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私のアプリケーションでは、特定の操作を計算するために2 つのAutoCompleteTextViewと aがあります。両方が満たされている場合にのみ が表示されるという意味で、レスポンシブを 2 つにButton設定しています。ButtonAutoCompleteTextViewAutoCompleteTextViewButton

これを行うと、Null Pointer Exceptionが発生します。プログラムは次のとおりです。

boolean isLocation=false;
boolean isDestination=false;

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        location=(AutoCompleteTextView)findViewById(R.id.locale);
        location.setAdapter(new PlacesAutoCompleteAdapter(this, R.layout.list_item));
        location.setOnItemClickListener(new OnItemClickListener()

    {

    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
            // TODO Auto-generated method stub
            place1 = (Places) adapterView.getItemAtPosition(position);
            location.setText(place1.description);
            location.clearFocus();
            destination.requestFocus();
            Log.d("AutoCompleteTask", location.getText().toString());
                }
    });

    location.addTextChangedListener(new TextWatcher()
    {

        @Override
        public void afterTextChanged(Editable arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
            // TODO Auto-generated method stub
            fillLocation=true;
        }

    });


    destination = (AutoCompleteTextView)findViewById(R.id.destination);
    destination.setAdapter(new PlacesAutoCompleteAdapter(this, R.layout.list_item));
    destination.setOnItemClickListener(new OnItemClickListener() 
    {

    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                // TODO Auto-generated method stub
            place2 = (Places) adapterView.getItemAtPosition(position);
            destination.setText(place2.description);
            destination.clearFocus();
            calculate.requestFocus();               
            Log.d("AutoCompleteTask2", destination.getText().toString());
                }
    });

    destination.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            // TODO Auto-generated method stub

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable s) {
            // TODO Auto-generated method stub
            fillDestination=true;
        }
    });

    if(fillLocation==true || fillDestination==true )
    {
        calculate.setVisibility(View.VISIBLE);
    }
    else
    {
        calculate.setVisibility(View.INVISIBLE);
    }


    calculate = (Button)findViewById(R.id.calculate);
    calculate.setOnClickListener(new View.OnClickListener() {



            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

            if(location.getText().toString().length()<1 || destination.getText().toString().length()<1) 
            {
                Toast.makeText(getApplicationContext(), "Give values before placing a query", Toast.LENGTH_LONG).show();
            }
            else{
                @SuppressWarnings("deprecation")
                String url = "http://maps.googleapis.com/maps/api/distancematrix/json?origins="+URLEncoder.encode(location.getText().toString())+"&destinations="+URLEncoder.encode(destination.getText().toString())+"&unit=metric&mode=driving&sensor=false";
                new ReadDistanceJSONFeedTask().execute(url);
                }
            }
        });

アプリの開発は初めてですが、このNull Pointer Exceptionとは何ですか? 誰か助けてくれませんか？

4

3 に答える 3

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あなたはNPEこれのために得ています:-

if(fillLocation==true || fillDestination==true )
{
    calculate.setVisibility(View.VISIBLE); // NPE here
}
else
{
    calculate.setVisibility(View.INVISIBLE); // NPE here
}
calculate = (Button)findViewById(R.id.calculate);

初期化する前であっても、計算ボタンの可視性を設定しようとしました。ブロックcalculate = (Button)findViewById(R.id.calculate);の上に移動すると、動作するはずです。if-else

于 2013-04-10T03:49:37.440 に答える