添加具有来自 json 的数据的 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没有显示要做什么的迹象 selected.Some 回答建议使用 prompt

 <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.How can i set something like hint or related to so that user can understand what spinner is all about even the moment app is off line. Below is my code snipe from here

    @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

首先将你的后腿添加到 ArrayList 0 索引中，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

更新此代码，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
                    }
                });
    }
}

添加具有来自 json 的数据的 Spinner Hint

Add Spinner Hint that has data from json

android

json

spinner

android-spinner