所以我正在创建一个待办事项应用程序，我是java编程和Android Studio的新手，所以我希望你能忍受我。
这是我的MainActivity包含一个SimpleAdapter来显示列表。
ListView lv;
ArrayList<HashMap<String, String>> list;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listview_main_activity);
lv=(ListView)findViewById(R.id.listingtasks);
DBconnector db=new DBconnector(this);
list=new ArrayList<HashMap<String,String>>();
list=db.display();
String[] from=new String[]{"_id","task"};
int[] to=new int[]{R.id.id,R.id.tasknamecustom1};
ListAdapter ad;
ad = new SimpleAdapter(listview_main_activity.this,list, R.layout.custom,from,to);
lv.setAdapter(ad);
DBconnector类从SQLiteOpenHelper类扩展，包含在SQLiteDatabase中插入和显示记录的方法。这是DBconnector类：
public class DBconnector extends SQLiteOpenHelper {
public Cursor cr;
public DBconnector(Context context) {
super(context, "DATABASE", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
String sqlquery = "CREATE TABLE TASKTABLE(_id INTEGER PRIMARY KEY AUTOINCREMENT, task TEXT);";
db.execSQL(sqlquery);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String sqlqueryupgrade = "DROP TABLE IF EXISTS TASKTABLE;";
db.execSQL(sqlqueryupgrade);
onCreate(db);
}
这是DBconnector类中的显示方法：
public ArrayList<HashMap<String,String>> display() {
ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
SQLiteDatabase sb = this.getReadableDatabase();
String sql = "SELECT * FROM TASKTABLE;";
cr = sb.rawQuery(sql, null); //takes cursor to a position before the first record
if (cr.moveToFirst()) {
do {
HashMap<String,String> hm = new HashMap<String,String>();
hm.put("_id", cr.getString(0));
hm.put("task", cr.getString(1));
list.add(hm);
} while (cr.moveToNext());
}
return list;
}
这是custom.xml文件：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="Small Text"
android:id="@+id/id" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/tasknamecustom1" />
没有语法错误。我没有找到任何红色下划线，应用程序在我的手机上运行。唯一的问题是我的主要活动的列表视图正确显示了任务的数量，但没有显示任务本身的文本。
这是SimpleAdapter类：
public class SimpleAdapter extends BaseAdapter implements Filterable, ThemedSpinnerAdapter {
private final LayoutInflater mInflater;
private int[] mTo;
private String[] mFrom;
private ViewBinder mViewBinder;
private List<? extends Map<String, ?>> mData;
private int mResource;
private int mDropDownResource;
/** Layout inflater used for {@link #getDropDownView(int, View, ViewGroup)}. */
private LayoutInflater mDropDownInflater;
private SimpleFilter mFilter;
private ArrayList<Map<String, ?>> mUnfilteredData;
/**
* Constructor
*
* @param context The context where the View associated with this SimpleAdapter is running
* @param data A List of Maps. Each entry in the List corresponds to one row in the list. The
* Maps contain the data for each row, and should include all the entries specified in
* "from"
* @param resource Resource identifier of a view layout that defines the views for this list
* item. The layout file should include at least those named views defined in "to"
* @param from A list of column names that will be added to the Map associated with each
* item.
* @param to The views that should display column in the "from" parameter. These should all be
* TextViews. The first N views in this list are given the values of the first N columns
* in the from parameter.
*/
public SimpleAdapter(Context context, List<? extends Map<String, ?>> data,
@LayoutRes int resource, String[] from, @IdRes int[] to) {
mData = data;
mResource = mDropDownResource = resource;
mFrom = from;
mTo = to;
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
/**
* @see android.widget.Adapter#getCount()
*/
public int getCount() {
return mData.size();
}
/**
* @see android.widget.Adapter#getItem(int)
*/
public Object getItem(int position) {
return mData.get(position);
}
/**
* @see android.widget.Adapter#getItemId(int)
*/
public long getItemId(int position) {
return position;
}
/**
* @see android.widget.Adapter#getView(int, View, ViewGroup)
*/
public View getView(int position, View convertView, ViewGroup parent) {
return createViewFromResource(mInflater, position, convertView, parent, mResource);
}
private View createViewFromResource(LayoutInflater inflater, int position, View convertView,
ViewGroup parent, int resource) {
View v;
if (convertView == null) {
v = inflater.inflate(resource, parent, false);
} else {
v = convertView;
}
bindView(position, v);
return v;
}
/**
* <p>Sets the layout resource to create the drop down views.</p>
*
* @param resource the layout resource defining the drop down views
* @see #getDropDownView(int, android.view.View, android.view.ViewGroup)
*/
public void setDropDownViewResource(int resource) {
mDropDownResource = resource;
}
/**
* Sets the {@link android.content.res.Resources.Theme} against which drop-down views are
* inflated.
* <p>
* By default, drop-down views are inflated against the theme of the
* {@link Context} passed to the adapter's constructor.
*
* @param theme the theme against which to inflate drop-down views or
* {@code null} to use the theme from the adapter's context
* @see #getDropDownView(int, View, ViewGroup)
*/
@Override
public void setDropDownViewTheme(Resources.Theme theme) {
if (theme == null) {
mDropDownInflater = null;
} else if (theme == mInflater.getContext().getTheme()) {
mDropDownInflater = mInflater;
} else {
final Context context = new ContextThemeWrapper(mInflater.getContext(), theme);
mDropDownInflater = LayoutInflater.from(context);
}
}
@Override
public Resources.Theme getDropDownViewTheme() {
return mDropDownInflater == null ? null : mDropDownInflater.getContext().getTheme();
}
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
final LayoutInflater inflater = mDropDownInflater == null ? mInflater : mDropDownInflater;
return createViewFromResource(inflater, position, convertView, parent, mDropDownResource);
}
private void bindView(int position, View view) {
final Map dataSet = mData.get(position);
if (dataSet == null) {
return;
}
final ViewBinder binder = mViewBinder;
final String[] from = mFrom;
final int[] to = mTo;
final int count = to.length;
for (int i = 0; i < count; i++) {
final View v = view.findViewById(to[i]);
if (v != null) {
final Object data = dataSet.get(from[i]);
String text = data == null ? "" : data.toString();
if (text == null) {
text = "";
}
boolean bound = false;
if (binder != null) {
bound = binder.setViewValue(v, data, text);
}
if (!bound) {
if (v instanceof Checkable) {
if (data instanceof Boolean) {
((Checkable) v).setChecked((Boolean) data);
} else if (v instanceof TextView) {
// Note: keep the instanceof TextView check at the bottom of these
// ifs since a lot of views are TextViews (e.g. CheckBoxes).
setViewText((TextView) v, text);
} else {
throw new IllegalStateException(v.getClass().getName() +
" should be bound to a Boolean, not a " +
(data == null ? "<unknown type>" : data.getClass()));
}
} else if (v instanceof TextView) {
// Note: keep the instanceof TextView check at the bottom of these
// ifs since a lot of views are TextViews (e.g. CheckBoxes).
setViewText((TextView) v, text);
} else if (v instanceof ImageView) {
if (data instanceof Integer) {
setViewImage((ImageView) v, (Integer) data);
} else {
setViewImage((ImageView) v, text);
}
} else {
throw new IllegalStateException(v.getClass().getName() + " is not a " +
" view that can be bounds by this SimpleAdapter");
}
}
}
}
}
/**
* Returns the {@link ViewBinder} used to bind data to views.
*
* @return a ViewBinder or null if the binder does not exist
*
* @see #setViewBinder(android.widget.SimpleAdapter.ViewBinder)
*/
public ViewBinder getViewBinder() {
return mViewBinder;
}
/**
* Sets the binder used to bind data to views.
*
* @param viewBinder the binder used to bind data to views, can be null to
* remove the existing binder
*
* @see #getViewBinder()
*/
public void setViewBinder(ViewBinder viewBinder) {
mViewBinder = viewBinder;
}
/**
* Called by bindView() to set the image for an ImageView but only if
* there is no existing ViewBinder or if the existing ViewBinder cannot
* handle binding to an ImageView.
*
* This method is called instead of {@link #setViewImage(ImageView, String)}
* if the supplied data is an int or Integer.
*
* @param v ImageView to receive an image
* @param value the value retrieved from the data set
*
* @see #setViewImage(ImageView, String)
*/
public void setViewImage(ImageView v, int value) {
v.setImageResource(value);
}
/**
* Called by bindView() to set the image for an ImageView but only if
* there is no existing ViewBinder or if the existing ViewBinder cannot
* handle binding to an ImageView.
*
* By default, the value will be treated as an image resource. If the
* value cannot be used as an image resource, the value is used as an
* image Uri.
*
* This method is called instead of {@link #setViewImage(ImageView, int)}
* if the supplied data is not an int or Integer.
*
* @param v ImageView to receive an image
* @param value the value retrieved from the data set
*
* @see #setViewImage(ImageView, int)
*/
public void setViewImage(ImageView v, String value) {
try {
v.setImageResource(Integer.parseInt(value));
} catch (NumberFormatException nfe) {
v.setImageURI(Uri.parse(value));
}
}
/**
* Called by bindView() to set the text for a TextView but only if
* there is no existing ViewBinder or if the existing ViewBinder cannot
* handle binding to a TextView.
*
* @param v TextView to receive text
* @param text the text to be set for the TextView
*/
public void setViewText(TextView v, String text) {
v.setText(text);
}
public Filter getFilter() {
if (mFilter == null) {
mFilter = new SimpleFilter();
}
return mFilter;
}
/**
* This class can be used by external clients of SimpleAdapter to bind
* values to views.
*
* You should use this class to bind values to views that are not
* directly supported by SimpleAdapter or to change the way binding
* occurs for views supported by SimpleAdapter.
*
* @see SimpleAdapter#setViewImage(ImageView, int)
* @see SimpleAdapter#setViewImage(ImageView, String)
* @see SimpleAdapter#setViewText(TextView, String)
*/
public static interface ViewBinder {
/**
* Binds the specified data to the specified view.
*
* When binding is handled by this ViewBinder, this method must return true.
* If this method returns false, SimpleAdapter will attempts to handle
* the binding on its own.
*
* @param view the view to bind the data to
* @param data the data to bind to the view
* @param textRepresentation a safe String representation of the supplied data:
* it is either the result of data.toString() or an empty String but it
* is never null
*
* @return true if the data was bound to the view, false otherwise
*/
boolean setViewValue(View view, Object data, String textRepresentation);
}
/**
* <p>An array filters constrains the content of the array adapter with
* a prefix. Each item that does not start with the supplied prefix
* is removed from the list.</p>
*/
private class SimpleFilter extends Filter {
@Override
protected FilterResults performFiltering(CharSequence prefix) {
FilterResults results = new FilterResults();
if (mUnfilteredData == null) {
mUnfilteredData = new ArrayList<Map<String, ?>>(mData);
}
if (prefix == null || prefix.length() == 0) {
ArrayList<Map<String, ?>> list = mUnfilteredData;
results.values = list;
results.count = list.size();
} else {
String prefixString = prefix.toString().toLowerCase();
ArrayList<Map<String, ?>> unfilteredValues = mUnfilteredData;
int count = unfilteredValues.size();
ArrayList<Map<String, ?>> newValues = new ArrayList<Map<String, ?>>(count);
for (int i = 0; i < count; i++) {
Map<String, ?> h = unfilteredValues.get(i);
if (h != null) {
int len = mTo.length;
for (int j=0; j<len; j++) {
String str = (String)h.get(mFrom[j]);
String[] words = str.split(" ");
int wordCount = words.length;
for (int k = 0; k < wordCount; k++) {
String word = words[k];
if (word.toLowerCase().startsWith(prefixString)) {
newValues.add(h);
break;
}
}
}
}
}
results.values = newValues;
results.count = newValues.size();
}
return results;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
//noinspection unchecked
mData = (List<Map<String, ?>>) results.values;
if (results.count > 0) {
notifyDataSetChanged();
} else {
notifyDataSetInvalidated();
}
}
}
}
请有人请帮帮我吗？ 谢谢！
答案 0 :(得分：0)
嘿首先用显示方法中的DBConnector替换此代码。
hm.put("_id", cr.getString(0));
与
hm.put("_id", cr.getInt(0)+"");
现在发布Simple Adapter的getView（）方法，或整个类，以便我可以进一步帮助你。
okk尝试替换
String text = data == null ? "" : data.toString();
带
String text = data == null ? "" : (String)data;
将此代码放入
View v;
if (convertView == null) {
v = inflater.inflate(resource, parent, false);
} else {
v = convertView;
}
bindView(position, v);
return v;
进入
@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) {
View v;
if (convertView == null) {
v = inflater.inflate(resource, parent, false);
} else {
v = convertView;
}
bindView(position, v);
return v;
}
希望这对你有用。