Google Play控制台報告應用程序崩潰，我無法復制

Question

Android Vitals報告中的Google Play控制台為我提供了此信息

java.lang.RuntimeException: 
  at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2955)
  at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:3030)
  at android.app.ActivityThread.-wrap11 (Unknown Source)
  at android.app.ActivityThread$H.handleMessage (ActivityThread.java:1696)
  at android.os.Handler.dispatchMessage (Handler.java:105)
  at android.os.Looper.loop (Looper.java:164)
  at android.app.ActivityThread.main (ActivityThread.java:6938)
  at java.lang.reflect.Method.invoke (Native Method)
  at com.android.internal.os.Zygote$MethodAndArgsCaller.run (Zygote.java:327)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1374)
Caused by: java.lang.NullPointerException: 
  at com.golendukhin.whitenoise.GridAdapter.getCount (GridAdapter.java:52)
  at android.widget.GridView.setAdapter (GridView.java:243)
  at com.golendukhin.whitenoise.FoldersGridActivity.onCreate (FoldersGridActivity.java:60)
  at android.app.Activity.performCreate (Activity.java:7183)
  at android.app.Instrumentation.callActivityOnCreate (Instrumentation.java:1220)
  at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2908)

據我了解，發生這種情況是因為網格適配器的getCount方法返回空值。 提示，網格適配器不起作用。 誠然，沒有創造出全部的狂熱。 僅三星設備有此問題。

首先，我嘗試創建具有相同Android版本，RAM和ARM的相同仿真設備。 仿真器的工作原理絕對出色。 沒錯

然后，我添加了一些測試，以確保getCount可以正常工作並創建活動。

@RunWith(AndroidJUnit4.class)
public class GridViewTest {

    @Rule
    public ActivityTestRule<FoldersGridActivity> foldersGridActivityTestRule  = new  ActivityTestRule<>(FoldersGridActivity.class);

    @Test
    public void ensureGridAdapterIsNotNull() {
        FoldersGridActivity foldersGridActivity = foldersGridActivityTestRule.getActivity();
        View view = foldersGridActivity.findViewById(R.id.grid_view);
        GridView gridView = (GridView) view;
        GridAdapter gridAdapter = (GridAdapter) gridView.getAdapter();
        assertThat(gridAdapter, notNullValue());
    }

    @Test
    public void ensureArrayAdapterInGridActivityIsNotEmpty() {
        FoldersGridActivity foldersGridActivity = foldersGridActivityTestRule.getActivity();
        View view = foldersGridActivity.findViewById(R.id.grid_view);
        GridView gridView = (GridView) view;
        GridAdapter gridAdapter = (GridAdapter) gridView.getAdapter();
        assertTrue(gridAdapter.getCount() > 0 );
    }

    @Test
    public void gridViewIsVisibleAndClickable() {
        onData(anything()).inAdapterView(withId(R.id.grid_view)).atPosition(0).perform(click());
        onView(withId(R.id.toolbar_title_text_view)).check(matches(withText("rain")));
    }
}

所有仿真設備再次成功通過測試。 然后，我添加了FireBase TestLab，並在裝有Android 8的Galaxy S9真實設備上啟動了我的測試。

適配器代碼。 是的，即使它沒有意義，我也重寫了getCount（）方法。

public class GridAdapter extends ArrayAdapter<TracksFolder> {
    @BindView(R.id.folder_text_view) TextView textView;
    @BindView(R.id.grid_item_image_view) ImageView imageView;

    private ArrayList<TracksFolder> tracksFolders;
    private Context context;

    GridAdapter(Context context, int resource, ArrayList<TracksFolder> tracksFolders) {
        super(context, resource, tracksFolders);
        this.tracksFolders = tracksFolders;
        this.context = context;
    }

    /**
     * @return grid item, customized via TracksFolder class instance
     */
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.grid_item, parent, false);
        }
        ButterKnife.bind(this, convertView);

        String folderName = tracksFolders.get(position).getFolderName();
        int imageResource = tracksFolders.get(position).getImageResource();
        textView.setText(folderName);
        imageView.setImageResource(imageResource);

        return convertView;
    }

    /**
     * Added to possibly avoid NPE on multiple devices
     * Could not reproduce this error
     * @return size of tracksFolders
     */
    @Override
    public int getCount() {
        return tracksFolders.size();
    }
}

因此，我有兩個問題：首先，此崩潰報告是否意味着每次Sumsung所有者啟動應用程序時都會發生此崩潰？ 由於某些三星設備仍在統計中，因此我認為沒有。 其次，我應該怎么做才能以某種方式重現此錯誤並最終修復該錯誤。

我知道問題太籠統了，但是我將不勝感激，因為我絕對不知道下一步該怎么做。

入門班。 使用適配器

import android.content.Intent;
import android.content.SharedPreferences;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.GridView;

import com.google.firebase.crash.FirebaseCrash;

import java.util.ArrayList;
import butterknife.BindArray;
import butterknife.BindView;
import butterknife.ButterKnife;

import static com.golendukhin.whitenoise.SharedPreferencesUtils.writeToSharedPreferences;

public class FoldersGridActivity extends AppCompatActivity {
    @BindView(R.id.grid_view) GridView gridView;
    @BindArray(R.array.labels) String[] foldersName;
    @BindView(R.id.toolbar_like_button) Button toolbarLikeButton;
    @BindView(R.id.toolbar_back_button) Button toolbarBackButton;

    private ArrayList<TracksFolder> tracksFolders;

    /**
     * Binds all UI views
     * Defines variables to feed adapter and listeners
     * Initializes grid adapter, sets number of columns via phone in portrait or landscape orientation
     * Sets onclick listener for every grid item
     * Sets onclick for toolbar "like" button
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.folders_grid_view);
        ButterKnife.bind(this);

        if (getIntent().getExtras() != null) { //activity is triggered via on back pressed
            Bundle bundle = getIntent().getExtras();
            tracksFolders = (ArrayList<TracksFolder>) bundle.getSerializable("tracksFolders");
        } else if (savedInstanceState != null) { //this happens after screen is rotated
            tracksFolders = (ArrayList<TracksFolder>) savedInstanceState.getSerializable("tracksFolders");
        } else { //this happens if app is launched by user
            tracksFolders = getTracksFolders();
            initService();
        }

        toolbarBackButton.setVisibility(View.GONE);

        GridAdapter gridAdapter;
        gridAdapter = new GridAdapter(this, R.id.grid_view, tracksFolders);
        gridView.setNumColumns(getResources().getInteger(R.integer.columns_number));
        gridView.setAdapter(gridAdapter);
        FirebaseCrash.log("Activity created");

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Bundle bundle = new Bundle();
                bundle.putSerializable("tracksFolders", tracksFolders);
                bundle.putInt("folderPosition", position);
                Intent intent = new Intent(FoldersGridActivity.this, TracksListActivity.class);
                intent.putExtras(bundle);
                startActivity(intent);
            }
        });

        toolbarLikeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Bundle bundle = new Bundle();
                bundle.putSerializable("tracksFolders", tracksFolders);
                bundle.putInt("activityFrom", Constants.FROM_FOLDERS_GRID_ACTIVITY);
                Intent intent = new Intent(FoldersGridActivity.this, LikedTracksListActivity.class);
                intent.putExtras(bundle);
                startActivity(intent);
            }
        });
    }

    /**
     * Saves tracksFolders array list to rebuild activity after rotation
     */
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        outState.putSerializable("tracksFolders", tracksFolders);
        writeToSharedPreferences(this, tracksFolders);
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        moveTaskToBack(true);
    }

    /**
     * After app is launched need to initialize audio player service
     */
    private void initService() {
        Intent intent = new Intent(FoldersGridActivity.this, AudioPlayerService.class);
        startService(intent);
    }

    /**
     * If tracksFolders is not stored in shared preferences, it is initialized from resources.
     * @return arrayList of folders with arrayList of tracks belonging to every folder
     */
    private ArrayList<TracksFolder> getTracksFolders() {
        Resources resources = getResources();
        TypedArray pictures = resources.obtainTypedArray(R.array.pictures);

        ArrayList<TracksFolder> tracksFolders = new ArrayList<>();
        for (int i = 0; i < foldersName.length; i++) {
            String folderName = foldersName[i];
            int imageResource = pictures.getResourceId(i, -1);
            ArrayList<Track> tracks = getArrayListOfTracks(resources, i, imageResource);
            tracksFolders.add(new TracksFolder(folderName, imageResource, tracks));
        }
        pictures.recycle();
        return tracksFolders;
    }

    /**
     * @param resources      need to get typedArray to get array of audio files names
     * @param folderPosition passed to Track constructor
     * @param imageResource  passed to Track constructor
     *                       Liked tracks are obtained from shared preferences
     * @return array list of tracks for every folder
     */
    private ArrayList<Track> getArrayListOfTracks(Resources resources, int folderPosition, int imageResource) {
        TypedArray audioTracksTypedArray = resources.obtainTypedArray(R.array.audio_tracks);
        int audioTracksId = audioTracksTypedArray.getResourceId(folderPosition, 0);
        String[] audio = resources.getStringArray(audioTracksId);
        audioTracksTypedArray.recycle();

        TypedArray trackNamesTypedArray = resources.obtainTypedArray(R.array.track_names);
        int trackNamesId = trackNamesTypedArray.getResourceId(folderPosition, 0);
        String[] trackNames = resources.getStringArray(trackNamesId);
        trackNamesTypedArray.recycle();

        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());

        ArrayList<Track> tracksInFolder = new ArrayList<>();
         for (int i = 0; i < trackNames.length; i++) {
            int audioResource = resources.getIdentifier(audio[i], "raw", this.getPackageName());
            String trackName = trackNames[i].replace("_", " ");
            boolean isLiked = sharedPreferences.getBoolean(String.valueOf(audioResource), false);
            tracksInFolder.add(new Track(audioResource, trackName, imageResource, isLiked));
        }
        return tracksInFolder;
    }
    //todo убрать полосы в списках треков
}

更新的課程：

@NonNull
    private  ArrayList<TracksFolder> getTracksFoldersAndInitService(Bundle savedInstanceState) {
        if (getIntent().getExtras() != null) { //activity is triggered via on back pressed
            Bundle bundle = getIntent().getExtras();
            tracksFolders = (ArrayList<TracksFolder>) bundle.getSerializable("tracksFolders");
        } else if (savedInstanceState != null) { //this happens after screen is rotated
            tracksFolders = (ArrayList<TracksFolder>) savedInstanceState.getSerializable("tracksFolders");
        } else { //this happens if app is launched by user
            tracksFolders = getTracksFoldersFromResources();
            initService();
        }
        return tracksFolders;
    }

@Nick Fortescue，@ Ranjan，感謝你們兩個的建議，但是tracksFolders絕不會為NULL。 我已經編輯了類（您可以在“更新的類：”下面看到它），並將tracksFolders實例化為帶有@NonNull批注的另一個方法。 我已經使用此更改更新了應用程序，后來又獲得了具有相同日志的相同NPE。 我知道這是在用戶上測試應用程序的最糟糕的方法，但是我別無選擇。 如果您是對的，則日志會說getTracksFoldersAndInitService方法中引發了Exception。 但事實並非如此。 因此，適配器存在問題。 如果我錯了糾正我。

Answer 1

發生在GridAdapter.getCount()中的NullPointerException並不意味着getCount（）返回null。 這意味着它正在訪問一個空值。 由於您上傳了代碼（太好了！），我們可以看到只有兩個可能的問題：

• trackFolders為null ，因此在訪問它時會得到一個NPE
• trackFolders返回一個null Integer，因此當將其轉換為int您會得到一個NPE

第二個選項是不可能的，因為ArrayList上的.size()返回一個int，因此它必須是第一個選項。

trackFolders是在構造函數中設置的，該構造函數是在bundle，保存的狀態或getTracksFolders() onCreate()方法中設置的。 看起來getTracksFolders()無法返回null，因此我的猜測是，您的活動是從將其設置為null的意圖開始的。 我會在您的onCreate（）方法中再次檢查，如果發生這種情況，請采取適當的措施，也許將其替換為new ArrayList() ？