RadioGroup 检索为空

Question

我尝试检索我的 RADIOGROUP 以检查选中了哪个单选按钮。为此，我在 onCreate() 中使用此代码：

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


    radioGroup_LANGUE = (RadioGroup) findViewById(R.id.RadioGroup_LANGUE);
    radioGroup_MODE = (RadioGroup) findViewById(R.id.RGroup_ModeConnexion);
... }

但是我用debug，AndroidStudio告诉我radioGroup_LANGUE是null。所以我得到 NULLPOINTER EXCEPTION.

在我的警报对话框中，当用户单击“确定”按钮时：

.setNegativeButton("OK", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    // if this button is clicked, just close
                    // the dialog box and do nothing
                    radioGroup_LANGUE.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
                        public void onCheckedChanged(RadioGroup radioGroup_LANGUE, int checkedId) {
                            // This will get the radiobutton that has changed in its check state
                            RadioButton checkedRadioButton = (RadioButton)radioGroup_LANGUE.findViewById(checkedId);

                            // This puts the value (true/false) into the variable
                            boolean isChecked = checkedRadioButton.isChecked();

                            /// If the radiobutton that has changed in check state is now checked...
                            if (isChecked)
                            {
                                // Changes the textview's text to "Checked: example radiobutton text"
                                Toast.makeText(MainActivity.this,"Checked:" + checkedRadioButton.getText(),Toast.LENGTH_LONG).show();
                            }
                     }
                    });
                }});

我的xml：

<RadioGroup
    android:layout_width="148dp"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:id="@+id/RadioGroup_LANGUE">

<RadioButton
        android:layout_width="137dp"
        android:layout_height="wrap_content"
        android:text="@string/Langue_1"
        android:id="@+id/BouttonRADIO_EN"
        android:layout_gravity="center_horizontal"
        android:textSize="20dp"
        android:textStyle="bold" />

<RadioButton
        android:layout_width="137dp"
        android:layout_height="wrap_content"
        android:text="@string/Langue_2"
        android:id="@+id/BouttonRADIO_FR"
        android:layout_gravity="center_horizontal"
        android:textSize="20dp"
        android:textStyle="bold" />

</RadioGroup>

错误日志：

06-01 22:51:53.053 21336-21336/com.example.my020571.sterela2 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.my020571.sterela2, PID: 21336
java.lang.NullPointerException
   at com.example.my020571.sterela2.MainActivity.onClick(MainActivity.java:321)
   at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:170)
   at android.os.Handler.dispatchMessage(Handler.java:102)
   at android.os.Looper.loop(Looper.java:146)
   at android.app.ActivityThread.main(ActivityThread.java:5598)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:515)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
   at dalvik.system.NativeStart.main(Native Method)

第 321 行：

int selectedID = rGroup_LANGUE.getCheckedRadioButtonId();

方法：

private void changerLangue() {

    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
            context);


    final View view = View.inflate(MainActivity.this, R.layout.changer_langue, null);


    alertDialogBuilder.setView(view);



    // Titre de la fenêtre
    alertDialogBuilder.setTitle("Langue");
    // set dialog message
    alertDialogBuilder
            .setMessage("Veuillez choisir votre langue :")
            .setCancelable(false)
            .setIcon(R.drawable.logo_langue)

            .setPositiveButton("ANNULER", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    // if this button is clicked, close
                    // current activity
                    dialog.cancel();
                }
            })
            .setNegativeButton("OK", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    // if this button is clicked, just close
                    // the dialog box and do nothing
                    int selectedID = rGroup_LANGUE.getCheckedRadioButtonId();
                    RadioButton selectedRadioButton = (RadioButton)findViewById(selectedID);
                    Toast.makeText(getApplicationContext(),selectedRadioButton.getText().toString(),Toast.LENGTH_SHORT).show();
                }});


                            // create alert dialog
    AlertDialog alertDialog = alertDialogBuilder.create();

    // show it
    alertDialog.show();
}

Answer 1

如果 onCreate 中没有 setContentView，您的所有视图都将为空。

private void RadioGroup radioGroup_LANGUE;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.YourLayoutFile); // TODO: Replace with your file

    radioGroup_LANGUE = (RadioGroup) findViewById(R.id.RadioGroup_LANGUE);
 }

它们为空的另一个原因是，如果您不使用 setContentView 中包含 @+id/RadioGroup_LANGUE（以及您想要查找的其他 ID）的 XML 文件。

编辑

由于您使用 AlertDialog 来显示视图，因此您需要在展开视图上使用 findViewById 而不是 Activity。

AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(MainActivity.this);

// Get the view for the dialog
final View view = View.inflate(MainActivity.this, R.layout.changer_langue, null);
// Find views within it
rGroup_LANGUE = (RadioGroup) view.findViewById(R.id.RadioGroup_LANGUE);

rGroup_LANGUE.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        RadioButton checkedRadioButton = (RadioButton) group.findViewById(checkedId);

        // TODO: Implement this
}});

// build the dialog
AlertDialog alertDialog = alertDialogBuilder
        .setView(view)      // load the view
        .setTitle("Langue")
        .setMessage("Veuillez choisir votre langue")
        ...
        .setNegativeButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {                
                // Need to use findViewById from the RadioGroup here
                int selectedID = rGroup_LANGUE.getCheckedRadioButtonId();
                String msg = null;
                if (selectedId != -1) {
                    RadioButton selectedRadioButton = (RadioButton)rGroup_LANGUE.findViewById(selectedID);                
                    msg = selectedRadioButton.getText().toString();
                } else {
                    msg = "Nothing selected";
                }
            Toast.makeText(getApplicationContext(),msg,Toast.LENGTH_SHORT).show();
        }})
        .create();

// show it
alertDialog.show();

旁注：我认为 setMessage 和 setView 不能同时使用。

Answer 2

使用自定义对话框尝试此代码：

public void changerLangue(){
        final Dialog mDialog;
        mDialog = new Dialog(MainActivity.this);
        mDialog.setContentView(R.layout.changer_langue);
        Button ok = (Button)mDialog.findViewById(R.id.btn_ok);
        ok.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                RadioGroup yourRadioGroup=(RadioGroup)mDialog.findViewById(R.id.RadioGroup_LANGUE);
                int selectedID = yourRadioGroup.getCheckedRadioButtonId();
                selectedRadioButton = (RadioButton)mDialog.findViewById(selectedID);
                Toast.makeText(getApplicationContext(),selectedRadioButton.getText().toString(),Toast.LENGTH_SHORT).show();
        });

        Button dismiss = (Button)mDialog.findViewById(R.id.btn_dismiss);
        dismiss.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mDialog.dismiss();
            }
        });
        mDialog.show();
    }
}

在您的 changer_langue xml 中添加两个按钮 btn_ok 和 btn_dismiss。它就像魅力一样！干杯

RadioGroup 检索为空

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