您好，我是 android 新手，请您帮我解决我的错误。当我要开始游戏时会发生错误，所以这是我的 logcat 数据库和活动
日志猫
08-06 04:02:31.350：E/AndroidRuntime（8261）：致命异常：主要
08-06 04:02:31.350: E/AndroidRuntime(8261): java.lang.RuntimeException: 无法实例化活动 ComponentInfo{com.example.windowcard/com.example.windowcard.Grade1}: java.lang.NullPointerException 08- 06 04:02:31.350: E/AndroidRuntime(8261): 在 android.content.ContextWrapper.getPackageName(ContextWrapper.java:127) 08-06 04:02:31.350: E/AndroidRuntime(8261): 在 com.example。 windowcard.dbHelp.(dbHelp.java:39) 08-06 04:02:31.350: E/AndroidRuntime(8261): at com.example.windowcard.Grade1.(Grade1.java:41)
数据库
package com.example.windowcard;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class dbHelp extends SQLiteOpenHelper{
//The Android's default system path of your application database.
private static String TAG = "dbHelp";
private static String DB_PATH = "";
private static String DB_NAME = "sample";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
public dbHelp(Context context) {
super(context, DB_NAME, null, 1); //
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
myContext.deleteDatabase(DB_NAME);
boolean dbExist = checkDataBase();
if(!dbExist){
//do nothing - database already exist
this.getReadableDatabase();
this.close();
try{
copyDataBase();
Log.e(TAG, "create Database database created");
}
catch (IOException e){
throw new Error ("Error Copying Database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
File dbFile = new File (DB_PATH + DB_NAME);
Log.v("dbFile", dbFile + " " + dbFile.exists());
return dbFile.exists();
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public boolean openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
// myDatabase =
SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
return myDataBase != null;
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
public Cursor getAllGrade1(){
this.openDataBase();
String sql = "Select * from gr1";
Cursor c = myDataBase.rawQuery(sql, null);
c.moveToFirst();
return c;
}
public String getScore(int score){
this.openDataBase();
String sql = "SELECT * FROM gr1 WHERE _id =" + score;
Cursor c = myDataBase.rawQuery(sql, null);
c.moveToFirst();
return c.getString(c.getColumnIndex("score"));
}
public String getMistakes(int Errors){
this.openDataBase();
String sql="SELECT * FROM gr1 WHERE _id=" + Errors;
Cursor c = myDataBase.rawQuery(sql, null);
c.moveToFirst();
return c.getString(c.getColumnIndex("Errors"));
}
}
活动
package com.example.windowcard;
import java.util.ArrayList;
import java.util.Collections;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class Grade1 extends Activity implements OnClickListener {
TextView tvQuestion,tvQuestionId,tvPlayer1,tvScore,tvMissCount;
EditText et;
Button submit,next,start;
Cursor c;
MediaPlayer sonic;
Handler mHandler = new Handler();
long startTime;
TextView timer,timems;
long elapsedTime;
final int REFRESH_RATE = 100;
String hours,minutes,seconds,milliseconds;
long secs,mins,hrs,msecs;
boolean stopped = false;
String s,timers;
int score=1;
int miss=1;
dbHelp dbh = new dbHelp(this);
ArrayList<Integer> rdm = new ArrayList<Integer>();
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.grade1);
sonic = MediaPlayer.create(Grade1.this,R.raw.sonic);
sonic.start();
sonic.setLooping(true);
sonic.setVolume(100, 100);
initialize();
}
public void updateTimer (float time){
secs = (long)(time/1000);
mins = (long)((time/1000)/60);
hrs = (long)(((time/1000)/60)/60);
secs = secs % 60;
seconds=String.valueOf(secs);
if(secs == 0){
seconds = "00";
}
if(secs <10 && secs > 0){
seconds = "0"+seconds;
}
mins = mins % 60;
minutes=String.valueOf(mins);
if(mins == 0){
minutes = "00";
}
if(mins <10 && mins > 0){
minutes = "0"+minutes;
}
hours=String.valueOf(hrs);
if(hrs == 0){
hours = "00";
}
if(hrs <10 && hrs > 0){
hours = "0"+hours;
}
milliseconds = String.valueOf((long)time);
if(milliseconds.length()==2){
milliseconds = "0"+milliseconds;
}
if(milliseconds.length()<=1){
milliseconds = "00";
}
//milliseconds = milliseconds.substring(milliseconds.length(), milliseconds.length());
(timer = (TextView)findViewById(R.id.tvTime)).setText(hours + ":" + minutes + ":" + seconds);
//((TextView)findViewById(R.id.tvTimeMs)).setText(":" + milliseconds);
}
public Runnable startTimer = new Runnable() {
public void run() {
elapsedTime = System.currentTimeMillis() - startTime;
updateTimer(elapsedTime);
mHandler.postDelayed(this,REFRESH_RATE);
}
};
public void startClick (View view){
if(stopped){
startTime = System.currentTimeMillis() - elapsedTime;
}
else{
startTime = System.currentTimeMillis();
}
mHandler.removeCallbacks(startTimer);
mHandler.postDelayed(startTimer, 0);
}
public void stopClick (View view){
mHandler.removeCallbacks(startTimer);
stopped = true;
}
public void resetClick (View view){
stopped = false;
((TextView)findViewById(R.id.tvTime)).setText("00:00:00");
//((TextView)findViewById(R.id.tvTimeMs)).setText(":0");
}
private void refresh(){
c = dbh.getAllGrade1();
c.moveToPosition(rdm.get(0));
rdm.remove(0);
tvScore.setText(dbh.getScore(score));
tvMissCount.setText(dbh.getMistakes(miss));
tvPlayer1.setText(s);
//tvQuestion.setText(c.getString(c.getColumnIndex("Question")));
tvQuestion.setText(c.getString(1));
et.setText("");
}
private void initialize() {
// TODO Auto-generated method stub
submit= (Button) findViewById(R.id.b1);
//tvQuestionId = (TextView) findViewById(R.id.tvQuestionId);
tvPlayer1 = (TextView) findViewById(R.id.tvPlayer1);
tvScore = (TextView) findViewById(R.id.tvScore);
tvQuestion = (TextView) findViewById(R.id.tvQuestion);
tvMissCount = (TextView) findViewById(R.id.tvMissCount);
start = (Button) findViewById(R.id.bStart);
et = (EditText) findViewById(R.id.et1);
Intent z = getIntent();
s = z.getExtras().getString("PlayerName");
submit.setVisibility(View.INVISIBLE);
et.setVisibility(View.INVISIBLE);
tvQuestion.setVisibility(View.INVISIBLE);
//Bundle receive = getIntent().getExtras();
//hold = receive.getString("PlayerName")
for(int count=0; count<10; count++){
rdm.add(count);
}
Collections.shuffle(rdm);
refresh();
final MediaPlayer mp = MediaPlayer.create(this, R.raw.answerright);
final MediaPlayer mp2= MediaPlayer.create(this, R.raw.answerwrong);
start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
if (start.isClickable()){
et.setVisibility(View.VISIBLE);
submit.setVisibility(View.VISIBLE);
tvQuestion.setVisibility(View.VISIBLE);
startClick(arg0);
start.setVisibility(View.INVISIBLE);
}
}
});
submit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(et.getText().toString().equalsIgnoreCase("")){
Toast.makeText(getApplicationContext(), "You need to answer first the question before proceeding to the next question", Toast.LENGTH_SHORT).show();
}else{
if (c.getString(c.getColumnIndex("Answer")).equalsIgnoreCase(et.getText().toString())){
mp.start();
if(score==10){
stopClick(v);
timers = timer.getText().toString();
// dbh.insertRecord1(s, score,timers,miss);
resetClick(v);
AlertDialog diaBox = makneAndShowDialogBox();
diaBox.show();
diaBox.setCanceledOnTouchOutside(false);
//Toast.makeText(getApplicationContext(), "Congratulations!", Toast.LENGTH_LONG).show();
sonic.release();
//Intent a = new Intent(Grade1.this,Menu.class);
//startActivity(a);
//finish();
}
String Score = tvScore.getText().toString();
score++;
//String newScore = dbh.getScore(score);
refresh();
}
else{
mp2.start();
String Miss = tvMissCount.getText().toString();
miss++;
// String newMiss = dbh.getMistakes(miss);
refresh();
}
}
}
});
}
private AlertDialog makneAndShowDialogBox() {
// TODO Auto-generated method stub
AlertDialog myDialogBox = new AlertDialog.Builder(this)
.setTitle("Congratulations!!")
.setMessage("Congratulations on finishing the game!")
.setPositiveButton("Main Menu", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
Intent i = new Intent(Grade1.this,Menu.class);
startActivity(i);
finish();
dialog.dismiss();
}
})
.create();
return myDialogBox;
/** next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int count = 0;
// TODO Auto-generated method stub
if(count==40){
Intent a = new Intent(Grade1.this,Menu.class);
startActivity(a);
finish();
}
count++;
refreshgame();
}
});
**/
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
sonic.release();
finish();
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
}