有弹性的ScrollView

铁石心肠 1年前 ⋅ 450 阅读
public class XScrollView extends ScrollView {

// 拖动的距离 size = 4 的意思 只允许拖动屏幕的1/4
private static final int size = 4;
private View inner;
private float y;
private Rect normal = new Rect();

public XScrollView(Context context) {
super(context);
setVerticalScrollBarEnabled(false);
setHorizontalScrollBarEnabled(false);
setFillViewport(true);
}

public XScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
setVerticalScrollBarEnabled(false);
setHorizontalScrollBarEnabled(false);
setFillViewport(true);
}

@Override
protected void onFinishInflate() {
if (getChildCount() > 0) {
inner = getChildAt(0);
}
super.onFinishInflate();
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
if (inner == null) {
return super.onTouchEvent(ev);
} else {
commOnTouchEvent(ev);
}
return super.onTouchEvent(ev);
}

public void commOnTouchEvent(MotionEvent ev) {
int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
y = ev.getY();
break;
case MotionEvent.ACTION_UP:
if (isNeedAnimation()) {
// Log.v("mlguitar", "will up and animation");
animation();
}
break;
case MotionEvent.ACTION_MOVE:
final float preY = y;
float nowY = ev.getY();
/**
* size=4 表示 拖动的距离为屏幕的高度的1/4
*/
int deltaY = (int) (preY - nowY) / size;
// 滚动
// scrollBy(0, deltaY);

y = nowY;
// 当滚动到最上或者最下时就不会再滚动,这时移动布局
if (isNeedMove()) {
if (normal.isEmpty()) {
// 保存正常的布局位置
normal.set(inner.getLeft(), inner.getTop(),
inner.getRight(), inner.getBottom());
return;
}
int yy = inner.getTop() - deltaY;

// 移动布局
inner.layout(inner.getLeft(), yy, inner.getRight(),
inner.getBottom() - deltaY);
}
break;
default:
break;
}
}

// 开启动画移动

public void animation() {
// 开启移动动画
// TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop(),
// normal.top);
TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop() - normal.top, 0);
ta.setDuration(200);
inner.startAnimation(ta);
// 设置回到正常的布局位置
inner.layout(normal.left, normal.top, normal.right, normal.bottom);
normal.setEmpty();
//MyLog.e("XScrollview 返回正常布局");
}

// 是否需要开启动画
public boolean isNeedAnimation() {
return !normal.isEmpty();
}

// 是否需要移动布局
public boolean isNeedMove() {
int offset = inner.getMeasuredHeight() - getHeight();
int scrollY = getScrollY();
return scrollY == 0 || scrollY == offset;
}

}

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