android - 微调器看起来不合适

Question

我的 Activity 上有一个 Spinner。我使用 ArrayList 和自定义 SpinnerAdapter 来填充按下 Spinner 时弹出的列表。

我的问题是 Spinner 在未按下时在 Activity 上的显示方式。全是灰色的。没有文字可见。即使在我按下微调器然后从结果列表中选择一个项目后，微调器也不会填充文本。

此外，当我从微调器中选择一个项目然后打印所选项目的位置时，它会打印 -1。许多人评论说我的微调器没有附加数据列表，但显然有。我还能如何按下微调器，然后从结果列表中进行选择？

        // This sets up the adapter and the arraylist that contains the data
            private void setUpAdapter() {
                mData = new ArrayList<MyData>();
                mAdapter = new MyAdapter(mData);
                mSpinner.setAdapter(mAdapter);

                mSpinner.setOnItemSelectedListener(new Spinner.OnItemSelectedListener() {
                    public void onItemSelected(AdapterView<?> parent,
                            View view, int pos, long id) {
                            MyData g = (MyData) parent.getItemAtPosition(pos);
                            // TODO
                        }

                        public void onNothingSelected(AdapterView parent) {
                          // Do nothing.
                        }
                });
            }


    // this populates the arraylist that is attached to the spinner's adapter
// it is called once an AsyncTask finishes pulling data from a local database
            private void populateSpinner(ArrayList<MyData> result) {
                if (result != null) {
                    if (mData == null) {
                        mData = new ArrayList<MyData>();
                    }
                    else {
                        mData.clear();
                    }

                    for (int index = 0; index < result.size(); index++) {
                        mData.add(result.get(index));
                    }

                    mSpinner.setSelected(0);
                }
            }




    // this is the adapter for the spinner
            private class MyAdapter implements SpinnerAdapter {

                ArrayList<MyData> data;

                public MyAdapter(ArrayList<MyData> data){
                    this.data = data;
                }

                @Override
                public int getCount() {
                    return data.size();
                }

                @Override
                public Object getItem(int position) {
                    return data.get(position);
                }

                @Override
                public long getItemId(int position) {
                    return position;
                }

                @Override
                public int getItemViewType(int position) {
                    return android.R.layout.simple_spinner_dropdown_item;
                }

                @Override
                public View getView(int position, View convertView, ViewGroup parent) {
                    TextView v = new TextView(getApplicationContext());
                    v.setTextColor(Color.BLACK);
                    v.setText(data.get(position).getName());
                    v.setPadding(0, 20, 0, 20);
                    return v;
                }

                @Override
                public int getViewTypeCount() {
                    return 1;
                }

                @Override
                public boolean hasStableIds() {
                    return false;
                }

                @Override
                public boolean isEmpty() {
                    return false;
                }

                @Override
                public void registerDataSetObserver(DataSetObserver observer) {
                    // TODO Auto-generated method stub
                }

                @Override
                public void unregisterDataSetObserver(DataSetObserver observer) {
                    // TODO Auto-generated method stub
                }

                @Override
                public View getDropDownView(int position, View convertView, ViewGroup parent) {
                    return this.getView(position, convertView, parent);
                }
            }


<Spinner
    android:id="@+id/my_spinner"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" />

Answer 1

When I select an item from the Spinner and then print the selected item position, it prints -1

这是因为您正在引用BLANK 列表

mData = new ArrayList<MyData>();
mAdapter = new MyAdapter(mData);
mSpinner.setAdapter(mAdapter);

在 AsynTask 的 onPostExecute() 中设置微调适配器。

@Override
protected void onPreExecute() {
        mData = new ArrayList<MyData>();
        super.onPreExecute();
}

@Override
protected Void doInBackground(String... params) {
        //gets "result" to fill mData
        return null;
}

@Override
protected void onPostExecute(Void result) {
    setUpAdapter();
}


private void setUpAdapter() {
    if (result != null) {
          if (mData == null) {
                 mData = new ArrayList<MyData>();
           }
           else {
                 mData.clear();
           }

           for (int index = 0; index < result.size(); index++) {
                 mData.add(result.get(index));
           }

            mAdapter = new MyAdapter(mData);
            mSpinner.setAdapter(mAdapter);
            mSpinner.setSelected(0);

            mSpinner.setOnItemSelectedListener(new Spinner.OnItemSelectedListener() {
                public void onItemSelected(AdapterView<?> parent,
                        View view, int pos, long id) {
                        MyData g = (MyData) parent.getItemAtPosition(pos);
                        // TODO
                    }

                    public void onNothingSelected(AdapterView parent) {
                      // Do nothing.
                    }
            });
        }