我想在片段中显示一个列表。我正在使用自定义arraylist。它给了我一个classcast异常。我搜索了soluo解决方案，但它解决了我的问题。我是android的新手，所以我不知道这是怎么回事..
this is my Item class
public class Item {
public String item_name;
public String item_desc;
public String item_qty;
public Item(String item_name, String item_desc,String item_qty) {
super();
this.item_name = item_name;
this.item_desc = item_desc;
this.item_qty = item_qty;
}
public String getItem_name(){
return item_name;
}
public void setItem_name(String item_name)
{
this.item_name=item_name;
}
public String getItem_desc()
{
return item_desc;
}
public void setItem_desc(String item_desc)
{
this.item_desc=item_desc;
}
public String getItem_qty()
{
return item_qty;
}
public void setItem_qty(String item_qty) {
this.item_qty = item_qty;
}
}
this is my addstock fragment
public class AddStock extends Fragment {
EditText edit_item_name,edit_item_desc,edit_item_qty;
Button btn_save;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_add_stock, container, false);
edit_item_name = (EditText)rootView.findViewById(R.id.edittext_item_name);
edit_item_desc = (EditText) rootView.findViewById(R.id.editText_item_desc);
edit_item_qty = (EditText) rootView.findViewById(R.id.editText_item_qty);
btn_save = (Button) rootView.findViewById(R.id.button_Save);
MainActivity act=(MainActivity)this.getActivity();
final ArrayList stock = act.arrayList;
btn_save.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String item_name=edit_item_name.getText().toString();
String item_desc=edit_item_desc.getText().toString();
String item_qty=edit_item_qty.getText().toString();
stock.add(item_name);
stock.add(item_desc);
stock.add(item_qty);
Toast.makeText(AddStock.this.getActivity(), "Saved", Toast.LENGTH_LONG).show();
}
});
return rootView;
}
}
this is my viewstock fragment
public class ViewStock extends Fragment {
public ViewStock() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootview= inflater.inflate(R.layout.fragment_view_stock, container, false);
ListView listview = (ListView)rootview.findViewById(R.id.list);
// Context mCtx = getActivity().getApplicationContext();
MainActivity act=(MainActivity)this.getActivity();
ItemAdapter adapter = new ItemAdapter(getActivity(),R.layout.list_item,act.arrayList);
listview.setAdapter(adapter);
return rootview;
}
}
this is my main activity
Public class MainActivity extends AppCompatActivity {
private Toolbar mToolbar;
private DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FrameLayout mContentFrame;
FragmentManager fragmentManager;
private static final String PREFERENCES_FILE = "mymaterialapp_settings";
private static final String PREF_USER_LEARNED_DRAWER = "navigation_drawer_learned";
private static final String STATE_SELECTED_POSITION = "selected_navigation_drawer_position";
private boolean mUserLearnedDrawer;
private boolean mFromSavedInstanceState;
private int mCurrentSelectedPosition;
public ArrayList<Item> arrayList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_nav_drawer);
setUpToolbar();
arrayList=new ArrayList<Item>();
mDrawerLayout = (DrawerLayout) findViewById(R.id.nav_drawer);
mUserLearnedDrawer = Boolean.valueOf(readSharedSetting(this, PREF_USER_LEARNED_DRAWER, "false"));
if (savedInstanceState != null) {
mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
mFromSavedInstanceState = true;
}
setUpNavDrawer();
mNavigationView = (NavigationView) findViewById(R.id.nav_view);
mContentFrame = (FrameLayout) findViewById(R.id.nav_contentframe);
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
Fragment newFragment;
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
menuItem.setChecked(true);
switch (menuItem.getItemId()) {
case R.id.navigation_item_1:
newFragment = new AddStock();
transaction.replace(R.id.nav_contentframe, newFragment);
transaction.addToBackStack(null);
transaction.commit();
mCurrentSelectedPosition = 0;
mDrawerLayout.closeDrawers();
return true;
case R.id.navigation_item_2:
newFragment = new ViewStock();
transaction.replace(R.id.nav_contentframe, newFragment);
transaction.addToBackStack(null);
transaction.commit();
mCurrentSelectedPosition = 1;
return true;
default:
return true;
}
}
});
//fragmentManager.beginTransaction().replace(R.id.nav_contentframe, fragment).commit();
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(STATE_SELECTED_POSITION, mCurrentSelectedPosition);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION, 0);
Menu menu = mNavigationView.getMenu();
menu.getItem(mCurrentSelectedPosition).setChecked(true);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.action_settings:
return true;
}
return super.onOptionsItemSelected(item);
}
private void setUpToolbar() {
mToolbar = (Toolbar) findViewById(R.id.toolbar);
if (mToolbar != null) {
setSupportActionBar(mToolbar);
}
}
private void setUpNavDrawer() {
if (mToolbar != null) {
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
mToolbar.setNavigationIcon(R.drawable.ic_drawer);
mToolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mDrawerLayout.openDrawer(GravityCompat.START);
}
});
}
if (!mUserLearnedDrawer) {
mDrawerLayout.openDrawer(GravityCompat.START);
mUserLearnedDrawer = true;
saveSharedSetting(this, PREF_USER_LEARNED_DRAWER, "true");
}
}
public static void saveSharedSetting(Context ctx, String settingName, String settingValue) {
SharedPreferences sharedPref = ctx.getSharedPreferences(PREFERENCES_FILE, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString(settingName, settingValue);
editor.apply();
}
public static String readSharedSetting(Context ctx, String settingName, String defaultValue) {
SharedPreferences sharedPref = ctx.getSharedPreferences(PREFERENCES_FILE, Context.MODE_PRIVATE);
return sharedPref.getString(settingName, defaultValue);
}
}
this is my ItemAdapter
public class ItemAdapter extends ArrayAdapter<Item> {
Context context;
public ItemAdapter(Context context, int resourceId,
ArrayList<Item> items) {
super(context, resourceId, items);
this.context = context;
}
/* public int getCount() {
return items.size();
}
public Item getItem(int position) {
return items.get(position);
}
public long getItemId(int position) {
return position;
}
*/
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
Item rowItem = getItem(position);
LayoutInflater mInflater = (LayoutInflater) context
.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
if (convertView == null) {
holder = new ViewHolder();
convertView = mInflater.inflate(R.layout.list_item, null);
holder.txtItemName = (TextView) convertView.findViewById(R.id.txt_item_name);
holder.txtItemDesc = (TextView) convertView.findViewById(R.id.txt_item_desc);
holder.txtItemQty = (TextView) convertView.findViewById(R.id.txt_item_qty);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.txtItemName.setText(rowItem.getItem_name());
holder.txtItemDesc.setText(rowItem.getItem_desc());
holder.txtItemQty.setText(rowItem.getItem_qty());
return convertView;
}
private class ViewHolder {
TextView txtItemName;
TextView txtItemDesc;
TextView txtItemQty;
}
}
this is the exception m getting
java.lang.ClassCastException: java.lang.String cannot be cast to com.example.owner.stock.Item
at com.example.owner.stock.ItemAdapter.getView(ItemAdapter.java:60)
at android.widget.AbsListView.obtainView(AbsListView.java:2344)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillDown(ListView.java:698)
at android.widget.ListView.fillFromTop(ListView.java:759)
at android.widget.ListView.layoutChildren(ListView.java:1673)
at android.widget.AbsListView.onLayout(AbsListView.java:2148)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:907)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15614)
at android.view.ViewGroup.layout(ViewGroup.java:4968)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2102)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1859)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1077)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5884)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
07-22 23:34:00.334 20992-20992/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
答案 0 :(得分：0)
您正在将String对象添加到键入的列表中以获取Item对象。
而不是：
stock.add(someString);
stock.add(someString);
stock.add(someString);
做
stock.add(new Item(someString, someString, someString));