Java-将单个字符串添加到数组的开头
这是一个android项目。我正在使用一个数组来构建一个微调器，它可以正常工作。但是，我现在尝试在数组的开头添加一条记录，以便在加载页面时不选择任何选项 我试图只使用Java-将单个字符串添加到数组的开头,java,android,arrays,Java,Android,Arrays,这是一个android项目。我正在使用一个数组来构建一个微调器，它可以正常工作。但是，我现在尝试在数组的开头添加一条记录，以便在加载页面时不选择任何选项 我试图只使用myarray.add（“--”）类型的东西，但它出现了以下错误： 11-05 10:50:36.995: D/AndroidRuntime(16763): Shutting down VM 11-05 10:50:36.995: W/dalvikvm(16763): threadid=1: thread exiting with
myarray.add（“--”）类型的东西，但它出现了以下错误：
11-05 10:50:36.995: D/AndroidRuntime(16763): Shutting down VM
11-05 10:50:36.995: W/dalvikvm(16763): threadid=1: thread exiting with uncaught exception (group=0x412b42a0)
11-05 10:50:37.000: E/AndroidRuntime(16763): FATAL EXCEPTION: main
11-05 10:50:37.000: E/AndroidRuntime(16763): java.lang.NullPointerException
11-05 10:50:37.000: E/AndroidRuntime(16763): at com.directenquiries.assessment.tool.AddAsset.updateLocalDesc(AddAsset.java:461)
11-05 10:50:37.000: E/AndroidRuntime(16763): at com.directenquiries.assessment.tool.AddAsset$3.onItemSelected(AddAsset.java:262)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.widget.AdapterView.fireOnSelected(AdapterView.java:892)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.widget.AdapterView.access$200(AdapterView.java:49)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:860)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.os.Handler.handleCallback(Handler.java:615)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.os.Handler.dispatchMessage(Handler.java:92)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.os.Looper.loop(Looper.java:137)
11-05 10:50:37.000: E/AndroidRuntime(16763): at android.app.ActivityThread.main(ActivityThread.java:4898)
11-05 10:50:37.000: E/AndroidRuntime(16763): at java.lang.reflect.Method.invokeNative(Native Method)
11-05 10:50:37.000: E/AndroidRuntime(16763): at java.lang.reflect.Method.invoke(Method.java:511)
11-05 10:50:37.000: E/AndroidRuntime(16763): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
11-05 10:50:37.000: E/AndroidRuntime(16763): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
11-05 10:50:37.000: E/AndroidRuntime(16763): at dalvik.system.NativeStart.main(Native Method)
11-05 10:50:37.020: D/dalvikvm(16763): GC_CONCURRENT freed 243K, 7% free 12989K/13831K, paused 1ms+3ms, total 25ms
我的代码是：
public void setupAssetType(Boolean beenSet){
Log.e("CamDebug", "Loading asset type");
Cursor c = db.rawQuery("select * from AssetTypes", null);
Log.e("Error Tracking", "Loading AssetTypes");
if(c.getCount() != 0) {
c.moveToFirst();
final ArrayList<String> mAssetType = new ArrayList<String>();
final ArrayList<String> mTypeID= new ArrayList<String>();
c.moveToFirst();
mAssetType.add("TEST");
mTypeID.add("TEST");
while(!c.isAfterLast()) {
mAssetType.add(c.getString(c.getColumnIndex("AssetType")));
mTypeID.add(c.getString(c.getColumnIndex("AssetTypeID")));
c.moveToNext();
}
ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, mAssetType);
spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spnAssetType.setAdapter(spinnerArrayAdapter);
int count = 0;
if(beenSet == true) {
for (String mID : mTypeID) {
Log.e("Set asset type", mID);
if(mID.equals(orAssetTypeID)){
spnAssetType.setSelection(count);
Log.e("Set asset type FOUND", mID);
break;
}
count++;
}
}
c.close();
spnAssetType.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
Log.e("CamDebug", "Selected asset type");
if(mAssetType.size() > 0){
setupGroup(mTypeID.get(position), false);
AssetType = mTypeID.get(position);
updateLocalDesc();
Log.e("Error Tracking", "Before Asset Type set");
if(mTypeID.get(position) != null) {
AssetTypeID = mTypeID.get(position);
} else {
AssetTypeID = "";
}
Log.e("Error Tracking", "After As");
}
}
@Override
public void onNothingSelected(AdapterView<?> parentView) {
}
});
}
}
测试。但它不起作用。如有任何意见，将不胜感激
编辑：第461行是：AssetGroup=spnAssetGroup.getSelectedItem（）.toString（）
编辑2-请不要在没有说明原因的情况下否决投票。这是毫无成效的
编辑3这似乎就是错误所在。此块包括like 461，用于创建从文本微调器到单行的文本：
public void updateLocalDesc(){
AssetType = spnAssetType.getSelectedItem().toString();
AssetGroup = spnAssetGroup.getSelectedItem().toString();
if(spnAssetSubGroup.getSelectedItem() != null && !spnAssetSubGroup.getSelectedItem().toString().equals("")){
AssetSubGroup = spnAssetSubGroup.getSelectedItem().toString();
tbLongDescription.setText(AssetType + "-" + AssetGroup + "-" + AssetSubGroup);
} else
{
tbLongDescription.setText(AssetType + "-" + AssetGroup);
}
}
我猜第461行是
mAssetType.add(c.getString(c.getColumnIndex("AssetType")));
空指针必须来自
c.getString()
检查
如果找不到该列，c.getColumnIndex（“AssetType”）将返回-1，导致c.getString（）抛出NullPointerException
您应该将该行分成3行，并对其进行调试，以准确地找到问题所在。我已经解决了。当我不向数组传递任何内容时，第二个光标返回为0。因此，当它试图设置描述区域的文本时，它为null且为空，因此：
public void updateLocalDesc(){
if(spnAssetType.getSelectedItem() != null){
AssetType = spnAssetType.getSelectedItem().toString();
} else {
AssetType = " ";
}
if(spnAssetGroup.getSelectedItem() != null){
AssetGroup = spnAssetGroup.getSelectedItem().toString();
} else {
AssetGroup = " ";
}
AssetType = spnAssetType.getSelectedItem().toString();
if(spnAssetSubGroup.getSelectedItem() != null && !spnAssetSubGroup.getSelectedItem().toString().equals("")){
AssetSubGroup = spnAssetSubGroup.getSelectedItem().toString();
tbLongDescription.setText(AssetType + "-" + AssetGroup + "-" + AssetSubGroup);
} else
{
tbLongDescription.setText(AssetType + "-" + AssetGroup);
}
}
修复了代码中第461行是哪一行？方法updateLocalDesc（）在哪里。资产类中的第461行是什么。删除ArrayList和make这两个类级别变量的final。我看不到您在代码中指出的行461
。要么spnAssetGroup
为null
要么spnAssetGroup。getSelectedItem（）
返回null
。（您的NPE被抛出com.directinquiries.assessment.tool.AddAsset.updateLocalDesc（AddAsset.java:461）
中，您向我们展示了方法setupAssetType
）@Tom如果工作正常，那很好，但您找到原因了吗？无法真正理解您现在给出代码的方式。
public void updateLocalDesc(){
if(spnAssetType.getSelectedItem() != null){
AssetType = spnAssetType.getSelectedItem().toString();
} else {
AssetType = " ";
}
if(spnAssetGroup.getSelectedItem() != null){
AssetGroup = spnAssetGroup.getSelectedItem().toString();
} else {
AssetGroup = " ";
}
AssetType = spnAssetType.getSelectedItem().toString();
if(spnAssetSubGroup.getSelectedItem() != null && !spnAssetSubGroup.getSelectedItem().toString().equals("")){
AssetSubGroup = spnAssetSubGroup.getSelectedItem().toString();
tbLongDescription.setText(AssetType + "-" + AssetGroup + "-" + AssetSubGroup);
} else
{
tbLongDescription.setText(AssetType + "-" + AssetGroup);
}
}