我想制作一个分数列表，从数据库中获取数据。
它给我的错误是：NullPointerException
这就是我所做的：
活动：
public class ScoresActivity extends Activity {
ScoreDataSource sds;
ArrayList<Score>scores;
ScoreAdapter adapter;
ListView listview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listview=(ListView) findViewById(R.id.AllScores);
sds=new ScoreDataSource(this);
sds.open();
scores=sds.getAllCustomers();
if(scores.size()==0)
{
createCustomers();
scores=sds.getAllCustomers();
}
adapter=new ScoreAdapter(this,R.layout.row,scores);
listview.setAdapter(adapter);
// Customer c=cds.getCustomerById(1);
//Log.i("getid","customer name is " + c.getFirstName());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.scores, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
switch (item.getItemId()) {
case R.id.menu_classic:
scores=sds.getAllCustomersByFIlter("Game==Classic", "waste ASC");
Log.i("filter", "list count is " + scores.size());
refreshMyAdapter();
break;
case R.id.menu_vscomp :
scores=sds.getAllCustomersByFIlter("Game==VScomp", "waste ASC");
Log.i("filter", "list count is " + scores.size());
refreshMyAdapter();
break;
case R.id.menu_allcustomers:
scores=sds.getAllCustomers();
Log.i("filter", "list count is " + scores.size());
refreshMyAdapter();
break;
default:
break;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
sds.open();
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
sds.close();
}
public void createCustomers()
{
Score s1=new Score(0,"a","1",50,"Classic");
s1=sds.createCustomer(s1);
Score s2=new Score(0,"b","2",600,"Classic");
s2=sds.createCustomer(s2);
Score s3=new Score(0,"c","2",600,"VScomp");
s3=sds.createCustomer(s3);
}
public void refreshMyAdapter()
{
adapter=new ScoreAdapter(this,R.layout.row,scores);
listview.setAdapter(adapter);
}
}
ScoreDataSource：
public class ScoreDataSource {
Context context;
ScoreOpenHelper helper;
SQLiteDatabase database;
String []allColumns={ScoreOpenHelper.COLUMN_ID, ScoreOpenHelper.COLUMN_NAME,
ScoreOpenHelper.COLUMN_DATE,ScoreOpenHelper.COLUMN_SCORE,ScoreOpenHelper.COLUMN_GAME};
public ScoreDataSource(Context context)
{
this.context=context;
helper=new ScoreOpenHelper(context);
}
public void open()
{
database=helper.getWritableDatabase();
Log.i("data", "Database connection open");
}
public void close()
{
helper.close();
Log.i("data", "Database connection close");
}
//quearies ......
public Score createCustomer(Score s)
{
ContentValues values=new ContentValues();
values.put(ScoreOpenHelper.COLUMN_NAME, s.getName());
values.put(ScoreOpenHelper.COLUMN_DATE, s.getScore());
values.put(ScoreOpenHelper.COLUMN_SCORE, s.getScore());
values.put(ScoreOpenHelper.COLUMN_GAME, s.getGame());
long insertId=database.insert(ScoreOpenHelper.TABLE_SCORES, null, values);
Log.i("data", "Score " + insertId + "insert to database");
s.setID(insertId);
return s;
}
public ArrayList<Score>getAllCustomers()
{
Cursor cursor=database.query(ScoreOpenHelper.TABLE_SCORES, allColumns, null, null, null, null, null);
ArrayList<Score>l=convertCurserToList(cursor);
return l;
}
public ArrayList<Score>getAllCustomersByFIlter(String selection,String OrderBy)
{
Cursor cursor=database.query(ScoreOpenHelper.TABLE_SCORES, allColumns, selection, null, null, null, OrderBy);
ArrayList<Score>l=convertCurserToList(cursor);
return l;
}
private ArrayList<Score> convertCurserToList(Cursor cursor) {
ArrayList<Score>l=new ArrayList<Score>();
if(cursor.getCount()>0)
{
while(cursor.moveToNext())
{
long id=cursor.getLong(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_ID));
String name=cursor.getString(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_NAME));
String date=cursor.getString(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_DATE));
int score=cursor.getInt(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_SCORE));
String game=cursor.getString(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_GAME));
Score c=new Score(id,name,date,score,game);
l.add(c);
}
}
return l;
}
public Score getCustomerById(long rowId)
{
Cursor cursor=database.query(ScoreOpenHelper.TABLE_SCORES, allColumns, ScoreOpenHelper.COLUMN_ID + "=" + rowId,
null, null, null, null);
cursor.moveToFirst();
if(cursor.getCount()>0)
{
long id=cursor.getLong(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_ID));
String name=cursor.getString(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_NAME));
String date=cursor.getString(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_DATE));
int score=cursor.getInt(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_SCORE));
String game=cursor.getString(cursor.getColumnIndex(ScoreOpenHelper.COLUMN_GAME));
Score c=new Score(id,name,date,score,game);
return c;
}
return null;
}
public long deleteAll()
{
return database.delete(ScoreOpenHelper.TABLE_SCORES, null, null);
}
public long deleteCustomerByRow(long rowId)
{
return database.delete(ScoreOpenHelper.TABLE_SCORES, ScoreOpenHelper.COLUMN_ID +"=" + rowId, null);
}
public long updateByRow(Score c)
{
ContentValues values=new ContentValues();
values.put(ScoreOpenHelper.COLUMN_ID, c.getID());
values.put(ScoreOpenHelper.COLUMN_NAME, c.getName());
values.put(ScoreOpenHelper.COLUMN_DATE, c.getDate());
values.put(ScoreOpenHelper.COLUMN_SCORE, c.getScore());
values.put(ScoreOpenHelper.COLUMN_GAME, c.getGame());
return database.update(ScoreOpenHelper.TABLE_SCORES, values,ScoreOpenHelper.COLUMN_ID +"=" + c.getID(), null);
}
}
SourceOpenHelp：
public class ScoreOpenHelper extends SQLiteOpenHelper {
public static final String DATABASENAME="scoredb.db";
public static final String TABLE_SCORES="scores";
public static final int DATABASEVERSION=2;
public static final String COLUMN_ID="ID";
public static final String COLUMN_NAME="Name";
public static final String COLUMN_DATE="Date";
public static final String COLUMN_SCORE="Score";
public static final String COLUMN_GAME="Game";
private static final String CREATE_TABLE_CUSTOMER="CREATE TABLE IF NOT EXISTS " +
TABLE_SCORES + "(" + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + COLUMN_NAME + " VARCHAR,"
+ COLUMN_DATE + " VARCHAR,"+ COLUMN_SCORE + " INTEGER,"+ COLUMN_GAME +" VARCHAR" + ");";
SQLiteDatabase database;
public ScoreOpenHelper(Context context) {
super(context, DATABASENAME, null, DATABASEVERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_CUSTOMER);
Log.i("data", "Table customer created");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_SCORES);
onCreate(db);
}
}
ScoreAdapter：
public class ScoreAdapter extends ArrayAdapter<Score> {
Context context;
int layoutResourceId;
ArrayList<Score>data;
public ScoreAdapter(Context context, int textViewResourceId,
List<Score> objects) {
super(context, textViewResourceId, objects);
this.context=context;
this.layoutResourceId=textViewResourceId;
this.data=(ArrayList<Score>) objects;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View row;
LayoutInflater inflater= ((Activity) context).getLayoutInflater();
row=inflater.inflate(layoutResourceId, parent,false);
Score s=data.get(position);
TextView name=(TextView) row.findViewById(R.id.name);
TextView date=(TextView) row.findViewById(R.id.date);
TextView score=(TextView) row.findViewById(R.id.score);
//Button btn=(Button) row.findViewById(R.id.btnDelete);
name.setText(s.getName());
date.setText(s.getDate());
score.setText(s.getScore());
return row;
}
}
row的xml或listview告诉我的位置。
感谢您的帮助
编辑：
新的Stack Trace：
03-13 12:56:09.109: I/data(949): Database connection open
03-13 12:56:09.160: I/data(949): Database connection open
03-13 12:56:09.339: W/ResourceType(949): No package identifier when getting value for resource number 0x00000032
03-13 12:56:09.349: D/AndroidRuntime(949): Shutting down VM
03-13 12:56:09.349: W/dalvikvm(949): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
03-13 12:56:09.499: E/AndroidRuntime(949): FATAL EXCEPTION: main
03-13 12:56:09.499: E/AndroidRuntime(949): android.content.res.Resources$NotFoundException: String resource ID #0x32
03-13 12:56:09.499: E/AndroidRuntime(949): at android.content.res.Resources.getText(Resources.java:230)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.TextView.setText(TextView.java:3769)
03-13 12:56:09.499: E/AndroidRuntime(949): at com.example.snake.ScoreAdapter.getView(ScoreAdapter.java:43)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.AbsListView.obtainView(AbsListView.java:2159)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.ListView.measureHeightOfChildren(ListView.java:1246)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.ListView.onMeasure(ListView.java:1158)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.View.measure(View.java:15518)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.View.measure(View.java:15518)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.View.measure(View.java:15518)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.LinearLayout.measureVertical(LinearLayout.java:847)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.View.measure(View.java:15518)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
03-13 12:56:09.499: E/AndroidRuntime(949): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2176)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.View.measure(View.java:15518)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.Choreographer.doFrame(Choreographer.java:532)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.os.Handler.handleCallback(Handler.java:725)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.os.Handler.dispatchMessage(Handler.java:92)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.os.Looper.loop(Looper.java:137)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.app.ActivityThread.main(ActivityThread.java:5041)
03-13 12:56:09.499: E/AndroidRuntime(949): at java.lang.reflect.Method.invokeNative(Native Method)
03-13 12:56:09.499: E/AndroidRuntime(949): at java.lang.reflect.Method.invoke(Method.java:511)
03-13 12:56:09.499: E/AndroidRuntime(949): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-13 12:56:09.499: E/AndroidRuntime(949): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-13 12:56:09.499: E/AndroidRuntime(949): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
由于NPE位于listview.setAdapter(adapter)，listview为null。它是null，因为findViewById(R.id.AllScores)会返回null。它返回null，因为布局activity_main不包含具有此ID的视图，或者资源ID和二进制XML文件不同步。在第一种情况下，将listview添加到布局中。在后一种情况下，清理并重建项目。
对于后续异常stacktrace：
03-13 12:56:09.499: E/AndroidRuntime(949): android.content.res.Resources$NotFoundException: String resource ID #0x32
03-13 12:56:09.499: E/AndroidRuntime(949): at android.content.res.Resources.getText(Resources.java:230)
03-13 12:56:09.499: E/AndroidRuntime(949): at android.widget.TextView.setText(TextView.java:3769)
03-13 12:56:09.499: E/AndroidRuntime(949): at com.example.snake.ScoreAdapter.getView(ScoreAdapter.java:43)
...在您的适配器getView()中，使用setText(String.valueOf(intValue))而不是setText(intValue)，因此int不会被视为资源ID。 （这可能是那里的int得分。）