项目中遇到这样个需求：app的功能导航需要可拖动排序，类似头条中的频道拖动管理。效果如下，gif不是很顺畅，真机会好很多。
虽然类似的文章网上搜一下有很多，但写的都不令人满意，注释不清晰，而且动画还不够流畅。经本人整理优化后，拿出来供后续有需要的使用。
实现原理：
- gridView作为基本控件
- WindowManager.addView的方式实现可拖动的view
- TranslateAnimation实现移动动画，动画完后更新adapter即可
主要的实现原理上面已经说明，源码中关键的地点也有注释，因此下面直接上源码。
package com.hai.draggrid; import android.content.Context; import android.graphics.Bitmap; import android.graphics.PixelFormat; import android.util.AttributeSet; import android.view.Gravity; import android.view.MotionEvent; import android.view.View; import android.view.WindowManager; import android.view.animation.Animation; import android.view.animation.TranslateAnimation; import android.widget.AdapterView; import android.widget.BaseAdapter; import android.widget.GridView; import android.widget.ImageView; /** * 长按拖动图标可以调整item位置的Gridview * Created by huanghp on 2019/10/15. * Email [email protected] */ public class DragGridView extends GridView { private static final String TAG = "DragGridView"; private int downX, downY; private int rawX, rawY; private int lastPosition = INVALID_POSITION; private int viewL, viewT; private int itemHeight, itemWidth; private int itemCount; private double dragScale = 1.2D;//拖动view的放大比例 private ImageView dragImageView; private WindowManager windowManager = null; private WindowManager.LayoutParams windowParams = null; private boolean isMoving = false; private Animation lastAnimation; private static final long TIME_ANIMATE = 300; public DragGridView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public DragGridView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); setOnItemLongClickListener(new OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView parent, View view, int position, long id) { lastPosition = position; View dragView = getChildAt(lastPosition - getFirstVisiblePosition()); itemHeight = dragView.getHeight(); itemWidth = dragView.getWidth(); itemCount = getCount(); int rows = itemCount / getNumColumns();// 算出行数 int left = (itemCount % getNumColumns());// 算出最后一行多余的数量 if (lastPosition != INVALID_POSITION) { viewL = downX - dragView.getLeft(); viewT = downY - dragView.getTop(); dragView.destroyDrawingCache(); dragView.setDrawingCacheEnabled(true); Bitmap bitmap = Bitmap.createBitmap(dragView.getDrawingCache()); startDrag(bitmap); dragView.setVisibility(INVISIBLE); isMoving = false; ((Adapter) getAdapter()).setIsDrag(true); requestDisallowInterceptTouchEvent(true); return true; } return false; } }); } private void startDrag(Bitmap dragBitmap) { stopDrag(); windowParams = new WindowManager.LayoutParams(); windowParams.gravity = Gravity.TOP | Gravity.LEFT; //得到preview左上角相对于屏幕的坐标 windowParams.x = rawX - viewL; windowParams.y = rawY - viewT; //设置拖拽item的宽和高 windowParams.width = (int) (dragScale * dragBitmap.getWidth());// 放大dragScale倍，可以设置拖动后的倍数 windowParams.height = (int) (dragScale * dragBitmap.getHeight());// 放大dragScale倍，可以设置拖动后的倍数 this.windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN; this.windowParams.format = PixelFormat.TRANSLUCENT; this.windowParams.windowAnimations = 0; ImageView iv = new ImageView(getContext()); iv.setImageBitmap(dragBitmap); windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE); windowManager.addView(iv, windowParams); dragImageView = iv; } private void stopDrag() { if (dragImageView != null && windowManager != null) { windowManager.removeView(dragImageView); dragImageView = null; } } @Override public boolean onTouchEvent(MotionEvent ev) { int x = (int) ev.getX(); int y = (int) ev.getY(); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: downX = x; downY = y; rawX = (int) ev.getRawX(); rawY = (int) ev.getRawY(); break; case MotionEvent.ACTION_MOVE: if (dragImageView != null && lastPosition != INVALID_POSITION) { updateDrag((int) ev.getRawX(), (int) ev.getRawY()); if (!isMoving) onMove(x, y, false); } break; case MotionEvent.ACTION_UP: // Log.e(TAG, "dragImageView is null=" + (dragImageView == null) + ",lastposition=" + lastPosition // + ",pointToPosition=" + pointToPosition(x, y) + ",ismove=" + isMoving); if (dragImageView != null && lastPosition != INVALID_POSITION) { // if (isMoving) onMove(x, y, true);//动画还未执行完的情况下，重设动画会清除之前设置的动画。 stopDrag(); ((Adapter) getAdapter()).setIsDrag(false); ((BaseAdapter) getAdapter()).notifyDataSetChanged(); requestDisallowInterceptTouchEvent(false); } break; } return super.onTouchEvent(ev); } private void onMove(int moveX, int moveY, boolean isMoveUp) { final int targetPosition = pointToPosition(moveX, moveY); if (targetPosition != INVALID_POSITION) { if (targetPosition == lastPosition) { //移动位置在还未到新item内 return; } //移需要移动的动ITEM数量 int moveCount = targetPosition - lastPosition; if (moveCount != 0) { if (isMoveUp) {//手指抬起时，不执行动画直接交换数据 Adapter adapter = (Adapter) getAdapter(); adapter.exchange(lastPosition, targetPosition); lastPosition = targetPosition; isMoving = false; } else { int moveCountAbs = Math.abs(moveCount); float toXvalue = 0, toYvalue = 0; //moveXP移动的距离百分比（相对于自己长度的百分比） float moveXP = ((float) getHorizontalSpacing() / (float) itemWidth) + 1.0f; float moveYP = ((float) getVerticalSpacing() / (float) itemHeight) + 1.0f; int holdPosition; // Log.d(TAG, "start annimation=" + moveCountAbs); for (int i = 0; i < moveCountAbs; i++) { //从左往右，或是从上往下 if (moveCount > 0) { holdPosition = lastPosition + i + 1; //同一行 if (lastPosition / getNumColumns() == holdPosition / getNumColumns()) { toXvalue = -moveXP; toYvalue = 0; } else if (holdPosition % getNumColumns() == 0) { toXvalue = (getNumColumns() - 1) * moveXP; toYvalue = -moveYP; } else { toXvalue = -moveXP; toYvalue = 0; } } else { //从右往左，或是从下往上 holdPosition = lastPosition - i - 1; if (lastPosition / getNumColumns() == holdPosition / getNumColumns()) { toXvalue = moveXP; toYvalue = 0; } else if ((holdPosition + 1) % getNumColumns() == 0) { toXvalue = -(getNumColumns() - 1) * moveXP; toYvalue = moveYP; } else { toXvalue = moveXP; toYvalue = 0; } } View holdView = getChildAt(holdPosition); Animation moveAnimation = createAnimation(toXvalue, toYvalue); moveAnimation.setAnimationListener(new Animation.AnimationListener() { @Override public void onAnimationStart(Animation animation) { isMoving = true; } @Override public void onAnimationRepeat(Animation animation) { } @Override public void onAnimationEnd(Animation animation) { // 如果为最后个动画结束，那执行下面的方法 if (animation == lastAnimation) { Adapter adapter = (Adapter) getAdapter(); adapter.exchange(lastPosition, targetPosition); lastPosition = targetPosition; isMoving = false; } } }); holdView.startAnimation(moveAnimation); if (holdPosition == targetPosition) { lastAnimation = moveAnimation; } } } } } } public Animation createAnimation(float toXValue, float toYValue) { TranslateAnimation mTranslateAnimation = new TranslateAnimation( Animation.RELATIVE_TO_SELF, 0.0F, Animation.RELATIVE_TO_SELF, toXValue, Animation.RELATIVE_TO_SELF, 0.0F, Animation.RELATIVE_TO_SELF, toYValue); mTranslateAnimation.setFillAfter(true);// 设置一个动画效果执行完毕后，View对象保留在终止的位置。 mTranslateAnimation.setDuration(TIME_ANIMATE); return mTranslateAnimation; } private void updateDrag(int rawX, int rawY) { windowParams.alpha = 0.6f; windowParams.x = rawX - viewL; windowParams.y = rawY - viewT; windowManager.updateViewLayout(dragImageView, windowParams); } static abstract class Adapter extends BaseAdapter { protected boolean isDrag; protected int holdPosition = -1; public void setIsDrag(boolean isDrag) { this.isDrag = isDrag; } public void exchange(int startPosition, int endPositon) { holdPosition = endPositon; } } }
主要的代码就是DragGridView，拿到此view实现起来就相当简单了。为了文章完整性，下面也贴上本效果图的主要使用代码。
String[] items = new String[]{"头条", "视频", "娱乐", "体育", "北京", "新时代"
, "网易号", "段子", "冰雪运动", "科技", "汽车", "轻松一刻"
, "时尚", "直播", "图片", "跟帖", "NBA", "态度公开课"
, "推荐", "热点", "社会", "趣图", "美女", "军事"};
gridView.setAdapter(new DragGridView.Adapter() {
@Override
public void exchange(int startPosition, int endPositon) {
super.exchange(startPosition, endPositon);
String item = list.get(startPosition);
if (startPosition < endPositon) {
list.add(endPositon + 1, item);
list.remove(startPosition);
} else {
list.add(endPositon, item);
list.remove(startPosition + 1);
}
for (int i = 0; i < list.size(); i++) {
Log.e(TAG, "exchange: =" + list.get(i));
}
notifyDataSetChanged();
}
...省略部分代码
@Override
public View getView(int position, View convertView, ViewGroup parent) {
//todo,这里需要优化，没有复用views。也不能按传统方式服用view，否则会造成拖动的view空白
// if (convertView == null) {
convertView = getLayoutInflater().inflate(R.layout.item, parent, false);
// }
((TextView) convertView.findViewById(R.id.tv)).setText(getItem(position));
if (isDrag && position == holdPosition) {
convertView.setVisibility(View.INVISIBLE);
} else convertView.setVisibility(View.VISIBLE);
return convertView;
}
});
本文到这就结束了，有需要的同学拿到轮子就可以直接使用了，谢谢！
不知道有没有眼尖的同学发现Adapterd的getView方法中有个 todo需要优化。原因是这样：如果打开注释中的代码，复用convertView，会造成gridView释放后的新位置一片空白，不知道什么原因，因此折中的方法就是每次都是新生成一个convertView。
希
总结
以上所述是小编给大家介绍的Android自定义gridView仿头条频道拖动管理功能，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持！
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