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嗨 大家好,我是不服不行 。
今天为大家带来一个手机界面中的这个,这个一个常客。经常被使用在时间,日期选择之中,让我们先看看效果。
那么是如何实现的,仅仅只涉及到一个类: 此类在github被我寻找出来(请原谅我不记得原类的地址),做了稍加改动。
地址找到啦[2015年11月20号]! https://github.com/wangjiegulu/WheelView
但不是非常推荐,实现原理是继承了ScrollView 。那么当内容过多的时候由于没有缓存机制,数据越多滑动越卡。
不过江湖救急能用就不错了,慢慢再去发现好的。如果有使用自定义view或者继承ListView、RecyclerView的就好了。
2016年1月17号 新方案~
http://blog.csdn.net/bfbx5173/article/details/50532187
此方案为自定义View,效果性能都不错。
public class WheelView extends ScrollView {
public static final String TAG = WheelView.class.getSimpleName();
public static class OnWheelViewListener {
public void onSelected(int selectedIndex, String item) {
}
}
private Context context;
private LinearLayout views;
public WheelView(Context context) {
super(context);
init(context);
}
public WheelView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public WheelView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}
List<String> items = new ArrayList<String>();
/** 设置内容 */
public void setItems(List<String> list) {
items.clear();
items.addAll(list);
// 前面和后面补全
for (int i = 0; i < offset; i++) {
items.add(0, "");
items.add("");
}
initData();
}
public static final int OFF_SET_DEFAULT = 1;
int offset = OFF_SET_DEFAULT; // 偏移量(需要在最前面和最后面补全)
public int getOffset() {
return offset;
}
/** 设置显示界面上展现多少个item */
public void setOffset(int offset) {
this.offset = offset;
}
int displayItemCount; // 每页显示的数量
int selectedIndex = 1;
private void init(Context context) {
this.context = context;
this.setVerticalScrollBarEnabled(false);
views = new LinearLayout(context);
views.setOrientation(LinearLayout.VERTICAL);
this.addView(views);
scrollerTask = new Runnable() {
public void run() {
int newY = getScrollY();
if (initialY - newY == 0) { // stopped
final int remainder = initialY % itemHeight;
final int divided = initialY / itemHeight;
if (remainder == 0) {
selectedIndex = divided + offset;
onSeletedCallBack();
} else {
if (remainder > itemHeight / 2) {
WheelView.this.post(new Runnable() {
@Override
public void run() {
WheelView.this.smoothScrollTo(0, initialY - remainder + itemHeight);
selectedIndex = divided + offset + 1;
onSeletedCallBack();
}
});
} else {
WheelView.this.post(new Runnable() {
@Override
public void run() {
WheelView.this.smoothScrollTo(0, initialY - remainder);
selectedIndex = divided + offset;
onSeletedCallBack();
}
});
}
}
} else {
initialY = getScrollY();
WheelView.this.postDelayed(scrollerTask, newCheck);
}
}
};
}
int initialY;
Runnable scrollerTask;
int newCheck = 50;
public void startScrollerTask() {
initialY = getScrollY();
this.postDelayed(scrollerTask, newCheck);
}
private void initData() {
displayItemCount = offset * 2 + 1;
for (String item : items) {
views.addView(createView(item));
}
refreshItemView(0);
}
int itemHeight = 0;
/** 滚轮控件中的View 在这里创建, 本方法里面只是简单的TextView */
private TextView createView(String item) {
TextView tv = new TextView(context);
itemHeight = BaseUtil.dip2px(context, 46);
LayoutParams tvlp = new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, itemHeight);
tv.setLayoutParams(tvlp);
tv.setSingleLine(true);
tv.setTextSize(TypedValue.COMPLEX_UNIT_SP, 20);
tv.setText(item);
tv.setGravity(Gravity.CENTER);
views.setLayoutParams(new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, itemHeight * displayItemCount));
FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) this.getLayoutParams();
this.setLayoutParams(new FrameLayout.LayoutParams(lp.width, itemHeight * displayItemCount));
int padding = BaseUtil.dip2px(context, 15);
this.setPadding(padding, 0, padding, 0);
return tv;
}
public static int getViewMeasuredHeight(View view) {
calcViewMeasure(view);
return view.getMeasuredHeight();
}
/**
* 获取控件的宽度,如果获取的宽度为0,则重新计算尺寸后再返回宽度
*
* @param view
* @return
*/
public static int getViewMeasuredWidth(View view) {
calcViewMeasure(view);
return view.getMeasuredWidth();
}
/**
* 测量控件的尺寸
*
* @param view
*/
public static void calcViewMeasure(View view) {
int width = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
int expandSpec = View.MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, View.MeasureSpec.AT_MOST);
view.measure(width, expandSpec);
}
/**
* 根据手机的分辨率从 dp 的单位 转成为 px(像素)
*/
public static int dip2px(Context context, float dpValue) {
final float scale = context.getResources().getDisplayMetrics().density;
return (int) (dpValue * scale + 0.5f);
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
refreshItemView(t);
if (t > oldt) {
// Logger.d(TAG, "向下滚动");
scrollDirection = SCROLL_DIRECTION_DOWN;
} else {
// Logger.d(TAG, "向上滚动");
scrollDirection = SCROLL_DIRECTION_UP;
}
}
private void refreshItemView(int y) {
int position = y / itemHeight + offset;
int remainder = y % itemHeight;
int divided = y / itemHeight;
if (remainder == 0) {
position = divided + offset;
} else {
if (remainder > itemHeight / 2) {
position = divided + offset + 1;
}
}
int childSize = views.getChildCount();
for (int i = 0; i < childSize; i++) {
TextView itemView = (TextView) views.getChildAt(i);
if (null == itemView) {
return;
}
if (position == i) {
itemView.setTextColor(Color.parseColor("#00a2ff"));
itemView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 20);
} else if (Math.abs(position - i) == 1) {
itemView.setTextColor(Color.parseColor("#afafaf"));
itemView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 16);
} else {
itemView.setTextColor(Color.parseColor("#dfdfdf"));
itemView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 12);
}
}
}
/**
* 获取选中区域的边界
*/
int[] selectedAreaBorder;
private int[] obtainSelectedAreaBorder() {
if (null == selectedAreaBorder) {
selectedAreaBorder = new int[2];
selectedAreaBorder[0] = itemHeight * offset;
selectedAreaBorder[1] = itemHeight * (offset + 1);
}
return selectedAreaBorder;
}
@SuppressWarnings("unused")
private int scrollDirection = -1;
private static final int SCROLL_DIRECTION_UP = 0;
private static final int SCROLL_DIRECTION_DOWN = 1;
Paint paint;
int viewWidth;
@SuppressWarnings("deprecation")
@Override
public void setBackgroundDrawable(Drawable background) {
if (viewWidth == 0) {
viewWidth = ((Activity) context).getWindowManager().getDefaultDisplay().getWidth();
}
if (null == paint) {
paint = new Paint();
paint.setColor(Color.parseColor("#919191"));
paint.setStrokeWidth(1);
}
background = new Drawable() {
@Override
public void draw(Canvas canvas) {
canvas.drawLine(viewWidth * 0 / 6, obtainSelectedAreaBorder()[0], viewWidth * 6 / 6, obtainSelectedAreaBorder()[0], paint);
canvas.drawLine(viewWidth * 0 / 6, obtainSelectedAreaBorder()[1], viewWidth * 6 / 6, obtainSelectedAreaBorder()[1], paint);
}
@Override
public void setAlpha(int alpha) {
}
@Override
public void setColorFilter(ColorFilter cf) {
}
@Override
public int getOpacity() {
return 0;
}
};
super.setBackgroundDrawable(background);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
viewWidth = w;
setBackgroundDrawable(null);
}
/**
* 选中回调
*/
private void onSeletedCallBack() {
if (null != onWheelViewListener) {
onWheelViewListener.onSelected(selectedIndex, items.get(selectedIndex));
}
}
public void setSeletion(int position) {
final int p = position;
selectedIndex = p + offset;
this.post(new Runnable() {
@Override
public void run() {
WheelView.this.smoothScrollTo(0, p * itemHeight);
}
});
}
public String getSeletedItem() {
return items.get(selectedIndex);
}
public int getSeletedIndex() {
return selectedIndex - offset;
}
@Override
public void fling(int velocityY) {
super.fling(velocityY / 3);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_UP) {
startScrollerTask();
}
return super.onTouchEvent(ev);
}
private OnWheelViewListener onWheelViewListener;
public OnWheelViewListener getOnWheelViewListener() {
return onWheelViewListener;
}
public void setOnWheelViewListener(OnWheelViewListener onWheelViewListener) {
this.onWheelViewListener = onWheelViewListener;
}
}
从代码中先寻找public对外公开方法,主要有setOffset() setItems()方法, 那么观察一下后会发现需要调用setItems()来初始化滚轮控件。在setItems()中又会调用initData(),而initData()的逻辑便是根据传入的参数创建一大堆TextView。最后放在了一个views对象中。查找views对象会发现在init(),它被添加在了ScrollView里面,同时它(views)自己又是个LinearLayout。这个时候便逻辑顺畅了。
这个WheelView 只不过是动态生成的,它对应的布局文件应该是这样的:
<span style="color:#333333;"><ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content" </span><strong><span style="color:#ff0000;">* n</span></strong><span style="color:#333333;">
android:layout_height="wrap_content" />
</LinearLayout>
</ScrollView></span>
那么他和普通的scrollView有什么区别了。关键是在于一个“回滚“。 因为当滑动完成后,它必须停留在一项上面。
分析出了不同的同时,该如何做的逻辑是不是也清晰了起来呢?由于是滑动完成,那么就和Touch有关:
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_UP) {
startScrollerTask();
}
return super.onTouchEvent(ev);
}
在手指抬起之后变会调用startScrollerTask()方法,用大腿想想就知道此方法应该就是”必须停留在一项上面“的收尾动作,没错!startScrollerTask会在50毫秒之后去执行scrollerTask,而scrollerTask的职责就是调用smoothScrollTo()滑动到某一个Child的位置,方法中顺手触发了onSeletedCallBack()回调供我们处理逻辑。
那么讲到这里就只剩下绘制的部分:因为界面会随着ScrollView 的滑动而变化,所以迅速定位到onScrollChanged()。
在代码在onScrollChanged()中调用了refreshItemView(int position) 这个根据名字就可以判断是根据一个位置参数来更新Child(一大堆的TextView)的样子。。。。剩下的事情就是根据界面需要修改其中内容。
如何去使用:
在布局中
<com.example.view.WheelView
android:id="@+id/wheel"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
在代码中:
WheelView wheelMin = (WheelView) content.findViewById(R.id.wheel);
wheelMin.setOffset(2);
wheelMin.setItems(Arrays.asList(getWheelContent(0, 60)));
wheelMin.setOnWheelViewListener(new OnWheelViewListener() {
@Override public void onSelected(int selectedIndex, String item) {
......
}
});
private String[] getWheelContent(int start, int num) {
if (start < 0 || num < 0) {
return null;
}
String[] content = new String[num];
for (int i = start; i < content.length; i++) {
content[i] = (i < 10 ? "0" : "") + String.valueOf(i);
}
return content;
}
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