android2.3 Launcher牆紙設定代碼追蹤

    case MENU_WALLPAPER_SETTINGS:                       startWallpaper();//點擊壁紙設定菜單，會調用startWallpaper()        private void startWallpaper() {        closeAllApps(true);        final Intent pickWallpaper = new Intent(Intent.ACTION_SET_WALLPAPER);        Intent chooser = Intent.createChooser(pickWallpaper,        getText(R.string.chooser_wallpaper));        startActivityForResult(chooser, REQUEST_PICK_WALLPAPER);    }  //createChooser 會彈出一個對話方塊，把能處理Intent.ACTION_SET_WALLPAPER          //的activity都列出來供使用者選擇

選擇“壁紙”後會啟動Activity：WallpaperChooser

介面由三個View組成：ImageView 、Gallery、Button，

點擊Button後，設定壁紙：

    private void selectWallpaper(int position) {        if (mIsWallpaperSet) {            return;        }        mIsWallpaperSet = true;        try {            WallpaperManager wpm = (WallpaperManager)getSystemService(WALLPAPER_SERVICE);            wpm.setResource(mImages.get(position));            setResult(RESULT_OK);            finish();        } catch (IOException e) {            Log.e(TAG, "Failed to set wallpaper: " + e);        }    }

Gallery的item被選擇後，ImageView會把相對應的大的圖片顯示出來，

此處通過非同步處理類asynctask來完成的：

    public void onItemSelected(AdapterView parent, View v, int position, long id) {        if (mLoader != null && mLoader.getStatus() != WallpaperLoader.Status.FINISHED) {            mLoader.cancel();        }        mLoader = (WallpaperLoader) new WallpaperLoader().execute(position);    }

其中execute的參數position就是AsyncTask的doInBackground後面的參數，

doInBackground  return的值，會作為onPostExecute的參數

   

 class WallpaperLoader extends AsyncTask<Integer, Void, Bitmap> {        BitmapFactory.Options mOptions;        WallpaperLoader() {            mOptions = new BitmapFactory.Options();            mOptions.inDither = false;            mOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;                    }                protected Bitmap doInBackground(Integer... params)//此處params為position {            if (isCancelled()) return null;            try {                return BitmapFactory.decodeResource(getResources(),                        mImages.get(params[0]), mOptions);            } catch (OutOfMemoryError e) {                Log.w(TAG, "Home no memory load current wallpaper", e);                return null;            }        }        @Override        protected void onPostExecute(Bitmap b) //此處的b為doInBackGround return的值  {            if (b == null) return;            if (!isCancelled() && !mOptions.mCancel) {                // Help the GC                if (mBitmap != null) {                    mBitmap.recycle();                }                    final ImageView view = mImageView;                view.setImageBitmap(b);                    mBitmap = b;                    final Drawable drawable = view.getDrawable();                drawable.setFilterBitmap(true);          //用來對Bitmap進行濾波處理，有消除鋸齒的效果                 drawable.setDither(true);//防震                view.postInvalidate();                mLoader = null;            } else {               b.recycle();             }        }        void cancel() {            mOptions.requestCancelDecode();            super.cancel(true);        }    }}