我一直在试图让它工作大约2个小时，我只是知道我很愚蠢，但是我无法让我的多列列表正常工作。首先，它知道数据库中有两个行，但是由于某些原因，第一行和第二行是完全相同的，其次，上下文菜单也无法正常工作，一旦我单击"视图"，就会崩溃该应用程序它。
inventory_list.java
private void populateListView() {
ListView ListView=(ListView)findViewById(R.id.listView1);
list=new ArrayList<HashMap<String,String>>();
db = new SQLiteHandler(getApplicationContext());
list = db.getSomeInvDetails();
ListViewAdapters adapter=new ListViewAdapters(this, list);
ListView.setAdapter(adapter);
registerForContextMenu(ListView);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo)
{
super.onCreateContextMenu(menu, v, menuInfo);
menu.setHeaderTitle("Select The Action");
menu.add(0, v.getId(), 0, "View");
menu.add(0, v.getId(), 0, "Delete");
}
@Override
public boolean onContextItemSelected(MenuItem item){
AdapterContextMenuInfo info = (AdapterContextMenuInfo)item.getMenuInfo();
if(item.getTitle()=="View"){
Intent i = new Intent(Inventory_List.this, Inventory_View.class);
i.putExtra("id", list.get(info.position));
startActivity(i);
}
else{
return false;
}
return true;
}
@Override
public void onResume() {
super.onResume();
populateListView();
}
sqlitehandler.java
public ArrayList<HashMap<String, String>> getSomeInvDetails() {
ArrayList<HashMap<String, String>> list=new ArrayList<HashMap<String,String>>();
HashMap<String, String> user = new HashMap<String, String>();
String selectQuery = "SELECT * FROM " + TABLE_INV;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// Move to first row
if (cursor.moveToFirst()) {
do {
user.put("title", cursor.getString(1));
user.put("stock", cursor.getString(5));
list.add(user);
}while(cursor.moveToNext());}
cursor.close();
db.close();
// return user
Log.d(TAG, "Fetching user from Sqlite: " + user.toString());
return list;
}
ListViewSadapter
public class ListViewAdapters extends BaseAdapter{
public ArrayList<HashMap<String, String>> list;
Activity activity;
TextView txtFirst;
TextView txtSecond;
public ListViewAdapters(Activity activity,ArrayList<HashMap<String, String>> list){
super();
this.activity=activity;
this.list=list;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
LayoutInflater inflater=activity.getLayoutInflater();
if(convertView == null){
convertView=inflater.inflate(R.layout.colum_row, null);
txtFirst=(TextView) convertView.findViewById(R.id.title);
txtSecond=(TextView) convertView.findViewById(R.id.stock);
}
HashMap<String, String> map=list.get(position);
txtFirst.setText(map.get(FIRST_COLUMN));
txtSecond.setText(map.get(SECOND_COLUMN));
return convertView;
}
stacktrace错误
03-10 08:12:38.665 13660-13660/com.example.mypc.inventory W/Bundle: Key id expected String but value was a java.util.HashMap. The default value <null> was returned.
03-10 08:12:38.666 13660-13660/com.example.mypc.inventory W/Bundle: Attempt to cast generated internal exception:
java.lang.ClassCastException: java.util.HashMap cannot be cast to java.lang.String
at android.os.BaseBundle.getString(BaseBundle.java:995)
at android.content.Intent.getStringExtra(Intent.java:6243)
at com.example.mypc.inventory.Inventory_View.onCreate(Inventory_View.java:59)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
03-10 08:12:38.671 13660-13660/com.example.mypc.inventory D/SQLiteHandler: Fetching user from Sqlite: {}
03-10 08:12:38.675 13660-13660/com.example.mypc.inventory D/AndroidRuntime: Shutting down VM
03-10 08:12:38.676 13660-13660/com.example.mypc.inventory E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.mypc.inventory, PID: 13660
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mypc.inventory/com.example.mypc.inventory.Inventory_View}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
at com.example.mypc.inventory.Inventory_View.onCreate(Inventory_View.java:61)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
您需要在循环时通过DO创建新用户。
使用上下文菜单时崩溃的堆栈跟踪是什么？
if(item.getTitle()=="View"){
...
}
这个块总是转到else，您应该使用euqals。
if(item.getTitle().equals("View")){
...
}