Question

这是我的Spinner代码，它将我的SQL数据库中的员工姓名作为对象加载并在屏幕上显示：

private void loadNames() {
    //database handler
    LysandrosDatabaseAdapter db = new LysandrosDatabaseAdapter(getApplicationContext());

    List<DataBean> list = db.getAllDat();

    //list for storing the names
    String[] nameList = new String[list.size()];
    //list for storing the ID and keeping it hidden
    employeeList = new int[list.size()];
    //loop to fill the list

    nameList[0] = "All Employees";
    employeeList[0] = 0;
    for (int i=0; i<list.size(); i++) {
        nameList[i+1] = list.get(i).getName() + " " + list.get(i).getSurname();
        employeeList[i+1] = list.get(i).getID();
    }
    //creating adapter for spinner
    ArrayAdapter<String > dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, nameList);
    //drop down layout style - list view with radio button
    dataAdapter.setDropDownViewResource(android.R.layout.select_dialog_multichoice);
    //attaching data adapter to spinner
    selectName.setAdapter(dataAdapter);
}

我正在尝试将“All Employees”文本作为第一个选项包含在内，因为我想实现一个If语句，当用户选择“所有员工”选项时，该应用程序将获取某些特定数据，当用户选择特定员工时，例如“John Smith”应用程序将仅为该记录获取数据。

上面的代码段是我到目前为止所得到的，我收到ArrayIndexOutOfBoundsException错误。

我的LogCat显示了这个：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lysandroslysandrou.marstest4/com.example.lysandroslysandrou.marstest4.Reports}: java.lang.ArrayIndexOutOfBoundsException: length=5; index=5
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
        at android.app.ActivityThread.access$800(ActivityThread.java:144)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: java.lang.ArrayIndexOutOfBoundsException: length=5; index=5
        at com.example.lysandroslysandrou.marstest4.Reports.loadNames(Reports.java:147)
        at com.example.lysandroslysandrou.marstest4.Reports.onCreate(Reports.java:78)

第147行是nameList[i+1] = list.get(i).getName() + " " + list.get(i).getSurname();

我尝试了很多其他方法，但都没有。从我的数据库加载保存为“所有员工”的值也不是一个可行的解决方案。

我正在寻找两件事：

A）为什么我特别在我的情况下会收到此错误？（我已经读过这个例外here和here，但无法理解为什么会发生这种情况）

和 B）我的问题有解决方案吗？

注意：如果删除了行nameList[0] = "All Employees和employeeList[0] = "0"，则代码段正常。

编辑：我的新堆栈跟踪：

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
        at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
        at android.widget.ArrayAdapter.getDropDownView(ArrayAdapter.java:415)
        at android.support.v7.widget.AppCompatSpinner$DropDownAdapter.getDropDownView(AppCompatSpinner.java:624)
        at android.support.v7.widget.AppCompatSpinner$DropDownAdapter.getView(AppCompatSpinner.java:620)
        at android.support.v7.widget.AppCompatSpinner.compatMeasureContentWidth(AppCompatSpinner.java:547)
        at android.support.v7.widget.AppCompatSpinner.access$500(AppCompatSpinner.java:65)
        at android.support.v7.widget.AppCompatSpinner$DropdownPopup.computeContentWidth(AppCompatSpinner.java:738)
        at android.support.v7.widget.AppCompatSpinner$DropdownPopup.show(AppCompatSpinner.java:763)
        at android.support.v7.widget.AppCompatSpinner.performClick(AppCompatSpinner.java:424)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

编辑2：这是我的onItemSelected方法：

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    //On selecting a spinner item
    String list = parent.getItemAtPosition(position).toString();
    //employeeId = employeeList[position];
    //showing selected spinner item
    Toast.makeText(parent.getContext(), "You selected: " + list, Toast.LENGTH_SHORT).show();
}

Answer 1

您需要更改

//list for storing the names
String[] nameList = new String[list.size()];
//list for storing the ID and keeping it hidden
employeeList = new int[list.size()];

到

//list for storing the names
String[] nameList = new String[list.size() + 1];
//list for storing the ID and keeping it hidden
employeeList = new int[list.size() + 1];

因为您需要为第一个“所有员工”元素分配一个项目。

当您尝试访问namesList[i + 1]元素时i == list.size() - 1，i + 1 == list.size()时，您会得到一个解释。例如，当您仅使用namesList[5]

分配0..4个元素时，请访问String[] nameList = new String[list.size()];

我评论了几行，因为我没有你的db。但以下代码对我来说很好：

private void loadSpinner(Spinner spinner, ArrayList<Integer> items) {
    //list for storing the names
    String[] nameList = new String[items.size() + 1];
    //list for storing the ID and keeping it hidden
    //employeeList = new int[list.size()];
    //loop to fill the list

    nameList[0] = "All Employees";
    //employeeList[0] = 0;
    for (int i = 0; i < items.size(); i++) {
        nameList[i + 1] = String.valueOf(i);
    }
    //creating adapter for spinner
    ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(getContext(), android.R.layout.simple_spinner_item, nameList);
    //drop down layout style - list view with radio button
    dataAdapter.setDropDownViewResource(android.R.layout.select_dialog_multichoice);
    //attaching data adapter to spinner
    spinner.setAdapter(dataAdapter);
}

使用对象和字符串加载微调器

1 个答案: