我正在尝试创建一个Android应用程序，它从SQLite数据库中获取数据并在PageView（滑动视图）中显示它们。应用程序在我尝试运行时崩溃。请帮我看一下我的代码，看看我弄错了。
我的主要活动是：
public class MainActivity extends AppCompatActivity {
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DataBaseAccess databaseAccess = DataBaseAccess.getInstance(this);
databaseAccess.open();
List<String> quotes = databaseAccess.getQuotes();
databaseAccess.close();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager(),getApplicationContext());
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
private static final String Name_Key = "Name_Key";
/*public PlaceholderFragment() {
}*/
/**
* Returns a new instance of this fragment for the given section
* number.
*/
/* public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Bundle bundle=getArguments();
if (bundle!=null)
{
String name=bundle.getString(Name_Key);
setValues(rootView,name);
}
return rootView;
}
private void setValues( View v, String name)
{
TextView textview=(TextView) v.findViewById(R.id.name);
textview.setText(name);
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
List<String> name;
String[] name1;
public SectionsPagerAdapter(FragmentManager fm, Context context) {
super(fm);
DataBaseAccess databaseAccess = DataBaseAccess.getInstance(null);
databaseAccess.open();
name=databaseAccess.getQuotes();
for (int i=0; i<=name.size();i++)
{
name1[i]=name.get(i);
}
}
@Override
public Fragment getItem(int position) {
Bundle bundle=new Bundle();
bundle.putString(PlaceholderFragment.Name_Key,name1[position]);
PlaceholderFragment deviceFragment= new PlaceholderFragment();
deviceFragment.setArguments(bundle);
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return deviceFragment;
}
@Override
public int getCount() {
// Show 3 total pages.
return name1.length;
}
@Override
public CharSequence getPageTitle(int position) {
return name1[position];
}
}
}
我的类访问数据库并返回字符串列表
public class DataBaseAccess {
private SQLiteOpenHelper openHelper;
private static SQLiteDatabase database;
private static DataBaseAccess instance;
/**
* Private constructor to aboid object creation from outside classes.
*
* @param context
*/
public DataBaseAccess(Context context) {
this.openHelper = new DatabaseOpenHelper(context);
}
/**
* Return a singleton instance of DatabaseAccess.
*
* @param context the Context
* @return the instance of DabaseAccess
*/
public static DataBaseAccess getInstance(Context context) {
if (instance == null) {
instance = new DataBaseAccess(context);
}
return instance;
}
/**
* Open the database connection.
*/
public void open() {
this.database = openHelper.getWritableDatabase();
}
/**
* Close the database connection.
*/
public void close() {
if (database != null) {
//this.database.close();
}
}
/**
* Read all quotes from the database.
*
* @return a List of quotes
*/
public ArrayList getQuotes() {
ArrayList<String> list = new ArrayList<>();
Cursor cursor = database.rawQuery("SELECT * FROM quotes", null);
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
list.add(cursor.getString(0));
cursor.moveToNext();
}
cursor.close();
return list;
}
}
我的Activity_main文件
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="org.heywhyconcept.myapplicationscroll.MainActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="@dimen/appbar_padding_top"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="@style/AppTheme.PopupOverlay">
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />
<android.support.design.widget.FloatingActionButton
android:id="@+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:layout_margin="@dimen/fab_margin"
android:src="@android:drawable/ic_dialog_email" />
我的Fragment_main文件
<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"
tools:context="org.heywhyconcept.myapplicationscroll.MainActivity$PlaceholderFragment">
<TextView
android:id="@+id/section_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="YUSUF AYOMIDE"
/>
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="text"
/>
</LinearLayout>
答案 0 :(得分：0)
从您提供的代码中，您似乎尝试使用quotes语句访问表SELECT，而无需先正确定义和创建数据库表< / em>的
您需要显式定义数据库中应存在的表。在docs中有一个很好的例子，我将在这里解释：
public class FeedReaderDbHelper extends SQLiteOpenHelper {
public static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "myDatabase.db";
private static final String SQL_CREATE_ENTRIES =
"CREATE TABLE quotes (" +
"id INTEGER PRIMARY KEY, " +
"quote TEXT)";
public FeedReaderDbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//Create tables here
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE_ENTRIES);
}
}