java - 根据选择 ArrayIndexOutOfBoundsException 填充 Spinner

Question

我使用相同的字符串数组将数据填充到两个微调器中，如下所示:

String[] arrayMonths = { "January", "Feburary", "March", "April", "May",
        "June", "July", "August", "September", "October", "November","December" };

adapter = new ArrayAdapter<String>(MainActivity.this, 
            android.R.layout.simple_spinner_item, arrayMonths);

spinner1.setAdapter(adapter);
spinner2.setAdapter(adapter);

现在，我希望每当我在 spinner1 中进行选择时，就像我选择了 August 然后将 September 显示为 spinner2 中的初始值(以及删除 spinner2 中的所有前几个月。

以同样的方式，如果我在 spinner1 中选择了 October，则 spinner2 开始为 November

        spinner1.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> parent, View view,
                    int position, long id) {
                // TODO Auto-generated method stub
                Toast.makeText(getApplicationContext(),
                        spinner1.getItemAtPosition(position).toString(), Toast.LENGTH_LONG)
                        .show();
            }

更新 - 根据@AMY 的建议

    public class MainActivity extends AppCompatActivity {

    Spinner spinner1, spinner2;
    ArrayAdapter<String> adapter;   

    String newArr[];

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

        spinner1 = (Spinner) findViewById(R.id.spinner1);
        spinner2 = (Spinner) findViewById(R.id.spinner2);

        final String[] arrayMonths = { "January", "Feburary", "March", "April", "May",
        "June", "July", "August", "September", "October", "November","December" };

        newArr = new String[] {"January", "Feburary", "March", "April", "May",
                "June", "July", "August", "September", "October", "November","December"};

        adapter = new ArrayAdapter<String> (MainActivity.this, 
                android.R.layout.simple_spinner_item, arrayMonths);

        spinner1.setAdapter(adapter);

        spinner1.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> parent, View view,
                    int position, long id) {
                // TODO Auto-generated method stub
                Toast.makeText(getApplicationContext(),
                        spinner1.getItemAtPosition(position).toString(), Toast.LENGTH_LONG)
                        .show();

                newArr = new String[arrayMonths.length-1];
                System.arraycopy(arrayMonths , position, newArr , 0, arrayMonths.length);
                adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_item, newArr);
                spinner2.setAdapter(adapter);
                adapter.notifyDataSetChanged();

            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {
                // TODO Auto-generated method stub

            }
        });

    }
}

获取异常: ArrayIndexOutOfBoundsException

 java.lang.ArrayIndexOutOfBoundsException: src.length=12 srcPos=0 dst.length=11 dstPos=0 length=12

Answer 1

这些行的代码中的问题:

newArr = new String[arrayMonths.length]; 
System.arraycopy(arrayMonths, position, newArr, 0, arrayMonths.length);

您需要将数组大小定义为arrayMonths.length - (selected_position+1)。

此外，检查方法arraycopy 的签名:

src : the source array to copy the content.

srcPos : the starting index of the content in src.

dst : the destination array to copy the data into.

dstPos : the starting index for the copied content in dst.

length : the number of elements to be copied.

因此，您需要将要复制的元素的长度更改为arrayMonths.length-selected_position。

代码 fragment

int nextPosition = position + 1;
int newSize= arrayMonths.length-nextPosition ;
newArr = new String[newSize]; 
System.arraycopy(arrayMonths, nextPosition , newArr, 0, newSize);

希望对你有帮助ツ