java - 使用注释在空对象引用上设置文本

Question

它不重复，没有 ANDROIDANNOTATIONS 的同一个应用程序工作正常。

由于使用 AndroidAnnotations Framework 修改项目，我的应用程序已停止工作。在我看来，一切看起来都很好，AndroidStudio 中没有任何警告，直到在手机上运行时，应用程序出现错误:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.annotationstest/com.example.annotationstest.MainActivity_}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

我应该修复或添加什么到代码中？

主要 Activity

 @EActivity(R.layout.activity_main)
    public class MainActivity extends AppCompatActivity implements CompoundButton.OnCheckedChangeListener {

        private static final String SHARED_PREFS_NAME = "abc";
        public static final int REQUEST_CODE = 100;
        private int number;

        @ViewById(R.id.tv2)
        TextView tv2;

        @ViewById(R.id.tv3)
        TextView tv3;

        @ViewById(R.id.switch1)
        Switch switch1;


        @Click
        void b1() {
            Intent intent = new Intent(MainActivity.this, Main2Activity.class);
            startActivityForResult(intent, REQUEST_CODE);
        }


        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            SharedPreferences preferences = getSharedPreferences(SHARED_PREFS_NAME, MODE_PRIVATE);
            number = preferences.getInt("NUMBER", 0);
            tv2.setText(""+number);
            switch1.setOnCheckedChangeListener(this);

        }

        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {
            super.onActivityResult(requestCode, resultCode, data);
            if (resultCode == RESULT_OK) {
                if (requestCode == REQUEST_CODE) {
                    number = data.getExtras().getInt("number");
                    tv2.setText("" + number);
                    saveNumberToSharedPrefs(number);

                }
            }
        }

        private void saveNumberToSharedPrefs(int num) {
            SharedPreferences preferences = getSharedPreferences(SHARED_PREFS_NAME, MODE_PRIVATE); 
            preferences.edit().putInt("NUMBER", num).apply(); 
        }

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            switch (buttonView.getId()) {
                case R.id.switch1:
                    if (isChecked == true) {
                        tv3.setVisibility(View.VISIBLE);
                    } else {
                        tv3.setVisibility(View.INVISIBLE);
                    }
                    break;
            }

        }
    }

Answer 1

根据文档， View 可能尚未注入(inject)到 onCreate() 方法中(请参阅 here ):

When onCreate() is called, @ViewById fields are not set yet. Therefore, you can use @AfterViews on methods to write code that depends on views.

也就是说，您应该将代码从 onCreate() 移至新方法，并使用 @AfterViews 进行注释