我在检查radiobutton内部是否选择了radiogroup之一时遇到问题，我已经尝试了很多类似if(rg.getCheckedRadioButtonId() == -1)的方法，但仍无法在我的代码上使用。
在我的logcat String selectedansText = selectedans.getText().toString();上在这一行中，我的logcat指出了问题，有人可以帮助我吗？
我也尝试过.isChecked，但它不起作用。
bt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
RadioButton selectedans = (RadioButton) findViewById(rg.getCheckedRadioButtonId());
String selectedansText = selectedans.getText().toString();
if (rg.getCheckedRadioButtonId()== -1){
Toast.makeText(grade_four_post_test.this,
"choose answer",
Toast.LENGTH_LONG).show();
} else { //do something }
PS：bt正确声明
01-28 22:27:07.390 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at android.view.View.performClick(View.java:4463)
01-28 22:27:07.391 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at android.view.View$PerformClick.run(View.java:18770)
01-28 22:27:07.391 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at android.os.Handler.handleCallback(Handler.java:808)
01-28 22:27:07.391 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at android.os.Handler.dispatchMessage(Handler.java:103)
01-28 22:27:07.392 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at android.os.Looper.loop(Looper.java:193)
01-28 22:27:07.392 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at android.app.ActivityThread.main(ActivityThread.java:5292)
01-28 22:27:07.392 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at java.lang.reflect.Method.invokeNative(Native Method)
01-28 22:27:07.393 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at java.lang.reflect.Method.invoke(Method.java:515)
01-28 22:27:07.393 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828)
01-28 22:27:07.393 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644)
01-28 22:27:07.394 27612-27612/com.example.computer.mathkiddofinal:second W/System.err: at dalvik.system.NativeStart.main(Native Method)
01-28 22:27:07.394 27612-27612/com.example.computer.mathkiddofinal:second W/dalvikvm: threadid=1: calling UncaughtExceptionHandler
01-28 22:27:07.396 27612-27612/com.example.computer.mathkiddofinal:second E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.computer.mathkiddofinal:second, PID: 27612
java.lang.NullPointerException
at com.example.computer.mathkiddofinal.grade_level.post_test.grade_four_post_test$1.onClick(grade_four_post_test.java:117)
at android.view.View.performClick(View.java:4463)
at android.view.View$PerformClick.run(View.java:18770)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5292)
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:828)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644)
at dalvik.system.NativeStart.main(Native Method)
01-28 22:27:07.400 696-9034/system_process V/Provider/Settings: from settings cache , name = dropbox:data_app_crash , value = null
01-28 22:27:07.401 696-9034/system_process D/dalvikvm: create interp thread : stack size=128KB
01-28 22:27:07.401 696-9034/system_process D/dalvikvm: create new thread
01-28 22:27:07.401 696-9034/system_process D/dalvikvm: new thread created
01-28 22:27:07.401 696-9034/system_process D/dalvikvm: update thread list
01-28 22:27:07.402 696-28496/system_process D/dalvikvm: threadid=79: interp stack at 0x63b53000
01-28 22:27:07.402 696-28496/system_process D/dalvikvm: threadid=79: created from interp
01-28 22:27:07.402 696-9034/system_process D/dalvikvm: start new thread
01-28 22:27:07.402 696-9034/system_process V/Provider/Settings: from settings cache , name = send_action_app_error , value = 1
01-28 22:27:07.402 696-28496/system_process D/dalvikvm: threadid=79: notify debugger
01-28 22:27:07.403 696-9034/system_process W/ActivityManager: Force finishing activity com.example.computer.mathkiddofinal/.grade_level.post_test.grade_four_post_test
您将为此获得NullPointerException：
RadioButton selectedans = (RadioButton) findViewById(rg.getCheckedRadioButtonId());
String selectedansText = selectedans.getText().toString();//NullPointer
因为如果未选择RadioButton，findViewById将不起作用，因此RadioButton未初始化。您应该这样做：
int radioButtonId = rg.getCheckedRadioButtonId();
if(radioButtonId!=-1){
//do Your stuff
RadioButton selectedans = (RadioButton) findViewById(radioButtonId);
String selectedansText = selectedans.getText().toString();
}else{
Toast.makeText(grade_four_post_test.this,
"choose answer",
Toast.LENGTH_LONG).show();
}
@Override
public void onClick(View v) {
// get selected radio button from radioGroup
int selectedId = radioSexGroup.getCheckedRadioButtonId();
// find the radiobutton by returned id
radioSexButton = (RadioButton) findViewById(selectedId);
Toast.makeText(MyAndroidAppActivity.this,
radioSexButton.getText(), Toast.LENGTH_SHORT).show();
//Start your work here
}
});
if(rg.getCheckedRadioButtonId()== -1) this means no radio button is selected.
在其他部分，添加以下行
int selectedId = rg.getCheckedRadioButtonId();
RadioButton selectedans = (RadioButton) findViewById(selectedId);
Toast.makeText(grade_four_post_test.this,selectedans.getText(),Toast.LENGTH_SHORT).show();