Android Image Browsing, scaling, dragging, and auto center

Http://www.cnblogs.com/dwinter/archive/2012/01/12/2321082.html

Activity:

/*** Image Browsing, scaling, dragging, automatic center */public class touch extends activity implements ontouchlistener {matrix = new matrix (); matrix savedmatrix = new matrix (); displaymetrics DM; imageview imgview; Bitmap bitmap; float minscaler; // static final float max_scale = 4f; // static final int none = 0; // initial state static final int drag = 1; // drag static final int zoom = 2; // zoom int mode = none; pointf PR Ev = new pointf (); pointf mid = new pointf (); float Dist = 1f; @ override public void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. scale); imgview = (imageview) findviewbyid (R. id. IMAG); // obtain the control bitmap = bitmapfactory. decoderesource (getresources (), this. getintent (). getextras (). getint ("IMG"); // obtain the image resource imgview. setimagebitmap (Bitmap); // fill control imgview. Setontouchlistener (this); // set the touch screen listener dm = new displaymetrics (); getwindowmanager (). getdefadisplay display (). getmetrics (DM); // get the resolution minzoom (); Center (); imgview. setimagematrix (matrix);}/*** touch screen listener */Public Boolean ontouch (view V, motionevent event) {Switch (event. getaction () & motionevent. action_mask) {// The master node presses case motionevent. action_down: savedmatrix. set (matrix); Prev. set (event. getx (), event. gety () ); Mode = drag; break; // subpoint: press case motionevent. action_pointer_down: Dist = spacing (event); // if the distance between two consecutive points is greater than 10, it is determined that the multi-point mode if (spacing (event)> 10f) {savedmatrix. set (matrix); midpoint (MID, event); mode = zoom;} break; Case motionevent. action_up: Case motionevent. action_pointer_up: mode = none; break; Case motionevent. action_move: If (mode = drag) {matrix. set (savedmatrix); matrix. posttranslate (event. Getx ()-Prev. x, event. gety ()-Prev. y);} else if (mode = zoom) {float newdist = spacing (event); If (newdist> 10f) {matrix. set (savedmatrix); float tscale = newdist/Dist; matrix. postscale (tscale, tscale, mid. x, mid. y) ;}} break;} imgview. setimagematrix (matrix); checkview (); Return true;}/*** limit the maximum and minimum scaling ratio, automatically center */private void checkview () {float P [] = new float [9]; matrix. getvalues (p); If (Mode = zoom) {If (P [0] <minscaler) {matrix. setscale (minscaler, minscaler);} If (P [0]> max_scale) {matrix. set (savedmatrix) ;}} Center () ;}/ *** min zoom ratio, Max.: 100% */private void minzoom () {minscaler = math. min (float) DM. widthpixels/(float) bitmap. getwidth (), (float) DM. heightpixels/(float) bitmap. getheight (); If (minscaler <1.0) {matrix. postscale (minscaler, minscaler) ;}} private Void Center () {Center (True, true);}/*** center horizontally and vertically */protected void Center (Boolean horizontal, Boolean vertical) {matrix m = new matrix (); M. set (matrix); rectf rect = new rectf (0, 0, bitmap. getwidth (), bitmap. getheight (); M. maprect (rect); float Height = rect. height (); float width = rect. width (); float deltax = 0, deltay = 0; If (vertical) {// if the image is smaller than the screen size, it is displayed in the center. Greater than the screen. If it is left empty, it is moved up. If it is left empty, int screenheight = DM is moved down. heightpixels; If (height <screenheight) {deltay = (screenheight-height)/2-rect. top;} else if (rect. top> 0) {deltay =-rect. top;} else if (rect. bottom <screenheight) {deltay = imgview. getheight ()-rect. bottom ;}}if (horizontal) {int screenwidth = DM. widthpixels; If (width <screenwidth) {deltax = (screenwidth-width)/2-rect. left;} else if (rect. left> 0) {deltax =-rect. left;} else if (rect. right <screenwidth) {deltax = screenwidth-rect. right ;}} matrix. posttranslate (deltax, deltay);}/*** distance between two points */private float spacing (motionevent event) {float x = event. getx (0)-event. getx (1); float y = event. gety (0)-event. gety (1); Return floatmath. SQRT (x + y * Y);}/*** midpoint of two points */private void midpoint (pointf point, motionevent event) {float x = event. getx (0) + event. getx (1); float y = event. gety (0) + event. gety (1); point. set (X/2, Y/2 );}}

<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:layout_gravity="center" >    <ImageView        android:id="@+id/imag"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:layout_gravity="center"        android:scaleType="matrix" >    </ImageView></FrameLayout>