带动态列表的数字选择器

Question

我一直在使用动态列表实现 numpicker，即，在某些事件上发生变化，比如可能是按钮单击或其他。问题是，每当我将列表从较大长度切换到较小长度时，它都可以工作，从较小长度切换到较大长度时它不会改变，虽然我总是将第一个项目设置为选定项目，但它会崩溃。

代码：

public class MainActivity extends Activity {
    NumberPicker numPicker = null;
    String values1[]    =   null;

    String values2[]    =   null;

    String values3[]    =   null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        values1 =new String []{
                "Yello",
                "Red",
                "White",
                "Green",
                "Black"
        };
        values2 =new String []{
                "Mango",
                "Orange"
        };
        values3 =new String []{
                "Class",
                "Pointer",
                "Function",
                "Interafce",
                "Constructor"
        };



        numPicker = (NumberPicker)findViewById(R.id.numberPicker1);
        numPicker.setDisplayedValues(values1);

        if(values1.length>1)
        {
            numPicker.setMaxValue(values1.length-1);
        }
        else
        {
            numPicker.setMaxValue(values1.length);          
        }
        numPicker.setMinValue(0);   
        numPicker.setValue(0);
        numPicker.setBackgroundColor(1);
        numPicker.setWrapSelectorWheel(false);
        numPicker.setDescendantFocusability(NumberPicker.FOCUS_BLOCK_DESCENDANTS);


        //On value change listner for changing values

        /*      //For Tint Values
        numPicker.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
            @Override
            public void onValueChange(NumberPicker numPic, int arg1, int arg2) {
                numPickerNewVal = values[numPic.getValue()].trim();

                tintTemp = getSelectedTintValue(numPickerNewVal);


            }
        });*/



    }
    public void onClick(View v)
    {
        switch(v.getId())
        {
        case R.id.button1:
            
            if(values1.length>1)
            {
                numPicker.setMaxValue(values1.length-1);
            }
            else
            {
                numPicker.setMaxValue(values1.length);          
            }
            numPicker.setMinValue(0);   
            numPicker.setValue(0);
            numPicker.setDisplayedValues(values1);
            break;
        case R.id.button2:
            
            if(values2.length>1)
            {
                numPicker.setMaxValue(values2.length-1);
            }
            else
            {
                numPicker.setMaxValue(values2.length);          
            }
            numPicker.setMinValue(0);   
            numPicker.setValue(0);
            numPicker.setDisplayedValues(values2);
            break;
        case R.id.button3:
            
            if(values3.length>1)
            {
                numPicker.setMaxValue(values3.length-1);
            }
            else
            {
                numPicker.setMaxValue(values3.length);          
            }
            numPicker.setMinValue(0);   
            numPicker.setValue(0);
            numPicker.setDisplayedValues(values3);
            break;
        }
    }

}

Logcat：

06-20 13:02:16.712: E/AndroidRuntime(16793): FATAL EXCEPTION: main
06-20 13:02:16.712: E/AndroidRuntime(16793): java.lang.IllegalStateException: Could not execute method of the activity
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.view.View$1.onClick(View.java:3606)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.view.View.performClick(View.java:4211)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.view.View$PerformClick.run(View.java:17446)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.os.Handler.handleCallback(Handler.java:725)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.os.Looper.loop(Looper.java:153)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.app.ActivityThread.main(ActivityThread.java:5297)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at java.lang.reflect.Method.invokeNative(Native Method)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at java.lang.reflect.Method.invoke(Method.java:511)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at dalvik.system.NativeStart.main(Native Method)
06-20 13:02:16.712: E/AndroidRuntime(16793): Caused by: java.lang.reflect.InvocationTargetException
06-20 13:02:16.712: E/AndroidRuntime(16793):    at java.lang.reflect.Method.invokeNative(Native Method)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at java.lang.reflect.Method.invoke(Method.java:511)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.view.View$1.onClick(View.java:3601)
06-20 13:02:16.712: E/AndroidRuntime(16793):    ... 11 more
06-20 13:02:16.712: E/AndroidRuntime(16793): Caused by: java.lang.ArrayIndexOutOfBoundsException: length=2; index=4
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.widget.NumberPicker.ensureCachedScrollSelectorValue(NumberPicker.java:1722)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.widget.NumberPicker.initializeSelectorWheelIndices(NumberPicker.java:1537)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at android.widget.NumberPicker.setMaxValue(NumberPicker.java:1345)
06-20 13:02:16.712: E/AndroidRuntime(16793):    at com.example.numpicker.MainActivity.onClick(MainActivity.java:85)
06-20 13:02:16.712: E/AndroidRuntime(16793):    ... 14 more

Answer 1

在setMaxValue 之前在onClick 中调用setDisplayedValues(null)。