Question

我有recyclerView，我想按字母顺序对项目进行排序。我已使用Collections.sort对列表进行排序，但当我尝试使用notifyDatasetChanged()更新列表时，它会向我显示无法访问的语句。

此问题是否与适配器的范围有关？

这是我的MainActivity：

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        setToolbar();
        mSort = (TextView) findViewById(R.id.sort);
        // mFilter = (TextView)findViewById(R.id.filter);
        mRecyclerView = (RecyclerView) findViewById(R.id.kictstarterRecycler);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        fetchKickStarter(mRecyclerView);
        setClickListner();
    }

    private void setClickListner() {
        mSort.setOnClickListener(this);
        //mFilter.setOnClickListener(this);
    }

    private void setToolbar() {
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);

        final MenuItem searchItem = menu.findItem(R.id.action_search);
        final SearchView searchView = (SearchView) MenuItemCompat.getActionView(searchItem);
        search(searchView);
        return true;
    }

    private void fetchKickStarter(final RecyclerView mRecyclerView) {
        ApiInterface apiService = ApiClient.getClient().create(ApiInterface.class);
        Call<JsonElement> call = apiService.getKickStarter();
        call.enqueue(new Callback<JsonElement>() {
            @Override
            public void onResponse(Call<JsonElement> call, Response<JsonElement> response) {
                Log.d("resonse", response.toString());
                JsonElement object = response.body();
                Type listType = new TypeToken<List<Kickstarter>>() {
                }.getType();
                mKickStarter = new Gson().fromJson(object.getAsJsonArray(), listType);
                mAdapter = new KickstarterAdapter(mKickStarter, R.layout.kickstarter_row_layout, MainActivity.this);
                mRecyclerView.setAdapter(mAdapter);
            }

            @Override
            public void onFailure(Call<JsonElement> call, Throwable t) { }
        });
    }

    @Override
    public void onClick(View view) {
        mSort.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Collections.sort(mKickStarter, new Comparator<Kickstarter>() {
                    @Override
                    public int compare(Kickstarter item1, Kickstarter item2) {
                        return item1.getTitle().compareToIgnoreCase(item2.getTitle());
                        **mAdapter.notifyDataSetChanged()**;
                    }
                });
            }
        });
    }

我很困惑，为什么我无法访问mAdapter。

Answer 1

Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of VALUE_NUMBER_INT token
at [Source: 1 2 3; line: 1, column: 1]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.DeserializationContext.reportMappingException(DeserializationContext.java:1234)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1122)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1075)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.handleNonArray(CollectionDeserializer.java:338)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:269)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:259)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3798)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2842)
at com.sample.Test.main(Test.java:17)

Answer 2

也就是说，你在return语句后调用mAdapter.notifyDataSetChanged()。

返回语句将在该点返回一个值。返回值时，代码执行模式也会路由到值接收方法。

return之后的语句是无法访问的语句。

试试这个

        @Override
        public void onClick(View view) {
            mSort.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Collections.sort(mKickStarter, new Comparator<Kickstarter>() {
                        @Override
                        public int compare(Kickstarter item1, Kickstarter item2) {
                            return item1.getTitle().compareToIgnoreCase(item2.getTitle());
                        }
                    });
                }
                mAdapter.notifyDataSetChanged();
            });
    }

按字母顺序更新RecyclerView项目

2 个答案: