Peut-on utiliser une échelle geste détecteur de zoom par pincement dans Android?

Vous pouvez créer une classe réutilisable qui implémente OnTouchListener pour accomplir cette tâche.

public class MyScaleGestures implements OnTouchListener, OnScaleGestureListener {       
private View view;
private ScaleGestureDetector gestureScale;
private float scaleFactor = 1;  
private boolean inScale = false;
public MyScaleGestures (Context c){ gestureScale = new ScaleGestureDetector(c, this); }
@Override
public boolean onTouch(View view, MotionEvent event) {
this.view = view; 
gestureScale.onTouchEvent(event);
return true;
}   
@Override
public boolean onScale(ScaleGestureDetector detector) {
scaleFactor *= detector.getScaleFactor();
scaleFactor = (scaleFactor < 1 ? 1 : scaleFactor); //prevent our view from becoming too small //
scaleFactor = ((float)((int)(scaleFactor * 100))) / 100; //Change precision to help with jitter when user just rests their fingers //
view.setScaleX(scaleFactor);
view.setScaleY(scaleFactor);
return true;
}
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
inScale = true;
return true;
}
@Override
public void onScaleEnd(ScaleGestureDetector detector) { inScale = false; }
}

Puis l'affecter en tant que votre View's OnTouchListener comme si.

myView.setOnTouchListener(new MyScaleGestures(context));

Si vous souhaitez ajouter un défilement de l'aptitude à la View vous aurez besoin de mettre en œuvre onScroll de la OnGestureListener interface. Vous pouvez ajouter cette substitution à la MyScaleGestures classe pour accomplir cette tâche.

@Override
public boolean onScroll(MotionEvent event1, MotionEvent event2, float x, float y) {
float newX = view.getX();
float newY = view.getY();
if(!inScale){
newX -= x;
newY -= y;
}
WindowManager wm = (WindowManager) view.getContext().getSystemService(Context.WINDOW_SERVICE);
Display d = wm.getDefaultDisplay();
Point p = new Point();
d.getSize(p);
if (newX > (view.getWidth() * scaleFactor - p.x) / 2){
newX = (view.getWidth() * scaleFactor - p.x) / 2;
} else if (newX < -((view.getWidth() * scaleFactor - p.x) / 2)){
newX = -((view.getWidth() * scaleFactor - p.x) / 2);
}
if (newY > (view.getHeight() * scaleFactor - p.y) / 2){
newY = (view.getHeight() * scaleFactor - p.y) / 2;
} else if (newY < -((view.getHeight() * scaleFactor - p.y) / 2)){
newY = -((view.getHeight() * scaleFactor - p.y) / 2);
}
view.setX(newX);
view.setY(newY);
return true;
}

Le résultat final de tous les ci-dessus vous donnera de la classe comme ceci:

public class StandardGestures implements OnTouchListener, OnGestureListener, OnDoubleTapListener, OnScaleGestureListener {
private View view;
private GestureDetector gesture;
private ScaleGestureDetector gestureScale;
private float scaleFactor = 1;
private boolean inScale;
public StandardGestures(Context c){
gesture = new GestureDetector(c, this);
gestureScale = new ScaleGestureDetector(c, this);
}
@Override
public boolean onTouch(View view, MotionEvent event) {
this.view = view;
gesture.onTouchEvent(event);
gestureScale.onTouchEvent(event);
return true;
}
@Override
public boolean onDown(MotionEvent event) {
return true;
}
@Override
public boolean onFling(MotionEvent event1, MotionEvent event2, float x, float y) {
return true;
}
@Override
public void onLongPress(MotionEvent event) {
}
@Override
public boolean onScroll(MotionEvent event1, MotionEvent event2, float x, float y) {
float newX = view.getX();
float newY = view.getY();
if(!inScale){
newX -= x;
newY -= y;
}
WindowManager wm = (WindowManager) view.getContext().getSystemService(Context.WINDOW_SERVICE);
Display d = wm.getDefaultDisplay();
Point p = new Point();
d.getSize(p);
if (newX > (view.getWidth() * scaleFactor - p.x) / 2){
newX = (view.getWidth() * scaleFactor - p.x) / 2;
} else if (newX < -((view.getWidth() * scaleFactor - p.x) / 2)){
newX = -((view.getWidth() * scaleFactor - p.x) / 2);
}
if (newY > (view.getHeight() * scaleFactor - p.y) / 2){
newY = (view.getHeight() * scaleFactor - p.y) / 2;
} else if (newY < -((view.getHeight() * scaleFactor - p.y) / 2)){
newY = -((view.getHeight() * scaleFactor - p.y) / 2);
}
view.setX(newX);
view.setY(newY);
return true;
}
@Override
public void onShowPress(MotionEvent event) {
}
@Override
public boolean onSingleTapUp(MotionEvent event) {
return true;
}
@Override
public boolean onDoubleTap(MotionEvent event) {
view.setVisibility(View.GONE);
return true;
}
@Override
public boolean onDoubleTapEvent(MotionEvent event) {
return true;
}
@Override
public boolean onSingleTapConfirmed(MotionEvent event) {
return true;
}
@Override
public boolean onScale(ScaleGestureDetector detector) {
scaleFactor *= detector.getScaleFactor();
scaleFactor = scaleFactor < 1 ? 1 : scaleFactor; //prevent our image from becoming too small
scaleFactor = (float) (int) (scaleFactor * 100) / 100; //Change precision to help with jitter when user just rests their fingers //
view.setScaleX(scaleFactor);
view.setScaleY(scaleFactor);
onScroll(null, null, 0, 0); //call scroll to make sure our bounds are still ok //
return true;
}
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
inScale = true;
return true;
}
@Override
public void onScaleEnd(ScaleGestureDetector detector) {
inScale = false;
onScroll(null, null, 0, 0); //call scroll to make sure our bounds are still ok //
}
}

en fait il y a une bibliothèque qui utilise cette classe pour le zoom des images.

il est appelé "TouchImageView"

TouchImageView

public class TouchImageView extends ImageView {
Matrix 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 last = new PointF();
PointF start = new PointF();
float minScale = 1f;
float maxScale = 3f;
float[] m;
int viewWidth, viewHeight;
static final int CLICK = 3;
float saveScale = 1f;
protected float origWidth, origHeight;
int oldMeasuredWidth, oldMeasuredHeight;
ScaleGestureDetector mScaleDetector;
Context context;
public TouchImageView(Context context) {
super(context);
sharedConstructing(context);
}
public TouchImageView(Context context, AttributeSet attrs) {
super(context, attrs);
sharedConstructing(context);
}
private void sharedConstructing(Context context) {
super.setClickable(true);
this.context = context;
mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
matrix = new Matrix();
m = new float[9];
setImageMatrix(matrix);
setScaleType(ScaleType.MATRIX);
setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
mScaleDetector.onTouchEvent(event);
PointF curr = new PointF(event.getX(), event.getY());
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
last.set(curr);
start.set(last);
mode = DRAG;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
float deltaX = curr.x - last.x;
float deltaY = curr.y - last.y;
float fixTransX = getFixDragTrans(deltaX, viewWidth, origWidth * saveScale);
float fixTransY = getFixDragTrans(deltaY, viewHeight, origHeight * saveScale);
matrix.postTranslate(fixTransX, fixTransY);
fixTrans();
last.set(curr.x, curr.y);
}
break;
case MotionEvent.ACTION_UP:
mode = NONE;
int xDiff = (int) Math.abs(curr.x - start.x);
int yDiff = (int) Math.abs(curr.y - start.y);
if (xDiff < CLICK && yDiff < CLICK)
performClick();
break;
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
break;
}
setImageMatrix(matrix);
invalidate();
return true; //indicate event was handled
}
});
}
public void setMaxZoom(float x) {
maxScale = x;
}
private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
mode = ZOOM;
return true;
}
@Override
public boolean onScale(ScaleGestureDetector detector) {
float mScaleFactor = detector.getScaleFactor();
float origScale = saveScale;
saveScale *= mScaleFactor;
if (saveScale > maxScale) {
saveScale = maxScale;
mScaleFactor = maxScale / origScale;
} else if (saveScale < minScale) {
saveScale = minScale;
mScaleFactor = minScale / origScale;
}
if (origWidth * saveScale <= viewWidth || origHeight * saveScale <= viewHeight)
matrix.postScale(mScaleFactor, mScaleFactor, viewWidth / 2, viewHeight / 2);
else
matrix.postScale(mScaleFactor, mScaleFactor, detector.getFocusX(), detector.getFocusY());
fixTrans();
return true;
}
}
void fixTrans() {
matrix.getValues(m);
float transX = m[Matrix.MTRANS_X];
float transY = m[Matrix.MTRANS_Y];
float fixTransX = getFixTrans(transX, viewWidth, origWidth * saveScale);
float fixTransY = getFixTrans(transY, viewHeight, origHeight * saveScale);
if (fixTransX != 0 || fixTransY != 0)
matrix.postTranslate(fixTransX, fixTransY);
}
float getFixTrans(float trans, float viewSize, float contentSize) {
float minTrans, maxTrans;
if (contentSize <= viewSize) {
minTrans = 0;
maxTrans = viewSize - contentSize;
} else {
minTrans = viewSize - contentSize;
maxTrans = 0;
}
if (trans < minTrans)
return -trans + minTrans;
if (trans > maxTrans)
return -trans + maxTrans;
return 0;
}
float getFixDragTrans(float delta, float viewSize, float contentSize) {
if (contentSize <= viewSize) {
return 0;
}
return delta;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
viewWidth = MeasureSpec.getSize(widthMeasureSpec);
viewHeight = MeasureSpec.getSize(heightMeasureSpec);
//
//Rescales image on rotation
//
if (oldMeasuredHeight == viewWidth && oldMeasuredHeight == viewHeight
|| viewWidth == 0 || viewHeight == 0)
return;
oldMeasuredHeight = viewHeight;
oldMeasuredWidth = viewWidth;
if (saveScale == 1) {
//Fit to screen.
float scale;
Drawable drawable = getDrawable();
if (drawable == null || drawable.getIntrinsicWidth() == 0 || drawable.getIntrinsicHeight() == 0)
return;
int bmWidth = drawable.getIntrinsicWidth();
int bmHeight = drawable.getIntrinsicHeight();
Log.e("bmSize", "bmWidth: " + bmWidth + " bmHeight : " + bmHeight);
float scaleX = (float) viewWidth / (float) bmWidth;
float scaleY = (float) viewHeight / (float) bmHeight;
scale = Math.min(scaleX, scaleY);
matrix.setScale(scale, scale);
//Center the image
float redundantYSpace = (float) viewHeight - (scale * (float) bmHeight);
float redundantXSpace = (float) viewWidth - (scale * (float) bmWidth);
redundantYSpace /= (float) 2;
redundantXSpace /= (float) 2;
matrix.postTranslate(redundantXSpace, redundantYSpace);
origWidth = viewWidth - 2 * redundantXSpace;
origHeight = viewHeight - 2 * redundantYSpace;
setImageMatrix(matrix);
}
fixTrans();
}
}

MainActivity.java

public class SecondActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
TouchImageView img = new TouchImageView(this);
img.setImageResource(R.drawable.ic_launcher);
img.setMaxZoom(4f);
setContentView(img);
}
}