使用 RecyclerView 时我的应用程序崩溃

Question

我的应用程序在尝试加载列表后立即崩溃，我搜索并发现有些错误是因为他们没有，但我这样做：

implementation 'com.android.support:recyclerview-v7:28.0.0-alpha3'

implementation 'com.android.support:cardview-v7:28.0.0-alpha3'

这是我得到的错误代码：

E/AndroidRuntime: FATAL EXCEPTION: main

              Process: com.yemencar.yemencar, PID: 28558

              java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$Adapter.notifyDataSetChanged()' on a null object reference

                  at com.yemencar.yemencar.homepageActivity.parseData(homepageActivity.java:144)

                  at com.yemencar.yemencar.homepageActivity.access$000(homepageActivity.java:26)

                  at com.yemencar.yemencar.homepageActivity$1.onResponse(homepageActivity.java:95)

                  at com.yemencar.yemencar.homepageActivity$1.onResponse(homepageActivity.java:91)

                  at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65)

                  at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)

                  at android.os.Handler.handleCallback(Handler.java:789)

                  at android.os.Handler.dispatchMessage(Handler.java:98)

                  at android.os.Looper.loop(Looper.java:164)

                  at android.app.ActivityThread.main(ActivityThread.java:6541)

                  at java.lang.reflect.Method.invoke(Native Method)

                  at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)

                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

E/Surface: queueBuffer: error queuing buffer to SurfaceTexture, -19

E/EGL_emulation: tid 28589: swapBuffers(550): error 0x300d (EGL_BAD_SURFACE)

我正在尝试使用标题制作 RecyclerView，以便我可以放置排序选项并查看为网格或列表选项。

Answer 1

进行这两个更改，您应该会很好。public class homepageActivity ... {    // 1. Change this to a CardAdapter    private CardAdapter adapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        // ...        // 2. Change this to reference the field adapter.        adapter = new CardAdapter(getHeader(),listSuperHeroes, this);    }}