Dagger 2：使用@Named获取同一对象的多个实例时出错

我怎么能得到像光标一样的多个相同返回类型的实例

例如 ：-

Module @CursorScope public class CursorModule { @Provides Cursor provideSongCursor( @Named("Song") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, new String[]{ BaseColumns._ID, MediaStore.Audio.AudioColumns.TITLE, MediaStore.Audio.AudioColumns.ARTIST, MediaStore.Audio.AudioColumns.ALBUM, MediaStore.Audio.AudioColumns.DURATION }, MediaStore.Audio.AudioColumns.IS_MUSIC + "=1", null, null); } @Provides Cursor provideAlbumCursor( @Named("Album") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI, new String[]{ BaseColumns._ID, MediaStore.Audio.AlbumColumns.ALBUM, MediaStore.Audio.AlbumColumns.ARTIST, MediaStore.Audio.AlbumColumns.NUMBER_OF_SONGS, MediaStore.Audio.AlbumColumns.FIRST_YEAR }, null, null, null); } @Provides Cursor provideArtistCursor(@Named("Artist") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Artists.EXTERNAL_CONTENT_URI, new String[] { BaseColumns._ID, MediaStore.Audio.ArtistColumns.ARTIST, MediaStore.Audio.ArtistColumns.NUMBER_OF_ALBUMS, MediaStore.Audio.ArtistColumns.NUMBER_OF_TRACKS }, null, null,null); } @Provides Cursor provideGenreCursor( @Named("Genres") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Genres.EXTERNAL_CONTENT_URI, new String[] { BaseColumns._ID, MediaStore.Audio.GenresColumns.NAME }, null, null, null); } @Provides Cursor providePlaylistCursor(@Named("Playlist") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, new String[] { BaseColumns._ID, MediaStore.Audio.PlaylistsColumns.NAME }, null, null, null); } } 

提供的

 @CursorScope @Subcomponent(modules = CursorModule.class) public interface CursorComponent { Cursor cursor(); } 

我收到这个错误

 Error:(17, 11) Gradle: error: android.database.Cursor is bound multiple times: @Provides android.database.Cursor com.merkmod.musician.dependency.CursorModule.provideSongCursor(@Named("Song") com.merkmod.musician.application.Musician) @Provides android.database.Cursor com.merkmod.musician.dependency.CursorModule.provideAlbumCursor(@Named("Album") com.merkmod.musician.application.Musician) @Provides android.database.Cursor com.merkmod.musician.dependency.CursorModule.provideArtistCursor(@Named("Artist") com.merkmod.musician.application.Musician) @Provides android.database.Cursor com.merkmod.musician.dependency.CursorModule.provideGenreCursor(@Named("Genres") com.merkmod.musician.application.Musician) @Provides android.database.Cursor com.merkmod.musician.dependency.CursorModule.providePlaylistCursor(@Named("Playlist") com.merkmod.musician.application.Musician) 

我创建了多个Cursor实例，并在提供程序级别使用@Named进行注释，然后它开始给我错误，无法提供@Provides注释，所以我转而在构造函数中使用它

就像上面的代码一样。 问题是一次又一次地运行一个循环，我就像陷入完成光标的工作一样，任何帮助都会得到应用。

Answer 1

当你想提供一种类型的多个变量时，你必须使用@Named注释，如下所示：

 Module @CursorScope public class CursorModule { @Provides @Named("songCursor") Cursor provideSongCursor( @Named("Song") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, new String[]{ BaseColumns._ID, MediaStore.Audio.AudioColumns.TITLE, MediaStore.Audio.AudioColumns.ARTIST, MediaStore.Audio.AudioColumns.ALBUM, MediaStore.Audio.AudioColumns.DURATION }, MediaStore.Audio.AudioColumns.IS_MUSIC + "=1", null, null); } @Provides @Named("albumCursor") Cursor provideAlbumCursor( @Named("Album") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI, new String[]{ BaseColumns._ID, MediaStore.Audio.AlbumColumns.ALBUM, MediaStore.Audio.AlbumColumns.ARTIST, MediaStore.Audio.AlbumColumns.NUMBER_OF_SONGS, MediaStore.Audio.AlbumColumns.FIRST_YEAR }, null, null, null); } @Provides @Named("artistCursor") Cursor provideArtistCursor(@Named("Artist") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Artists.EXTERNAL_CONTENT_URI, new String[] { BaseColumns._ID, MediaStore.Audio.ArtistColumns.ARTIST, MediaStore.Audio.ArtistColumns.NUMBER_OF_ALBUMS, MediaStore.Audio.ArtistColumns.NUMBER_OF_TRACKS }, null, null,null); } @Provides @Named("genreCursor") Cursor provideGenreCursor( @Named("Genres") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Genres.EXTERNAL_CONTENT_URI, new String[] { BaseColumns._ID, MediaStore.Audio.GenresColumns.NAME }, null, null, null); } @Provides @Named("playListCursor") Cursor providePlaylistCursor(@Named("Playlist") Musician musician) { return musician.getApplicationContext().getContentResolver().query(MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, new String[] { BaseColumns._ID, MediaStore.Audio.PlaylistsColumns.NAME }, null, null, null); } } 

那么当你想要像下面这样注入时：

 @Inject @Named("soundCursor") Cursor soundCursor; @Inject @Named("albumCursor") Cursor albumCursor; @Inject @Named("artistCursor") Cursor artistCursor; @Inject @Named("genreCursor") Cursor genreCursor; @Inject @Named("playListCursor") Cursor playListCursor; 

如果你想在构造函数注射中注射它们，请执行以下操作：

 @Inject public SomeClassConstructor(@Named("album") Cursor cursur) 

以及你在子组件界面中写的内容我无法得到它是什么，它必须像：

 @CursorScope @Subcomponent(modules = CursorModule.class) public interface CursorComponent { void inject(TheClassThatWantsToUseInject1 obj); void inject(TheClassThatWantsToUseInject2 obj); } 

在您的应用程序组件中：

  YourSubComponentInterface plus(CursorModule module); 

Answer 2

所以最后我得到了我自己的问题的答案，它是组件本身，你知道软件开发是如此繁忙，当你退出cigerrates时它也变得更加负担。

所以上面所有的都是一个简单的方法，我用sharepreference做了一个不同的例子，因为我的lappy在archlinux上崩溃了。

所以这里是我生成的代码的片段。

所以我唯一应该做的就是我应该从组件接口中删除游标注入参数。

然而，片段可能会帮助人们。

零件 ：-

 @Singleton @Component(modules = {MusicianModule.class, SharedPreferencesModule.class}) public interface MusicianComponent { void inject(MainActivity mainActivity); Musician musician(); } 

模块： –

 @Module public class SharedPreferencesModule { @Provides @Named("default") SharedPreferences provideDefaultsharedPreferences(Musician musician) { return musician.getSharedPreferences("default", Context.MODE_PRIVATE); } @Provides @Named("secret") SharedPreferences provideSecretsharedPreferences(Musician musician) { return musician.getSharedPreferences("secret", Context.MODE_PRIVATE); } } 

音乐家模块： –

 @Module public class MusicianModule { private Musician musician; public MusicianModule(Musician musician) { this.musician = musician; } @Provides @Singleton Musician providemusician() { return musician; } @Provides @Singleton Application provideapplication(Musician musician) { return musician; } } 

申请类： –

 public class Musician extends Application { private MusicianComponent musicianComponent; @Override public void onCreate() { resolvedependency(); super.onCreate(); } private void resolvedependency() { musicianComponent = DaggerMusicianComponent.builder() .musicianModule(new MusicianModule(this)) .sharedPreferencesModule(new SharedPreferencesModule()) .build(); } public static MusicianComponent getMusicianComponent(Context context) { return ((Musician)context.getApplicationContext()).musicianComponent; } } 

并且MainActivity注入： –

 public class MainActivity extends AppCompatActivity { /** * The {@link android.support.v4.view.PagerAdapter} that will provide * fragments for each of the sections. We use a * {@link FragmentPagerAdapter} derivative, which will keep every * loaded fragment in memory. If this becomes too memory intensive, it * may be best to switch to a * {@link android.support.v4.app.FragmentStatePagerAdapter}. */ private SectionsPagerAdapter mSectionsPagerAdapter; /** * The {@link ViewPager} that will host the section contents. */ private ViewPager mViewPager; @Inject @Named("default") SharedPreferences defSharedPreferences; @Inject @Named("secret") SharedPreferences secSharedPreferences; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Musician.getMusicianComponent(this).inject(this); Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); setSupportActionBar(toolbar); // Create the adapter that will return a fragment for each of the three // primary sections of the activity. mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager()); defSharedPreferences.edit().putString("status", "worked").apply(); secSharedPreferences.edit().putString("status", "worked").apply(); // Set up the ViewPager with the sections adapter. mViewPager = (ViewPager) findViewById(R.id.container); mViewPager.setAdapter(mSectionsPagerAdapter); TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs); tabLayout.setupWithViewPager(mViewPager); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.menu_main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); //noinspection SimplifiableIfStatement if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } /** * A placeholder fragment containing a simple view. */ public static class PlaceholderFragment extends Fragment { /** * The fragment argument representing the section number for this * fragment. */ private static final String ARG_SECTION_NUMBER = "section_number"; public PlaceholderFragment() { } /** * Returns a new instance of this fragment for the given section * number. */ public static PlaceholderFragment newInstance(int sectionNumber) { PlaceholderFragment fragment = new PlaceholderFragment(); Bundle args = new Bundle(); args.putInt(ARG_SECTION_NUMBER, sectionNumber); fragment.setArguments(args); return fragment; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_song, container, false); TextView textView = (TextView) rootView.findViewById(R.id.section_label); textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER))); return rootView; } } /** * A {@link FragmentPagerAdapter} that returns a fragment corresponding to * one of the sections/tabs/pages. */ public class SectionsPagerAdapter extends FragmentPagerAdapter { public SectionsPagerAdapter(FragmentManager fm) { super(fm); } @Override public Fragment getItem(int position) { // getItem is called to instantiate the fragment for the given page. // Return a PlaceholderFragment (defined as a static inner class below). return PlaceholderFragment.newInstance(position + 1); } @Override public int getCount() { // Show 3 total pages. return 3; } @Override public CharSequence getPageTitle(int position) { switch (position) { case 0: return "SECTION 1"; case 1: return "SECTION 2"; case 2: return "SECTION 3"; } return null; } }