[英]Error in fetching data from database table
我正在制作一個Android應用程序。 並試圖從列,名稱和分數中獲取數據
數據庫表,但在運行時出現此錯誤,
抱歉,此應用程序已意外停止。
這是我來自數據庫類的代碼,
public long addscore(String name, int score)
{
ContentValues values = new ContentValues();
values.put(KEY_name, name);
values.put(KEY_score, score);
// Inserting Row
return db.insert(DATABASE_TABLE, null, values);
}
public Cursor getScore(long rowId) throws SQLException
{
Cursor mCursor = db.query(true,DATABASE_TABLE, new String[] {
KEY_scoreid,KEY_name,KEY_score },,KEY_scoreid + "="
+ rowid,null,null,null,null,null);
if (mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}
這是我試圖從中獲取的類代碼
從數據庫表(Highscore.java)中獲取數據,
public class Highscore extends Activity
{
TextView name1,name2,name3,name4,name5,score1,score2,score3,score4,score5;
DBAdapter db1;
Cursor c;
int id;
String n1,n2,n3,n4,n5;
String s1,s2,s3,s4,s5;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.highscore);
Button backbtn=(Button)findViewById(R.id.backbtn);
OnClickListener listener=new OnClickListener()
{
public void onClick(View v)
{
Intent i=new Intent(Highscore.this,MainActivity.class);
startActivity(i);
finish();
}
};
backbtn.setOnClickListener(listener);
id=1;
name1=(TextView)findViewById(R.id.name1);
score1=(TextView)findViewById(R.id.score1);
db1=new DBAdapter(this);
db1.open();
c=db1.getScore(1);
n1=c.getString(1);
name1.setText(n1);
s1=c.getString(2);
score1.setText(s1);
c=db1.getScore(2);
n2=c.getString(1);
name2.setText(n2);
s2=c.getString(2);
score2.setText(s2);
c=db1.getScore(3);
n3=c.getString(1);
name3.setText(n3);
s3=c.getString(2);
score3.setText(s3);
id++;
c=db1.getScore(4);
n4=c.getString(1);
name4.setText(n4);
s4=c.getString(2);
score4.setText(s4);
id++;
c=db1.getScore(5);
n5=c.getString(1);
name5.setText(n5);
s5=c.getString(2);
score5.setText(s5);
c.deactivate();
c.close();
db1.close();
}
}
這次我只獲取5個名稱和分數。
這是我的Logcat錯誤,
09-19 12:01:36.046: D/AndroidRuntime(455): Shutting down VM
09-19 12:01:36.046: W/dalvikvm(455): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
09-19 12:01:36.066: E/AndroidRuntime(455): FATAL EXCEPTION: main
09-19 12:01:36.066: E/AndroidRuntime(455): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.quizapp/com.example.quizapp.Highscore}: java.lang.NullPointerException
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.os.Handler.dispatchMessage(Handler.java:99)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.os.Looper.loop(Looper.java:123)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.ActivityThread.main(ActivityThread.java:4627)
09-19 12:01:36.066: E/AndroidRuntime(455): at java.lang.reflect.Method.invokeNative(Native Method)
09-19 12:01:36.066: E/AndroidRuntime(455): at java.lang.reflect.Method.invoke(Method.java:521)
09-19 12:01:36.066: E/AndroidRuntime(455): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-19 12:01:36.066: E/AndroidRuntime(455): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-19 12:01:36.066: E/AndroidRuntime(455): at dalvik.system.NativeStart.main(Native Method)
09-19 12:01:36.066: E/AndroidRuntime(455): Caused by: java.lang.NullPointerException
09-19 12:01:36.066: E/AndroidRuntime(455): at com.example.quizapp.Highscore.onCreate(Highscore.java:59)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-19 12:01:36.066: E/AndroidRuntime(455): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
09-19 12:01:36.066: E/AndroidRuntime(455): ... 11 more
如果您的人沒有從我的問題中得到任何幫助,請提出..請幫助我解決錯誤。
提前致謝
從我看來,您的問題不在數據庫連接中,您有一些未處理的異常。 在onCreate(Highscore.java:59)中也有一個NULL指針異常
您可以做一件事:注釋部分代碼,直到獲得可以運行的應用程序(不執行任何操作),然后取消注釋,直到找到使應用程序崩潰的確切代碼,這很容易做到,通常您會找到有問題的
祝好運
使用此代碼插入您的.....
public Cursor getScore(long rowId) throws SQLException
{
Cursor mCursor = db.query(true,DATABASE_TABLE, new String[] {
KEY_scoreid,KEY_name,KEY_score },KEY_scoreid + " ='"
+ rowid + "'",null,null,null,null,null);
if (mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}
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