我的 Android 列表视图不会通过 notifydatasetchanged() 调用进行更新。
主要代码活动：
package com.example.jokesbook;
import java.util.ArrayList;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.jokesbook.MESSAGE";
CustomAdapter Adapter;
ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
JokeDB.jokesList = new ArrayList<Joke>();
JokeDB.jokesList.add(new Joke("DDD"));
lv = (ListView)findViewById(android.R.id.list);
Adapter= new CustomAdapter(MainActivity.this, R.layout.joke_list_item, JokeDB.jokesList);
lv.setAdapter(Adapter);
}//onCreate
@Override
public void onResume() {
super.onResume(); // Always call the superclass method first
Log.d("jokesbook", "onResume ");
Adapter.notifyDataSetChanged();
}
class CustomAdapter extends ArrayAdapter<Joke>{
Context context;
int layoutResourceId;
ArrayList<Joke> data = null;
private LayoutInflater mInflater;
public CustomAdapter(Context customAdapter, int layoutResourceId, ArrayList<Joke> data) {
super(customAdapter, layoutResourceId, data);
Log.d("jokesbook", "CustomAdapter ");
this.layoutResourceId = layoutResourceId;
this.context = customAdapter;
this.data = data;
this.mInflater = LayoutInflater.from(customAdapter);
}
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
//item_list
convertView = mInflater.inflate(R.layout.joke_list_item, null);
holder = new ViewHolder();
//fill the views
holder.joke = (TextView) convertView.findViewById(R.id.ListTextView1);
convertView.setTag(holder);
}
else {
// Get the ViewHolder back to get fast access to the TextView
// and the ImageView.
holder = (ViewHolder) convertView.getTag();//
}
holder.joke.setText(data.get(position).jokeStr);
return convertView;
}
class ViewHolder {
TextView joke;
}
}
/** Called when the user clicks the Add a new joke button */
public void goNewJoke(View view) {
Intent intent = new Intent(this, New_joke.class);
startActivity(intent);
}
}
它的xml：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
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"
android:orientation="vertical"
tools:context=".MainActivity" >
<Button
android:id="@+id/ButtonAboveList"
android:layout_width="500dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:onClick="goNewJoke"
android:text="@string/Add_a_new_joke"/>
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
在另一个活动中将内容添加到 JokeDB.jokesList 时，其代码为：
package com.example.jokesbook;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
public class New_joke extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_new_joke);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.new_joke, menu);
return true;
}
public void addJoke(View view){
EditText editTextJoke= (EditText)findViewById(R.id.edit_text_jokeToAdd);
JokeDB.jokesList.add(new Joke(editTextJoke.getText().toString()));
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
}
}
它的XML是：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/green"
android:orientation="vertical"
android:paddingLeft="3dp"
android:paddingRight="3dp"
android:paddingTop="3dp"
tools:context=".New_joke" >
<EditText
android:id="@+id/edit_text_jokeToAdd"
android:layout_width="fill_parent"
android:layout_height="150dp"
android:layout_marginBottom="40dp"
android:background="@color/white"
android:hint="@string/edit_message" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:orientation="horizontal"
tools:context=".New_joke" >
<TextView
android:id="@+id/AuthorText"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:gravity="left"
android:text="@string/Author"
android:textColor="@android:color/white"
android:textSize="25sp" />
<EditText
android:id="@+id/edit_text_Author"
android:layout_width="fill_parent"
android:layout_height="40dp"
android:background="@color/white"
android:hint="@string/Only_letters_allowed"
android:inputType="textPersonName" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="60dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:orientation="horizontal"
tools:context=".New_joke" >
<TextView
android:id="@+id/DateText"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:gravity="left"
android:text="@string/Date"
android:textColor="@android:color/white"
android:textSize="25sp" />
<EditText
android:id="@+id/edit_text_Date"
android:layout_width="fill_parent"
android:layout_height="40dp"
android:background="@color/white"
android:hint="@string/Only_digits_allowed"
android:inputType="number" />
</LinearLayout>
<Button
android:id="@+id/ButtonAboveList"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:onClick="addJoke"
android:text="@string/Add" />
</LinearLayout>
尽管在 onResume 中我使用了 notifydatasetchanged() 函数，但我在主要活动前夕看不到更新的列表。