Question

我认为在尝试添加数据时app会出现制动并显示错误。

public class Employee extends AppCompatActivity {


    EmployeeDatabase dbEmployee;

    EditText editId, editIme, editPrezime, editCena ;
    Button btnDodaj, btnPregledaj;

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

        dbEmployee = new EmployeeDatabase(this);
        editId = (EditText)findViewById(R.id.editId);
        editIme = (EditText)findViewById(R.id.editUserName);
        editPrezime = (EditText)findViewById(R.id.editPrezime);
        editCena = (EditText)findViewById(R.id.editCena);


        addData();  
        viewAll();
    }

    public void addData(){
        btnDodaj.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        boolean isInserted = dbEmployee.insertData(editIme.getText().toString(),
                                editPrezime.getText().toString(),
                                editCena.getText().toString());
                        if (isInserted ==true){
                            Toast.makeText(Employee.this, "Zaposleni je dodat", Toast.LENGTH_SHORT).show();
                        } else{
                            Toast.makeText(Employee.this, "Zaposleni nije dodat", Toast.LENGTH_SHORT).show();
                        }
                    }
                }
        );
    }

    public void viewAll(){
        btnPregledaj.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Cursor res = dbEmployee.getAllData();
                        if (res.getCount() == 0) {
                            //show message
                            showMessage("Error", "Nothing found");
                            return;
                        }
                        StringBuffer buffer = new StringBuffer();
                        while (res.moveToNext()) {
                            buffer.append("id: " + res.getString(0)+"\n");
                            buffer.append("ime: " + res.getString(1)+"\n");
                            buffer.append("prezime: " + res.getString(2)+"\n");
                            buffer.append("cena: " + res.getString(3)+"\n");
                        }

                        // Show all data
                        showMessage("Zaposleni", buffer.toString());
                    }
                }
        );
    }

    public  void showMessage(String title, String message){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(message);
        builder.show();
    }
}

基本上我有一个表单，我填写信息，当按下按钮时，它应该添加到数据库。但是当我点击按钮进入表格时我收到错误，所以我甚至无法填写它并点击添加到数据库。

现在，当我点击添加到数据库时，我收到此错误：

08-31 06:38:21.234 9528-9528/student1.metropolitan.com.cs330_pz E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                  Process: student1.metropolitan.com.cs330_pz, PID: 9528
                                                                                  java.lang.NullPointerException
                                                                                      at student1.metropolitan.com.cs330_pz.Employee$1.onClick(Employee.java:44)
                                                                                      at android.view.View.performClick(View.java:4438)
                                                                                      at android.view.View$PerformClick.run(View.java:18422)
                                                                                      at android.os.Handler.handleCallback(Handler.java:733)
                                                                                      at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                      at android.os.Looper.loop(Looper.java:136)
                                                                                      at android.app.ActivityThread.main(ActivityThread.java:5017)
                                                                                      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:779)
                                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
                                                                                      at dalvik.system.NativeStart.main(Native Method)

Answer 1

好吧，看起来Button btnDodaj, btnPregledaj从未与任何观点相关联。

你为EditTexts正确地做了，就像你在这里做的那样：

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

但你的按钮在哪里？

您的按钮应该与您对EditTexts的操作类似。

btnDodaj = (Button) findViewById(R.id.___);
btnPregledaj = (Button) findViewById(R.id.___);

启动应用程序时出现致命错误

1 个答案: