java - 如何在android studio中调用另一个方法中的许多方法

Question

我正在 Android Studio 上创建一个测验应用程序。我需要在用户提交时显示带有用户分数的 toast 。我想在submitOnClick 方法内部调用calculateScore 方法，但calculateScore 方法会使应用程序崩溃。

如果我在提交中调用calculateScore，应用程序就会崩溃，如果我在onClick 上调用它，应用程序就会崩溃。

我的代码:

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

        final Button button = findViewById(R.id.submit);
        button.setOnClickListener(submitOnClick);

    }

    final View.OnClickListener submitOnClick = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            calculateScore();

            Toast.makeText(MainActivity.this, "Your score is " + score, Toast.LENGTH_LONG).show();
        }
    };

        public void checkQuestion1(View view) {
            boolean checked = ((RadioButton) view).isChecked();

            // Check which radio button was clicked
            switch (view.getId()) {
                case R.id.right:
                    if (checked)
                        score += 1;
                    break;
                case R.id.wrong:
                    if (checked)
                        score += 0;
                    break;
            }

        }

        public void checkQuestion2(View view) {

            CheckBox function = findViewById(R.id.checkbox_function);
            CheckBox undefined = findViewById(R.id.checkbox_undefined);
            CheckBox booleans = findViewById(R.id.checkbox_booleans);

            boolean isCheckedFunction = function.isChecked();
            boolean isCheckedUndefined = undefined.isChecked();
            boolean isCheckedBooleans = booleans.isChecked();

            if (isCheckedUndefined && isCheckedBooleans && !isCheckedFunction) {
                score += 1;
            } else {
                score += 0;
            }

        }

        public void checkQuestion3(View view) {

            EditText userInput = findViewById(R.id.inputAnswer);
            String name = userInput.getText().toString();

            if (name.trim().equalsIgnoreCase("Class")) {
                score += 1;
            } else {
                score += 0;
            }
        }

        public void checkQuestion4(View view) {
            boolean checked = ((RadioButton) view).isChecked();
            switch (view.getId()) {
                case R.id.correct:
                    if (checked)
                        score += 1;
                    break;
                case R.id.incorrect:
                    if (checked)
                        score += 0;
                    break;
            }

        }

        public void checkQuestion5(View view) {

            CheckBox correctOne = findViewById(R.id.checkbox_correct_one);
            CheckBox correctTwo = findViewById(R.id.checkbox_correct_two);
            CheckBox incorrectOne = findViewById(R.id.checkbox_incorrect_one);
            CheckBox incorrectTwo = findViewById(R.id.checkbox_incorrect_two);
            boolean isCheckedCorrectOne = correctOne.isChecked();
            boolean isCheckedCorrectTwo = correctTwo.isChecked();
            boolean isCheckedIncorrectOne = incorrectOne.isChecked();
            boolean isCheckedIncorrectTwo = incorrectTwo.isChecked();

            if (isCheckedCorrectOne && isCheckedCorrectTwo && !isCheckedIncorrectOne & !isCheckedIncorrectTwo) {
                score += 1;
            } else {
                score += 0 ;
            }

        }


        public void calculateScore(){
            checkQuestion2(null);
            checkQuestion1(null );
            checkQuestion3(null);
            checkQuestion4(null);
            checkQuestion5(null);
        }

日志猫: --------- 崩溃开始

2019-11-04 10:09:57.514 11886-11886/com.example.android.quizzapp E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.android.quizzapp, PID: 11886 java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.widget.CompoundButton.isChecked()' on a null object reference at com.example.android.quizzapp.MainActivity.checkQuestion1(MainActivity.java:39) at com.example.android.quizzapp.MainActivity.calculateScore(MainActivity.java:122) at com.example.android.quizzapp.MainActivity$1.onClick(MainActivity.java:32) at android.view.View.performClick(View.java:5610) at android.view.View$PerformClick.run(View.java:22265) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6077) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

Answer 1

你打电话

checkQuestion1(null )

使用null，所以它会因NPE而崩溃