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我試圖從Android開發人員指南實施記事本教程的修改，但我的應用程序在啓動時意外停止。這裏是我的代碼：Android記事本教程修改 - 應用程序在啓動時意外停止 - 佈局/視圖問題？
我呼籲啓動主要方法...
public class MyList extends ListActivity
{
private MyListDBAdapter listDBHelper;
/** Called when the activity is first created. */
@Override
public void onCreate (Bundle savedInstanceState)
{
super.onCreate (savedInstanceState);
setContentView (R.layout.home_layout);
listDBHelper = new MyListDBAdapter (this);
listDBHelper.open();
fillData();
Button btnAddItem = (Button) findViewById (R.id.add_item_button);
btnAddItem.setOnClickListener (new OnClickListener()
{
@Override
public void onClick (View v)
{
Intent goToAddItem = new Intent (MyList.this,AddItem.class);
startActivity(goToAddItem);
}
});
}
private void fillData()
{
// Get all of the items from the database and create the item list
Cursor allItems = listDBHelper.fetchAllItems();
startManagingCursor (allItems);
String [] from = new String [] {MyListDBAdapter.FIELD_ATTR1,
MyListDBAdapter.FIELD_ATTR2,
MyListDBAdapter.FIELD_ATTR3};
int [] to = new int [] {R.id.list_attr1, R.id.list_attr2,
R.id.list_attr3};
// Now create an array adapter and set it to display using the item_record_view layout
SimpleCursorAdapter items = new SimpleCursorAdapter(this,R.layout.item_record_view,
allItems, from, to);
setListAdapter(items);
}
}
它的佈局XML文件...
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id = "@+id/home_layout"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
xmlns:android = "http://schemas.android.com/apk/res/android">
<Button android:id = "@+id/add_item_button"
android:layout_width = "fill_parent"
android:layout_height = "wrap_content"
android:text = "@string/add_item"/>
<ListView android:id = "@android:id/list"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"/>
<TextView android:id = "@android:id/empty"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
android:text = "@string/no_items"/>
</LinearLayout>
...和我試圖使用ListView顯示我的項目...
<?xml version="1.0" encoding="utf-8"?>
<ListView
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView android:id = "@+id/list_attr1"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
android:layout_alignParentLeft = "true"
xmlns:android="http://schemas.android.com/apk/res/android"/>
<TextView android:id = "@+id/list_attr2"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
android:paddingLeft = "60dip"
xmlns:android="http://schemas.android.com/apk/res/android"/>
<TextView android:id = "@+id/list_attr3"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
android:paddingLeft = "160dip"
android:gravity = "left"
xmlns:android="http://schemas.android.com/apk/res/android"/>
</ListView>
爲MyListDBAdapter代碼...
public class MyListDBAdapter
{
private static final String TABLE_ITEMS = "MyList";
public static final String FIELD_RECORD_ID = "_ID";
public static final String FIELD_TYPE = "Type";
public static final String FIELD_ATTR1 = "Attr1";
public static final String FIELD_ATTR2 = "Attr2";
public static final String FIELD_ATTR3 = "Attr3";
public static final String FIELD_MY_RATING = "MyRating";
public static final String [] COLUMNS = {FIELD_RECORD_ID, FIELD_TYPE, FIELD_ATTR1,
FIELD_ATTR2, FIELD_ATTR3};
private static final String TAG = "MyListDBHelper";
private DatabaseHelper listDBHelper;
private SQLiteDatabase itemDB;
/**
* Database creation sql statement
*/
private static final String DATABASE_CREATE = ("CREATE TABLE IF NOT EXISTS " +
TABLE_ITEMS + " (" + FIELD_RECORD_ID +
" INTEGER PRIMARY KEY AUTOINCREMENT,"
+ FIELD_TYPE + " TEXT NOT NULL, " +
FIELD_ATTR1 + " INTEGER NOT NULL, " +
FIELD_ATTR2 + " TEXT" + " NOT NULL,"
+ FIELD_ATTR3 + " TEXT NOT NULL," +
FIELD_MY_RATING + " INTEGER);");
private static final String DATABASE_NAME = "Items";
private static final int DATABASE_VERSION = 1;
private final Context thisContext;
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper (Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate (SQLiteDatabase db)
{
db.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade (SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w (TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS notes");
onCreate(db);
}
}
/**
* Constructor - takes the context to allow the database to be
* opened/created
*
* @param context the Context within which to work
*/
public MyListDBAdapter (Context context)
{
this.thisContext = context;
}
/**
* Open the items database. If it cannot be opened, try to create a new
* instance of the database. If it cannot be created, throw an exception to
* signal the failure
*
* @return this (self reference, allowing this to be chained in an
* initialization call)
* @throws SQLException if the database could be neither opened or created
*/
public MyListDBAdapter open() throws SQLException
{
listDBHelper = new DatabaseHelper (thisContext);
itemsDB = listDBHelper.getWritableDatabase();
return this;
}
public void close()
{
listDBHelper.close();
}
/**
* Create a new item entry using the information provided. If the item is
* successfully created return the new record ID for that item, otherwise return
* a -1 to indicate failure.
*
* @param Type the type of the item
* @param attr1
* @param attr2
* @param attr3
* @return rowId or -1 if failed
*/
public long addItem (String type, int attr1, String attr2, String attr3)
{
ContentValues initialValues = new ContentValues();
initialValues.put (FIELD_TYPE, type);
initialValues.put (FIELD_ATTR1, attr1);
initialValues.put (FIELD_ATTR2, attr2);
initialValues.put (FIELD_ATTR3, attr3);
return itemsDB.insert (TABLE_ITEMS, null, initialValues);
}
public long addItem (String type, int attr1, String attr2, String attr3,
int myRating)
{
ContentValues initialValues = new ContentValues();
initialValues.put (FIELD_TYPE, type);
initialValues.put (FIELD_ATTR1, attr1);
initialValues.put (FIELD_ATTR2, attr2);
initialValues.put (FIELD_ATTR3, attr3);
initialValues.put (FIELD_MY_RATING, myRating);
return itemsDB.insert (TABLE_ITEMS, null, initialValues);
}
/**
* Delete the item with the given record ID
*
* @param _ID ID of item to delete
* @return true if deleted, false otherwise
*/
public boolean deleteItem (long recordID)
{
return (itemsDB.delete (TABLE_ITEMS, FIELD_RECORD_ID + "=" + recordID,
null) > 0);
}
/**
* Return a Cursor over the list of all items in the database
*
* @return Cursor over all notes
*/
public Cursor fetchAllItems()
{
return itemsDB.query (TABLE_ITEMS, COLUMNS, null, null, null, null, null);
}
/**
* Return a Cursor positioned at the item that matches the given record ID
*
* @param _ID ID of item to retrieve
* @return Cursor positioned to matching item, if found
* @throws SQLException if item could not be found/retrieved
*/
public Cursor fetchItem (long recordID) throws SQLException
{
Cursor itemCursor = itemsDB.query (true, TABLE_ITEMS, COLUMNS,
FIELD_RECORD_ID + "=" + recordID, null, null, null, null, null);
if (itemCursor != null)
{
itemCursor.moveToFirst();
}
return itemCursor;
}
/**
* Update the item using the details provided. The item to be updated is
* specified using the record ID, and it is altered to use the values passed in
*
* @param _ID ID of item to update
* @param type type value to set item type to
* @param attr1
* @param attr2
* @param attr3
* @return true if the item was successfully updated, false otherwise
*/
public boolean updateItem (long recordID, String type, int attr1,
String attr2, String attr3)
{
ContentValues editVals = new ContentValues();
editVals.put (FIELD_TYPE, type);
editVals.put (FIELD_ATTR1, attr1);
editVals.put (FIELD_ATTR2, attr2);
editVals.put (FIELD_ATTR3, attr3);
return (itemsDB.update (TABLE_ITEMS, editVals, FIELD_RECORD_ID + "=" +
recordID, null) > 0);
}
}
我不認爲問題是與我的AddItem類或其關聯的佈局，我真的厭倦格式化這篇文章的代碼。任何人都可以幫我看看出了什麼問題嗎？
如果你發佈的logcat日誌使用堆棧跟蹤，這將是更容易幫助。 – MByD
我不知道有關logcat，但它絕對有用...感謝提及它！ –