模拟手机手指放大图片

首先自定义一个View来实现放大图片的效果

import java.util.Observable;import java.util.Observer;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.util.Log;import android.view.MotionEvent;import android.view.View;public class ZoomImageView 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();/** Object holding aspect quotient */private final AspectQuotient mAspectQuotient = new AspectQuotient();/** The bitmap that we're zooming in, and drawing on the screen. */private Bitmap mBitmap;/** State of the zoom. */private ZoomState mState;private BasicZoomControl mZoomControl;private BasicZoomListener mZoomListener;public ZoomImageView(Context context, AttributeSet attrs) {super(context, attrs);mZoomControl = new BasicZoomControl();mZoomListener = new BasicZoomListener();mZoomListener.setZoomControl(mZoomControl);setZoomState(mZoomControl.getZoomState());setOnTouchListener(mZoomListener);mZoomControl.setAspectQuotient(getAspectQuotient());}public void zoomImage(float f, float x, float y) {mZoomControl.zoom(f, x, y);}public void setImage(Bitmap bitmap) {mBitmap = bitmap;mAspectQuotient.updateAspectQuotient(getWidth(), getHeight(),mBitmap.getWidth(), mBitmap.getHeight());mAspectQuotient.notifyObservers();invalidate();}private void setZoomState(ZoomState state) {if (mState != null) {mState.deleteObserver(this);}mState = state;mState.addObserver(this);invalidate();}private AspectQuotient getAspectQuotient() {return mAspectQuotient;}@Overrideprotected void onDraw(Canvas canvas) {if (mBitmap != null && mState != null) {Log.d("ZoomImageView", "OnDraw");final float aspectQuotient = mAspectQuotient.get();final int viewWidth = getWidth();final int viewHeight = getHeight();final int bitmapWidth = mBitmap.getWidth();final int bitmapHeight = mBitmap.getHeight();Log.d("ZoomImageView", "viewWidth = " + viewWidth);Log.d("ZoomImageView", "viewHeight = " + viewHeight);Log.d("ZoomImageView", "bitmapWidth = " + bitmapWidth);Log.d("ZoomImageView", "bitmapHeight = " + bitmapHeight);final float panX = mState.getPanX();final float panY = mState.getPanY();final float zoomX = mState.getZoomX(aspectQuotient) * viewWidth/ bitmapWidth;final float zoomY = mState.getZoomY(aspectQuotient) * viewHeight/ bitmapHeight;// Setup source and destination rectanglesmRectSrc.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.left = 0;mRectDst.top = 0;// mRectDst.right = getRight();mRectDst.right = getWidth();mRectDst.bottom = getHeight();// 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;}mRectDst.left = 0;mRectDst.top = 0;mRectDst.right = viewWidth;mRectDst.bottom = viewHeight;Log.d("ZoomImageView", "mRectSrc.top" + mRectSrc.top);Log.d("ZoomImageView", "mRectSrc.bottom" + mRectSrc.bottom);Log.d("ZoomImageView", "mRectSrc.left" + mRectSrc.left);Log.d("ZoomImageView", "mRectSrc.right" + mRectSrc.right);Log.d("ZoomImageView", "mRectDst.top" + mRectDst.top);Log.d("ZoomImageView", "mRectDst.bottom" + mRectDst.bottom);Log.d("ZoomImageView", "mRectDst.left" + mRectDst.left);Log.d("ZoomImageView", "mRectDst.right" + mRectDst.right);canvas.drawBitmap(mBitmap, mRectSrc, mRectDst, mPaint);}}@Overrideprotected void onLayout(boolean changed, int left, int top, int right,int bottom) {super.onLayout(changed, left, top, right, bottom);mAspectQuotient.updateAspectQuotient(right - left, bottom - top,mBitmap.getWidth(), mBitmap.getHeight());mAspectQuotient.notifyObservers();}@Overridepublic void update(Observable observable, Object data) {invalidate();}private class BasicZoomListener implements View.OnTouchListener {/** Zoom control to manipulate */private BasicZoomControl mZoomControl;private float mFirstX = -1;private float mFirstY = -1;private float mSecondX = -1;private float mSecondY = -1;private int mOldCounts = 0;/** * Sets the zoom control to manipulate *  * @param control *            Zoom control */public void setZoomControl(BasicZoomControl control) {mZoomControl = control;}public boolean onTouch(View v, MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:mOldCounts = 1;mFirstX = event.getX();mFirstY = event.getY();break;case MotionEvent.ACTION_MOVE: {float fFirstX = event.getX();float fFirstY = event.getY();int nCounts = event.getPointerCount();if (1 == nCounts) {mOldCounts = 1;float dx = (fFirstX - mFirstX) / v.getWidth();float dy = (fFirstY - mFirstY) / v.getHeight();mZoomControl.pan(-dx, -dy);} else if (1 == mOldCounts) {mSecondX = event.getX(event.getPointerId(nCounts - 1));mSecondY = event.getY(event.getPointerId(nCounts - 1));mOldCounts = nCounts;} else {float fSecondX = event.getX(event.getPointerId(nCounts - 1));float fSecondY = event.getY(event.getPointerId(nCounts - 1));double nLengthOld = getLength(mFirstX, mFirstY, mSecondX,mSecondY);double nLengthNow = getLength(fFirstX, fFirstY, fSecondX,fSecondY);float d = (float) ((nLengthNow - nLengthOld) / v.getWidth());mZoomControl.zoom((float) Math.pow(20, d),((fFirstX + fSecondX) / 2 / v.getWidth()),((fFirstY + fSecondY) / 2 / v.getHeight()));mSecondX = fSecondX;mSecondY = fSecondY;}mFirstX = fFirstX;mFirstY = fFirstY;break;}}return true;}private double getLength(float x1, float y1, float x2, float y2) {return Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));}}private class BasicZoomControl implements Observer {/** Minimum zoom level limit */private static final float MIN_ZOOM = 1;/** Maximum zoom level limit */private static final float MAX_ZOOM = 16;/** Zoom state under control */private final ZoomState mState = new ZoomState();/** Object holding aspect quotient of view and content */private AspectQuotient mAspectQuotient;/** * Set reference object holding aspect quotient *  * @param aspectQuotient *            Object holding aspect quotient */public void setAspectQuotient(AspectQuotient aspectQuotient) {if (mAspectQuotient != null) {mAspectQuotient.deleteObserver(this);}mAspectQuotient = aspectQuotient;mAspectQuotient.addObserver(this);}/** * Get zoom state being controlled *  * @return The zoom state */public ZoomState getZoomState() {return mState;}/** * Zoom *  * @param f *            Factor of zoom to apply * @param x *            X-coordinate of invariant position * @param y *            Y-coordinate of invariant position */public void zoom(float f, float x, float y) {// Log.d("Zoom", "zoom f = " + f);final float aspectQuotient = mAspectQuotient.get();final float prevZoomX = mState.getZoomX(aspectQuotient);final float prevZoomY = mState.getZoomY(aspectQuotient);mState.setZoom(mState.getZoom() * f);limitZoom();final float newZoomX = mState.getZoomX(aspectQuotient);final float newZoomY = mState.getZoomY(aspectQuotient);// Pan to keep x and y coordinate invariantmState.setPanX(mState.getPanX() + (x - .5f)* (1f / prevZoomX - 1f / newZoomX));mState.setPanY(mState.getPanY() + (y - .5f)* (1f / prevZoomY - 1f / newZoomY));limitPan();mState.notifyObservers();}/** * Pan *  * @param dx *            Amount to pan in x-dimension * @param dy *            Amount to pan in y-dimension */public void pan(float dx, float dy) {final float aspectQuotient = mAspectQuotient.get();mState.setPanX(mState.getPanX() + dx/ mState.getZoomX(aspectQuotient));mState.setPanY(mState.getPanY() + dy/ mState.getZoomY(aspectQuotient));limitPan();mState.notifyObservers();}/** * Help function to figure out max delta of pan from center position. *  * @param zoom *            Zoom value * @return Max delta of pan */private float getMaxPanDelta(float zoom) {return Math.max(0f, .5f * ((zoom - 1) / zoom));}/** * Force zoom to stay within limits */private void limitZoom() {if (mState.getZoom() < MIN_ZOOM) {mState.setZoom(MIN_ZOOM);} else if (mState.getZoom() > MAX_ZOOM) {mState.setZoom(MAX_ZOOM);}}/** * Force pan to stay within limits */private void limitPan() {final float aspectQuotient = mAspectQuotient.get();final float zoomX = mState.getZoomX(aspectQuotient);final float zoomY = mState.getZoomY(aspectQuotient);final float panMinX = .5f - getMaxPanDelta(zoomX);final float panMaxX = .5f + getMaxPanDelta(zoomX);final float panMinY = .5f - getMaxPanDelta(zoomY);final float panMaxY = .5f + getMaxPanDelta(zoomY);if (mState.getPanX() < panMinX) {mState.setPanX(panMinX);}if (mState.getPanX() > panMaxX) {mState.setPanX(panMaxX);}if (mState.getPanY() < panMinY) {mState.setPanY(panMinY);}if (mState.getPanY() > panMaxY) {mState.setPanY(panMaxY);}}// Observable interface implementationpublic void update(Observable observable, Object data) {limitZoom();limitPan();}}private class AspectQuotient extends Observable {/** * Aspect quotient */private float mAspectQuotient;// Public methods/** * Gets aspect quotient *  * @return The aspect quotient */public float get() {return mAspectQuotient;}/** * Updates and recalculates aspect quotient based on supplied view and * content dimensions. *  * @param viewWidth *            Width of view * @param viewHeight *            Height of view * @param contentWidth *            Width of content * @param contentHeight *            Height of content */public void updateAspectQuotient(float viewWidth, float viewHeight,float contentWidth, float contentHeight) {final float aspectQuotient = (contentWidth / contentHeight)/ (viewWidth / viewHeight);if (aspectQuotient != mAspectQuotient) {mAspectQuotient = aspectQuotient;setChanged();}}}private class ZoomState extends Observable {/** * Zoom level A value of 1.0 means the content fits the view. */private float mZoom;/** * Pan position x-coordinate X-coordinate of zoom window center * position, relative to the width of the content. */private float mPanX;/** * Pan position y-coordinate Y-coordinate of zoom window center * position, relative to the height of the content. */private float mPanY;// Public methods/** * Get current x-pan *  * @return current x-pan */public float getPanX() {return mPanX;}/** * Get current y-pan *  * @return Current y-pan */public float getPanY() {return mPanY;}/** * Get current zoom value *  * @return Current zoom value */public float getZoom() {return mZoom;}/** * Help function for calculating current zoom value in x-dimension *  * @param aspectQuotient *            (Aspect ratio content) / (Aspect ratio view) * @return Current zoom value in x-dimension */public float getZoomX(float aspectQuotient) {return Math.min(mZoom, mZoom * aspectQuotient);}/** * Help function for calculating current zoom value in y-dimension *  * @param aspectQuotient *            (Aspect ratio content) / (Aspect ratio view) * @return Current zoom value in y-dimension */public float getZoomY(float aspectQuotient) {return Math.min(mZoom, mZoom / aspectQuotient);}/** * Set pan-x *  * @param panX *            Pan-x value to set */public void setPanX(float panX) {if (panX != mPanX) {mPanX = panX;setChanged();}}/** * Set pan-y *  * @param panY *            Pan-y value to set */public void setPanY(float panY) {if (panY != mPanY) {mPanY = panY;setChanged();}}/** * Set zoom *  * @param zoom *            Zoom value to set */public void setZoom(float zoom) {if (zoom != mZoom) {mZoom = zoom;setChanged();}}}}

然后再xml中找到这个view；

    <com.ymw.zoomimage.ZoomImageView        android:id="@+id/image"        android:layout_width="wrap_content"        android:layout_height="wrap_content" >    </com.ymw.zoomimage.ZoomImageView>

最后在Activity中找到view

ZoomImageView zoomImg = (ZoomImageView) findViewById(R.id.image);Bitmap bitmap = BitmapFactory.decodeResource(this.getResources(),R.drawable.a);zoomImg.setImage(bitmap);