android - 尝试在空对象引用上调用虚拟方法 'java.lang.CharSequence android.widget.TextView.getText()'

Question

我得到这个空异常:

java.lang.NullPointerException:尝试在空对象引用上调用虚方法“java.lang.CharSequence android.widget.TextView.getText()”

我也不知道为什么。

protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setTheme(R.style.LoginRegister);
        setContentView(R.layout.activity_report);

final TextView infoid = (TextView) findViewById(R.id.idInfo);

        RadioGroup rg = (RadioGroup)findViewById(R.id.rg);
        final String radiovalue = ((RadioButton)findViewById(rg.getCheckedRadioButtonId())).getText().toString();

...

        Button sendButton = (Button) findViewById(R.id.button2);
        sendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String text = infoid.getText().toString(); //what is wrong?
                Log.w("message: ", radiovalue);
            }
        });


}

我的xml

   <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/idInfo"
        android:hint="Add some extra information"
        android:layout_weight="0.09"
        android:layout_marginTop="20dp"
        android:layout_marginBottom="20dp" />

    <Button
        android:text="Report"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/button2" />

有什么想法吗？

Answer 1

1. 确保 TextView idInfo 存在于您的 activity_report.xml

2. 尝试将 idInfo 声明为全局。

   ..............
   ....................
   
   TextView infoid;
   
   protected void onCreate(Bundle savedInstanceState) {
   
       super.onCreate(savedInstanceState);   
       setContentView(R.layout.activity_report);
   
       infoid = (TextView) findViewById(R.id.idInfo);
   
       .............
       ...................
   
       Button sendButton = (Button) findViewById(R.id.button2);
       sendButton.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View view) {
               String text = infoid.getText().toString();
               ..........
               .................
           }
       });
   
   }
   

更新:

获取选中的radioButton文本:

RadioGroup radioGroup = (RadioGroup)findViewById(R.id.rg);

// get selected radioButton from radioGroup
int selectedId = radioGroup.getCheckedRadioButtonId();

// find the radioButton by returned id
radioButton = (RadioButton) findViewById(selectedId);

// radioButton text
String radiovalue = radioButton.getText();

希望对你有帮助~