Develop Reference

Zoom Rotate and Drag Bitmap with onTouchEvent

I want to drag, zoom and rotate Bitmap with two fingers (onTouchEvent) but unable to find any solution. There are many solutions to drag, zoom and rotate imageview but no solution for bitmap.
Need help, Thanks

U can detect touch gesture and applied them to the bitmap through matrix.
Defined the scale type : ImageView.setImageMatrix(Matrix)
Detect gesture from any view that U want
Use matrix translation for dragging and rotation and matrix scale for zooming using the values that U got in touch event.
BTW there is gesture helper U can use for simplify your work
https://developer.android.com/training/gestures/detector

Below is the solution to Drag, Rotate and Zoom
public class MainActivity extends BaseActivity implements OnTouchListener {
// these matrices will be used to move and zoom image
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
// we can be in one of these 3 states
private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;
private PointF start = new PointF();
private PointF mid = new PointF();
private float oldDist = 1f;
private float d = 0f;
private float newRot = 0f;
private float[] lastEvent = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageView view = (ImageView) findViewById(R.id.imageView);
view.setOnTouchListener(this);
}
public boolean onTouch(View v, MotionEvent event) {
// handle touch events here
ImageView view = (ImageView) v;
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
lastEvent = null;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
lastEvent = new float[4];
lastEvent[0] = event.getX(0);
lastEvent[1] = event.getX(1);
lastEvent[2] = event.getY(0);
lastEvent[3] = event.getY(1);
d = rotation(event);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
lastEvent = null;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
matrix.set(savedMatrix);
float dx = event.getX() - start.x;
float dy = event.getY() - start.y;
matrix.postTranslate(dx, dy);
} else if (mode == ZOOM) {
float newDist = spacing(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = (newDist / oldDist);
matrix.postScale(scale, scale, mid.x, mid.y);
}
if (lastEvent != null && event.getPointerCount() == 2) {
newRot = rotation(event);
float r = newRot - d;
float[] values = new float[9];
matrix.getValues(values);
float tx = values[0];
float ty = values[4];
float sx = values[8];
float xc = (view.getWidth() / 2) * sx;
float yc = (view.getHeight() / 2) * sx;
matrix.postRotate(r, tx + xc, ty + yc);
}
}
break;
}
view.setImageMatrix(matrix);
return true;
}
/**
* Determine the space between the first two fingers
*/
private float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return (float) Math.sqrt(x * x + y * y);
}
/**
* Calculate the mid point of the first two fingers
*/
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);
}
/**
* Calculate the degree to be rotated by.
*
* #param event
* #return Degrees
*/
private float rotation(MotionEvent event) {
double delta_x = (event.getX(0) - event.getX(1));
double delta_y = (event.getY(0) - event.getY(1));
double radians = Math.atan2(delta_y, delta_x);
return (float) Math.toDegrees(radians);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK && requestCode == UCrop.REQUEST_CROP) {
final Uri resultUri = UCrop.getOutput(data);
} else if (resultCode == UCrop.RESULT_ERROR) {
final Throwable cropError = UCrop.getError(data);
}
}
public void clickedListener(View view) {
startActivity(new Intent(MainActivity.this, CropActivity.class));
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:background="#android:color/transparent"
android:layout_height="match_parent" >
<ImageView android:id="#+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:src="#android:drawable/btn_radio"
android:scaleType="matrix" />
<ImageView android:id="#+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:src="#android:drawable/gallery_thumb"
android:onClick="clickedListener"
android:layout_gravity="bottom"
android:scaleType="centerInside" >
</ImageView>

Moving image with it's touch event in android?

I am trying to make that one image is moving automatically in whole screen as per resolution of mobile device. Now, i want its click or touch event. I have refereed many things but couldn't find any relevant answer. Is there any example related it so i can refer in android.

Use following code to move image.I am using it and it is working fine for me.
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
public class Touch implements OnTouchListener {
// These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
// We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;
// Remember some things for zooming
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;
#Override
public boolean onTouch(View v, MotionEvent event) {
ImageView view = (ImageView) v;
// Dump touch event to log
dumpEvent(event);
// Handle touch events here...
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if (oldDist > 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() - start.x, event.getY() - start.y);
} else if (mode == ZOOM) {
float newDist = spacing(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oldDist;
matrix.postScale(scale, scale, mid.x, mid.y);
}
}
break;
}
view.setImageMatrix(matrix);
return true; // indicate event was handled
}
/** Show an event in the LogCat view, for debugging */
private void dumpEvent(MotionEvent event) {
String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE", "POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };
StringBuilder sb = new StringBuilder();
int action = event.getAction();
int actionCode = action & MotionEvent.ACTION_MASK;
sb.append("event ACTION_").append(names[actionCode]);
if (actionCode == MotionEvent.ACTION_POINTER_DOWN || actionCode == MotionEvent.ACTION_POINTER_UP) {
sb.append("(pid ").append(action >> MotionEvent.ACTION_POINTER_INDEX_SHIFT);
sb.append(")");
}
sb.append("[");
for (int i = 0; i < event.getPointerCount(); i++) {
sb.append("#").append(i);
sb.append("(pid ").append(event.getPointerId(i));
sb.append(")=").append((int) event.getX(i));
sb.append(",").append((int) event.getY(i));
if (i + 1 < event.getPointerCount())
sb.append(";");
}
sb.append("]");
}
/** Determine the space between the first two fingers */
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 * x + y * y);
}
/** Calculate the mid point of the first two fingers */
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);
}
}
note->
from your activity attach this listener by doing
imageview.setOnTouchListener(new Touch());

public class MainActivity extends Activity implements View.OnTouchListener {
// these matrices will be used to move and zoom image
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
// we can be in one of these 3 states
private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;
// remember some things for zooming
private PointF start = new PointF();
private PointF mid = new PointF();
private float oldDist = 1f;
private float d = 0f;
private float newRot = 0f;
private float[] lastEvent = null;
private ImageView view, fin;
private Bitmap bmap;
FrameLayout frm;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
view = (ImageView) findViewById(R.id.imageView);
fin = (ImageView) findViewById(R.id.imageView1);
view.setOnTouchListener(this);
frm=(FrameLayout)findViewById(R.id.frm);
}
public boolean onTouch(View v, MotionEvent event) {
// handle touch events here
view = (ImageView) v;
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
lastEvent = null;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
lastEvent = new float[4];
lastEvent[0] = event.getX(0);
lastEvent[1] = event.getX(1);
lastEvent[2] = event.getY(0);
lastEvent[3] = event.getY(1);
d = rotation(event);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
lastEvent = null;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
matrix.set(savedMatrix);
float dx = event.getX() - start.x;
float dy = event.getY() - start.y;
matrix.postTranslate(dx, dy);
} else if (mode == ZOOM) {
float newDist = spacing(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = (newDist / oldDist);
matrix.postScale(scale, scale, mid.x, mid.y);
}
if (lastEvent != null && event.getPointerCount() == 2 || event.getPointerCount() == 3) {
newRot = rotation(event);
float r = newRot - d;
float[] values = new float[9];
matrix.getValues(values);
float tx = values[2];
float ty = values[5];
float sx = values[0];
float xc = (view.getWidth() / 2) * sx;
float yc = (view.getHeight() / 2) * sx;
matrix.postRotate(r, tx + xc, ty + yc);
}
}
break;
}
view.setBackgroundResource(R.mipmap.ic_launcher);
view.setImageMatrix(matrix);
bmap= Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bmap);
view.draw(canvas);
//fin.setImageBitmap(bmap);
return true;
}
public void ButtonClick(View v){
fin.setImageBitmap(bmap);
}
/**
* Determine the space between the first two fingers
*/
private float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
float s=x * x + y * y;
return (float)Math.sqrt(s);
}
/**
* Calculate the mid point of the first two fingers
*/
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);
}
/**
* Calculate the degree to be rotated by.
*
* #param event
* #return Degrees
*/
private float rotation(MotionEvent event) {
double delta_x = (event.getX(0) - event.getX(1));
double delta_y = (event.getY(0) - event.getY(1));
double radians = Math.atan2(delta_y, delta_x);
return (float) Math.toDegrees(radians);
}
}
-> Try this.

Get width and height of the imageView after resizing using matrix

I want to get the width and height of the scaled imageView using this code that I got from the internet:
public class MultiTouch extends Activity implements OnTouchListener {
// these matrices will be used to move and zoom image
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
// we can be in one of these 3 states
private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;
// remember some things for zooming
private PointF start = new PointF();
private PointF mid = new PointF();
private float oldDist = 1f;
private float d = 0f;
private float newRot = 0f;
private float[] lastEvent = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ImageView view = (ImageView) findViewById(R.id.imageView);
view.setOnTouchListener(this);
}
public boolean onTouch(View v, MotionEvent event) {
// handle touch events here
ImageView view = (ImageView) v;
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
lastEvent = null;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
lastEvent = new float[4];
lastEvent[0] = event.getX(0);
lastEvent[1] = event.getX(1);
lastEvent[2] = event.getY(0);
lastEvent[3] = event.getY(1);
d = rotation(event);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
lastEvent = null;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
matrix.set(savedMatrix);
float dx = event.getX() - start.x;
float dy = event.getY() - start.y;
matrix.postTranslate(dx, dy);
} else if (mode == ZOOM) {
float newDist = spacing(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = (newDist / oldDist);
matrix.postScale(scale, scale, mid.x, mid.y);
}
if (lastEvent != null && event.getPointerCount() == 3) {
newRot = rotation(event);
float r = newRot - d;
float[] values = new float[9];
matrix.getValues(values);
float tx = values[2];
float ty = values[5];
float sx = values[0];
float xc = (view.getWidth() / 2) * sx;
float yc = (view.getHeight() / 2) * sx;
matrix.postRotate(r, tx + xc, ty + yc);
}
}
break;
}
view.setImageMatrix(matrix);
return true;
}
/**
* Determine the space between the first two fingers
*/
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 * x + y * y);
}
/**
* Calculate the mid point of the first two fingers
*/
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);
}
/**
* Calculate the degree to be rotated by.
*
* #param event
* #return Degrees
*/
private float rotation(MotionEvent event) {
double delta_x = (event.getX(0) - event.getX(1));
double delta_y = (event.getY(0) - event.getY(1));
double radians = Math.atan2(delta_y, delta_x);
return (float) Math.toDegrees(radians);
}
}
My problem is if my original imageview is smaller than the scaled image, the image is showing but with the original size of my imageview. This is the part where the image is zooming:
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = (newDist / oldDist);
matrix.postScale(scale, scale, mid.x, mid.y);
}
I want also to resize the container of my imageview.
This is the actual what is happening. the left image is the original, and the right side image is the actual result. I want the imageview container will be the same size of the scaled image.

you can get scaleFactor from your matrix by calling
float[] matrixValues = new float[9];
yourMatrix.getValues(matrixValues);
float scaleX = matrixValues[Matrix.MSCALE_X];
float scaleY = matrixValues[Matrix.MSCALE_Y];
and then multiplying your main width and height by appropriate values

Use WrapContent for both Height and Width of your ImageView

Move a view with OnTouchEvent

I Have this code to put a View where I touch in a Screen.
But the View doesn't follow exactly the point where my finger touch.
Can I improve this behavior?
To works like Drag and Drop API but using onTouchEvent?
Thanks for all!
#Override
public boolean onTouchEvent(final MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
moveView(x, y);
return super.onTouchEvent(event);
}
private void moveView(float x, float y) {
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
params.leftMargin = Math.round(x);
params.topMargin = Math.round(y);
selectedView.setLayoutParams(params);
}

try playing around with some offsets to your x and y coordinates.
//should be on the order of magnitude of the size of the view
float x_offset= 10; //Play with this.
float y_offset= 10; //Play with this.
final float x = event.getX() + x_offset;
final float y = event.getY() + y_offset;
moveView(x, y);

// These matrices will be used to scale points of the image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
// The 3 states (events) which the user is trying to perform
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
//private static final float MAX_ZOOM = 5f;
int mode = NONE;
// these PointF objects are used to record the point(s) the user is touching
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;
float[] lastEvent = null;
float degrees = 0f;
float newRot = 0f;
OnTouchListener touchAction = new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
//perfrom zoom & drag & rotate operations on touch of imageview
dragZoomRotate((ImageView)v, event);
return true;
}
};
private void dragZoomRotate(ImageView view, MotionEvent event){
view.setScaleType(ImageView.ScaleType.MATRIX);
// Handle touch events here...
switch (event.getAction() & MotionEvent.ACTION_MASK)
{
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX() , event.getY() );
mode = DRAG;
lastEvent = null;
break;
case MotionEvent.ACTION_POINTER_DOWN: // first and second finger down
oldDist = spacing(event);
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
lastEvent = new float[4];
lastEvent[0] = event.getX(0);
lastEvent[1] = event.getX(1);
lastEvent[2] = event.getY(0);
lastEvent[3] = event.getY(1);
degrees = rotation(event);
break;
case MotionEvent.ACTION_UP: // first finger lifted
case MotionEvent.ACTION_POINTER_UP: // second finger lifted
mode = NONE;
lastEvent = null;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
// ...
matrix.set(savedMatrix);
matrix.postTranslate(event.getX() - start.x , event.getY() - start.y );
}
else if (mode == ZOOM && event.getPointerCount()==2) {
float newDist = spacing(event);
matrix.set(savedMatrix);
if (newDist > 10f) {
float scale = newDist / oldDist;
matrix.postScale(scale, scale, mid.x, mid.y);
}
if (lastEvent!=null){
newRot = rotation(event);
float r = newRot-degrees;
matrix.postRotate(r, view.getMeasuredWidth()/2, view.getMeasuredHeight()/2);
}
}
//
break;
}
view.setImageMatrix(matrix);
}
private float rotation(MotionEvent event)
{
double delta_x = (event.getX(0) - event.getX(1));
double delta_y = (event.getY(0) - event.getY(1));
double radians = Math.atan2(delta_y, delta_x);
return (float) Math.toDegrees(radians);
}
/*
* --------------------------------------------------------------------------
* Method: spacing Parameters: MotionEvent Returns: float Description:
*
* checks the spacing between the two fingers on touch
* ----------------------------------------------------
*/
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 * x + y * y);
}
/*
* --------------------------------------------------------------------------
* Method: midPoint Parameters: PointF object, MotionEvent Returns: void
* Description: calculates the midpoint between the two fingers
* ------------------------------------------------------------
*/
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);
}
Now add the touchAction listener to the view which you want to move...
myImageView.setOnTouchListener(touchAction);

try change your layout from RelativeLayout to AbsoluteLayout

Android finger rotate , zoom and move image together?

i would like to ask can the three functions rotate, zoom and move the image with user's finger happen together in one application?
I found the source code to drag an image plus the zoom feature. However, i cannot find the way to add the rotation function to the code.
Can any one teach how to build these three functions together?

Try with below code its working for me.
float[] lastEvent = null;
float d = 0f;
float newRot = 0f;
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
public static String fileNAME;
public static int framePos = 0;
private float scale = 0;
private float newDist = 0;
// Fields
private String TAG = this.getClass().getSimpleName();
// We can be in one of these 3 states
private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;
// Remember some things for zooming
private PointF start = new PointF();
private PointF mid = new PointF();
float oldDist = 1f;
public boolean onTouch(View v, MotionEvent event) {
ImageView view = (ImageView) v;
// Handle touch events here...
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
lastEvent = null;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
lastEvent = new float[4];
lastEvent[0] = event.getX(0);
lastEvent[1] = event.getX(1);
lastEvent[2] = event.getY(0);
lastEvent[3] = event.getY(1);
d = rotation(event);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
lastEvent = null;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
// ...
matrix.set(savedMatrix);
matrix.postTranslate(event.getX() - start.x, event.getY()
- start.y);
} else if (mode == ZOOM && event.getPointerCount() == 2) {
float newDist = spacing(event);
matrix.set(savedMatrix);
if (newDist > 10f) {
float scale = newDist / oldDist;
matrix.postScale(scale, scale, mid.x, mid.y);
}
if (lastEvent != null) {
newRot = rotation(event);
float r = newRot - d;
matrix.postRotate(r, view.getMeasuredWidth() / 2,
view.getMeasuredHeight() / 2);
}
}
break;
}
view.setImageMatrix(matrix);
return true;
}
//For rotate image on multi-touch.
private float rotation(MotionEvent event) {
double delta_x = (event.getX(0) - event.getX(1));
double delta_y = (event.getY(0) - event.getY(1));
double radians = Math.atan2(delta_y, delta_x);
return (float) Math.toDegrees(radians);
}
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 * x + y * y);
}
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);
}

I would recommend using the android-multitouch-controller. It has worked great for me, and it offers multi-touch zoom, pan, and rotate just like you want. It's licensed under Apache v2. Be careful with the rotation. Multi-touch rotation only works well with certain devices.
NOTE: rotation is quirky on older touchscreen devices that use a
Synaptics or Synaptics-like "2x1D" sensor (G1, MyTouch, Droid, Nexus
One) and not a true 2D sensor like the HTC Incredible or HTC EVO 4G.