有一段时间我一直在使用我正在编写的Android应用程序出错。 （我是Android新手，相对于Java。）当我觉得我已经通过创建一个简单的表并向其添加数据来覆盖所有基础时，我无法弄清楚何时出现此错误。对于我的应用程序中的每个其他表，我没有遇到麻烦。但是，我的“设置”数据库一直给我带来麻烦。 （使用Android的Preferences类不是一种选择。）
以下是我使用Google API测试AVD的堆栈跟踪。
01-19 16:51:43.848: W/ActivityThread(388): Application com.lakesidebaptist.lakesidelife is waiting for the debugger on port 8100...
01-19 16:51:43.897: I/System.out(388): Sending WAIT chunk
01-19 16:51:44.107: I/dalvikvm(388): Debugger is active
01-19 16:51:44.107: I/System.out(388): Debugger has connected
01-19 16:51:44.107: I/System.out(388): waiting for debugger to settle...
01-19 16:51:44.307: I/System.out(388): waiting for debugger to settle...
01-19 16:51:44.507: I/System.out(388): waiting for debugger to settle...
01-19 16:51:44.738: I/System.out(388): waiting for debugger to settle...
01-19 16:51:44.937: I/System.out(388): waiting for debugger to settle...
01-19 16:51:45.137: I/System.out(388): waiting for debugger to settle...
01-19 16:51:45.337: I/System.out(388): waiting for debugger to settle...
01-19 16:51:45.537: I/System.out(388): waiting for debugger to settle...
01-19 16:51:45.737: I/System.out(388): debugger has settled (1321)
01-19 16:51:46.867: I/dalvikvm(388): Could not find method com.actionbarsherlock.internal.nineoldandroids.widget.NineFrameLayout.onHoverEvent, referenced from method com.actionbarsherlock.internal.widget.ActionBarContainer.onHoverEvent
01-19 16:51:46.867: W/dalvikvm(388): VFY: unable to resolve virtual method 5075: Lcom/actionbarsherlock/internal/nineoldandroids/widget/NineFrameLayout;.onHoverEvent (Landroid/view/MotionEvent;)Z
01-19 16:51:46.867: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x0000
01-19 16:51:46.878: D/dalvikvm(388): VFY: dead code 0x0003-0004 in Lcom/actionbarsherlock/internal/widget/ActionBarContainer;.onHoverEvent (Landroid/view/MotionEvent;)Z
01-19 16:51:46.897: I/dalvikvm(388): Could not find method android.widget.FrameLayout.getAlpha, referenced from method com.actionbarsherlock.internal.nineoldandroids.widget.NineFrameLayout.getAlpha
01-19 16:51:46.897: W/dalvikvm(388): VFY: unable to resolve virtual method 3801: Landroid/widget/FrameLayout;.getAlpha ()F
01-19 16:51:46.897: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000b
01-19 16:51:46.897: D/dalvikvm(388): VFY: dead code 0x000e-000f in Lcom/actionbarsherlock/internal/nineoldandroids/widget/NineFrameLayout;.getAlpha ()F
01-19 16:51:46.897: I/dalvikvm(388): Could not find method android.widget.FrameLayout.getTranslationY, referenced from method com.actionbarsherlock.internal.nineoldandroids.widget.NineFrameLayout.getTranslationY
01-19 16:51:46.897: W/dalvikvm(388): VFY: unable to resolve virtual method 3802: Landroid/widget/FrameLayout;.getTranslationY ()F
01-19 16:51:46.897: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000b
01-19 16:51:46.897: D/dalvikvm(388): VFY: dead code 0x000e-000f in Lcom/actionbarsherlock/internal/nineoldandroids/widget/NineFrameLayout;.getTranslationY ()F
01-19 16:51:46.897: I/dalvikvm(388): Could not find method android.widget.FrameLayout.setAlpha, referenced from method com.actionbarsherlock.internal.nineoldandroids.widget.NineFrameLayout.setAlpha
01-19 16:51:46.897: W/dalvikvm(388): VFY: unable to resolve virtual method 3805: Landroid/widget/FrameLayout;.setAlpha (F)V
01-19 16:51:46.897: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000a
01-19 16:51:46.897: D/dalvikvm(388): VFY: dead code 0x000d-000d in Lcom/actionbarsherlock/internal/nineoldandroids/widget/NineFrameLayout;.setAlpha (F)V
01-19 16:51:46.897: I/dalvikvm(388): Could not find method android.widget.FrameLayout.setTranslationY, referenced from method com.actionbarsherlock.internal.nineoldandroids.widget.NineFrameLayout.setTranslationY
01-19 16:51:46.897: W/dalvikvm(388): VFY: unable to resolve virtual method 3813: Landroid/widget/FrameLayout;.setTranslationY (F)V
01-19 16:51:46.897: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000a
01-19 16:51:46.907: D/dalvikvm(388): VFY: dead code 0x000d-000d in Lcom/actionbarsherlock/internal/nineoldandroids/widget/NineFrameLayout;.setTranslationY (F)V
01-19 16:51:46.947: I/dalvikvm(388): Could not find method android.content.pm.PackageManager.getActivityLogo, referenced from method com.actionbarsherlock.internal.widget.ActionBarView.<init>
01-19 16:51:46.947: W/dalvikvm(388): VFY: unable to resolve virtual method 326: Landroid/content/pm/PackageManager;.getActivityLogo (Landroid/content/ComponentName;)Landroid/graphics/drawable/Drawable;
01-19 16:51:46.947: D/dalvikvm(388): VFY: replacing opcode 0x6e at 0x01d1
01-19 16:51:46.947: I/dalvikvm(388): Could not find method android.content.pm.ApplicationInfo.loadLogo, referenced from method com.actionbarsherlock.internal.widget.ActionBarView.<init>
01-19 16:51:46.947: W/dalvikvm(388): VFY: unable to resolve virtual method 322: Landroid/content/pm/ApplicationInfo;.loadLogo (Landroid/content/pm/PackageManager;)Landroid/graphics/drawable/Drawable;
01-19 16:51:46.947: D/dalvikvm(388): VFY: replacing opcode 0x6e at 0x01df
01-19 16:51:46.947: D/dalvikvm(388): VFY: dead code 0x01d4-01d8 in Lcom/actionbarsherlock/internal/widget/ActionBarView;.<init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
01-19 16:51:46.957: D/dalvikvm(388): VFY: dead code 0x01e2-01e8 in Lcom/actionbarsherlock/internal/widget/ActionBarView;.<init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
01-19 16:51:47.047: I/dalvikvm(388): Could not find method android.view.ViewGroup.getAlpha, referenced from method com.actionbarsherlock.internal.nineoldandroids.view.NineViewGroup.getAlpha
01-19 16:51:47.047: W/dalvikvm(388): VFY: unable to resolve virtual method 3546: Landroid/view/ViewGroup;.getAlpha ()F
01-19 16:51:47.047: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000b
01-19 16:51:47.047: D/dalvikvm(388): VFY: dead code 0x000e-000f in Lcom/actionbarsherlock/internal/nineoldandroids/view/NineViewGroup;.getAlpha ()F
01-19 16:51:47.047: I/dalvikvm(388): Could not find method android.view.ViewGroup.getTranslationX, referenced from method com.actionbarsherlock.internal.nineoldandroids.view.NineViewGroup.getTranslationX
01-19 16:51:47.047: W/dalvikvm(388): VFY: unable to resolve virtual method 3556: Landroid/view/ViewGroup;.getTranslationX ()F
01-19 16:51:47.047: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000b
01-19 16:51:47.057: D/dalvikvm(388): VFY: dead code 0x000e-000f in Lcom/actionbarsherlock/internal/nineoldandroids/view/NineViewGroup;.getTranslationX ()F
01-19 16:51:47.057: I/dalvikvm(388): Could not find method android.view.ViewGroup.getTranslationY, referenced from method com.actionbarsherlock.internal.nineoldandroids.view.NineViewGroup.getTranslationY
01-19 16:51:47.057: W/dalvikvm(388): VFY: unable to resolve virtual method 3557: Landroid/view/ViewGroup;.getTranslationY ()F
01-19 16:51:47.057: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000b
01-19 16:51:47.057: D/dalvikvm(388): VFY: dead code 0x000e-000f in Lcom/actionbarsherlock/internal/nineoldandroids/view/NineViewGroup;.getTranslationY ()F
01-19 16:51:47.057: I/dalvikvm(388): Could not find method android.view.ViewGroup.setAlpha, referenced from method com.actionbarsherlock.internal.nineoldandroids.view.NineViewGroup.setAlpha
01-19 16:51:47.057: W/dalvikvm(388): VFY: unable to resolve virtual method 3572: Landroid/view/ViewGroup;.setAlpha (F)V
01-19 16:51:47.057: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000a
01-19 16:51:47.057: D/dalvikvm(388): VFY: dead code 0x000d-000d in Lcom/actionbarsherlock/internal/nineoldandroids/view/NineViewGroup;.setAlpha (F)V
01-19 16:51:47.057: I/dalvikvm(388): Could not find method android.view.ViewGroup.setTranslationX, referenced from method com.actionbarsherlock.internal.nineoldandroids.view.NineViewGroup.setTranslationX
01-19 16:51:47.057: W/dalvikvm(388): VFY: unable to resolve virtual method 3576: Landroid/view/ViewGroup;.setTranslationX (F)V
01-19 16:51:47.057: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000a
01-19 16:51:47.057: D/dalvikvm(388): VFY: dead code 0x000d-000d in Lcom/actionbarsherlock/internal/nineoldandroids/view/NineViewGroup;.setTranslationX (F)V
01-19 16:51:47.067: I/dalvikvm(388): Could not find method android.view.ViewGroup.setTranslationY, referenced from method com.actionbarsherlock.internal.nineoldandroids.view.NineViewGroup.setTranslationY
01-19 16:51:47.067: W/dalvikvm(388): VFY: unable to resolve virtual method 3577: Landroid/view/ViewGroup;.setTranslationY (F)V
01-19 16:51:47.067: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x000a
01-19 16:51:47.067: D/dalvikvm(388): VFY: dead code 0x000d-000d in Lcom/actionbarsherlock/internal/nineoldandroids/view/NineViewGroup;.setTranslationY (F)V
01-19 16:51:47.127: I/dalvikvm(388): Could not find method com.actionbarsherlock.internal.widget.ActionBarView$HomeView.onHoverEvent, referenced from method com.actionbarsherlock.internal.widget.ActionBarView$HomeView.dispatchHoverEvent
01-19 16:51:47.127: W/dalvikvm(388): VFY: unable to resolve virtual method 5936: Lcom/actionbarsherlock/internal/widget/ActionBarView$HomeView;.onHoverEvent (Landroid/view/MotionEvent;)Z
01-19 16:51:47.127: D/dalvikvm(388): VFY: replacing opcode 0x6e at 0x0000
01-19 16:51:47.127: D/dalvikvm(388): VFY: dead code 0x0003-0004 in Lcom/actionbarsherlock/internal/widget/ActionBarView$HomeView;.dispatchHoverEvent (Landroid/view/MotionEvent;)Z
01-19 16:51:47.137: I/dalvikvm(388): Could not find method android.widget.FrameLayout.onPopulateAccessibilityEvent, referenced from method com.actionbarsherlock.internal.widget.ActionBarView$HomeView.onPopulateAccessibilityEvent
01-19 16:51:47.137: W/dalvikvm(388): VFY: unable to resolve virtual method 3804: Landroid/widget/FrameLayout;.onPopulateAccessibilityEvent (Landroid/view/accessibility/AccessibilityEvent;)V
01-19 16:51:47.137: D/dalvikvm(388): VFY: replacing opcode 0x6f at 0x0006
01-19 16:51:47.537: D/AndroidRuntime(388): Shutting down VM
01-19 16:51:47.537: W/dalvikvm(388): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
01-19 16:51:47.597: E/AndroidRuntime(388): FATAL EXCEPTION: main
01-19 16:51:47.597: E/AndroidRuntime(388): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lakesidebaptist.lakesidelife/com.lakesidebaptist.lakesidelife.MainActivity}: java.lang.NullPointerException
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.os.Handler.dispatchMessage(Handler.java:99)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.os.Looper.loop(Looper.java:123)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.ActivityThread.main(ActivityThread.java:4627)
01-19 16:51:47.597: E/AndroidRuntime(388): at java.lang.reflect.Method.invokeNative(Native Method)
01-19 16:51:47.597: E/AndroidRuntime(388): at java.lang.reflect.Method.invoke(Method.java:521)
01-19 16:51:47.597: E/AndroidRuntime(388): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
01-19 16:51:47.597: E/AndroidRuntime(388): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
01-19 16:51:47.597: E/AndroidRuntime(388): at dalvik.system.NativeStart.main(Native Method)
01-19 16:51:47.597: E/AndroidRuntime(388): Caused by: java.lang.NullPointerException
01-19 16:51:47.597: E/AndroidRuntime(388): at com.lakesidebaptist.lakesidelife.update.database.dbAdapter.doOnFirstRun(dbAdapter.java:118)
01-19 16:51:47.597: E/AndroidRuntime(388): at com.lakesidebaptist.lakesidelife.update.database.dbAdapter$DatabaseHelper.onCreate(dbAdapter.java:139)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:106)
01-19 16:51:47.597: E/AndroidRuntime(388): at com.lakesidebaptist.lakesidelife.update.database.dbAdapter.open(dbAdapter.java:38)
01-19 16:51:47.597: E/AndroidRuntime(388): at com.lakesidebaptist.lakesidelife.MainActivity.onCreate(MainActivity.java:54)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-19 16:51:47.597: E/AndroidRuntime(388): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
01-19 16:51:47.597: E/AndroidRuntime(388): ... 11 more
根据我的理解，日志中的ABS内容与实际问题无关。
MainActivity.class
package com.lakesidebaptist.lakesidelife;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.ActionBar.Tab;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;
import com.actionbarsherlock.view.MenuItem;
import com.lakesidebaptist.lakesidelife.ui.PagerAdapter;
import com.lakesidebaptist.lakesidelife.update.Updater;
import com.lakesidebaptist.lakesidelife.update.UpdaterTask;
import com.lakesidebaptist.lakesidelife.update.database.dbAdapter;
public class MainActivity extends SherlockFragmentActivity implements
ActionBar.TabListener {
// The context used for the Updater class
public static Context context;
PagerAdapter pagerAdapter;
/*
* I'm not entirely sure what this does, but it's key in implementing the
* tab/swiping navigation. See documentation here:
* http://developer.android.com
* /reference/android/support/v4/view/ViewPager.html
*/
ViewPager viewPager;
// The AsyncTask class Updater
public static Updater updater;
private static ProgressDialog pd = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
// Perform initial update
dbAdapter dba = new dbAdapter(this);
dba.open();
String doesDBexist = dba.getSetting("firstRun");
if(doesDBexist == null) {
dba.doOnFirstRun();
}
if (dba.getSetting("firstRun").equals("true")) {
/*
* Checks if network connection is available and if so, starts the
* updater
*/
NetworkInfo ni = ((ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE))
.getActiveNetworkInfo();
if (ni != null) {
// Updates if there is a connection
new UpdaterTask().execute();
pd = new ProgressDialog(this, ProgressDialog.STYLE_SPINNER)
.show(this, "@string/progress_dialog_updating_title",
"@string/progress_dialog_updating_body");
dba.addSetting("firstRun", "false");
} else {
// Tells user there's no connection and closes activity
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("@string/no_internet_dialog_title")
.setMessage("@string/no_internet_dialog_body")
.setCancelable(false)
.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
finish();
}
});
}
}
dba.close();
// Sets up tabs
pagerAdapter = new PagerAdapter(getSupportFragmentManager());
final ActionBar actionBar = getSupportActionBar();
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(pagerAdapter);
// The method is called when a tab is clicked or the user swipes.
viewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// Creates "Life" tab
actionBar.addTab(actionBar.newTab().setText("Life")
.setTabListener(this));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = getSupportMenuInflater();
menuInflater.inflate(R.menu.activity_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.menu_settings:
Intent intent = new Intent(this, SettingsActivity.class);
startActivity(intent);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
// Called when a tab is selected.
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
}
dbAdapter.class
package com.lakesidebaptist.lakesidelife.update.database;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
/**
* The database adapter for the application database.
*
* @author andrew
*/
public class dbAdapter {
private static final String DATABASE_NAME = "lakeside";
/**
* This should be changed whenever the format of the application database
* changes in such a way that the onUpgrade() method must be called.
*/
private static final int VERSION = 1;
private DatabaseHelper dbHelper;
private SQLiteDatabase db;
private final Context context;
public dbAdapter(Context context) {
this.context = context;
}
/**
* Opens the database.
*
* @return
*/
public dbAdapter open() {
dbHelper = new DatabaseHelper(context);
db = dbHelper.getWritableDatabase();
return this;
}
/**
* Sumbits query to database. Note this function does NOT return anything.
* You must use the read() function to read from the database.
*
* @param command
*/
public void query(String command) {
db.execSQL(command);
}
/**
* This function should be used to read from a database. Notice "table" is
* the only required parameter.
+ setting + "', '" + value + "');";
query(command);
}
public void changeSetting(String setting, String value) {
String command = "UPDATE 'settings' SET 'value'='" + value + "' WHERE '" + setting + "'='" + value + "';";
query(command);
}
public String getSetting(String setting) {
Cursor cursor = db.rawQuery(
"SELECT 'value' FROM 'settings' WHERE 'setting'='" + setting
+ "';", null);
cursor.moveToFirst();
return cursor.getString(cursor.getColumnIndex("value"));
}
public void doOnFirstRun() {
db.execSQL("CREATE TABLE IF NOT EXISTS 'settings' ('setting' text, 'value' text);");
addSetting("firstRun", "true");
addSetting("updateServiceTimout", "60");
addSetting("updateTimeUnit", "minute");
}
/**
* I don't normally use nested classes due to my OCD, but I caved with this,
* because all the online examples did it, and I didn't have time to figure
* out how to make this class in its own file.
*
* @author andrew
*
*/
public class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
doOnFirstRun();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
}
答案 0 :(得分：2)
您没有初始化db（即它仍然引用null），这就是抛出NullPointerException的原因。