我正在以测验的形式开发这个简单的应用程序，用户可以获得问题和4个选项。这些问题是从SQLite DB中提取的。在我的succ.java活动中，我显示问题以及点击下一个按钮获取下一个问题。
现在当它在模拟器上运行时，如果我不选择任何4个单选按钮，我的应用程序最终会停止，我必须强行关闭。为了解决这个问题，我想在我的succ.java页面中检查如果所选择的选项都没有从具有相同问题ID的db中获取问题，并且如果我选择了其中任何一个，则使用下一个问题ID获取问题。
但它仍然行不通，我已经尽了一切可能做到的。我附上了我的succ.java。还有logcat。
succ.java
public class succ extends Activity {
private static String[] response = new String[10];
RadioButton op1,op2,op3,op4;
private int token_page;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainquespage);
int qno=0;
String ques="";
String ans1="";
String ans2="";
String ans3="";
String ans4="";
//int token=0;
Bundle extras=getIntent().getExtras();
//token=extras.getInt("SESS_ID");
ques=extras.getString("KEY_QUES");
ans1=extras.getString("KEY_ANS1");
ans2=extras.getString("KEY_ANS2");
ans3=extras.getString("KEY_ANS3");
ans4=extras.getString("KEY_ANS4");
qno=extras.getInt("KEY_ID");
token_page=qno+1;
TextView quesnumber=(TextView)findViewById(R.id.quesIDTEXT);
quesnumber.setText("QUESTION: "+ qno );
TextView quescont=(TextView)findViewById(R.id.quesContText);
quescont.setText(ques);
TextView opt1=(TextView)findViewById(R.id.op1Text);
opt1.setText(ans1);
TextView opt2=(TextView)findViewById(R.id.op2Text);
opt2.setText(ans2);
TextView opt3=(TextView)findViewById(R.id.op3Text);
opt3.setText(ans3);
TextView opt4=(TextView)findViewById(R.id.op4Text);
opt4.setText(ans4);
}
public void onRadioButtonClicked(View view) {
op1 = (RadioButton) findViewById(R.id.op1Text);
op2 = (RadioButton) findViewById(R.id.op2Text);
op3 = (RadioButton) findViewById(R.id.op3Text);
op4 = (RadioButton) findViewById(R.id.op4Text);
if(op1.isChecked())
{
response[token_page-2]=op1.getText().toString();
}
else if(op2.isChecked()){
response[token_page-2]=op2.getText().toString();
}
else if(op3.isChecked()){
response[token_page-2]=op3.getText().toString();
}
else if(op4.isChecked()){
response[token_page-2]=op4.getText().toString();
}
else
response[token_page-2]="";
}
public void nextClick(View view)
{
final Context context=this;
Question question=new Question();
MyAdapter questionAdapter=new MyAdapter(this);
if(token_page!=11)
{
questionAdapter.open();
if(op1.isChecked()||op2.isChecked()||op3.isChecked()||op4.isChecked())
{
question=questionAdapter.showQues(token_page);
}
else
{
question=questionAdapter.showQues(token_page-1);
}
//please note when i'm just writing: question=questionAdapter.showQues(token_page) //without checking for the selection of radio buttons i get the error i the end after the //last question is answered but when i'm checking it here and using if els then am getting //an error on the same screen. i'm stuck on this since forever. HELP !!
questionAdapter.close();
int qno;
String ques;
String ans1;
String ans2;
String ans3;
String ans4;
qno=question.getQno();
ques=question.getQues();
ans1=question.getAns1();
ans2=question.getAns2();
ans3=question.getAns3();
ans4=question.getAns4();
Intent intent=new Intent(context, succ.class);
intent.putExtra("KEY_ID", qno);
intent.putExtra("KEY_QUES",ques);
intent.putExtra("KEY_ANS1",ans1);
intent.putExtra("KEY_ANS2",ans2);
intent.putExtra("KEY_ANS3",ans3);
intent.putExtra("KEY_ANS4",ans4);
startActivity(intent);
}//token_page
else
{
Toast.makeText(this, "FINISHED", Toast.LENGTH_LONG).show();
Bundle b=new Bundle();
b.putStringArray("ARRAY", response);
Intent i=new Intent(context, result.class);
i.putExtras(b);
startActivity(i);
}
}
}
logcat的
06-26 11:26:48.401: D/opendb(357): EXIST
06-26 11:26:52.321: W/KeyCharacterMap(357): No keyboard for id 0
06-26 11:26:52.321: W/KeyCharacterMap(357): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
06-26 11:26:53.781: D/dalvikvm(357): GC_EXTERNAL_ALLOC freed 122K, 51% free 2699K/5447K, external 2128K/2137K, paused 63ms
06-26 11:26:59.923: W/KeyCharacterMap(357): No keyboard for id 0
06-26 11:26:59.923: W/KeyCharacterMap(357): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
06-26 11:29:49.512: D/opendb(478): EXIST
06-26 11:29:58.981: D/AndroidRuntime(478): Shutting down VM
06-26 11:29:58.981: W/dalvikvm(478): threadid=1: thread exiting with uncaught exception (group=0x40015560)
06-26 11:29:59.011: E/AndroidRuntime(478): FATAL EXCEPTION: main
06-26 11:29:59.011: E/AndroidRuntime(478): java.lang.IllegalStateException: Could not execute method of the activity
06-26 11:29:59.011: E/AndroidRuntime(478): at android.view.View$1.onClick(View.java:2144)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.view.View.performClick(View.java:2485)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.view.View$PerformClick.run(View.java:9080)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.os.Handler.handleCallback(Handler.java:587)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.os.Handler.dispatchMessage(Handler.java:92)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.os.Looper.loop(Looper.java:123)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.app.ActivityThread.main(ActivityThread.java:3683)
06-26 11:29:59.011: E/AndroidRuntime(478): at java.lang.reflect.Method.invokeNative(Native Method)
06-26 11:29:59.011: E/AndroidRuntime(478): at java.lang.reflect.Method.invoke(Method.java:507)
06-26 11:29:59.011: E/AndroidRuntime(478): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-26 11:29:59.011: E/AndroidRuntime(478): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-26 11:29:59.011: E/AndroidRuntime(478): at dalvik.system.NativeStart.main(Native Method)
06-26 11:29:59.011: E/AndroidRuntime(478): Caused by: java.lang.reflect.InvocationTargetException
06-26 11:29:59.011: E/AndroidRuntime(478): at java.lang.reflect.Method.invokeNative(Native Method)
06-26 11:29:59.011: E/AndroidRuntime(478): at java.lang.reflect.Method.invoke(Method.java:507)
06-26 11:29:59.011: E/AndroidRuntime(478): at android.view.View$1.onClick(View.java:2139)
06-26 11:29:59.011: E/AndroidRuntime(478): ... 11 more
06-26 11:29:59.011: E/AndroidRuntime(478): Caused by: java.lang.NullPointerException
06-26 11:29:59.011: E/AndroidRuntime(478): at my.pkg.newquiz.succ.nextClick(succ.java:98)
06-26 11:29:59.011: E/AndroidRuntime(478): ... 14 more
06-26 11:30:02.821: I/Process(478): Sending signal. PID: 478 SIG: 9
答案 0 :(得分：1)
如果我不选择任何4个单选按钮，我的应用程序最终会停止 我必须强行关闭。
根据您的代码，它正在按预期发生。
你正在做的最大的错误就是你在检查它们时正在初始化你的单选按钮。下面是你写的一个片段。
public void onRadioButtonClicked(View view) {
op1 = (RadioButton) findViewById(R.id.op1Text);
op2 = (RadioButton) findViewById(R.id.op2Text);
op3 = (RadioButton) findViewById(R.id.op3Text);
op4 = (RadioButton) findViewById(R.id.op4Text);
因此，如果情况是你没有选择任何单选按钮也不会被初始化，然后如果点击下一个按钮，你显然会得到NPE。
if(op1.isChecked()||op2.isChecked()||op3.isChecked()||op4.isChecked())
{
question=questionAdapter.showQues(token_page);
}
因此解决方法是在onCreate中初始化所有单选按钮。
以下是经过修改的代码段。
public class succ extends Activity {
private static String[] response = new String[10];
RadioButton op1,op2,op3,op4;
private int token_page;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainquespage);
op1 = (RadioButton) findViewById(R.id.op1Text);
op2 = (RadioButton) findViewById(R.id.op2Text);
op3 = (RadioButton) findViewById(R.id.op3Text);
op4 = (RadioButton) findViewById(R.id.op4Text);
int qno=0;
String ques="";
String ans1="";
String ans2="";
String ans3="";
String ans4="";
//int token=0;
Bundle extras=getIntent().getExtras();
//token=extras.getInt("SESS_ID");
ques=extras.getString("KEY_QUES");
ans1=extras.getString("KEY_ANS1");
ans2=extras.getString("KEY_ANS2");
ans3=extras.getString("KEY_ANS3");
ans4=extras.getString("KEY_ANS4");
qno=extras.getInt("KEY_ID");
token_page=qno+1;
TextView quesnumber=(TextView)findViewById(R.id.quesIDTEXT);
quesnumber.setText("QUESTION: "+ qno );
TextView quescont=(TextView)findViewById(R.id.quesContText);
quescont.setText(ques);
TextView opt1=(TextView)findViewById(R.id.op1Text);
opt1.setText(ans1);
TextView opt2=(TextView)findViewById(R.id.op2Text);
opt2.setText(ans2);
TextView opt3=(TextView)findViewById(R.id.op3Text);
opt3.setText(ans3);
TextView opt4=(TextView)findViewById(R.id.op4Text);
opt4.setText(ans4);
}
public void onRadioButtonClicked(View view) {
if(op1.isChecked())
{
response[token_page-2]=op1.getText().toString();
}
else if(op2.isChecked()){
response[token_page-2]=op2.getText().toString();
}
else if(op3.isChecked()){
response[token_page-2]=op3.getText().toString();
}
else if(op4.isChecked()){
response[token_page-2]=op4.getText().toString();
}
else
response[token_page-2]="";
}
public void nextClick(View view)
{
final Context context=this;
Question question=new Question();
MyAdapter questionAdapter=new MyAdapter(this);
if(token_page!=11)
{
questionAdapter.open();
if(op1.isChecked()||op2.isChecked()||op3.isChecked()||op4.isChecked())
{
question=questionAdapter.showQues(token_page);
}
else
{
question=questionAdapter.showQues(token_page-1);
}
//please note when i'm just writing: question=questionAdapter.showQues(token_page) //without checking for the selection of radio buttons i get the error i the end after the //last question is answered but when i'm checking it here and using if els then am getting //an error on the same screen. i'm stuck on this since forever. HELP !!
questionAdapter.close();
int qno;
String ques;
String ans1;
String ans2;
String ans3;
String ans4;
qno=question.getQno();
ques=question.getQues();
ans1=question.getAns1();
ans2=question.getAns2();
ans3=question.getAns3();
ans4=question.getAns4();
Intent intent=new Intent(context, succ.class);
intent.putExtra("KEY_ID", qno);
intent.putExtra("KEY_QUES",ques);
intent.putExtra("KEY_ANS1",ans1);
intent.putExtra("KEY_ANS2",ans2);
intent.putExtra("KEY_ANS3",ans3);
intent.putExtra("KEY_ANS4",ans4);
startActivity(intent);
}//token_page
else
{
Toast.makeText(this, "FINISHED", Toast.LENGTH_LONG).show();
Bundle b=new Bundle();
b.putStringArray("ARRAY", response);
Intent i=new Intent(context, result.class);
i.putExtras(b);
startActivity(i);
}
}
}