J'essaie de créer une application de liste de courses, basée sur les champs de saisie ArrayList
, et ListView
. L'application sera basée sur Fragments
. Cependant, j'ai rencontré un problème et je ne sais pas comment le résoudre.
J'ai regardé partout sur Google et StackOverflow et j'ai trouvé des informations. Cependant, je ne l'ai pas fait fonctionner. J'espère maintenant pouvoir obtenir de l'aide avec mon code.
Je suis relativement inexpérimenté dans le développement Android.
Main.java
import java.util.ArrayList;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.view.MenuItem;
public class Main extends FragmentActivity {
ArrayList<Detail> items = new ArrayList<Detail>();
FragmentManager FM;
FragmentTransaction FT;
Input input = new Input();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
replaceFragment(R.id.container, input);
}
public void replaceFragment(int container, Fragment fragment){
FM = getFragmentManager();
FT = FM.beginTransaction();
FT.replace(container, fragment);
FT.commit();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
ListAdapter.java
public class ListAdapter extends BaseAdapter {
Context context;
ArrayList<Detail> items;
public ListAdapter(Context context, ArrayList<Detail> items) {
this.context = context;
this.items = items;
}
@Override
public int getCount() {
return items.size();
}
@Override
public Object getItem(int position) {
return items.get(position);
}
@Override
public long getItemId(int position) {
return items.indexOf(getItem(position));
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
LayoutInflater lInflater = (LayoutInflater)context.getSystemService(
Activity.LAYOUT_INFLATER_SERVICE);
convertView = lInflater.inflate(R.layout.list_row, null);
}
TextView title = (TextView)convertView.findViewById(R.id.itemTitle);
CheckBox done = (CheckBox)convertView.findViewById(R.id.itemDone);
Detail detail_position = items.get(position);
title.setText(detail_position.getTitle());
done.setChecked(detail_position.isDone());
return null;
}
}
List.java
import java.util.ArrayList;
import android.app.ListFragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
public class List extends ListFragment implements OnItemClickListener{
ArrayList<Detail> items;
ListAdapter adapter;
private onClickListener OCL;
interface onClickListener{
public void onItemClick(int id);
}
public List(ArrayList<Detail> items) {
this.items = items;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.list_layout, container, false);
return root;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if(items != null){
adapter = new ListAdapter(getActivity(), items);
setListAdapter(adapter);
getListView().setOnItemClickListener(this);
}
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
if(OCL != null){
OCL.onItemClick(position);
}
}
}
list_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@+id/android:list"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ListView>
</LinearLayout>
list_row
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:padding="10dp" >
<TextView
android:id="@+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.96"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<CheckBox
android:id="@+id/itemDone"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Done" />
</LinearLayout>
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.com.hermods.lab2_2.Main" >
</RelativeLayout>
Journal
02-19 09:10:47.421: E/AndroidRuntime(12745): Process: com.example.com.hermods.lab2_2, PID: 12745
02-19 09:10:47.421: E/AndroidRuntime(12745): java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.AbsListView.obtainView(AbsListView.java:2360)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.makeAndAddView(ListView.java:1864)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.fillDown(ListView.java:698)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.fillFromTop(ListView.java:759)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.ListView.layoutChildren(ListView.java:1673)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.AbsListView.onLayout(AbsListView.java:2148)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.View.layout(View.java:15596)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewGroup.layout(ViewGroup.java:4966)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2072)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1829)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer.doCallbacks(Choreographer.java:580)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer.doFrame(Choreographer.java:550)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.os.Handler.handleCallback(Handler.java:739)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.os.Handler.dispatchMessage(Handler.java:95)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.os.Looper.loop(Looper.java:135)
02-19 09:10:47.421: E/AndroidRuntime(12745): at android.app.ActivityThread.main(ActivityThread.java:5221)
02-19 09:10:47.421: E/AndroidRuntime(12745): at java.lang.reflect.Method.invoke(Native Method)
02-19 09:10:47.421: E/AndroidRuntime(12745): at java.lang.reflect.Method.invoke(Method.java:372)
02-19 09:10:47.421: E/AndroidRuntime(12745): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
02-19 09:10:47.421: E/AndroidRuntime(12745): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
android
android-layout
android-fragments
android-listview
utilisateur2734182
la source
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return items.indexOf(getItem(position));
est égal àposition
dans votre cas? La première chose à essayer est de supprimer le constructeur deList
.Réponses:
Dans votre
public View getView
méthode, passezreturn null;
àreturn convertView;
.la source
convertView
arriveraitnull
, a-t-il une signification particulière?View
. Si vous reveneznull
, vous obtiendrez exactement le même message d'erreur.#utilisation
return convertView;
Code:
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dans votre constructeur de classe baseadapter , essayez d'initialiser LayoutInflater , normalement je préfère de cette façon,
en haut de la classe, créez la variable LayoutInflater , j'espère que cela vous aidera
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cela se produit parfois lorsque nous utilisons un adaptateur personnalisé dans toute activité de fragment. et nous retournons un objet nul, c'est-à-dire une vue nulle, de sorte que l'activité se confond avec la vue à charger, c'est pourquoi cette exception se produit
montre la position où changer la vue
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