我有一个 CountDownTimer,它每 15 秒调用一次 ChangeWallpaper() 方法。壁纸会发生应有的变化,但是当我尝试打开应用程序时,它会使应用程序抽屉屏幕在几秒钟内无响应。当应用程序最终打开时,我选择的所有内容都需要 5-10 秒才能响应。我在 Android Developer 中阅读了有关 AsyncTask 的内容,它应该在 UI 线程之外加载位图并防止应用程序挂起,但它似乎不起作用。
以下代码在我的 Activity 类中:
/** changeWallpaper() **/ - called by CountDownTimer every 15 seconds
protected void changeWallpaper() throws IOException {
Integer totalimages = finallist.size();
if (lastloopcount == totalimages) { // if end of the list of images is reached, it resets and goes back to top.
loopcount = 0;
lastloopcount = 0;
}
for (String imagepath : finallist) { // "finallist" is global variable with all the image's paths in an array list. The Loop count is to select the next image in the array list every 15 seconds.
loopcount++;
if (loopcount > lastloopcount) {
lastloopcount = loopcount;
loopcount = 0;
WallpaperManager wm = WallpaperManager.getInstance(this);
wm.setBitmap(decodeImageFromPath(imagepath));
break;
}
}
}
/** AsyncTask Wallpaper Load **/
class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {
public BitmapWorkerTask(ImageView imageView) {
new WeakReference<ImageView>(imageView);
}
@Override
protected Bitmap doInBackground(Integer... params) {
return null;
}
}
/** decodeImageFromPath() **/
public Bitmap decodeImageFromPath(String imagepath) {
DisplayMetrics displayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
int height = displayMetrics.heightPixels;
int width = displayMetrics.widthPixels << 2;
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(imagepath, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, width, height);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFile(imagepath, options);
}
/** WallpaperManager (Method) **/
public static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// ... Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int stretch_width = Math.round((float)width / (float)reqWidth);
int stretch_height = Math.round((float)height / (float)reqHeight);
if (stretch_width <= stretch_height) return stretch_height;
else return stretch_width;
}
- 我是否正确使用了 AsyncTask 功能?
- 有没有更简单的方法来写这个?
提前致谢。
编辑:
/** Spinner **/
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String chosenTime = parent.getItemAtPosition(position).toString();
int chosenTimeNew = 0;
if (chosenTime.contains("sec")) {
chosenTime = chosenTime.replace(" sec","");
chosenTimeNew = Integer.parseInt(chosenTime) * 500;
} else if (chosenTime.contains("min") ) {
chosenTime = chosenTime.replace(" min","");
chosenTimeNew = Integer.parseInt(chosenTime) * 30000;
} else if (chosenTime.contains("hour")) {
chosenTime = chosenTime.replace(" hour","");
chosenTimeNew = (Integer.parseInt(chosenTime) * 30000) * 60;
} else if (chosenTime.contains("day")) {
chosenTime = chosenTime.replace(" day","");
chosenTimeNew = ((Integer.parseInt(chosenTime) * 30000) * 60) * 24;
}
rSpeed = chosenTimeNew;
}
编辑2:
由 CountDownTimer() 调用:
new BitmapWorkerTask(null).execute(imagepath);
然后:
/** AsyncTask Wallpaper Load **/
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
public BitmapWorkerTask(ImageView imageView) {
new WeakReference<ImageView>(imageView);
}
@Override
protected Bitmap doInBackground(String... params) {
DisplayMetrics displayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
int height = displayMetrics.heightPixels;
int width = displayMetrics.widthPixels << 2;
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(params[0], options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, width, height);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
Bitmap bmp = BitmapFactory.decodeFile(params[0], options);
return bmp;
}
protected void onPostExecute(Bitmap bmp) {
Context context = getApplicationContext();
WallpaperManager wm = WallpaperManager.getInstance(context);
try {
wm.setBitmap(bmp);
} catch (IOException e) {
e.printStackTrace();
}
}
}
/** WallpaperManager (Method) **/
public static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// ... Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int stretch_width = Math.round((float)width / (float)reqWidth);
int stretch_height = Math.round((float)height / (float)reqHeight);
if (stretch_width <= stretch_height) return stretch_height;
else return stretch_width;
}