There is a draggable object over the imageview which has been set as background in android. When the background imageview zooms, I want the object to stay in the same position as it was before.for example, if it was over a text called "smile" in that image then, it should stay there even after zooming.
I want the image works just like google maps when we add marker to a map the marker moves according to zoom in and out.
Use the below class of Framlayout for that, It will zoom all the content inside that.
public class ZoomableLayout extends FrameLayout {
public ZoomableLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
}
public ZoomableLayout(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
}
public ZoomableLayout(final Context context) {
super(context);
}
/**
* Zooming view listener interface.
*
* @author karooolek
*
*/
public interface ZoomViewListener {
void onZoomStarted(float zoom, float zoomx, float zoomy);
void onZooming(float zoom, float zoomx, float zoomy);
void onZoomEnded(float zoom, float zoomx, float zoomy);
}
// zooming
float zoom = 1.0f;
float maxZoom = 2.0f;
float smoothZoom = 1.0f;
float zoomX, zoomY;
float smoothZoomX, smoothZoomY;
private boolean scrolling; //
// minimap variables
private boolean showMinimap = false;
private int miniMapColor = Color.WHITE;
private int miniMapHeight = -1;
private String miniMapCaption;
private float miniMapCaptionSize = 10.0f;
private int miniMapCaptionColor = Color.WHITE;
// touching variables
private long lastTapTime;
private float touchStartX, touchStartY;
private float touchLastX, touchLastY;
private float startd;
private boolean pinching;
private float lastd;
private float lastdx1, lastdy1;
private float lastdx2, lastdy2;
// drawing
private final Matrix m = new Matrix();
private final Paint p = new Paint();
// listener
ZoomViewListener listener;
private Bitmap ch;
public float getZoom() {
return zoom;
}
public float getMaxZoom() {
return maxZoom;
}
public void setMaxZoom(final float maxZoom) {
if (maxZoom < 1.0f) {
return;
}
this.maxZoom = maxZoom;
}
public void setMiniMapEnabled(final boolean showMiniMap) {
this.showMinimap = showMiniMap;
}
public boolean isMiniMapEnabled() {
return showMinimap;
}
public void setMiniMapHeight(final int miniMapHeight) {
if (miniMapHeight < 0) {
return;
}
this.miniMapHeight = miniMapHeight;
}
public int getMiniMapHeight() {
return miniMapHeight;
}
public void setMiniMapColor(final int color) {
miniMapColor = color;
}
public int getMiniMapColor() {
return miniMapColor;
}
public String getMiniMapCaption() {
return miniMapCaption;
}
public void setMiniMapCaption(final String miniMapCaption) {
this.miniMapCaption = miniMapCaption;
}
public float getMiniMapCaptionSize() {
return miniMapCaptionSize;
}
public void setMiniMapCaptionSize(final float size) {
miniMapCaptionSize = size;
}
public int getMiniMapCaptionColor() {
return miniMapCaptionColor;
}
public void setMiniMapCaptionColor(final int color) {
miniMapCaptionColor = color;
}
public void zoomTo(final float zoom, final float x, final float y) {
this.zoom = Math.min(zoom, maxZoom);
zoomX = x;
zoomY = y;
smoothZoomTo(this.zoom, x, y);
}
public void smoothZoomTo(final float zoom, final float x, final float y) {
smoothZoom = clamp(1.0f, zoom, maxZoom);
smoothZoomX = x;
smoothZoomY = y;
if (listener != null) {
listener.onZoomStarted(smoothZoom, x, y);
}
}
public ZoomViewListener getListener() {
return listener;
}
public void setListner(final ZoomViewListener listener) {
this.listener = listener;
}
public float getZoomFocusX() {
return zoomX * zoom;
}
public float getZoomFocusY() {
return zoomY * zoom;
}
@Override
public boolean dispatchTouchEvent(final MotionEvent ev) {
// single touch
if (ev.getPointerCount() == 1) {
processSingleTouchEvent(ev);
}
// // double touch
if (ev.getPointerCount() == 2) {
processDoubleTouchEvent(ev);
}
// redraw
getRootView().invalidate();
invalidate();
return true;
}
private void processSingleTouchEvent(final MotionEvent ev) {
final float x = ev.getX();
final float y = ev.getY();
final float w = miniMapHeight * (float) getWidth() / getHeight();
final float h = miniMapHeight;
final boolean touchingMiniMap = x >= 10.0f && x <= 10.0f + w
&& y >= 10.0f && y <= 10.0f + h;
if (showMinimap && smoothZoom > 1.0f && touchingMiniMap) {
processSingleTouchOnMinimap(ev);
} else {
processSingleTouchOutsideMinimap(ev);
}
}
private void processSingleTouchOnMinimap(final MotionEvent ev) {
final float x = ev.getX();
final float y = ev.getY();
final float w = miniMapHeight * (float) getWidth() / getHeight();
final float h = miniMapHeight;
final float zx = (x - 10.0f) / w * getWidth();
final float zy = (y - 10.0f) / h * getHeight();
smoothZoomTo(smoothZoom, zx, zy);
}
private void processSingleTouchOutsideMinimap(final MotionEvent ev) {
final float x = ev.getX();
final float y = ev.getY();
float lx = x - touchStartX;
float ly = y - touchStartY;
final float l = (float) Math.hypot(lx, ly);
float dx = x - touchLastX;
float dy = y - touchLastY;
touchLastX = x;
touchLastY = y;
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
touchStartX = x;
touchStartY = y;
touchLastX = x;
touchLastY = y;
dx = 0;
dy = 0;
lx = 0;
ly = 0;
scrolling = false;
break;
case MotionEvent.ACTION_MOVE:
if (scrolling || (smoothZoom > 1.0f && l > 30.0f)) {
if (!scrolling) {
scrolling = true;
ev.setAction(MotionEvent.ACTION_CANCEL);
super.dispatchTouchEvent(ev);
}
smoothZoomX -= dx / zoom;
smoothZoomY -= dy / zoom;
return;
}
break;
case MotionEvent.ACTION_OUTSIDE:
case MotionEvent.ACTION_UP:
// tap
if (l < 30.0f) {
// check double tap
if (System.currentTimeMillis() - lastTapTime < 500) {
if (smoothZoom == 1.0f) {
smoothZoomTo(maxZoom, x, y);
} else {
smoothZoomTo(1.0f, getWidth() / 2.0f,
getHeight() / 2.0f);
}
lastTapTime = 0;
ev.setAction(MotionEvent.ACTION_CANCEL);
super.dispatchTouchEvent(ev);
return;
}
lastTapTime = System.currentTimeMillis();
performClick();
}
break;
default:
break;
}
ev.setLocation(zoomX + (x - 0.5f * getWidth()) / zoom, zoomY
+ (y - 0.5f * getHeight()) / zoom);
ev.getX();
ev.getY();
super.dispatchTouchEvent(ev);
}
private void processDoubleTouchEvent(final MotionEvent ev) {
final float x1 = ev.getX(0);
final float dx1 = x1 - lastdx1;
lastdx1 = x1;
final float y1 = ev.getY(0);
final float dy1 = y1 - lastdy1;
lastdy1 = y1;
final float x2 = ev.getX(1);
final float dx2 = x2 - lastdx2;
lastdx2 = x2;
final float y2 = ev.getY(1);
final float dy2 = y2 - lastdy2;
lastdy2 = y2;
// pointers distance
final float d = (float) Math.hypot(x2 - x1, y2 - y1);
final float dd = d - lastd;
lastd = d;
final float ld = Math.abs(d - startd);
Math.atan2(y2 - y1, x2 - x1);
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
startd = d;
pinching = false;
break;
case MotionEvent.ACTION_MOVE:
if (pinching || ld > 30.0f) {
pinching = true;
final float dxk = 0.5f * (dx1 + dx2);
final float dyk = 0.5f * (dy1 + dy2);
smoothZoomTo(Math.max(1.0f, zoom * d / (d - dd)), zoomX - dxk
/ zoom, zoomY - dyk / zoom);
}
break;
case MotionEvent.ACTION_UP:
default:
pinching = false;
break;
}
ev.setAction(MotionEvent.ACTION_CANCEL);
super.dispatchTouchEvent(ev);
}
private float clamp(final float min, final float value, final float max) {
return Math.max(min, Math.min(value, max));
}
private float lerp(final float a, final float b, final float k) {
return a + (b - a) * k;
}
private float bias(final float a, final float b, final float k) {
return Math.abs(b - a) >= k ? a + k * Math.signum(b - a) : b;
}
@Override
protected void dispatchDraw(final Canvas canvas) {
// do zoom
zoom = lerp(bias(zoom, smoothZoom, 0.05f), smoothZoom, 0.2f);
smoothZoomX = clamp(0.5f * getWidth() / smoothZoom, smoothZoomX,
getWidth() - 0.5f * getWidth() / smoothZoom);
smoothZoomY = clamp(0.5f * getHeight() / smoothZoom, smoothZoomY,
getHeight() - 0.5f * getHeight() / smoothZoom);
zoomX = lerp(bias(zoomX, smoothZoomX, 0.1f), smoothZoomX, 0.35f);
zoomY = lerp(bias(zoomY, smoothZoomY, 0.1f), smoothZoomY, 0.35f);
if (zoom != smoothZoom && listener != null) {
listener.onZooming(zoom, zoomX, zoomY);
}
final boolean animating = Math.abs(zoom - smoothZoom) > 0.0000001f
|| Math.abs(zoomX - smoothZoomX) > 0.0000001f
|| Math.abs(zoomY - smoothZoomY) > 0.0000001f;
// nothing to draw
if (getChildCount() == 0) {
return;
}
// prepare matrix
m.setTranslate(0.5f * getWidth(), 0.5f * getHeight());
m.preScale(zoom, zoom);
m.preTranslate(
-clamp(0.5f * getWidth() / zoom, zoomX, getWidth() - 0.5f
* getWidth() / zoom),
-clamp(0.5f * getHeight() / zoom, zoomY, getHeight() - 0.5f
* getHeight() / zoom));
// get view
final View v = getChildAt(0);
m.preTranslate(v.getLeft(), v.getTop());
// get drawing cache if available
if (animating && ch == null && isAnimationCacheEnabled()) {
v.setDrawingCacheEnabled(true);
ch = v.getDrawingCache();
}
// draw using cache while animating
if (animating && isAnimationCacheEnabled() && ch != null) {
p.setColor(0xffffffff);
canvas.drawBitmap(ch, m, p);
} else { // zoomed or cache unavailable
ch = null;
canvas.save();
canvas.concat(m);
v.draw(canvas);
canvas.restore();
}
// draw minimap
if (showMinimap) {
if (miniMapHeight < 0) {
miniMapHeight = getHeight() / 4;
}
canvas.translate(10.0f, 10.0f);
p.setColor(0x80000000 | 0x00ffffff & miniMapColor);
final float w = miniMapHeight * (float) getWidth() / getHeight();
final float h = miniMapHeight;
canvas.drawRect(0.0f, 0.0f, w, h, p);
if (miniMapCaption != null && miniMapCaption.length() > 0) {
p.setTextSize(miniMapCaptionSize);
p.setColor(miniMapCaptionColor);
p.setAntiAlias(true);
canvas.drawText(miniMapCaption, 10.0f,
10.0f + miniMapCaptionSize, p);
p.setAntiAlias(false);
}
p.setColor(0x80000000 | 0x00ffffff & miniMapColor);
final float dx = w * zoomX / getWidth();
final float dy = h * zoomY / getHeight();
canvas.drawRect(dx - 0.5f * w / zoom, dy - 0.5f * h / zoom, dx
+ 0.5f * w / zoom, dy + 0.5f * h / zoom, p);
canvas.translate(-10.0f, -10.0f);
}
// redraw
// if (animating) {
getRootView().invalidate();
invalidate();
// }
}
}
Add this to your xml as below,
<com.example.myapplication.Activities.Utils.ZoomableLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/zoom_layout"
>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
>
// Your contents here
</RelativeLayout>
</com.example.myapplication.Activities.Utils.ZoomableLayout>