Question

我是初学者所以请耐心等待。我创建了一个带有微调器的应用程序，用于控制编辑文本的可见性。当我运行此应用程序时，catch语句捕获空点异常，并且不使用我的字符串数组填充微调器。有什么想法或帮助吗？

这是我的代码

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        try {

        player1.findViewById(R.id.editTextPlayer1);
        player2.findViewById(R.id.editTextPlayer2);
        player3.findViewById(R.id.editTextPlayer3);
        player4.findViewById(R.id.editTextPlayer4);
        player5.findViewById(R.id.editTextPlayer5);
        player6.findViewById(R.id.editTextPlayer6);
        player7.findViewById(R.id.editTextPlayer7);
        player8.findViewById(R.id.editTextPlayer8);

        Spinner spinner = (Spinner)findViewById(R.id.spinnerplayers);

        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
                this, R.array.peoplearray, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);

        spinner.setOnItemSelectedListener(this);
        }catch (Exception e) {

            // handle any errors

            Log.e("TestActivity", "Error in activity", e);  // log the error

            // Also let the user know something went wrong

            Toast.makeText(getApplicationContext(), e.getClass().getName() + " " + e.getMessage(),Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public void onItemSelected(AdapterView<?> arg0, View arg1, int pos,
            long id) {
            numberOfPlayers = pos + 2;

        switch(pos){
        case 0:
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            break;
        case 1:
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            player3.setVisibility(View.VISIBLE);
            break;
        case 2:
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            player3.setVisibility(View.VISIBLE);
            player4.setVisibility(View.VISIBLE);
            break;
        case 3:         
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            player3.setVisibility(View.VISIBLE);
            player4.setVisibility(View.VISIBLE);
            player5.setVisibility(View.VISIBLE);
            break;
        case 4:
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            player3.setVisibility(View.VISIBLE);
            player4.setVisibility(View.VISIBLE);
            player5.setVisibility(View.VISIBLE);
            player6.setVisibility(View.VISIBLE);
            break;
        case 5:
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            player3.setVisibility(View.VISIBLE);
            player4.setVisibility(View.VISIBLE);
            player5.setVisibility(View.VISIBLE);
            player6.setVisibility(View.VISIBLE);
            player7.setVisibility(View.VISIBLE);
            break;
        case 6:
            player1.setVisibility(View.VISIBLE);
            player2.setVisibility(View.VISIBLE);
            player3.setVisibility(View.VISIBLE);
            player4.setVisibility(View.VISIBLE);
            player5.setVisibility(View.VISIBLE);
            player6.setVisibility(View.VISIBLE);
            player7.setVisibility(View.VISIBLE);
            player8.setVisibility(View.VISIBLE);
            break;
        }

    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0) {
    }

这是logcat错误：

06-05 15:10:03.986: E/TestActivity(1815): Error in activity
06-05 15:10:03.986: E/TestActivity(1815): java.lang.NullPointerException
06-05 15:10:03.986: E/TestActivity(1815):   at com.brightdesign.truthordare.Main.onCreate(Main.java:42)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.Activity.performCreate(Activity.java:4465)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.ActivityThread.access$600(ActivityThread.java:123)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
06-05 15:10:03.986: E/TestActivity(1815):   at android.os.Handler.dispatchMessage(Handler.java:99)
06-05 15:10:03.986: E/TestActivity(1815):   at android.os.Looper.loop(Looper.java:137)
06-05 15:10:03.986: E/TestActivity(1815):   at android.app.ActivityThread.main(ActivityThread.java:4424)
06-05 15:10:03.986: E/TestActivity(1815):   at java.lang.reflect.Method.invokeNative(Native Method)
06-05 15:10:03.986: E/TestActivity(1815):   at java.lang.reflect.Method.invoke(Method.java:511)
06-05 15:10:03.986: E/TestActivity(1815):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-05 15:10:03.986: E/TestActivity(1815):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-05 15:10:03.986: E/TestActivity(1815):   at dalvik.system.NativeStart.main(Native Method)

Answer 1

<强>替换

    Spinner spinner = (Spinner)findViewById(R.id.spinnerplayers);  
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
            this, R.array.peoplearray, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);

通过此

    Spinner spinner = (Spinner)findViewById(R.id.spinnerplayers);
    ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,android.R.layout.simple_spinner_dropdown_item, getResources().getStringArray(R.array.peoplearray))
    spinner.setAdapter(adapter);

Answer 2

确保您在此声明中未获得null。

Spinner spinner = (Spinner)findViewById(R.id.spinnerplayers);

您可以清理项目，然后再次重建。它可能会解决您的问题。

Android Spinner抛出Java.lang.nullpointerexception - Android初学者

2 个答案: