整個activity或者View組件顯示的內容可以通過cache機制儲存為bitmap, 使用到的api有
void setDrawingCacheEnabled(boolean flag),
Bitmap getDrawingCache(boolean autoScale),
void buildDrawingCache(boolean autoScale),
void destroyDrawingCache()
我們要擷取它的cache先要通過setDrawingCacheEnable方法把cache開啟,然後再調用getDrawingCache方法就可以獲得view的cache圖片了。buildDrawingCache方法可以不用調用,因為調用getDrawingCache方法時,若果 cache沒有建立,系統會自動調用buildDrawingCache方法產生cache。若果要更新cache, 必須要調用destoryDrawingCache方法把舊的cache銷毀,才能建立新的。
當調用setDrawingCacheEnabled方法設定為false, 系統也會自動把原來的cache銷毀。
ViewGroup在繪製子view時,而外提供了兩個方法
void setChildrenDrawingCacheEnabled(boolean enabled)
setChildrenDrawnWithCacheEnabled(boolean enabled)
setChildrenDrawingCacheEnabled方法可以使viewgroup裡所有的子view開啟cache, setChildrenDrawnWithCacheEnabled使在繪製子view時,若該子view開啟了cache, 則使用它的cache進行繪製,從而節省繪製時間。
擷取cache通常會佔用一定的記憶體,所以通常不需要的時候有必要對其進行清理,通過destroyDrawingCache或setDrawingCacheEnabled(false)實現。
1. android 螢幕 代碼如下:
android螢幕 import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.Rect; import android.view.View; public class ScreenShot { // 擷取指定Activity的截屏,儲存到png檔案 private static Bitmap takeScreenShot(Activity activity){ //View是你需要的View View view = activity.getWindow().getDecorView(); view.setDrawingCacheEnabled(true); view.buildDrawingCache(); Bitmap b1 = view.getDrawingCache(); //擷取狀態列高度 Rect frame = new Rect(); activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(frame); int statusBarHeight = frame.top; System.out.println(statusBarHeight); //擷取螢幕長和高 int width = activity.getWindowManager().getDefaultDisplay().getWidth(); int height = activity.getWindowManager().getDefaultDisplay().getHeight(); //去掉標題列 //Bitmap b = Bitmap.createBitmap(b1, 0, 25, 320, 455); Bitmap b = Bitmap.createBitmap(b1, 0, statusBarHeight, width, height - statusBarHeight); view.destroyDrawingCache(); return b; } //儲存到sdcard private static void savePic(Bitmap b,String strFileName){ FileOutputStream fos = null; try { fos = new FileOutputStream(strFileName); if (null != fos) { b.compress(Bitmap.CompressFormat.PNG, 90, fos); fos.flush(); fos.close(); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } //程式入口 public static void shoot(Activity a){ ScreenShot.savePic(ScreenShot.takeScreenShot(a), "sdcard/xx.png"); } }
2. 截取listview中的Item 代碼:
private AdapterView.OnItemLongClickListener mListenerLongClickMemItem = new AdapterView.OnItemLongClickListener() {@Overridepublic boolean onItemLongClick(AdapterView<?> adapter, View view,int pos, long id) {// TODO Auto-generated method stubAvcRoomItem item = mCore.getRoomShowMembers().get(pos);if (item.getmType() == RoomItemType.ROOM_ITEM_CARD&& mCore.getMyself().isPresider()) {view.destroyDrawingCache();view.setDrawingCacheEnabled(true);Bitmap bm = Bitmap.createBitmap(view.getDrawingCache());if (!mTemplate.isShown())mCore.doShowPScreen();mTempDevItem = item;startDrag(bm, (int) mListMember.getLastMotionEvent().getRawX(),(int) mListMember.getLastMotionEvent().getRawY());}return false;}};