最近研究了下系统的music源码,随便看了下,里面有很多东西值得我们去学习的。在研究过程中看到了源码中的TrackBrowserActivity类实现了listview的拖拽功能,就想单独拿出来看看怎么实现的。
网上其实也有很多拖拽listview的实现,但感觉效果还是不如music中的好。闲话不说,先上效果图,后上代码。
效果图:
1、music中实现拖拽的核心代码,基本没做什么修改,就是加了些个人理解后的注释和调试过程中的打印语句,TouchInterceptor类:
/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package ldw.listview; import android.content.Context; import android.content.SharedPreferences; import android.content.res.Resources; import android.graphics.Bitmap; import android.graphics.PixelFormat; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.graphics.drawable.LevelListDrawable; import android.util.AttributeSet; import android.util.Log; import android.view.GestureDetector; import android.view.Gravity; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.WindowManager; import android.view.GestureDetector.SimpleOnGestureListener; import android.widget.AdapterView; import android.widget.ImageView; import android.widget.ListView; public class TouchInterceptor extends ListView { private ImageView mDragView; private WindowManager mWindowManager; private WindowManager.LayoutParams mWindowParams; /** * At which position is the item currently being dragged. Note that this * takes in to account header items. */ private int mDragPos; /** * At which position was the item being dragged originally */ private int mSrcDragPos; private int mDragPointX; // at what x offset inside the item did the user // grab it private int mDragPointY; // at what y offset inside the item did the user // grab it private int mXOffset; // the difference between screen coordinates and // coordinates in this view private int mYOffset; // the difference between screen coordinates and // coordinates in this view private DragListener mDragListener; private DropListener mDropListener; private RemoveListener mRemoveListener; private int mUpperBound; private int mLowerBound; private int mHeight; private GestureDetector mGestureDetector; private static final int FLING = 0; private static final int SLIDE = 1; private static final int TRASH = 2; private int mRemoveMode = -1; private Rect mTempRect = new Rect(); private Bitmap mDragBitmap; private final int mTouchSlop; private int mItemHeightNormal; private int mItemHeightExpanded; private int mItemHeightHalf; private Drawable mTrashcan; public TouchInterceptor(Context context, AttributeSet attrs) { super(context, attrs); SharedPreferences pref = context.getSharedPreferences("Music", 3); mRemoveMode = pref.getInt("deletemode", -1); mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); Resources res = getResources(); mItemHeightNormal = res.getDimensionPixelSize(R.dimen.normal_height); mItemHeightHalf = mItemHeightNormal / 2; mItemHeightExpanded = res .getDimensionPixelSize(R.dimen.expanded_height); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (mRemoveListener != null && mGestureDetector == null) { if (mRemoveMode == FLING) { mGestureDetector = new GestureDetector(getContext(), new SimpleOnGestureListener() { @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { if (mDragView != null) { if (velocityX > 1000) { Rect r = mTempRect; mDragView.getDrawingRect(r); if (e2.getX() > r.right * 2 / 3) { // fast fling right with release // near the right edge of the screen stopDragging(); mRemoveListener.remove(mSrcDragPos); unExpandViews(true); } } // flinging while dragging should have no // effect return true; } return false; } }); } } //getX是以widget左上角为坐标原点计算的 //getRawX是以屏幕左上角为原点计算的 if (mDragListener != null || mDropListener != null) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: int x = (int) ev.getX(); int y = (int) ev.getY(); int itemnum = pointToPosition(x, y); if (itemnum == AdapterView.INVALID_POSITION) { break; } int first = getFirstVisiblePosition(); ViewGroup item = (ViewGroup) getChildAt(itemnum - first); mDragPointX = x - item.getLeft(); mDragPointY = y - item.getTop(); mXOffset = ((int) ev.getRawX()) - x; mYOffset = ((int) ev.getRawY()) - y; // System.out.println("++++++=============="); // The left side of the item is the grabber for dragging the // item if (x < 64) { item.setDrawingCacheEnabled(true); // Create a copy of the drawing cache so that it does not // get recycled // by the framework when the list tries to clean up memory Bitmap bitmap = Bitmap.createBitmap(item.getDrawingCache()); startDragging(bitmap, x, y); mDragPos = itemnum; mSrcDragPos = mDragPos; mHeight = getHeight(); int touchSlop = mTouchSlop; mUpperBound = Math.min(y - touchSlop, mHeight / 3); mLowerBound = Math.max(y + touchSlop, mHeight * 2 / 3); System.out.println("mDragPos--->" + mDragPos + " mHeight--->" + mHeight + " mUpperBound--->" + mUpperBound + " mLowerBound--->" + mLowerBound); return false; } stopDragging(); break; } } return super.onInterceptTouchEvent(ev); } /* * pointToPosition() doesn't consider invisible views, but we need to, so * implement a slightly different version. */ private int myPointToPosition(int x, int y) { if (y < 0) { // when dragging off the top of the screen, calculate position // by going back from a visible item int pos = myPointToPosition(x, y + mItemHeightNormal); if (pos > 0) { return pos - 1; } } Rect frame = mTempRect; final int count = getChildCount(); for (int i = count - 1; i >= 0; i--) { final View child = getChildAt(i); child.getHitRect(frame); if (frame.contains(x, y)) { return getFirstVisiblePosition() + i; } } return INVALID_POSITION; } private int getItemForPosition(int y) { //如果只是点击item的左侧还没有开始drag的时候 y-mDragPointY实际上是表示item.getTop(),也就是该item距离顶部多少 //但是y随着手机的移动在变化 相当于y1 + (y - mDragPointY) //当没有发生拖拽的时候 y1=0, 这样就相当于在计算y1-mItemHeightHalf int adjustedy = y - mDragPointY - mItemHeightHalf; // System.out.println(adjustedy+"============"); int pos = myPointToPosition(0, adjustedy); if (pos >= 0) { // System.out.println("pos--->"+pos+" mSrcDragPos--->"+mSrcDragPos); if (pos <= mSrcDragPos) { pos += 1; } } else if (adjustedy < 0) { // this shouldn't happen anymore now that myPointToPosition deals // with this situation pos = 0; } return pos; } private void adjustScrollBounds(int y) { if (y >= mHeight / 3) { mUpperBound = mHeight / 3; } if (y <= mHeight * 2 / 3) { mLowerBound = mHeight * 2 / 3; } } /* * Restore size and visibility for all listitems */ private void unExpandViews(boolean deletion) { for (int i = 0;; i++) { View v = getChildAt(i); if (v == null) { if (deletion) { // HACK force update of mItemCount int position = getFirstVisiblePosition(); int y = getChildAt(0).getTop(); setAdapter(getAdapter()); setSelectionFromTop(position, y); // end hack } try { layoutChildren(); // force children to be recreated where // needed v = getChildAt(i); } catch (IllegalStateException ex) { // layoutChildren throws this sometimes, presumably because // we're // in the process of being torn down but are still getting // touch // events } if (v == null) { return; } } ViewGroup.LayoutParams params = v.getLayoutParams(); params.height = mItemHeightNormal; v.setLayoutParams(params); v.setVisibility(View.VISIBLE); } } /* * Adjust visibility and size to make it appear as though an item is being * dragged around and other items are making room for it: If dropping the * item would result in it still being in the same place, then make the * dragged listitem's size normal, but make the item invisible. Otherwise, * if the dragged listitem is still on screen, make it as small as possible * and expand the item below the insert point. If the dragged item is not on * screen, only expand the item below the current insertpoint. */ private void doExpansion() { // System.out.println("doExpansion---------------------************"); int childnum = mDragPos - getFirstVisiblePosition(); // System.out.println("mDragPos--->"+mDragPos+" getFirstVisiblePosition()--->"+getFirstVisiblePosition()); if (mDragPos > mSrcDragPos) { childnum++; } int numheaders = getHeaderViewsCount(); View first = getChildAt(mSrcDragPos - getFirstVisiblePosition()); for (int i = 0;; i++) { View vv = getChildAt(i); if (vv == null) { break; } int height = mItemHeightNormal; int visibility = View.VISIBLE; if (mDragPos < numheaders && i == numheaders) { // dragging on top of the header item, so adjust the item below // instead if (vv.equals(first)) { visibility = View.INVISIBLE; } else { height = mItemHeightExpanded; } } else if (vv.equals(first)) { // processing the item that is being dragged if (mDragPos == mSrcDragPos || getPositionForView(vv) == getCount() - 1) { // hovering over the original location visibility = View.INVISIBLE; } else { // not hovering over it // Ideally the item would be completely gone, but neither // setting its size to 0 nor settings visibility to GONE // has the desired effect. //这地方的作用是:A和B两个item,A上B下,当A移动到可以和B互换位置的时候,A的高度设为1 //这样B就自动跑上去了,此时A到了以前B的位置 height = 1; } } else if (i == childnum) { if (mDragPos >= numheaders && mDragPos < getCount() - 1) { //后面height = mItemHeightExpanded; ABC三个item自上到下排列,A移动到B的位置 //B由于在A的height设为1之后跑上面去了,那么C的height要求设置为2倍的item的高度才能保持不动 height = mItemHeightExpanded; } } ViewGroup.LayoutParams params = vv.getLayoutParams(); params.height = height; vv.setLayoutParams(params); vv.setVisibility(visibility); } } @Override public boolean onTouchEvent(MotionEvent ev) { if (mGestureDetector != null) { mGestureDetector.onTouchEvent(ev); } if ((mDragListener != null || mDropListener != null) && mDragView != null) { int action = ev.getAction(); switch (action) { case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: Rect r = mTempRect; mDragView.getDrawingRect(r); stopDragging(); if (mRemoveMode == SLIDE && ev.getX() > r.right * 3 / 4) { if (mRemoveListener != null) { mRemoveListener.remove(mSrcDragPos); } unExpandViews(true); } else { if (mDropListener != null && mDragPos >= 0 && mDragPos < getCount()) { mDropListener.drop(mSrcDragPos, mDragPos); } unExpandViews(false); } break; case MotionEvent.ACTION_DOWN: case MotionEvent.ACTION_MOVE: int x = (int) ev.getX(); int y = (int) ev.getY(); dragView(x, y); int itemnum = getItemForPosition(y); // System.out.println("itemnum--->"+itemnum); if (itemnum >= 0) { if (action == MotionEvent.ACTION_DOWN || itemnum != mDragPos) { if (mDragListener != null) { mDragListener.drag(mDragPos, itemnum); } mDragPos = itemnum; //该方法控制移动item的时候其他item的位置变化 doExpansion(); } int speed = 0; adjustScrollBounds(y); if (y > mLowerBound) { // scroll the list up a bit if (getLastVisiblePosition() < getCount() - 1) { speed = y > (mHeight + mLowerBound) / 2 ? 16 : 4; } else { speed = 1; } } else if (y < mUpperBound) { // scroll the list down a bit speed = y < mUpperBound / 2 ? -16 : -4; if (getFirstVisiblePosition() == 0 && getChildAt(0).getTop() >= getPaddingTop()) { // if we're already at the top, don't try to scroll, // because // it causes the framework to do some extra drawing // that messes // up our animation speed = 0; } } if (speed != 0) { //移动listview smoothScrollBy(speed, 30); } } break; } return true; } return super.onTouchEvent(ev); } private void startDragging(Bitmap bm, int x, int y) { stopDragging(); mWindowParams = new WindowManager.LayoutParams(); mWindowParams.gravity = Gravity.TOP | Gravity.LEFT; mWindowParams.x = x - mDragPointX + mXOffset; mWindowParams.y = y - mDragPointY + mYOffset; mWindowParams.height = WindowManager.LayoutParams.WRAP_CONTENT; mWindowParams.width = WindowManager.LayoutParams.WRAP_CONTENT; mWindowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS; mWindowParams.format = PixelFormat.TRANSLUCENT; mWindowParams.windowAnimations = 0; Context context = getContext(); ImageView v = new ImageView(context); // int backGroundColor = // context.getResources().getColor(R.color.dragndrop_background); // v.setBackgroundColor(backGroundColor); v.setBackgroundResource(R.drawable.playlist_tile_drag); v.setPadding(0, 0, 0, 0); v.setImageBitmap(bm); mDragBitmap = bm; mWindowManager = (WindowManager) context .getSystemService(Context.WINDOW_SERVICE); mWindowManager.addView(v, mWindowParams); mDragView = v; } private void dragView(int x, int y) { if (mRemoveMode == SLIDE) { float alpha = 1.0f; int width = mDragView.getWidth(); if (x > width / 2) { alpha = ((float) (width - x)) / (width / 2); } mWindowParams.alpha = alpha; } if (mRemoveMode == FLING || mRemoveMode == TRASH) { mWindowParams.x = x - mDragPointX + mXOffset; } else { mWindowParams.x = 0; } mWindowParams.y = y - mDragPointY + mYOffset; mWindowManager.updateViewLayout(mDragView, mWindowParams); if (mTrashcan != null) { int width = mDragView.getWidth(); if (y > getHeight() * 3 / 4) { mTrashcan.setLevel(2); } else if (width > 0 && x > width / 4) { mTrashcan.setLevel(1); } else { mTrashcan.setLevel(0); } } } private void stopDragging() { if (mDragView != null) { mDragView.setVisibility(GONE); WindowManager wm = (WindowManager) getContext().getSystemService( Context.WINDOW_SERVICE); wm.removeView(mDragView); mDragView.setImageDrawable(null); mDragView = null; } if (mDragBitmap != null) { mDragBitmap.recycle(); mDragBitmap = null; } if (mTrashcan != null) { mTrashcan.setLevel(0); } } public void setTrashcan(Drawable trash) { mTrashcan = trash; mRemoveMode = TRASH; } public void setDragListener(DragListener l) { mDragListener = l; } public void setDropListener(DropListener l) { mDropListener = l; } public void setRemoveListener(RemoveListener l) { mRemoveListener = l; } public interface DragListener { void drag(int from, int to); } public interface DropListener { void drop(int from, int to); } public interface RemoveListener { void remove(int which); } }
上面关键部分都写了注释,包括源码中自带的和我的个人理解加上去的,主要思路大概是这样的:当点击item的左侧,也就是代码中的x < 64的判断,表示开始要拖拽listview了,此时记录下一些后面会用到的变量、隐藏选中的item、使用WindowManager来显示浮动的view、重新设置listview中的item的高度等。主要用到的方法是:pointToPosition,根据x,y来确定点击的item。当然还有其他重要的方法,可以看代码的详细注释和如下草图。
2、MainActivity类
package ldw.listview; import java.util.ArrayList; import java.util.List; import android.app.ListActivity; import android.content.Context; import android.os.Bundle; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.AbsListView.OnScrollListener; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.TextView; public class MainActivity extends ListActivity { private TouchInterceptor mListView; private ArrayList<String> list = new ArrayList<String>(); private ArrayAdapter<String> adapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mListView = (TouchInterceptor) getListView(); mListView.setSelector(R.drawable.list_selector_background); mListView.setBackgroundColor(0xff000000); mListView.setDropListener(mDropListener); mListView.setOnScrollListener(scrollListener); mListView .setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) { // TODO Auto-generated method stub return false; } }); initData(); adapter = new MyAdapter(this, R.layout.list_item, R.id.line1, list); // adapter = new SimpleAdapter(this, list, R.layout.list_item, // new String[] { "line1" }, new int[] { R.id.line1 }); mListView.setAdapter(adapter); } private class MyAdapter extends ArrayAdapter<String> { public MyAdapter(Context context, int resource, int textViewResourceId, List<String> objects) { super(context, resource, textViewResourceId, objects); } @Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = getLayoutInflater().inflate(R.layout.list_item, null); } TextView tv = (TextView) convertView.findViewById(R.id.line1); tv.setText(list.get(position)); return convertView; } } private TouchInterceptor.DropListener mDropListener = new TouchInterceptor.DropListener() { public void drop(int from, int to) { String item = adapter.getItem(from); adapter.remove(item); adapter.insert(item, to); // for (String temp : list) { // System.out.println(temp); // } // adapter.notifyDataSetChanged(); mListView.setAdapter(adapter); mListView.invalidateViews(); mListView.setSelectionFromTop(scrollPos, scrollTop); // mListView.setSelection(first); // mListView.scrollTo(0, first); // System.out.println(from + "--------" + to); } }; protected int scrollPos; protected int scrollTop; private void initData() { for (int i = 0; i < 20; i++) { list.add("很好" + i); } } private OnScrollListener scrollListener = new OnScrollListener() { @Override public void onScroll(AbsListView arg0, int arg1, int arg2, int arg3) { } @Override public void onScrollStateChanged(AbsListView view, int scrollState) { if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) { // ListPos记录当前可见的List顶端的一行的位置 scrollPos = mListView.getFirstVisiblePosition(); } if (list != null) { View v = mListView.getChildAt(0); scrollTop = (v == null) ? 0 : v.getTop(); } } }; }
MainActivity中主要代码是scrollListener监听类用于监听listview的滑动的顶端的item和位置,然后通过mListView.setSelectionFromTop(scrollPos, scrollTop);方法来实现拖拽过后listview的定位,因为每次拖拽完后使用setAdapter会让listview重新刷新然后定位到第一个item,有人肯定会问为什么不用notifyDataSetChanged方法,该方法试过了,可以很好的实现拖拽过后的定位,但是拖拽完后然后再点击被置换的那个item,会显示错乱,至今没有找到原因,估计是listview的drawingCache没有刷新的缘故吧。
下面附上源码
伟哥V5~完全看不懂。
跪求教育!