1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.app; 18 19 import android.os.Bundle; 20 import android.os.Handler; 21 import android.view.View; 22 import android.widget.AdapterView; 23 import android.widget.ListAdapter; 24 import android.widget.ListView; 25 26 /** 27 * An activity that displays a list of items by binding to a data source such as 28 * an array or Cursor, and exposes event handlers when the user selects an item. 29 * <p> 30 * ListActivity hosts a {@link android.widget.ListView ListView} object that can 31 * be bound to different data sources, typically either an array or a Cursor 32 * holding query results. Binding, screen layout, and row layout are discussed 33 * in the following sections. 34 * <p> 35 * <strong>Screen Layout</strong> 36 * </p> 37 * <p> 38 * ListActivity has a default layout that consists of a single, full-screen list 39 * in the center of the screen. However, if you desire, you can customize the 40 * screen layout by setting your own view layout with setContentView() in 41 * onCreate(). To do this, your own view MUST contain a ListView object with the 42 * id "@android:id/list" (or {@link android.R.id#list} if it's in code) 43 * <p> 44 * Optionally, your custom view can contain another view object of any type to 45 * display when the list view is empty. This "empty list" notifier must have an 46 * id "android:id/empty". Note that when an empty view is present, the list view 47 * will be hidden when there is no data to display. 48 * <p> 49 * The following code demonstrates an (ugly) custom screen layout. It has a list 50 * with a green background, and an alternate red "no data" message. 51 * </p> 52 * 53 * <pre> 54 * <?xml version="1.0" encoding="utf-8"?> 55 * <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 56 * android:orientation="vertical" 57 * android:layout_width="match_parent" 58 * android:layout_height="match_parent" 59 * android:paddingLeft="8dp" 60 * android:paddingRight="8dp"> 61 * 62 * <ListView android:id="@android:id/list" 63 * android:layout_width="match_parent" 64 * android:layout_height="match_parent" 65 * android:background="#00FF00" 66 * android:layout_weight="1" 67 * android:drawSelectorOnTop="false"/> 68 * 69 * <TextView android:id="@android:id/empty" 70 * android:layout_width="match_parent" 71 * android:layout_height="match_parent" 72 * android:background="#FF0000" 73 * android:text="No data"/> 74 * </LinearLayout> 75 * </pre> 76 * 77 * <p> 78 * <strong>Row Layout</strong> 79 * </p> 80 * <p> 81 * You can specify the layout of individual rows in the list. You do this by 82 * specifying a layout resource in the ListAdapter object hosted by the activity 83 * (the ListAdapter binds the ListView to the data; more on this later). 84 * <p> 85 * A ListAdapter constructor takes a parameter that specifies a layout resource 86 * for each row. It also has two additional parameters that let you specify 87 * which data field to associate with which object in the row layout resource. 88 * These two parameters are typically parallel arrays. 89 * </p> 90 * <p> 91 * Android provides some standard row layout resources. These are in the 92 * {@link android.R.layout} class, and have names such as simple_list_item_1, 93 * simple_list_item_2, and two_line_list_item. The following layout XML is the 94 * source for the resource two_line_list_item, which displays two data 95 * fields,one above the other, for each list row. 96 * </p> 97 * 98 * <pre> 99 * <?xml version="1.0" encoding="utf-8"?> 100 * <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 101 * android:layout_width="match_parent" 102 * android:layout_height="wrap_content" 103 * android:orientation="vertical"> 104 * 105 * <TextView android:id="@+id/text1" 106 * android:textSize="16sp" 107 * android:textStyle="bold" 108 * android:layout_width="match_parent" 109 * android:layout_height="wrap_content"/> 110 * 111 * <TextView android:id="@+id/text2" 112 * android:textSize="16sp" 113 * android:layout_width="match_parent" 114 * android:layout_height="wrap_content"/> 115 * </LinearLayout> 116 * </pre> 117 * 118 * <p> 119 * You must identify the data bound to each TextView object in this layout. The 120 * syntax for this is discussed in the next section. 121 * </p> 122 * <p> 123 * <strong>Binding to Data</strong> 124 * </p> 125 * <p> 126 * You bind the ListActivity's ListView object to data using a class that 127 * implements the {@link android.widget.ListAdapter ListAdapter} interface. 128 * Android provides two standard list adapters: 129 * {@link android.widget.SimpleAdapter SimpleAdapter} for static data (Maps), 130 * and {@link android.widget.SimpleCursorAdapter SimpleCursorAdapter} for Cursor 131 * query results. 132 * </p> 133 * <p> 134 * The following code from a custom ListActivity demonstrates querying the 135 * Contacts provider for all contacts, then binding the Name and Company fields 136 * to a two line row layout in the activity's ListView. 137 * </p> 138 * 139 * <pre> 140 * public class MyListAdapter extends ListActivity { 141 * 142 * @Override 143 * protected void onCreate(Bundle savedInstanceState){ 144 * super.onCreate(savedInstanceState); 145 * 146 * // We'll define a custom screen layout here (the one shown above), but 147 * // typically, you could just use the standard ListActivity layout. 148 * setContentView(R.layout.custom_list_activity_view); 149 * 150 * // Query for all people contacts using the {@link android.provider.Contacts.People} convenience class. 151 * // Put a managed wrapper around the retrieved cursor so we don't have to worry about 152 * // requerying or closing it as the activity changes state. 153 * mCursor = this.getContentResolver().query(People.CONTENT_URI, null, null, null, null); 154 * startManagingCursor(mCursor); 155 * 156 * // Now create a new list adapter bound to the cursor. 157 * // SimpleListAdapter is designed for binding to a Cursor. 158 * ListAdapter adapter = new SimpleCursorAdapter( 159 * this, // Context. 160 * android.R.layout.two_line_list_item, // Specify the row template to use (here, two columns bound to the two retrieved cursor 161 * rows). 162 * mCursor, // Pass in the cursor to bind to. 163 * new String[] {People.NAME, People.COMPANY}, // Array of cursor columns to bind to. 164 * new int[] {android.R.id.text1, android.R.id.text2}); // Parallel array of which template objects to bind to those columns. 165 * 166 * // Bind to our new adapter. 167 * setListAdapter(adapter); 168 * } 169 * } 170 * </pre> 171 * 172 * @see #setListAdapter 173 * @see android.widget.ListView 174 */ 175 public class ListActivity extends Activity { 176 /** 177 * This field should be made private, so it is hidden from the SDK. 178 * {@hide} 179 */ 180 protected ListAdapter mAdapter; 181 /** 182 * This field should be made private, so it is hidden from the SDK. 183 * {@hide} 184 */ 185 protected ListView mList; 186 187 private Handler mHandler = new Handler(); 188 private boolean mFinishedStart = false; 189 190 private Runnable mRequestFocus = new Runnable() { 191 public void run() { 192 mList.focusableViewAvailable(mList); 193 } 194 }; 195 196 /** 197 * This method will be called when an item in the list is selected. 198 * Subclasses should override. Subclasses can call 199 * getListView().getItemAtPosition(position) if they need to access the 200 * data associated with the selected item. 201 * 202 * @param l The ListView where the click happened 203 * @param v The view that was clicked within the ListView 204 * @param position The position of the view in the list 205 * @param id The row id of the item that was clicked 206 */ 207 protected void onListItemClick(ListView l, View v, int position, long id) { 208 } 209 210 /** 211 * Ensures the list view has been created before Activity restores all 212 * of the view states. 213 * 214 *@see Activity#onRestoreInstanceState(Bundle) 215 */ 216 @Override 217 protected void onRestoreInstanceState(Bundle state) { 218 ensureList(); 219 super.onRestoreInstanceState(state); 220 } 221 222 /** 223 * @see Activity#onDestroy() 224 */ 225 @Override 226 protected void onDestroy() { 227 mHandler.removeCallbacks(mRequestFocus); 228 super.onDestroy(); 229 } 230 231 /** 232 * Updates the screen state (current list and other views) when the 233 * content changes. 234 * 235 * @see Activity#onContentChanged() 236 */ 237 @Override 238 public void onContentChanged() { 239 super.onContentChanged(); 240 View emptyView = findViewById(com.android.internal.R.id.empty); 241 mList = (ListView)findViewById(com.android.internal.R.id.list); 242 if (mList == null) { 243 throw new RuntimeException( 244 "Your content must have a ListView whose id attribute is " + 245 "'android.R.id.list'"); 246 } 247 if (emptyView != null) { 248 mList.setEmptyView(emptyView); 249 } 250 mList.setOnItemClickListener(mOnClickListener); 251 if (mFinishedStart) { 252 setListAdapter(mAdapter); 253 } 254 mHandler.post(mRequestFocus); 255 mFinishedStart = true; 256 } 257 258 /** 259 * Provide the cursor for the list view. 260 */ 261 public void setListAdapter(ListAdapter adapter) { 262 synchronized (this) { 263 ensureList(); 264 mAdapter = adapter; 265 mList.setAdapter(adapter); 266 } 267 } 268 269 /** 270 * Set the currently selected list item to the specified 271 * position with the adapter's data 272 * 273 * @param position 274 */ 275 public void setSelection(int position) { 276 mList.setSelection(position); 277 } 278 279 /** 280 * Get the position of the currently selected list item. 281 */ 282 public int getSelectedItemPosition() { 283 return mList.getSelectedItemPosition(); 284 } 285 286 /** 287 * Get the cursor row ID of the currently selected list item. 288 */ 289 public long getSelectedItemId() { 290 return mList.getSelectedItemId(); 291 } 292 293 /** 294 * Get the activity's list view widget. 295 */ 296 public ListView getListView() { 297 ensureList(); 298 return mList; 299 } 300 301 /** 302 * Get the ListAdapter associated with this activity's ListView. 303 */ 304 public ListAdapter getListAdapter() { 305 return mAdapter; 306 } 307 308 private void ensureList() { 309 if (mList != null) { 310 return; 311 } 312 setContentView(com.android.internal.R.layout.list_content_simple); 313 314 } 315 316 private AdapterView.OnItemClickListener mOnClickListener = new AdapterView.OnItemClickListener() { 317 public void onItemClick(AdapterView<?> parent, View v, int position, long id) 318 { 319 onListItemClick((ListView)parent, v, position, id); 320 } 321 }; 322 } 323
