Android 图片拖拽、放大缩小的自定义控件

需求：像相册中的图片跟随手指拖动，双指的放大和缩小，相册中拖出范围之后有弹回的动画，感觉上很圆润，很舒服，我写的例子中并没有加动画

思路：1.自定义DragImageView.java

            2.自定义中先画图片，图片大于屏幕就把图片缩小后显示，图片小于屏幕就直接显示，显示之前要计算显示图片的Rect，Rect是其实就是四个坐标，用来控制显示图片的范                  围，这个Rect是根据图片的长宽比例计算而来，显示在屏幕中间。

            3.跟随手指移动：在touchEvent事件中处理好单双指的各种事件之后，跟随手指就是不断的改变Rect的坐标，然后不断的invalidate()(该方法是重新强制绘制View);

            4.双指缩放：双指缩放的时候从图片Rect的中心缩放的，没有实现相册那种从手指中心缩放的那种。

            5.单指和双指的事件在touc事件中已近处理好了

                   event.getPointerCount()==2的情况就是双指部分

                   float    X0,Y0,X1,Y1双指的四个坐标

                   在双指移动的时候计算一个双指的距离出来m1,在MOVE执行的时候重新计算一个新的距离m2，去判断m1和m2大小来判断双指是张开还是捏合，并且执行相应事件，判断之后把m2复制给m1，这时的MOVE事件会有新的m2出来，所以就一直判断就ok了。放大和缩小就是按照一定的比例去改变Rect的值。

DragImageView.java

public class DragImageView extends View {

	private Paint mPaint;
	private Drawable mDrawable;
	private Rect mDrawableRect = new Rect();
	// private Rect mDrawableOffsetRect = new Rect();
	private Context mContext;
	private float mRation_WH = 0;
	private float mOldX = 0;
	private float mOldY = 0;
	private float mOldX0, mOldY0, mOldX1, mOldY1, mOldK, mOldB, mOldHandsX,
			mOldHandsY;
	private double mD1;
	private boolean isFirst = true;
	private int SINGALDOWN = 1;// 单点按下
	private int MUTILDOWM = 2;// 双点按下
	private int MUTILMOVE = 3;// 双点拖拽
	private int mStatus = 0;

	enum STATUS {
		SINGAL, MUTILDOWN, MUTILMOVE;
	}

	public DragImageView(Context context) {
		super(context);
		this.mContext = context;
		mPaint = new Paint();
		mPaint.setAntiAlias(true);
		mPaint.setColor(Color.BLACK);
		mPaint.setStyle(Style.FILL);
		mPaint.setTextSize(35.0f);
	}

	@SuppressLint("DrawAllocation")
	@Override
	protected void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		super.onDraw(canvas);
		if (mDrawable == null || mDrawable.getIntrinsicHeight() == 0
				|| mDrawable.getIntrinsicWidth() == 0) {
			return;
		}
		setBounds();
		mDrawable.draw(canvas);
		// Log.i("draw", "draw+++++++++++++++++++++++++++++++++++++++");

	}

	@SuppressLint("ClickableViewAccessibility")
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// TODO Auto-generated method stub
		switch (event.getPointerCount()) {
		case 1:

			switch (event.getAction()) {
			case MotionEvent.ACTION_DOWN:
				mStatus = SINGALDOWN;
				mOldX = event.getX();
				mOldY = event.getY();
				// Log.i("x_y_down", event.getX() + "__" + event.getY());
				break;
			case MotionEvent.ACTION_UP:
				checkBounds();
				// Log.i("x_y_up", event.getX() + "__" + event.getY());
				break;
			case MotionEvent.ACTION_MOVE:
				// Log.i("x_y_move", event.getX() + "__" + event.getY());
				if (mStatus == SINGALDOWN) {
					int offsetWidth = (int) (event.getX() - mOldX);
					int offsetHeight = (int) (event.getY() - mOldY);
					// Log.i("x_y_offset", offsetWidth + "__" + offsetHeight);
					mOldX = event.getX();
					mOldY = event.getY();
					mDrawableRect.offset(offsetWidth, offsetHeight);
					invalidate();
				}

				break;
			default:
				break;
			}
			break;
		default:
			/*
			 * mStatus = MUTILDOWM; if (mStatus == MUTILDOWM) { mOldX0 =
			 * event.getX(0); mOldY0 = event.getY(0); mOldX1 = event.getX(1);
			 * mOldY1 = event.getY(1); mOldK = (mOldY1 - mOldY0) / (mOldX1 -
			 * mOldX0); mOldB = (mOldY0 * mOldX1 - mOldY1 * mOldX0) / (mOldX1 -
			 * mOldX0); mOldHandsX = (mOldX0 + mOldX1) / 2; mOldHandsY =
			 * mOldHandsX * mOldK + mOldB; mD1 = Math.sqrt(Math.pow(mOldX0 -
			 * mOldX1, 2) + Math.pow(mOldY0 - mOldY1, 2)); Log.i("mD1", mD1 +
			 * "________________"); }
			 */
			switch (event.getAction()) {
			case MotionEvent.ACTION_POINTER_DOWN:
				Log.i("DOUBLETOWDOWN", "true");
				break;
			case MotionEvent.ACTION_MOVE:
				// Log.i("x_y_move", event.getX(0) + "__" + event.getY(0) +
				// "___"
				// + event.getX(1) + "__" + event.getY(1));
				mStatus = MUTILMOVE;
				float X0 = event.getX(0);
				float Y0 = event.getY(0);
				float X1 = event.getX(1);
				float Y1 = event.getY(1);
				float k = (Y1 - Y0) / (X1 - X0);
				float b = (Y0 * X1 - Y1 * X0) / (X1 - X0);
				int RectCenterX = mDrawableRect.centerX();
				int RectCenterY = mDrawableRect.centerY();
				float mHandsX = (X0 + X1) / 2;
				float mHandsY = mHandsX * k + b;
				double mD2 = Math.sqrt(Math.pow(X0 - X1, 2)
						+ Math.pow(Y0 - Y1, 2));

				Log.i("GCM", mD2 + "________________X:" + mHandsX + "___Y:"
						+ mHandsY);
				if (mD1 < mD2) {

					// double mMultiple = mD2 / mD1;
					// int newWidth = (int) (mDrawableRect.width() * mMultiple);
					// int newHeight = (int) (newWidth / mRation_WH);
					//
					// int newleft = mDrawableRect.left / 2;
					// int newtop = mDrawableRect.top / 2;
					// int newright = mDrawableRect.right * (3 / 2);
					// int newbotto = mDrawableRect.bottom * (3 / 2);
					// // mDrawableRect.set(newleft, newtop, newright,
					// newbotto);
					//
					// mDrawableRect.set(RectCenterX - newWidth / 2, RectCenterY
					// - newHeight / 2, RectCenterX + newWidth / 2,
					// RectCenterY + newHeight / 2);
					// invalidate();
					if (mDrawableRect.width() < mContext.getResources()
							.getDisplayMetrics().widthPixels * 2) {
						int offsetwidth = 10;
						int offsettop = (int) (offsetwidth / mRation_WH);
						mDrawableRect.set(mDrawableRect.left - offsetwidth,
								mDrawableRect.top - offsettop,
								mDrawableRect.right + offsetwidth,
								mDrawableRect.bottom + offsettop);
						Log.i("GCM", "aaaaaaaaaaaaaaa");

						invalidate();
					}
					// mDrawableRect.offset((int) mHandsX, (int) mHandsY);

				} else {
					if (mDrawableRect.width() > mContext.getResources()
							.getDisplayMetrics().widthPixels / 3) {
						int offsetwidth = 10;
						int offsettop = (int) (offsetwidth / mRation_WH);
						mDrawableRect.set(mDrawableRect.left + offsetwidth,
								mDrawableRect.top + offsettop,
								mDrawableRect.right - offsetwidth,
								mDrawableRect.bottom - offsettop);
						invalidate();
						Log.i("GCM", "bbbbbbbbbbbbbbb");
					}
				}
				mD1 = mD2;
				if (mHandsX < RectCenterX) {
					if (mHandsY < RectCenterY) {
						Log.i("PPPPPPP", "1");

					} else {
						Log.i("PPPPPPP", "3");
					}
				} else {
					if (mHandsY < RectCenterY) {
						Log.i("PPPPPPP", "2");
					} else {
						Log.i("PPPPPPP", "4");
					}
				}

				//

				break;
			case MotionEvent.ACTION_UP:
				Log.i("mStatus", "mutildouble_up");
				mStatus = 0;
				break;
			default:
				break;
			}
			break;
		}

		return true;
	}

	public void setBounds() {
		if (isFirst) {
			mRation_WH = (float) mDrawable.getIntrinsicWidth()
					/ (float) mDrawable.getIntrinsicHeight();
			int px_w = Math.min(getWidth(),
					dip2px(mContext, mDrawable.getIntrinsicWidth()));
			int px_h = (int) (px_w / mRation_WH);
			int left = (getWidth() - px_w) / 2;
			int top = (getHeight() - px_h) / 2;
			int right = px_w + left;
			int bottom = px_h + top;
			mDrawableRect.set(left, top, right, bottom);
			// mDrawableOffsetRect.set(mDrawableRect);
			isFirst = false;
			Log.i("rect1______", mDrawableRect.left + "," + mDrawableRect.top
					+ "," + mDrawableRect.right + "," + mDrawableRect.bottom);
		}
		mDrawable.setBounds(mDrawableRect);
		Log.i("rect2______", mDrawableRect.left + "," + mDrawableRect.top + ","
				+ mDrawableRect.right + "," + mDrawableRect.bottom);
		Log.i("center_______",
				mDrawableRect.centerX() + "," + mDrawableRect.centerY());

	}

	public void checkBounds() {
		int newLeft = mDrawableRect.left;
		int newTop = mDrawableRect.top;
		boolean isChange = false;
		if (newLeft < -mDrawableRect.width()) {
			newLeft = -mDrawableRect.width();
			isChange = true;
		}
		if (newTop < -mDrawableRect.height()) {
			newTop = -mDrawableRect.height();
			isChange = true;
		}
		if (newLeft > getWidth()) {
			newLeft = getWidth();
			isChange = true;
		}
		if (newTop > getHeight()) {
			newTop = getHeight();
			isChange = true;
		}
		if (isChange) {
			mDrawableRect.offsetTo(newLeft, newTop);
			invalidate();
		}
	}

	public Drawable getmDrawable() {
		return mDrawable;
	}

	public void setmDrawable(Drawable mDrawable) {
		this.mDrawable = mDrawable;
	}

	public int dip2px(Context context, int value) {
		final float scale = context.getResources().getDisplayMetrics().density;
		return (int) (value * scale + 0.5f);
	}

}

public class MainActivity extends Activity {

	Context mContext;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		this.mContext = getApplicationContext();
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		DragImageView mView = new DragImageView(mContext);
		mView.setmDrawable(mContext.getResources().getDrawable(R.drawable.bbb));
		setContentView(mView);
		
	}
}