Question

我只是想存储用户输入的值。只是将数据存储在变量中会导致我的应用程序在打开之前立即崩溃。老实说，我不知道为什么会这样。

public class MainActivity extends Activity {


EditText StudentID;
EditText Name1;
EditText CStudy;
EditText Exam1;
EditText Exam2;
EditText Ass2;
EditText ass1;
EditText Examprog2;
Button save;

double studID = 0;
String SavedName = " ";
double CaseStudy = 0;
double Ex1 = 0;
double Ex2 = 0;
double assignment1 = 0;
double assignment2 = 0;
double prog2Exam = 0;

@Override
protected void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.activity_main);

    StudentID = (EditText) findViewById(R.id.StudentID);

    Name1 = (EditText) findViewById(R.id.Name1);
    CStudy = (EditText) findViewById(R.id.CStudy);
    Exam1 = (EditText) findViewById(R.id.Exam1);
    Exam2 = (EditText) findViewById(R.id.Exam2);
    ass1 = (EditText) findViewById(R.id.ass1);
    Ass2 = (EditText) findViewById(R.id.Ass2);
    Examprog2 = (EditText) findViewById(R.id.Examprog2);

    save = (Button) findViewById(R.id.save);

    String SavedName = Name1.getText().toString();
    double CaseStudy = Double.parseDouble(CStudy.getText().toString());
    double Ex1 = Double.parseDouble(Exam1.getText().toString());
    double Ex2 = Double.parseDouble(Exam2.getText().toString());
    double assignment1 = Double.parseDouble(ass1.getText().toString());
    double assignment2 = Double.parseDouble(Ass2.getText().toString());
    double prog2Exam = Double.parseDouble(Examprog2.getText().toString());
}

}

问题似乎在于这段代码

    String SavedName = Name1.getText().toString();
    double CaseStudy = Double.parseDouble(CStudy.getText().toString());
    double Ex1 = Double.parseDouble(Exam1.getText().toString());
    double Ex2 = Double.parseDouble(Exam2.getText().toString());
    double assignment1 = Double.parseDouble(ass1.getText().toString());
    double assignment2 = Double.parseDouble(Ass2.getText().toString());
    double prog2Exam = Double.parseDouble(Examprog2.getText().toString());

Answer 1

您必须将值保存代码放入buttonclick listner

中

       save.setOnClickListner(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
                String SavedName = Name1.getText().toString();
            try {
                double CaseStudy = Double.parseDouble(CStudy.getText().toString());
                double Ex1 = Double.parseDouble(Exam1.getText().toString());
                double Ex2 = Double.parseDouble(Exam2.getText().toString());
                double assignment1 = Double.parseDouble(ass1.getText().toString());
                double assignment2 = Double.parseDouble(Ass2.getText().toString());
                double prog2Exam = Double.parseDouble(Examprog2.getText().toString());
            } catch (NumberFormatException exception) {
                //can't parse
            }
        }
    });

否则，您正在解析null / empty值，然后它可能会抛出异常。

最好用try - catch包装解析代码。因为它可能会抛出NumberFormatException，具体取决于值

Answer 2

在Double.parseDouble(CStudy.getText().toString())我认为，第一次有空值，所以当你试图将null解析为Double时，这就是它崩溃的原因。

所以，你必须检查条件，

if(!CStudy.getText().toString().equals(""))
{
     Double.parseDouble(CStudy.getText().toString())
}

并添加按钮的onClickListener，如下面的代码：

save.setOnClickListner(new View.OnClickListener() {
    public void onClick(View view) {
        String SavedName;
        double CaseStudy, Ex1, Ex2, assignment1,assignment2, prog2Exam;
        if(!Name1.getText().toString().equals(""))
            SavedName = Name1.getText().toString();
        if(!CStudy.getText().toString().equals(""))           
            CaseStudy = Double.parseDouble(CStudy.getText().toString());
        if(!Exam1.getText().toString().equals(""))           
            Ex1 = Double.parseDouble(Exam1.getText().toString());
        if(!Exam2.getText().toString().equals(""))           
            Ex2 = Double.parseDouble(Exam2.getText().toString());
        if(!ass1.getText().toString().equals(""))           
            assignment1 = Double.parseDouble(ass1.getText().toString());
        if(!Ass2.getText().toString().equals(""))           
            assignment2 = Double.parseDouble(Ass2.getText().toString());
        if(!Examprog2.getText().toString().equals(""))           
            prog2Exam = Double.parseDouble(Examprog2.getText().toString());
    }
});

Answer 3

只是将数据存储在变量中会导致我的应用程序在打开之前立即崩溃。

你提到它在打开之前就崩溃了，这意味着那些EditText中没有数据并且你将NULL值设置到变量中，这会导致错误。

Answer 4

即使在用户有机会填充edittext之前，您也在解析值，这将导致nullpointerexception。如果您在用户单击＆＃34; save＆＃34;之后尝试保存值。按钮，尝试以下代码：

save = (Button) findViewById(R.id.save);
save.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            String SavedName = Name1.getText().toString();
            double CaseStudy = Double.parseDouble(CStudy.getText().toString());
            double Ex1 = Double.parseDouble(Exam1.getText().toString());
            double Ex2 = Double.parseDouble(Exam2.getText().toString());
            double assignment1 = Double.parseDouble(ass1.getText().toString());
            double assignment2 = Double.parseDouble(Ass2.getText().toString());
            double prog2Exam = Double.parseDouble(Examprog2.getText().toString());
       };

Answer 5

String SavedName = Name1.getText().toString();
    double CaseStudy = Double.parseDouble(CStudy.getText().toString());
    double Ex1 = Double.parseDouble(Exam1.getText().toString());
    double Ex2 = Double.parseDouble(Exam2.getText().toString());
    double assignment1 = Double.parseDouble(ass1.getText().toString());
    double assignment2 = Double.parseDouble(Ass2.getText().toString());
    double prog2Exam = Double.parseDouble(Examprog2.getText().toString());

此代码不应位于onCreate方法中。只需将此代码放在按钮单击的事件上即可。

Answer 6

正如其他人所指出的，您正在OnCreate事件上编写此代码，该事件在活动初始化时调用。此时EditText值始终为NULL，因此不需要在那里编写代码。您应该将此代码放在保存数据的位置，或者使用按钮单击等数据执行某些操作。

应用程序在尝试存储edittext值时立即崩溃

6 个答案: