• packages/apps/Launcher3/src/com/android/launcher3/allapps/AllAppsTransitionController.java

 private void updateAllAppsBg(float progress) {
        // gradient
        if (mGradientView == null) {
            mGradientView = (GradientView) mLauncher.findViewById(R.id.gradient_bg);
            mGradientView.setVisibility(View.INVISIBLE);//把VISIBLE修改為INVISIBLE
        }
        mGradientView.setProgress(progress);
    }