对话框中按钮上的 onclick 侦听器强制关闭应用程序

Question

我有两个按钮显示在我的 android 应用程序中弹出的对话框中。我的问题是我的一个 onclick 监听器的一个按钮工作，而另一个力关闭。

我得到的错误是：

06-28 22:32:51.494: E/AndroidRuntime(29309): FATAL EXCEPTION: main
06-28 22:32:51.494: E/AndroidRuntime(29309): java.lang.NullPointerException
06-28 22:32:51.494: E/AndroidRuntime(29309):    at com.example.beerportfoliopro.TasteTags$2.onClick(TasteTags.java:83)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at android.view.View.performClick(View.java:4102)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at android.view.View$PerformClick.run(View.java:17126)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at android.os.Handler.handleCallback(Handler.java:615)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at android.os.Looper.loop(Looper.java:155)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at android.app.ActivityThread.main(ActivityThread.java:5536)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at java.lang.reflect.Method.invokeNative(Native Method)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at java.lang.reflect.Method.invoke(Method.java:511)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1074)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:841)
06-28 22:32:51.494: E/AndroidRuntime(29309):    at dalvik.system.NativeStart.main(Native Method)

我的启动对话框并处理点击的 java 类是：

public class TasteTags extends Activity {

    BeerData e;
    Dialog dialog = null;


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

        //get beer data
        Intent intent = getIntent();
        Bundle b = intent.getExtras();
        e = b.getParcelable("myBeerObject");

        TextView beerTitle = (TextView) findViewById(R.id.beerTitleTaste);

        beerTitle.setText(e.beerName + " Taste Profile");

        String url = "myURL1";

        url = url + "b=" +e.beerId;

        //async task to get beer taste tag percents
        new GetTasteJSON(this).execute(url);




    }

    public void addTaste(View v){

        // custom dialog
        dialog = new Dialog(this);

        dialog.setContentView(R.layout.add_taste_dialog);

        dialog.setTitle("Add Taste");
        Spinner spinner = (Spinner) dialog.findViewById(R.id.spinner1);


        Spinner spinner2 = (Spinner) dialog.findViewById(R.id.spinner2);

        Button dialogButton = (Button) dialog.findViewById(R.id.cancelButton);
        // if button is clicked, close the custom dialog
        dialogButton.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {

                dialog.dismiss();
            }
        });

        Button dialogButton2 = (Button) dialog.findViewById(R.id.addTasteButton);
        // if button is clicked, close the custom dialog
        dialogButton2.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {

                //get spinner text
                Spinner tasteSpinner = (Spinner)findViewById(R.id.spinner1);
                String tasteText = tasteSpinner.getSelectedItem().toString();

                Spinner ammountSpinner = (Spinner)findViewById(R.id.spinner2);
                String ammountText = ammountSpinner.getSelectedItem().toString();

                int ammount = 0;

                if(ammountText.equals("A Hint")){
                    ammount = 1;
                }

                if(ammountText.equals("Medium")){
                    ammount = 2;
                }

                if(ammountText.equals("Strong")){
                    ammount = 3;
                }

                //construct url
                String url = "myURL";

                String tasteURL = "&tasteNam=" + tasteText ;

                String ammountURL = "&tasteNum=" + ammount;

                String beerURL = "bID=" + e.beerId;


                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(TasteTags.this);
                String userName = prefs.getString("userName", null);
                String userID = prefs.getString("userID", null);

                String userURL = "uID=" + userID;

                url = url + userURL + beerURL + tasteURL + ammountURL;

                //async task to submit tastes
                new UpdateTaste(TasteTags.this, dialog).execute(url);

                dialog.dismiss();
            }
        });

        dialog.show();


    }







}

Answer 1

Spinner tasteSpinner = (Spinner)findViewById(R.id.spinn
Spinner ammountSpinner = (Spinner)findViewById(R.id.spinner2);

如果对话框内的上述微调器意味着将其更改为，

Spinner tasteSpinner = (Spinner) dialog.findViewById(R.id.spinn
Spinner ammountSpinner = (Spinner) dialog.findViewById(R.id.spinner2);

如果你在 spinner2 下面添加微调器初始化会好得多，而不是在按钮点击内部。

Answer 2

你的错误应该在下面几行：

Spinner tasteSpinner = (Spinner)findViewById(R.id.spinner1);
Spinner ammountSpinner = (Spinner)findViewById(R.id.spinner2);

您正在使用对话框微调器，因此您必须使用如下对话框进行初始化：

Spinner tasteSpinner = (Spinner)dialog.findViewById(R.id.spinner1);
Spinner ammountSpinner = (Spinner)dialog.findViewById(R.id.spinner2);

Answer 3

请更改此内容。

String userName = prefs.getString("userName", null);
String userID = prefs.getString("userID", null);

到

 String userName = prefs.getString("userName", "");
 String userID = prefs.getString("userID", "");

如果您在对话框中旋转，则更改。

Spinner tasteSpinner = (Spinner) dialog.findViewById(R.id.spinn
Spinner ammountSpinner = (Spinner) dialog.findViewById(R.id.spinner2);

Answer 4

1. AlertDialog 使用 builder 模式，使用起来更简单。
2. AlertDialog 在按钮按下时关闭，不需要显式调用它。

3. 始终在非空常量上调用equals()，并将另一个对象作为参数传递。

   private void AddTaste(){
     final View v = getLayoutInflater().inflate(R.layout.add_taste_dialog,null);
     final Spinner s1 = (Spinner) v.findViewById(R.id.spinner1);
     final Spinner s2 = (Spinner) v.findViewById(R.id.spinner2);
   
     final  DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
       @Override
       public void onClick(DialogInterface dialogInterface, int i) {
           String taste = String.valueOf(s1.getSelectedItem());
           String amount = String.valueOf(s2.getSelectedItem());
           AcceptTaste(taste,amount);
       }
     };
   
     new AlertDialog.Builder(this)
           .setTitle("Add Taste")
           .setView(v)
           .setNegativeButton("Cancel",null)
           .setPositiveButton("Add Taste",listener)
           .show();
   }
   
   private void AcceptTaste(String taste, String amount){
     int a = 0;
     if("A Hint".equals(amount)){
       a= 1;
     }
   
     //--- more stuff---
   }