如何使用ImageView实现此功能,PullToZoom (不需要在示例中使用ListView)?
类似的问题,但没有答案 :(
public class MainActivity extends AppCompatActivity {
private static final String DEBUG_TAG = "Gestures";
private GestureDetectorCompat mDetector;
private ImageView imageView;
private MyGestureListener myGestureListener;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.image);
myGestureListener = new MyGestureListener();
mDetector = new GestureDetectorCompat(this, myGestureListener);
imageView.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
int action = MotionEventCompat.getActionMasked(event);
if (action == MotionEvent.ACTION_UP) {
myGestureListener.upDetected();
}
return mDetector.onTouchEvent(event);
}
});
imageView.setImageDrawable(ContextCompat.getDrawable(this, R.drawable.test));
}
class MyGestureListener extends GestureDetector.SimpleOnGestureListener {
private static final float MAX_ZOOM = 0.5f;
private static final float PCT = 300f;
private float delta;
private ValueAnimator valueAnimator;
@Override
public boolean onDown(MotionEvent event) {
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
if (valueAnimator != null) {
valueAnimator.cancel();
}
delta += distanceY;
float pct = getPct(delta);
imageView.setScaleX(1.0f + pct);
imageView.setScaleY(1.0f + pct);
return false;
}
void upDetected() {
float pct = getPct(delta);
valueAnimator = new ValueAnimator();
valueAnimator.setFloatValues(pct, 0.0f);
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
imageView.setScaleX(1.0f + (float) animation.getAnimatedValue());
imageView.setScaleY(1.0f + (float) animation.getAnimatedValue());
}
});
valueAnimator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
delta = 0f;
imageView.setScaleX(1.0f);
imageView.setScaleY(1.0f);
}
@Override
public void onAnimationCancel(Animator animation) {
}
@Override
public void onAnimationRepeat(Animator animation) {
}
});
valueAnimator.start();
}
private float getPct(float delta) {
float pct = delta / PCT;
if (pct >= MAX_ZOOM) {
pct = MAX_ZOOM;
}
else if (pct <= -MAX_ZOOM) {
pct = -MAX_ZOOM;
}
return pct;
}
}
}
MainActivity有一个简单的ImageView。 当你在其中“滚动”时,会检测手势并缩放图像(向上或向下)。 当你从屏幕上放开手指时,图像会通过简单的动画缩放回到原始大小。 如果你想避免缩小,只需要在getPct()方法上进行修改。
例如,如果你只想实现缩放功能,可以像这样修改getPct:
private float getPct(float delta) {
float pct = -delta / PCT;
if (pct >= MAX_ZOOM) {
pct = MAX_ZOOM;
}
else if (pct <= 0) {
pct = 0;
}
return pct;
}
似乎手势检测器的第一个滚动事件是宽广的。我已经添加了一些代码来忽略它。
class MyGestureListener extends GestureDetector.SimpleOnGestureListener {
private static final float MAX_ZOOM = 0.8f;
private static final float PCT = 300f;
private float delta;
private ValueAnimator valueAnimator;
private boolean mFirstEvent = true;
@Override
public boolean onDown(MotionEvent event) {
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
if (valueAnimator != null) {
valueAnimator.cancel();
}
if (mFirstEvent) {
mFirstEvent = false;
return false;
}
delta += distanceY;
float pct = getPct(delta);
imageView.setScaleX(1.0f + pct);
imageView.setScaleY(1.0f + pct);
textView.setScaleY(1.0f - pct);
return false;
}
void upDetected() {
mFirstEvent = true;
float pct = getPct(delta);
valueAnimator = new ValueAnimator();
valueAnimator.setFloatValues(pct, 0.0f);
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
imageView.setScaleX(1.0f + (Float) animation.getAnimatedValue());
imageView.setScaleY(1.0f + (Float) animation.getAnimatedValue());
textView.setScaleY(1.0f - (Float) animation.getAnimatedValue());
}
});
valueAnimator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
delta = 0f;
imageView.setScaleX(1.0f);
imageView.setScaleY(1.0f);
textView.setScaleY(1.0f);
}
@Override
public void onAnimationCancel(Animator animation) {
}
@Override
public void onAnimationRepeat(Animator animation) {
}
});
valueAnimator.start();
}
private float getPct(float delta) {
float pct = -delta / PCT;
if (pct >= MAX_ZOOM) {
pct = MAX_ZOOM;
}
else if (pct <= 0) {
pct = 0;
}
return pct;
}
/*private float getPct(float delta) {
float pct = delta / PCT;
if (pct >= MAX_ZOOM) {
pct = MAX_ZOOM;
}
else if (pct <= -MAX_ZOOM) {
pct = -MAX_ZOOM;
}
return pct;
}*/
}
安卓上的Tinder应用程序通过覆盖onTouchEvent()
方法来实现类似的功能。查看this帖子以了解更多信息。
onTouchEvent()
方法可能会解决它。 - frgnvolaonTouchEvent()
方法。 - frgnvola