Android Content provider

manifest配置provider

 <provider
            android:name="CatProvider"
            android:authorities="com.zeolite.contentprovider.data.Cat"
            android:exported="true" />

继承content provider

public class CatProvider extends ContentProvider {

    public static final String AUTHORITY = "com.zeolite.contentprovider.data.Cat";
    private static final UriMatcher uriMatcher;

    private static final int QUERY = 1;
    private static final int INSERT = 1;

    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(AUTHORITY, "query", QUERY);
        uriMatcher.addURI(AUTHORITY, "insert", INSERT);
    }

    @Override
    public boolean onCreate() {
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] strings, @Nullable String s, @Nullable String[] strings1, @Nullable String s1) {
        if (uriMatcher.match(uri) == QUERY)
            return CatDataBase.getInstance(getContext()).catDao().query();
        return null;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues contentValues) {
        if (uriMatcher.match(uri) == INSERT) {
            if (contentValues.get("name") != null && contentValues.get("color") != null)
                CatDataBase.getInstance(getContext()).catDao().add(new Cat(String.valueOf(contentValues.get("name")),
                        String.valueOf(contentValues.get("color"))));
        }
        return null;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String s, @Nullable String[] strings) {
    //省略...
        return 0;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues contentValues, @Nullable String s, @Nullable String[] strings) {
   //省略...
        return 0;
    }
}

数据库实体

@Entity
public class Cat {

    @PrimaryKey(autoGenerate = true)
    private long id;
    @ColumnInfo(name = "name")
    private String name;
    @ColumnInfo(name = "color")
    private String color;

    public Cat(String name, String color) {
        this.name = name;
        this.color = color;
    }
}

数据库操作

@Dao
public interface CatDao {

    @Query("SELECT * FROM CAT")
    Cursor query();

    @Insert
    void add(Cat cat);

    @Delete
    void delete(Cat cat);

    @Update
    void update(Cat cat);
}

数据库初始化

@Database(entities = {Cat.class}, version = 1)
public abstract class CatDataBase extends RoomDatabase {

    private static CatDataBase instance;


    public abstract CatDao catDao();

    private static CatDataBase buildDataBase(Context context) {
        return Room.databaseBuilder(context.getApplicationContext(),
                CatDataBase.class, "cats.db")
                .allowMainThreadQueries()
                .build();
    }

    public static CatDataBase getInstance(Context context) {
        if (instance == null) {
            synchronized (CatDataBase.class) {
                if (instance == null)
                    return buildDataBase(context);
            }
        }
        return instance;
    }
}

ContentResolver通过Uri查询数据

ContentResolver contentResolver = getContentResolver();
       Uri uri = Uri.parse("content://com.zeolite.contentprovider.data.Cat/query");
       Cursor cursor = contentResolver.query(uri, null, null, null, null);
       while (cursor.moveToNext()) {
           Log.d("name", cursor.getString(cursor.getColumnIndex("name")));
       }