对话框没有显示和应用程序崩溃

时间：2015-05-21 00:33:09

标签： java android dialog

我想显示包含动态添加的单选按钮的对话框，然后当用户选择单选按钮并按下OK按钮时，它应该返回该单选按钮的名称。 我已经制作了应用程序，但是当我尝试在手机上运行时应用程序崩溃了？我正在学习本教程，然后将其用于我的工作。 http://www.codeproject.com/Tips/659766/Android-Custom-DialogBox。

代码导致应用崩溃的错误是什么？

MainActivity.java 

public class MainActivity extends ActionBarActivity {

String countryName[] = { "India", "Pakistan", "China", "Nepal", "Bangladesh" };
TextView textDialog;
RadioGroup rg;
Button btn;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    textDialog = (TextView)findViewById(R.id.textView1);
    showCustomDialog(textDialog);
}

public void showCustomDialog(final TextView _textDialog) {
    // TODO Auto-generated method stub

    final Dialog dialog = new Dialog(MainActivity.this);
    dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
    dialog.setContentView(R.layout.activity_main);

    rg = (RadioGroup)findViewById(R.id.radio_group);
    btn = (Button)findViewById(R.id.button);

    final RadioButton[] rb = new RadioButton[countryName.length];
    rg.setOrientation(RadioGroup.VERTICAL);
    for (int i = 0; i < countryName.length; i++) {
        rb[i] = new RadioButton(this);
        rg.addView(rb[i]);
        rb[i].setText(countryName[i]);
    }

    Button button = (Button)dialog.findViewById(R.id.button);    
    button.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            String text = "";

            if(rg.getCheckedRadioButtonId()==-1){
                Toast.makeText(getApplicationContext(), "Please select Gender", Toast.LENGTH_SHORT).show();
            }
            else{
                int selectedId = rg.getCheckedRadioButtonId();
                RadioButton selectedRadioButton = (RadioButton)findViewById(selectedId);
                text = selectedRadioButton.getText().toString();
                Toast.makeText(getApplicationContext(), selectedRadioButton.getText().toString()+" is selected", Toast.LENGTH_SHORT).show();
            }
            _textDialog.setText(text);
            dialog.dismiss();
        }
    });

    dialog.show();
}
}

main.xml中 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
    <TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_marginLeft="18dp"
    android:text="TextView" />
</RelativeLayout>

activity_main.xml中 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" >

<ScrollView 
    android:id="@+id/scrollView"
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content">

    <RadioGroup  
        android:id="@+id/radio_group"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:orientation="horizontal">
    </RadioGroup>
</ScrollView>

<Button
    android:layout_below="@+id/scrollView"
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button" />
</RelativeLayout>

的logcat 

05-21 05:48:06.291: E/AndroidRuntime(14823): FATAL EXCEPTION: main
05-21 05:48:06.291: E/AndroidRuntime(14823): Process: com.example.dialogbox, PID: 14823
05-21 05:48:06.291: E/AndroidRuntime(14823): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.dialogbox/com.example.dialogbox.MainActivity}: java.lang.NullPointerException
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2200)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.ActivityThread.access$800(ActivityThread.java:139)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.os.Handler.dispatchMessage(Handler.java:102)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.os.Looper.loop(Looper.java:136)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.ActivityThread.main(ActivityThread.java:5105)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at java.lang.reflect.Method.invokeNative(Native Method)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at java.lang.reflect.Method.invoke(Method.java:515)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at dalvik.system.NativeStart.main(Native Method)
05-21 05:48:06.291: E/AndroidRuntime(14823): Caused by: java.lang.NullPointerException
05-21 05:48:06.291: E/AndroidRuntime(14823):    at com.example.dialogbox.MainActivity.showCustomDialog(MainActivity.java:42)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at com.example.dialogbox.MainActivity.onCreate(MainActivity.java:28)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.Activity.performCreate(Activity.java:5275)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-21 05:48:06.291: E/AndroidRuntime(14823):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2164)
05-21 05:48:06.291: E/AndroidRuntime(14823):    ... 11 more

2 个答案:

答案 0 :(得分：0)

rg在此行中为空：

rg.setOrientation(RadioGroup.VERTICAL);

这意味着findViewById()无法找到您在此行中设置时传递的ID：

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

如果findViewById()找不到指定的ID，则会返回null，因为您可以阅读in the docs。

这是因为R.id.radio_group位于活动activity_main中，但您却夸大了main：

setContentView(R.layout.main);

因此，您的R.id.radio_group此时无法找到。

答案 1 :(得分：0)

进行这些更改，肯定会有效

我。在onCreate（）之前删除 RadioGroup rg;和Button btn;

II。 将 rg = (RadioGroup)findViewById(R.id.radio_group);替换为final RadioGroup rg = (RadioGroup)dialog.findViewById(R.id.radio_group);

III。 删除 btn = (Button)findViewById(R.id.button);

IV。 将 Button button = (Button)findViewById(R.id.button);替换为Button button = (Button)dialog.findViewById(R.id.button);

诉在其他地方，将 RadioButton selectedRadioButton = (RadioButton)findViewById(selectedId);替换为RadioButton selectedRadioButton = (RadioButton)dialog.findViewById(selectedId);

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