本文来自http://blog.csdn.net/hellogv/ ，欢迎转摘，引用必须注明出处！
以前曾经介绍过《Android提高第十九篇之"多方向"抽屉》，当这个抽屉组件不与周围组件发生压挤的情况下(周围组件布局不变)，是比较好使的，但是如果需要对周围组件挤压，则用起来欠缺美观了。
如下图。在对周围压挤的情况下，抽屉是先把周围的组件一次性压挤，再通过动画效果展开/收缩的，这种做法的好处是快速简单，坏处是如果挤压范围过大，则效果生硬。
本文实现的自定义抽屉组件，主要针对这种压挤效果做出改良，渐进式压挤周围组件，使得过渡效果更加美观。如下图。
本文实现的抽屉原理是酱紫：
1.抽屉组件主要在屏幕不可视区域，手柄在屏幕边缘的可视区域。即 抽屉.rightMargin=-XXX + 手柄.width
2.指定一个周围组件为可压挤，即LayoutParams.weight=1;当然用户也可以指定多个View.
3.使用AsyncTask来实现弹出/收缩的动画，弹出：抽屉.rightMargin+=XX，收缩：抽屉.rightMargin-=XX
总结，本文的自定义抽屉虽然对压挤周围组件有过渡效果，但是比较耗资源，读者可以针对不同的情况考虑使用。
本文的源码可以到http://download.csdn.net/detail/hellogv/3615686 下载。
接下来贴出本文全部源代码：
main.xml的源码:
[html] view plain copy <span style="font-family:Comic Sans MS;font-size:18px;"><?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:id="@+id/container"> <GridView android:id="@+id/gridview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:numColumns="auto_fit" android:verticalSpacing="10dp" android:gravity="center" android:columnWidth="50dip" android:horizontalSpacing="10dip" /> </LinearLayout></span>GridView的Item.xml的源码：
[html] view plain copy <span style="font-family:Comic Sans MS;font-size:18px;"><?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="wrap_content" android:paddingBottom="4dip" android:layout_width="fill_parent"> <ImageView android:layout_height="wrap_content" android:id="@+id/ItemImage" android:layout_width="wrap_content" android:layout_centerHorizontal="true"> </ImageView> <TextView android:layout_width="wrap_content" android:layout_below="@+id/ItemImage" android:layout_height="wrap_content" android:text="TextView01" android:layout_centerHorizontal="true" android:id="@+id/ItemText"> </TextView> </RelativeLayout> </span>Panel.java是本文核心，抽屉组件的源码，这个抽屉只实现了从右往左的弹出/从左往右的收缩，读者可以根据自己的需要修改源码来改变抽屉动作的方向：
[java] view plain copy <span style="font-family:Comic Sans MS;font-size:18px;">public class Panel extends LinearLayout{ public interface PanelClosedEvent { void onPanelClosed(View panel); } public interface PanelOpenedEvent { void onPanelOpened(View panel); } /**Handle的宽度，与Panel等高*/ PRivate final static int HANDLE_WIDTH=30; /**每次自动展开/收缩的范围*/ private final static int MOVE_WIDTH=20; private Button btnHandle; private LinearLayout panelContainer; private int mRightMargin=0; private Context mContext; private PanelClosedEvent panelClosedEvent=null; private PanelOpenedEvent panelOpenedEvent=null; /** * otherView自动布局以适应Panel展开/收缩的空间变化 * @author GV * */ public Panel(Context context,View otherView,int width,int height) { super(context); this.mContext=context; //改变Panel附近组件的属性 LayoutParams otherLP=(LayoutParams) otherView.getLayoutParams(); otherLP.weight=1;//支持压挤 otherView.setLayoutParams(otherLP); //设置Panel本身的属性 LayoutParams lp=new LayoutParams(width, height); lp.rightMargin=-lp.width+HANDLE_WIDTH;//Panel的Container在屏幕不可视区域，Handle在可视区域 mRightMargin=Math.abs(lp.rightMargin); this.setLayoutParams(lp); this.setOrientation(LinearLayout.HORIZONTAL); //设置Handle的属性 btnHandle=new Button(context); btnHandle.setLayoutParams(new LayoutParams(HANDLE_WIDTH,height)); btnHandle.setOnClickListener(new OnClickListener(){ @Override public void onClick(View arg0) { LayoutParams lp = (LayoutParams) Panel.this.getLayoutParams(); if (lp.rightMargin < 0)// CLOSE的状态 new AsynMove().execute(new Integer[] { MOVE_WIDTH });// 正数展开 else if (lp.rightMargin >= 0)// OPEN的状态 new AsynMove().execute(new Integer[] { -MOVE_WIDTH });// 负数收缩 } }); //btnHandle.setOnTouchListener(HandleTouchEvent); this.addView(btnHandle); //设置Container的属性 panelContainer=new LinearLayout(context); panelContainer.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT)); this.addView(panelContainer); } /** * 定义收缩时的回调函数 * @param event */ public void setPanelClosedEvent(PanelClosedEvent event) { this.panelClosedEvent=event; } /** * 定义展开时的回调函数 * @param event */ public void setPanelOpenedEvent(PanelOpenedEvent event) { this.panelOpenedEvent=event; } /** * 把View放在Panel的Container * @param v */ public void fillPanelContainer(View v) { panelContainer.addView(v); } /** * 异步移动Panel * @author hellogv */ class AsynMove extends AsyncTask<Integer, Integer, Void> { @Override protected Void doInBackground(Integer... params) { int times; if (mRightMargin % Math.abs(params[0]) == 0)// 整除 times = mRightMargin / Math.abs(params[0]); else // 有余数 times = mRightMargin / Math.abs(params[0]) + 1; for (int i = 0; i < times; i++) { publishProgress(params); try { Thread.sleep(Math.abs(params[0])); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return null; } @Override protected void onProgressUpdate(Integer... params) { LayoutParams lp = (LayoutParams) Panel.this.getLayoutParams(); if (params[0] < 0) lp.rightMargin = Math.max(lp.rightMargin + params[0], (-mRightMargin)); else lp.rightMargin = Math.min(lp.rightMargin + params[0], 0); if(lp.rightMargin==0 && panelOpenedEvent!=null){//展开之后 panelOpenedEvent.onPanelOpened(Panel.this);//调用OPEN回调函数 } else if(lp.rightMargin==-(mRightMargin) && panelClosedEvent!=null){//收缩之后 panelClosedEvent.onPanelClosed(Panel.this);//调用CLOSE回调函数 } Panel.this.setLayoutParams(lp); } } } </span>
main.Java是主控部分，演示了Panel的使用：
[java] view plain copy <span style="font-family:Comic Sans MS;font-size:18px;">public class main extends Activity { public Panel panel; public LinearLayout container; public GridView gridview; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); this.setTitle("“可动态布局”的抽屉组件之构建基础-----hellogv"); gridview = (GridView) findViewById(R.id.gridview); container=(LinearLayout)findViewById(R.id.container); panel=new Panel(this,gridview,200,LayoutParams.FILL_PARENT); container.addView(panel);//加入Panel控件 //新建测试组件 TextView tvTest=new TextView(this); tvTest.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT)); tvTest.setText("测试组件，红字白底"); tvTest.setTextColor(Color.RED); tvTest.setBackgroundColor(Color.WHITE); //加入到Panel里面 panel.fillPanelContainer(tvTest); panel.setPanelClosedEvent(panelClosedEvent); panel.setPanelOpenedEvent(panelOpenedEvent); //往GridView填充测试数据 ArrayList<HashMap<String, Object>> lstImageItem = new ArrayList<HashMap<String, Object>>(); for (int i = 0; i < 100; i++) { HashMap<String, Object> map = new HashMap<String, Object>(); map.put("ItemImage", R.drawable.icon); map.put("ItemText", "NO." + String.valueOf(i)); lstImageItem.add(map); } SimpleAdapter saImageItems = new SimpleAdapter(this, lstImageItem, R.layout.item, new String[] { "ItemImage", "ItemText" }, new int[] { R.id.ItemImage, R.id.ItemText }); gridview.setAdapter(saImageItems); gridview.setOnItemClickListener(new ItemClickListener()); } PanelClosedEvent panelClosedEvent =new PanelClosedEvent(){ @Override public void onPanelClosed(View panel) { Log.e("panelClosedEvent","panelClosedEvent"); } }; PanelOpenedEvent panelOpenedEvent =new PanelOpenedEvent(){ @Override public void onPanelOpened(View panel) { Log.e("panelOpenedEvent","panelOpenedEvent"); } }; class ItemClickListener implements OnItemClickListener { @Override public void onItemClick(AdapterView<?> arg0,View arg1, int arg2, long arg3) { @SuppressWarnings("unchecked") HashMap<String, Object> item = (HashMap<String, Object>) arg0 .getItemAtPosition(arg2); setTitle((String) item.get("ItemText")); } }</span>后面还会继续介绍如何在Panel加入拖拉效果的处理！
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