android 单指缩放功能

/* * Copyright (c) 2010, Sony Ericsson Mobile Communication AB. All rights reserved. * * Redistribution and use in source and binary forms, with or without modification, * are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * Neither the name of the Sony Ericsson Mobile Communication AB nor the names * of its contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. */ package com.sonyericsson.zoom; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.Rect; import android.util.AttributeSet; import android.view.View; import java.util.Observable; import java.util.Observer; /** * View capable of drawing an image at different zoom state levels */ public class ImageZoomView extends View implements Observer { /** Paint object used when drawing bitmap. */ private final Paint mPaint = new Paint(Paint.FILTER_BITMAP_FLAG); /** Rectangle used (and re-used) for cropping source image. */ private final Rect mRectSrc = new Rect(); /** Rectangle used (and re-used) for specifying drawing area on canvas. */ private final Rect mRectDst = new Rect(); /** The bitmap that we're zooming in, and drawing on the screen. */ private Bitmap mBitmap; /** Pre-calculated aspect quotient. */ private float mAspectQuotient; /** State of the zoom. */ private ZoomState mState; // Public methods /** * Constructor */ public ImageZoomView(Context context, AttributeSet attrs) { super(context, attrs); } /** * Set image bitmap * * @param bitmap The bitmap to view and zoom into */ public void setImage(Bitmap bitmap) { mBitmap = bitmap; calculateAspectQuotient(); invalidate(); } /** * Set object holding the zoom state that should be used * * @param state The zoom state */ public void setZoomState(ZoomState state) { if (mState != null) { mState.deleteObserver(this); } mState = state; mState.addObserver(this); invalidate(); } // Private methods private void calculateAspectQuotient() { if (mBitmap != null) { mAspectQuotient = (((float)mBitmap.getWidth()) / mBitmap.getHeight()) / (((float)getWidth()) / getHeight()); } } // Superclass overrides @Override protected void onDraw(Canvas canvas) { if (mBitmap != null && mState != null) { final int viewWidth = getWidth(); final int viewHeight = getHeight(); final int bitmapWidth = mBitmap.getWidth(); final int bitmapHeight = mBitmap.getHeight(); final float panX = mState.getPanX(); final float panY = mState.getPanY(); final float zoomX = mState.getZoomX(mAspectQuotient) * viewWidth / bitmapWidth; final float zoomY = mState.getZoomY(mAspectQuotient) * viewHeight / bitmapHeight; // Setup source and destination rectangles mRectSrc.left = (int)(panX * bitmapWidth - viewWidth / (zoomX * 2)); mRectSrc.top = (int)(panY * bitmapHeight - viewHeight / (zoomY * 2)); mRectSrc.right = (int)(mRectSrc.left + viewWidth / zoomX); mRectSrc.bottom = (int)(mRectSrc.top + viewHeight / zoomY); mRectDst.left = getLeft(); mRectDst.top = getTop(); mRectDst.right = getRight(); mRectDst.bottom = getBottom(); // Adjust source rectangle so that it fits within the source image. if (mRectSrc.left < 0) { mRectDst.left += -mRectSrc.left * zoomX; mRectSrc.left = 0; } if (mRectSrc.right > bitmapWidth) { mRectDst.right -= (mRectSrc.right - bitmapWidth) * zoomX; mRectSrc.right = bitmapWidth; } if (mRectSrc.top < 0) { mRectDst.top += -mRectSrc.top * zoomY; mRectSrc.top = 0; } if (mRectSrc.bottom > bitmapHeight) { mRectDst.bottom -= (mRectSrc.bottom - bitmapHeight) * zoomY; mRectSrc.bottom = bitmapHeight; } canvas.drawBitmap(mBitmap, mRectSrc, mRectDst, mPaint); } } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); calculateAspectQuotient(); } // implements Observer public void update(Observable observable, Object data) { invalidate(); } }