offsetX = 0;
	public int offsetY = 0;
	public int postion = 0;

	private Bitmap[] bitmaps;

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

	public FlingView(Context context, Bitmap[] bitmaps) {
		super(context);

		this.bitmaps = bitmaps;
		bitmap = getBitmap(0);
		nBitmap = getBitmap(1);
	}

	// 在滑動過程中，通過實現View的Draw()方法繪制圖片，注意：此時需要同時繪制當前圖片（獲取焦點）和下一張圖片（即將獲取焦點）共兩張圖片
	@Override
	public void draw(Canvas canvas) {
		Paint paint = new Paint();
		Rect rect = new Rect();
		canvas.drawColor(Color.BLACK);

		// 繪制當前圖片
		if (bitmap != null) {
			int left = offsetX;
			int top = offsetY;
			int right = offsetX + MainActivity.deviceScreenWidth;
			int bottom = offsetY + MainActivity.deviceScreenHeight;
			rect.set(left, top, right, bottom);
			canvas.drawBitmap(bitmap, null, rect, paint);
		}

		// 繪制下一張圖片
		if (offsetX < 0) { // 向左滑動
			if (nBitmap != null) {
				int left = MainActivity.deviceScreenWidth + 15 + offsetX;
				int top = 0;
				int right = left + MainActivity.deviceScreenWidth;
				int bottom = MainActivity.deviceScreenHeight;
				rect.set(left, top, right, bottom);
				canvas.drawBitmap(nBitmap, null, rect, paint);
			}
		} else if (offsetX > 0) { // 向右滑動
			if (fBitmap != null) {
				int left = -MainActivity.deviceScreenWidth - 15 + offsetX;
				int top = 0;
				int right = left + MainActivity.deviceScreenWidth;
				int bottom = MainActivity.deviceScreenHeight;
				rect.set(left, top, right, bottom);
				canvas.drawBitmap(fBitmap, null, rect, paint);
			}
		}
	}

	public void handleScroll(int deltaX) {
		if (deltaX > 0) {
			offsetX -= -deltaX;
		} else {
			offsetX += deltaX;
		}
		invalidate();
	}

	boolean isFling = false; // 標記是否需要切換到下一張（滑動距離超過屏幕寬度的 1/3）
	boolean isFlingRight = false; // 標記為需要向右滑動
	boolean isFlingLeft = false; // 標記為需要向左滑動

	class MyAnimation extends Animation {
		private int tmpOffsetX;

		@Override
		public void initialize(int width, int height, int parentWidth,
				int parentHeight) {
			tmpOffsetX = offsetX;
			super.initialize(width, height, parentWidth, parentHeight);
			setDuration(500);
			setFillAfter(true);
			setInterpolator(new LinearInterpolator());
		}

		@Override
		protected void applyTransformation(float interpolatedTime,
				Transformation t) {
			// Log.i("bb", "offsetX==>"+offsetX);

			if (isFling) { // 需要滑動圖片時根據方向來變換offsetX大小
				if (tmpOffsetX > 0) {
					offsetX = (int) ((MainActivity.deviceScreenWidth - tmpOffsetX)
							* interpolatedTime + tmpOffsetX);
				} else {
					offsetX = (int) ((-MainActivity.deviceScreenWidth - tmpOffsetX)
							* interpolatedTime + tmpOffsetX);
				}
			} else { // 不需要變換的情況
				offsetX = (int) (tmpOffsetX * (1 - interpolatedTime));
			}

			invalidate();
		}
	}

	// 動畫結束後需要做一些工作
	//在滑動圖片結束後，需要做滑動動畫後的處理，重新設置當前圖片和當前圖片的上一張和下一張的狀態，為下次滑動做准備
	@Override
	protected void onAnimationEnd() {
		if (isFlingRight) { // 向右滑動，position減1
			nBitmap = bitmap;
			bitmap = fBitmap;
			fBitmap = null;
			postion = postion - 1;
		} else if (isFlingLeft) { // 向左滑動，position加1
			fBitmap = bitmap;
			bitmap = nBitmap;
			nBitmap = null;
			postion = postion + 1;
		}

		isFlingRight = false;
		isFlingLeft = false;
		isFling = false;
		offsetX = 0;
		if (fBitmap == null && offsetX == 0) { // 如果前一張圖片為空（向右滑），則重置前一張圖片（position
												// - 1）
			if (postion > 0) {
				fBitmap = getBitmap(postion - 1);
			}

		} else if (nBitmap == null && offsetX == 0) { // 如果後一張圖片為空（向左滑），則重置後一張圖片（position
														// + 1）
			if (postion < bitmaps.length - 1) {
				nBitmap = getBitmap(postion + 1);
			}
		}
		clearAnimation();
	}

	/** 獲得當前位置的圖片 */
	public Bitmap getBitmap(int currentPos) {
		if (currentPos > bitmaps.length - 1) {
			return null;
		}
		Bitmap currBitmap = bitmaps[currentPos];
		offsetX = 0;
		offsetY = 0;

		return currBitmap;
	}

	//獲取來自Activity中的手勢速度
	public void onFling(int paramFloat1) {
		if (offsetX > MainActivity.deviceScreenWidth / 5) {
			if (fBitmap != null) {
				isFling = true;
				isFlingRight = true;
			}
		} else if (offsetX < -MainActivity.deviceScreenWidth / 5) {
			if (nBitmap != null) {
				isFling = true;
				isFlingLeft = true;
			}
		}
		// 開始動畫效果
		startAnimation(new MyAnimation());
	}

}

下面是MainActivity.java主界面文件：（沒layout文件）

public class MainActivity extends Activity implements OnGestureListener {

	private FlingView flingView;
	private GestureDetector myGesture;

	public static int deviceScreenWidth;
	public static int deviceScreenHeight;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		
		// 獲得手機的寬帶和高度像素單位為px
		DisplayMetrics dm = new DisplayMetrics();
		getWindowManager().getDefaultDisplay().getMetrics(dm);
		deviceScreenWidth   = dm.widthPixels;
		deviceScreenHeight = dm.heightPixels;
		Log.i("mActivity", "deviceScreenWidth = " + deviceScreenWidth + "; deviceScreenHeight = " + deviceScreenHeight);

		Bitmap[] bitmaps = {
				BitmapFactory.decodeResource(getResources(), R.drawable.img1),
				BitmapFactory.decodeResource(getResources(), R.drawable.img2),
				BitmapFactory.decodeResource(getResources(), R.drawable.img3),
				BitmapFactory.decodeResource(getResources(), R.drawable.img4),
				BitmapFactory.decodeResource(getResources(), R.drawable.img5) };

		myGesture = new GestureDetector(this);
		flingView = new FlingView(this, bitmaps);
		setContentView(flingView);
	}

	//Activity中，通過onTouchEvent() 注冊 myGesture.onTouchEvent(event)
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		switch (event.getAction()) {
		case MotionEvent.ACTION_UP:
			flingView.onFling(0);			// 手指抬起後，重置滑動距離offsetX = 0
			break;
		}

		return myGesture.onTouchEvent(event);
	}

	@Override
	public boolean onDown(MotionEvent e) {
		return false;
	}

	@Override
	public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
		Log.i("mActivity", "velocityX = " + velocityX + "; velocityY = " + velocityY);
		flingView.onFling((int) - velocityX);
		return true;
	}

	@Override
	public void onLongPress(MotionEvent e) {
	}

	//獲取滑動的x軸距離
	@Override
	public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
		Log.i("mActivity", "distanceX = " + distanceX + "; distanceY = " + distanceY);
		flingView.handleScroll(-1 * (int) distanceX);
		return true;
	}

	//獲取手勢的速度
	@Override
	public void onShowPress(MotionEvent e) {
	}

	@Override
	public boolean onSingleTapUp(MotionEvent e) {
		return false;
	}
}