我修改了一些代码以创建支持多点触控（> 2.1）的TouchImageView。它的灵感来自Android的《Hello》一书！（第三版）
它包含在以下3个文件中：TouchImageView.java WrapMotionEvent.java EclairMotionEvent.java
TouchImageView.java
import se.robertfoss.ChanImageBrowser.Viewer;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
public class TouchImageView extends ImageView {
private static final String TAG = "Touch";
// 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;
Context context;
public TouchImageView(Context context) {
super(context);
super.setClickable(true);
this.context = context;
matrix.setTranslate(1f, 1f);
setImageMatrix(matrix);
setScaleType(ScaleType.MATRIX);
setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent rawEvent) {
WrapMotionEvent event = WrapMotionEvent.wrap(rawEvent);
// Dump touch event to log
if (Viewer.isDebug == true){
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());
Log.d(TAG, "mode=DRAG");
mode = DRAG;
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
Log.d(TAG, "oldDist=" + oldDist);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
Log.d(TAG, "mode=ZOOM");
}
break;
case MotionEvent.ACTION_UP:
int xDiff = (int) Math.abs(event.getX() - start.x);
int yDiff = (int) Math.abs(event.getY() - start.y);
if (xDiff < 8 && yDiff < 8){
performClick();
}
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
Log.d(TAG, "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);
Log.d(TAG, "newDist=" + newDist);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oldDist;
matrix.postScale(scale, scale, mid.x, mid.y);
}
}
break;
}
setImageMatrix(matrix);
return true; // indicate event was handled
}
});
}
public void setImage(Bitmap bm, int displayWidth, int displayHeight) {
super.setImageBitmap(bm);
//Fit to screen.
float scale;
if ((displayHeight / bm.getHeight()) >= (displayWidth / bm.getWidth())){
scale = (float)displayWidth / (float)bm.getWidth();
} else {
scale = (float)displayHeight / (float)bm.getHeight();
}
savedMatrix.set(matrix);
matrix.set(savedMatrix);
matrix.postScale(scale, scale, mid.x, mid.y);
setImageMatrix(matrix);
// Center the image
float redundantYSpace = (float)displayHeight - (scale * (float)bm.getHeight()) ;
float redundantXSpace = (float)displayWidth - (scale * (float)bm.getWidth());
redundantYSpace /= (float)2;
redundantXSpace /= (float)2;
savedMatrix.set(matrix);
matrix.set(savedMatrix);
matrix.postTranslate(redundantXSpace, redundantYSpace);
setImageMatrix(matrix);
}
/** Show an event in the LogCat view, for debugging */
private void dumpEvent(WrapMotionEvent 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_ID_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("]");
Log.d(TAG, sb.toString());
}
/** Determine the space between the first two fingers */
private float spacing(WrapMotionEvent 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, WrapMotionEvent event) {
// ...
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x / 2, y / 2);
}
}
WrapMotionEvent.java
import android.view.MotionEvent;
public class WrapMotionEvent {
protected MotionEvent event;
protected WrapMotionEvent(MotionEvent event) {
this.event = event;
}
static public WrapMotionEvent wrap(MotionEvent event) {
try {
return new EclairMotionEvent(event);
} catch (VerifyError e) {
return new WrapMotionEvent(event);
}
}
public int getAction() {
return event.getAction();
}
public float getX() {
return event.getX();
}
public float getX(int pointerIndex) {
verifyPointerIndex(pointerIndex);
return getX();
}
public float getY() {
return event.getY();
}
public float getY(int pointerIndex) {
verifyPointerIndex(pointerIndex);
return getY();
}
public int getPointerCount() {
return 1;
}
public int getPointerId(int pointerIndex) {
verifyPointerIndex(pointerIndex);
return 0;
}
private void verifyPointerIndex(int pointerIndex) {
if (pointerIndex > 0) {
throw new IllegalArgumentException(
"Invalid pointer index for Donut/Cupcake");
}
}
}
EclairMotionEvent.java
import android.view.MotionEvent;
public class EclairMotionEvent extends WrapMotionEvent {
protected EclairMotionEvent(MotionEvent event) {
super(event);
}
public float getX(int pointerIndex) {
return event.getX(pointerIndex);
}
public float getY(int pointerIndex) {
return event.getY(pointerIndex);
}
public int getPointerCount() {
return event.getPointerCount();
}
public int getPointerId(int pointerIndex) {
return event.getPointerId(pointerIndex);
}
}