android 应用程序显示空白屏幕而不是书单

Question

https://github.com/kamaleshdas1997/BookListing2

here is the code. The app opens with a search bar (I didn't start working on search bar so search bar is not functional - let's say dummy search bar ) on button click it will redirect to another activity (BookListActivity.java) where from an API get a list of book to suppose to display on-screen instead of which it shows a blank screen.
I don't know where it is going wrong. As in logcat there is no error.

LogCat:-

2020-12-07 12:35:22.124 32007-32036/com.example.booklisting \
    I/Adreno: QUALCOMM build                   : 365e321, I294de8bafa
    Build Date                       : 01/08/19
    OpenGL ES Shader Compiler Version: EV031.25.03.02
    Local Branch                     : 
    Remote Branch                    : refs/tags/AU_LINUX_ANDROID_LA.UM.7.5.R1.09.00.00.464.040
    Remote Branch                    : NONE
    Reconstruct Branch               : NOTHING
2020-12-07 12:35:22.124 32007-32036/com.example.booklisting \
    I/Adreno: Build Config                     : S L 6.0.7 AArch64
2020-12-07 12:35:22.124 32007-32036/com.example.booklisting \
    D/vndksupport: Loading /vendor/lib64/hw/gralloc.msm8996.so from current namespace instead of sphal namespace.
2020-12-07 12:35:22.132 32007-32036/com.example.booklisting \
    I/Adreno: PFP: 0x005ff110, ME: 0x005ff066
2020-12-07 12:35:22.146 32007-32036/com.example.booklisting \
    I/ConfigStore: android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasWideColorDisplay retrieved: 0
2020-12-07 12:35:22.147 32007-32036/com.example.booklisting \
    I/ConfigStore: android::hardware::configstore::V1_0::ISurfaceFlingerConfigs::hasHDRDisplay retrieved: 0
2020-12-07 12:35:22.148 32007-32036/com.example.booklisting \
    I/OpenGLRenderer: Initialized EGL, version 1.4
2020-12-07 12:35:22.148 32007-32036/com.example.booklisting \
    D/OpenGLRenderer: Swap behavior 2
2020-12-07 12:35:22.205 32007-32036/com.example.booklisting \
    D/vndksupport: Loading /vendor/lib64/hw/android.hardware.graphics.mapper@2.0-impl.so from current namespace instead of sphal namespace.
2020-12-07 12:35:22.207 32007-32036/com.example.booklisting \
    D/vndksupport: Loading /vendor/lib64/hw/gralloc.msm8996.so from current namespace instead of sphal namespace.
2020-12-07 12:35:30.716 32007-32007/com.example.booklisting \
    W/ActivityThread: handleWindowVisibility: no activity for token android.os.BinderProxy@2cdc1a2

Answer 1

You are missing the init call to the loader API. Add this

LoaderManager.getInstance(this).initLoader(1, null, this); in the onCreate function of

BookListActivity.class everything else looks good.

NB: Make sure you are not using the deprecated API. the one above is from AndroidX. getLoaderManager().initLoader(1, null, this) this will be for older API's.