Android的 - 更新列表视图 [英] Android - Updating a List View
问题描述
我一直坚持这样做很长时间，同时，这真的令人沮丧。基本上，应用程序开始与包含电影片名一个，其的ListView 总和年度。
I've been stuck with this for a long while and it's really frustrating. Basically the app starts off with a ListView containing Movie Titles, their Gross, and Year.
然后用户可以使用从菜单中选择不同的活动添加一个新的电影，毛利率和年份。然后将这些值返回到第一个活动和被放置在列表的底部。
The user then can add a new movie, gross, and year using a different activity from the menu. The values are then returned back to the first activity and is placed at the bottom of the list.
这是我的问题开始的地方。我的第一个问题是，应用程序强制关闭时，它要显示新项目。现在，它不希望在所有显示量。这里的code：
This is where my problem begins. The first problem I had is that the app Force Closes when it's about to display the new item. Now, it doesn't want to display at all. Here's the Code:
public class Lab7_084106 extends ListActivity {
private SampleCustomAdapter adapter;
private ArrayList<MyMovies> movieList;
public static boolean Flag = false;
@SuppressWarnings("null")
@Override
public void onCreate(Bundle savedInstanceState) {
//create stuff
super.onCreate(savedInstanceState);
movieList = new ArrayList<MyMovies>();
Intent data = getIntent();
//Flag = data.getStringExtra("Flag");
String[] oldMovieList = getResources().getStringArray(R.array.movieArray);
String[] oldGrossList = getResources().getStringArray(R.array.worldwideGross);
String[] oldYearList = getResources().getStringArray(R.array.yearArray);
//if there's no new movie to display
if(!Flag){
for (int i = 0; i < oldMovieList.length; i++) {
MyMovies newMovie = new MyMovies();
newMovie.setMovie(oldMovieList[i] + "NEW");
newMovie.setGross(oldGrossList[i]);
newMovie.setYear(oldYearList[i]);
movieList.add(newMovie);
}
//adapter = new SampleCustomAdapter(movieList);
//setContentView(R.layout.row);
//setListAdapter(adapter);
}
else{
Toast.makeText(getApplicationContext(), "Else Entered", Toast.LENGTH_SHORT).show();
int newLength = 50; //oldMovieList.length + 1;
//create new array to store the new value
String[] newMovieArray = new String[newLength];
String[] newGrossArray = new String[newLength];
String[] newYearArray = new String[newLength];
//populate the new list with the old one plus the new one
for (int i = 0; i < newLength; i++) {
if( i != newLength - 1){
newMovieArray[i] = oldMovieList[i];
newGrossArray[i] = oldGrossList[i];
newYearArray[i] = oldYearList[i];
}
else{
newMovieArray[i] = data.getStringExtra("Title");
newGrossArray[i] = data.getStringExtra("Gross");
newYearArray[i] = data.getStringExtra("Year");
}
}
//populate the old one using the new list
for (int i = 0; i < newLength; i++) {
oldMovieList[i] = newMovieArray[i];
oldGrossList[i] = newGrossArray[i];
oldYearList[i] = newYearArray[i];
}
//display stuff
for (int i = 0; i < newLength; i++) {
MyMovies newMovie = new MyMovies();
newMovie.setMovie(oldMovieList[i]);
newMovie.setGross(oldGrossList[i]);
newMovie.setYear(oldYearList[i]);
movieList.add(newMovie);
}
//adapter = new SampleCustomAdapter(movieList);
//setListAdapter(adapter);
}
adapter = new SampleCustomAdapter(movieList);
setListAdapter(adapter);
ListView lv = getListView();
lv.setTextFilterEnabled(true);
//set stuff such that Page2 sends back a result to page 1
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
TextView t = (TextView) view.findViewById(R.id.title);
String name = (String) t.getText();
Toast.makeText(getApplicationContext(), name, Toast.LENGTH_SHORT).show();
}
});
}
private class SampleCustomAdapter extends BaseAdapter {
private ArrayList<MyMovies> internalList;
String[] oldMovieList = getResources().getStringArray(R.array.movieArray);
String[] oldGrossList = getResources().getStringArray(R.array.worldwideGross);
String[] oldYearList = getResources().getStringArray(R.array.yearArray);
private ArrayList<MyMovies> GetSearchResults(){
ArrayList<MyMovies> results = new ArrayList<MyMovies>();
// make sure the arrays have the same length
for (int i = 0; i < oldMovieList.length; i++) {
MyMovies sr = new MyMovies();
sr.setMovie(oldMovieList[i]);
sr.setGross(oldGrossList[i]);
sr.setYear(oldYearList[i]);
results.add(sr);
}
return results;
}
public SampleCustomAdapter(ArrayList<MyMovies> contacts){
internalList = contacts;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return internalList.size();
}
@Override
public Object getItem(int index) {
// TODO Auto-generated method stub
return internalList.get(index);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// NOTE: you can only do this if you have access to the Activity object
// which is why this is an inner class
LayoutInflater inflater = getLayoutInflater();
View view;
//System.out.println(parent.getClass().getName());
//System.out.println(position);
if (convertView==null){
view = inflater.inflate(R.layout.row, null);
}
else{
view = convertView;
}
// extract the views to be populated
TextView movie = (TextView) view.findViewById(R.id.title);
TextView gross = (TextView) view.findViewById(R.id.gross);
TextView date = (TextView) view.findViewById(R.id.date);
// extract the object that will fill these
MyMovies movies = GetSearchResults().get(position);
//MyMovies movies = internalList.get(position);
movie.setText(movies.getMovie());
gross.setText(movies.getGross());
date.setText(movies.getYear());
// return the view
return view;
}
}
//menu lawl
@Override
public boolean onCreateOptionsMenu(Menu menu){
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menupage1, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
//Handle item selection using item.getItemId()
switch(item.getItemId()){
case R.id.addMovie:
AddMovie();
break;
}
return true;
}
//end menu stuff lol
public void AddMovie(){
Intent intent2 = new Intent(this, com.Android.Lab7.addMovie.class);
startActivity(intent2);
finish();
}
}
旗布尔变量基本上告知用户，如果用户添加电影。如果用户增加了一个电影，它会从那里进入else语句和更新。我真的很困惑在哪里把这个的if-else 语句。
The Flag Boolean variable basically tells if the user added a movie. If the user added a movie, it will enter the else statement and update from there. I'm really confused where to put this if-else statement.
我跑了的 SampleCustomAdapter 的 GetSearchResult 函数的几个实验，发现它直接影响的输出在的ListView 。我试着放置的if-else 语句有，但我结束了在的ListView 的项目很多。
I ran a few experiments with the GetSearchResult function of SampleCustomAdapter and found out that it directly affects the output of the ListView. I tried placing the if-else statement there but I ended up with a LOT of items in the ListView.
使用 adapter.notifyDataSetChanged（）; 给出NullPointerException错误，并指出，我把它。所以，即使这样做：
Using adapter.notifyDataSetChanged(); gives a NullPointerException error and points to where I placed it. So even if do something like:
MyMovies newMovie = new MyMovies();
newMovie.setMovie(data.getStringExtra("Title"));
newMovie.setGross(data.getStringExtra("Gross"));
newMovie.setYear(data.getStringExtra("Year"));
movieList.add(newMovie);
adapter.notifyDataSetChanged();
由于其他块，这是行不通的。我认为这是与我正在从string.xml资源文件夹而不是通过硬code或用户输入让我的初始值的事实。
As the else block, it does not work. I think it has something to do with the fact that I'm getting my initial values from the string.xml resource folder and not via hardcode or user input.
此问题已经折腾我自从2-3天前和帮助实在是AP preciated。谢谢你。
This problem has been frustrating me ever since 2-3 days ago and help is really appreciated. Thanks.
推荐答案
您只需要通知改变了你的适配器上的数据集
you just have to notify the data set Changed on your adapter
movieList.add(newMovie);
adapter.notifyDataSetChanged();
在ListView将自动更新
the listview will be updated automatically
更新
你总是可以使用下面的它会工作，但我preFER通知适配器。
UPDATE you can always use the following it'll work but I prefer notifying the adapter.
movieList.add(newMovie);
adapter = new SampleCustomAdapter(movieList);
setListAdapter(adapter);
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