开机壁纸下半部分黑屏2-3秒

屏蔽掉AsyncTask，将异步改为同步，可能由于机器性能原因导致下半部分黑屏（加载太慢了）。

//vendor/mediatek/proprietary/packages/apps/SystemUI/src/com/android/systemui/ImageWallpaper.java
        private void loadWallpaper(boolean needsDraw, boolean needsReset) {
            mNeedsDrawAfterLoadingWallpaper |= needsDraw;
            if (mLoader != null) {
                if (needsReset) {
                    mLoader.cancel(false /* interrupt */);
                    mLoader = null;
                } else {
                    if (DEBUG) {
                        Log.d(TAG, "Skipping loadWallpaper, already in flight ");
                    }
                    return;
                }
            }
         /*   mLoader = new AsyncTask<Void, Void, Bitmap>() {
                @Override
                protected Bitmap doInBackground(Void... params) {
                    Throwable exception;
                    try {
                        if (needsReset) {
                            mWallpaperManager.forgetLoadedWallpaper();
                        }
                        return mWallpaperManager.getBitmap();
                    } catch (RuntimeException | OutOfMemoryError e) {
                        exception = e;
                    }

                    if (isCancelled()) {
                        return null;
                    }

                    if (exception != null) {
                        // Note that if we do fail at this, and the default wallpaper can't
                        // be loaded, we will go into a cycle.  Don't do a build where the
                        // default wallpaper can't be loaded.
                        Log.w(TAG, "Unable to load wallpaper!", exception);
                        try {
                            mWallpaperManager.clear();
                        } catch (IOException ex) {
                            // now we're really screwed.
                            Log.w(TAG, "Unable reset to default wallpaper!", ex);
                        }

                        if (isCancelled()) {
                            return null;
                        }

                        try {
                            return mWallpaperManager.getBitmap();
                        } catch (RuntimeException | OutOfMemoryError e) {
                            Log.w(TAG, "Unable to load default wallpaper!", e);
                        }
                    }
                    return null;
                }

                @Override
                protected void onPostExecute(Bitmap b) {
                    mBackground = null;
                    mBackgroundWidth = -1;
                    mBackgroundHeight = -1;

                    if (b != null) {
                        mBackground = b;
                        mBackgroundWidth = mBackground.getWidth();
                        mBackgroundHeight = mBackground.getHeight();
                    }

                    if (DEBUG) {
                        Log.d(TAG, "Wallpaper loaded: " + mBackground);
                    }
                    updateSurfaceSize(getSurfaceHolder(), getDefaultDisplayInfo(),
                            false *//* forDraw *//*);
                    if (mNeedsDrawAfterLoadingWallpaper) {
                        drawFrame();
                    }

                    mLoader = null;
                    mNeedsDrawAfterLoadingWallpaper = false;
                }
            }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);*/
            Bitmap  b = null;
            Throwable exception = null;
            try {
                if (needsReset) {
                    mWallpaperManager.forgetLoadedWallpaper();
                }
                b =  mWallpaperManager.getBitmap();
            } catch (RuntimeException | OutOfMemoryError e) {
                exception = e;
            }

            if (exception != null) {
                // Note that if we do fail at this, and the default wallpaper can't
                // be loaded, we will go into a cycle.  Don't do a build where the
                // default wallpaper can't be loaded.
                Log.w(TAG, "Unable to load wallpaper!", exception);
                try {
                    mWallpaperManager.clear();
                } catch (IOException ex) {
                    // now we're really screwed.
                    Log.w(TAG, "Unable reset to default wallpaper!", ex);
                }


                try {
                    b =  mWallpaperManager.getBitmap();
                } catch (RuntimeException | OutOfMemoryError e) {
                    Log.w(TAG, "Unable to load default wallpaper!", e);
                }
            }

            mBackground = null;
            mBackgroundWidth = -1;
            mBackgroundHeight = -1;

            if (b != null) {
                mBackground = b;
                mBackgroundWidth = mBackground.getWidth();
                mBackgroundHeight = mBackground.getHeight();
            }

            if (DEBUG) {
                Log.d(TAG, "Wallpaper loaded: " + mBackground);
            }
            updateSurfaceSize(getSurfaceHolder(), getDefaultDisplayInfo(),
                    false );
            if (mNeedsDrawAfterLoadingWallpaper) {
                drawFrame();
            }

            mLoader = null;
            mNeedsDrawAfterLoadingWallpaper = false;
        }

参考链接：
android 8.1 开机壁纸下半部分黑屏2-3秒的问题解决