这个问题可能是重复的，但是我没有找到关于虚拟问题的虚拟解释。 我现在放弃了，我试图使其正常运行，但似乎可以做到。 您如何处理
问题是我得到
java.lang.NullPointerException：尝试从空数组读取
使用我的transformChoices方法
我知道一些C，但是Java完全不同，我对此一无所知。我仍然很惊讶，在我努力工作以至于没有值之后，某个地方有一个空值。 到目前为止，我的代码很乱，我试图绕过null指针异常。
一些注意事项：如果您有一个更好的主意，请随机调整字符串，让我知道。
另外，如果您有一种经过测试的工作方式可以将2d数组有意传递给其他活动，那也会对我产生影响。目前，我将二维数组转换为一维数组。它可能不是最好的，但是我不必为捆绑包和其他东西而苦恼。我搜索了一种使用Intent和2d数组的方法，但找不到适合我的方法。
请记住，这只是一个原型，数组将具有约1000个值。如果您知道与他们合作的更好更快的方法，请分享。
问题出在这里
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import java.lang.Math;
public class LevelsActivity extends Activity {
private QuestionLibrary mQuestionLibrary = new QuestionLibrary();
int iSize = mQuestionLibrary.mQuestion.length;
private String[] sNewQuestion = new String[iSize];
private String[][] sNewChoice = new String[iSize][4];
private String[] sNewAnswer = new String[iSize];
public String[] sFinalQuestion;
public String[][] sFinalChoice;
public String[] sChoice0;
public String[] sChoice1;
public String[] sChoice2;
public String[] sChoice3;
//public String[] sChoice4;
public String[] sFinalAnswer;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_levels);
for (int i = 0; i < iSize ; i++) {
sNewQuestion[i] = mQuestionLibrary.getQuestion(i);
sNewChoice[i][0] = mQuestionLibrary.getChoice1(i);
sNewChoice[i][1] = mQuestionLibrary.getChoice2(i);
sNewChoice[i][2] = mQuestionLibrary.getChoice3(i);
sNewChoice[i][3] = mQuestionLibrary.getChoice4(i);
//sNewChoice[i][4] =mQuestionLibrary.getChoice5(i);
sNewAnswer[i] = mQuestionLibrary.getCorrectAnswer(i);
}
configureCardiovascularButton();
}
private void configureCardiovascularButton() {
Button mButtonCardiovascular;
mButtonCardiovascular = findViewById(R.id.cadiovascularButton);
//Start CardiovascularButton Listener
mButtonCardiovascular.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int iFrom = 0;
int jTo = 4;
shuffleQuestionsChoicesAnswers(iFrom, jTo);
Intent intent = new Intent(getBaseContext(), MainQuestionsActivity.class);
intent.putExtra("Questions", sFinalQuestion);
intent.putExtra("Answer", sFinalAnswer);
intent.putExtra("Choice0", sChoice0);
intent.putExtra("Choice1", sChoice1);
intent.putExtra("Choice2", sChoice2);
intent.putExtra("Choice3", sChoice3);
//intent.putExtra("Choice4", sChoice4);
startActivity(intent);
}
});
//End CardiovascularButton Listener
}
public void shuffleQuestionsChoicesAnswers(int i, int j) {
String[] sFinalQuestion = new String[j+1];
String[][] sFinalChoice = new String[j+1][4];
String[] sFinalAnswer = new String[j+1];
for (int a = i; a <= j; a++){
sFinalQuestion[a] = "";
sFinalChoice[a][0] = "";
sFinalChoice[a][1] = "";
sFinalChoice[a][2] = "";
sFinalChoice[a][3] = "";
//sFinalChoice[a][4] = "";
sFinalAnswer[a] = "";
}
int range = j - i + 1;
for (int z = i; z <= j/2; z++) {
while (true){
int rand = (int) (Math.random() * range) + i;
if (sFinalQuestion[z] == null){
sFinalQuestion[z] = "";
}
if (sNewQuestion[rand] == null) {
sNewQuestion[rand] = "";
}
if (sFinalChoice[rand][0] == null) {
sFinalChoice[rand][0] = "";
}
if (sFinalChoice[rand][1] == null) {
sFinalChoice[rand][1] = "";
}
if (sFinalChoice[rand][2] == null) {
sFinalChoice[rand][2] = "";
}
if (sFinalChoice[rand][3] == null) {
sFinalChoice[rand][3] = "";
}
//if (sFinalChoice[rand][4] == null) {
// sFinalChoice[rand][4] = "";
//}
if ( (sFinalQuestion[z].length() == 0) && (sNewQuestion[rand].length() != 0) ) {
sFinalQuestion[z] = sNewQuestion[rand];
sNewQuestion[rand] = "";
sFinalChoice[z][0] = sNewChoice[rand][0];
sFinalChoice[z][1] = sNewChoice[rand][1];
sFinalChoice[z][2] = sNewChoice[rand][2];
sFinalChoice[z][3] = sNewChoice[rand][3];
//sFinalChoice[z][4] = sNewChoice[rand][4];
sFinalAnswer[z] = sNewAnswer[rand];
break;
}
}
}
for (int x = j; x > j/2; x--){
for (int y = 0; y < j; y++) {
if (sFinalQuestion[x] == null){
sFinalQuestion[x] = "";
}
if (sNewQuestion[y] == null) {
sNewQuestion[y] = "";
}
if (sFinalQuestion[x].length() == 0 && sNewQuestion[y].length() != 0) {
sFinalQuestion[x] = sNewQuestion[y];
sFinalChoice[x][0] = sNewChoice[y][0];
sFinalChoice[x][1] = sNewChoice[y][1];
sFinalChoice[x][2] = sNewChoice[y][2];
sFinalChoice[x][3] = sNewChoice[y][3];
//sFinalChoice[x][4] = sNewChoice[y][4];
sFinalAnswer[x] = sNewAnswer[y];
}
}
}
transformChoices(i, j);
}
public void transformChoices(int i, int j){
String[] sChoice0 = new String[j];
String[] sChoice1 = new String[j];
String[] sChoice2 = new String[j];
String[] sChoice3 = new String[j];
//String[] sChoice4 = new String[j+1];
for (int a = i; a<=j; a++){
sChoice0[a] = "";
sChoice1[a] = "";
sChoice2[a] = "";
sChoice3[a] = "";
//sChoice4[a] = "";
if (sFinalChoice[a][0]!=null) {
sChoice0[a] = sFinalChoice[a][0];
}
else {
sChoice0[a] = "";
}
if (sFinalChoice[a][1]!=null) {
sChoice1[a] = sFinalChoice[a][1];
}
else {
sChoice1[a]= "";
}
if (sFinalChoice[a][2]!=null) {
sChoice2[a] = sFinalChoice[a][2];
}
else {
sChoice2[a] = "";
}
if (sFinalChoice[a][3]!=null) {
sChoice3[a] = sFinalChoice[a][3];
}
else {
sChoice3[a] = "";
}
//sChoice4[a] = sFinalChoice[a][4];
}
}
}
由于某些原因，看来sFinalChoice为空。由于我的改组方法不好，是否有无人看管的变量可能为空？
如果您需要更多信息，请告诉我，我会添加它。
答案 0 :(得分：1)
您两次声明 sFinalChoice ，一次在类中声明为@ATTRIBUTE，一次在 shuffleQuestionsChoicesAnswers（）中声明为public String[][] sFinalChoice
我假设在 shuffleQuestionsChoicesAnswers（）中，您只想对其进行初始化：
String[][] sFinalChoice = new String[j+1][4]