添加具有来自 json 数据的 Spinner Hint

Question

我从 json 数据填充微调器，我想设置提示，以便用户可以理解必须选择的内容，因为当没有互联网连接时微调器显示没有选择的迹象。一些答案建议使用提示

 <Spinner
    android:layout_width="match_parent"
    android:id="@+id/spinner"
    android:prompt="@string/country_prompt"
    />

和其他人建议使用微调器的最后一个索引作为提示，如here。我如何设置提示或相关的内容，以便用户即使在应用程序离线时也能理解微调器的全部含义.下面是我从here 截取的代码

    @Override
    protected Void doInBackground(Void... params) {
        // Locate the WorldPopulation Class 
        world = new ArrayList<WorldPopulation>();
        // Create an array to populate the spinner 
        worldlist = new ArrayList<String>();
        // JSON file URL address
        jsonobject = JSONfunctions
                .getJSONfromURL("http://www.androidbegin.com/tutorial/jsonparsetutorial.txt");

        try {
            // Locate the NodeList name
            jsonarray = jsonobject.getJSONArray("worldpopulation");
            for (int i = 0; i < jsonarray.length(); i++) {
                jsonobject = jsonarray.getJSONObject(i);

                WorldPopulation worldpop = new WorldPopulation();

                worldpop.setRank(jsonobject.optString("rank"));
                worldpop.setCountry(jsonobject.optString("country"));
                worldpop.setPopulation(jsonobject.optString("population"));
                worldpop.setFlag(jsonobject.optString("flag"));
                world.add(worldpop);

                // Populate spinner with country names
                worldlist.add(jsonobject.optString("country"));

            }
        } catch (Exception e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void args) {
        // Locate the spinner in activity_main.xml
        Spinner mySpinner = (Spinner) findViewById(R.id.my_spinner);

        // Spinner adapter
        mySpinner
                .setAdapter(new ArrayAdapter<String>(MainActivity.this,
                        android.R.layout.simple_spinner_dropdown_item,
                        worldlist));

        // Spinner on item click listener
        mySpinner
                .setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

                    @Override
                    public void onItemSelected(AdapterView<?> arg0,
                            View arg1, int position, long arg3) {
                        // TODO Auto-generated method stub
                        // Locate the textviews in activity_main.xml
                        TextView txtrank = (TextView) findViewById(R.id.rank);
                        TextView txtcountry = (TextView) findViewById(R.id.country);
                        TextView txtpopulation = (TextView) findViewById(R.id.population);

                        // Set the text followed by the position 
                        txtrank.setText("Rank : "
                                + world.get(position).getRank());
                        txtcountry.setText("Country : "
                                + world.get(position).getCountry());
                        txtpopulation.setText("Population : "
                                + world.get(position).getPopulation());
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> arg0) {
                        // TODO Auto-generated method stub
                    }
                });
    }
}

Answer 1

首先在 ArrayList 0 索引中添加你的后，它将被显示：

    worldlist = new ArrayList<String>();
    worldlist.add("Your first hint");

对于最后一个提示，在 for 循环之后添加您的提示：

try{
    for(......){

  }
  worldlist.add("Your last hint");
 }catch(Exception e){ }

Answer 2

@Override
protected void onPostExecute(Void args) {
    // Locate the spinner in activity_main.xml
    Spinner mySpinner = (Spinner) findViewById(R.id.my_spinner);

//add a check if worldlist is empty. Initialize it where you have declared it.
if(!worldlist.size() > 0){
    worldlist.add(“select country”);
}

// Spinner adapter
mySpinner.setAdapter(new ArrayAdapter<String>(MainActivity.this,
        android.R.layout.simple_spinner_dropdown_item, worldlist));

//your rest of the code here. . . 

}

Answer 3

试试这个

    @Override
        protected Void doInBackground(Void... params) {
            // Locate the WorldPopulation Class 
            world = new ArrayList<WorldPopulation>();
            // Create an array to populate the spinner 
            worldlist = new ArrayList<String>();
            worldlist.add("Selct Country");
            // JSON file URL address
            jsonobject = JSONfunctions
                    .getJSONfromURL("http://www.androidbegin.com/tutorial/jsonparsetutorial.txt");

            try {
                // Locate the NodeList name
                jsonarray = jsonobject.getJSONArray("worldpopulation");
                for (int i = 0; i < jsonarray.length(); i++) {
                    jsonobject = jsonarray.getJSONObject(i);

                    WorldPopulation worldpop = new WorldPopulation();

                    worldpop.setRank(jsonobject.optString("rank"));
                    worldpop.setCountry(jsonobject.optString("country"));
                    worldpop.setPopulation(jsonobject.optString("population"));
                    worldpop.setFlag(jsonobject.optString("flag"));
                    world.add(worldpop);

                    // Populate spinner with country names
                    worldlist.add(jsonobject.optString("country"));

                }
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return null;
        }

@Override
    protected void onPostExecute(Void args) {
        // Locate the spinner in activity_main.xml
        Spinner mySpinner = (Spinner) findViewById(R.id.my_spinner);

        // Spinner adapter
        mySpinner
                .setAdapter(new ArrayAdapter<String>(MainActivity.this,
                        android.R.layout.simple_spinner_dropdown_item,
                        worldlist));

        // Spinner on item click listener
        mySpinner
                .setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

                    @Override
                    public void onItemSelected(AdapterView<?> arg0,
                            View arg1, int position, long arg3) {
                        // TODO Auto-generated method stub
                        // Locate the textviews in activity_main.xml
                        if(position > 0){
                        TextView txtrank = (TextView) findViewById(R.id.rank);
                        TextView txtcountry = (TextView) findViewById(R.id.country);
                        TextView txtpopulation = (TextView) findViewById(R.id.population);

                        // Set the text followed by the position 
                        txtrank.setText("Rank : "
                                + world.get(position).getRank());
                        txtcountry.setText("Country : "
                                + world.get(position).getCountry());
                        txtpopulation.setText("Population : "
                                + world.get(position).getPopulation());
                            }
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> arg0) {
                        // TODO Auto-generated method stub
                    }
                });
    }
}

Answer 4

使用此代码更新，在数组 0 位置添加提示。

@Override
    protected Void doInBackground(Void... params) {
        // Locate the WorldPopulation Class 
        world = new ArrayList<WorldPopulation>();
        // Create an array to populate the spinner 
        worldlist = new ArrayList<String>();
        worldlist.add(0,"your hint");
        // JSON file URL address
        jsonobject = JSONfunctions
                .getJSONfromURL("http://www.androidbegin.com/tutorial/jsonparsetutorial.txt");

        try {
            // Locate the NodeList name
            jsonarray = jsonobject.getJSONArray("worldpopulation");
            for (int i = 0; i < jsonarray.length(); i++) {
                jsonobject = jsonarray.getJSONObject(i);

                WorldPopulation worldpop = new WorldPopulation();

                worldpop.setRank(jsonobject.optString("rank"));
                worldpop.setCountry(jsonobject.optString("country"));
                worldpop.setPopulation(jsonobject.optString("population"));
                worldpop.setFlag(jsonobject.optString("flag"));
                world.add(worldpop);

                // Populate spinner with country names
                worldlist.add(jsonobject.optString("country"));

            }
        } catch (Exception e) {
            Log.e("Error", e.getMessage());
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void args) {
        // Locate the spinner in activity_main.xml
        Spinner mySpinner = (Spinner) findViewById(R.id.my_spinner);

        // Spinner adapter
        mySpinner
                .setAdapter(new ArrayAdapter<String>(MainActivity.this,
                        android.R.layout.simple_spinner_dropdown_item,
                        worldlist));

        // Spinner on item click listener
        mySpinner
                .setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

                    @Override
                    public void onItemSelected(AdapterView<?> arg0,
                            View arg1, int position, long arg3) {
                        // TODO Auto-generated method stub
                        // Locate the textviews in activity_main.xml
                        TextView txtrank = (TextView) findViewById(R.id.rank);
                        TextView txtcountry = (TextView) findViewById(R.id.country);
                        TextView txtpopulation = (TextView) findViewById(R.id.population);

                        // Set the text followed by the position 
                        txtrank.setText("Rank : "
                                + world.get(position).getRank());
                        txtcountry.setText("Country : "
                                + world.get(position).getCountry());
                        txtpopulation.setText("Population : "
                                + world.get(position).getPopulation());
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> arg0) {
                        // TODO Auto-generated method stub
                    }
                });
    }
}