應用程序在長時間處於後臺時崩潰

我正在開發可正常工作的Android應用程序。但問題是當我導航到我的設備中的另一個應用程序我當前的應用程序在後臺。一段時間後，我恢復該應用程序崩潰。我沒有看到任何問題。請幫助我。應用程序在長時間處於後臺時崩潰

我的日誌如下

01-13 15:02:38.520: E/AndroidRuntime(15875): FATAL EXCEPTION: main 
01-13 15:02:38.520: E/AndroidRuntime(15875):java.lang.RuntimeException:Unable to start activity ComponentInfo{shoppy.online.com/shoppy.online.com.HomeFragment}: java.lang.NullPointerException 
01-13 15:02:38.520: E/AndroidRuntime(15875):at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364) 
01-13 15:02:38.520: E/AndroidRuntime(15875):at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2416) 
01-13 15:02:38.520: E/AndroidRuntime(15875):at android.app.ActivityThread.access$600(ActivityThread.java:174) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1382) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.os.Handler.dispatchMessage(Handler.java:107) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.os.Looper.loop(Looper.java:194) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.app.ActivityThread.main(ActivityThread.java:5409) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at java.lang.reflect.Method.invokeNative(Native Method) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at java.lang.reflect.Method.invoke(Method.java:525) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:606) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at dalvik.system.NativeStart.main(Native Method) 
01-13 15:02:38.520: E/AndroidRuntime(15875): Caused by: java.lang.NullPointerException 
01-13 15:02:38.520: E/AndroidRuntime(15875): at shoppy.online.com.cart_db.Cart_DB.getAllItems(Cart_DB.java:39) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at shoppy.online.com.MainActivity.getCartData(MainActivity.java:677) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at shoppy.online.com.MainActivity.onCreate(MainActivity.java:103) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at shoppy.online.com.HomeFragment.onCreate(HomeFragment.java:112) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.app.Activity.performCreate(Activity.java:5122) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1150) 
01-13 15:02:38.520: E/AndroidRuntime(15875): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2328) 
01-13 15:02:38.520: E/AndroidRuntime(15875): ... 11 more

，因爲它說NullPointerException上Caet_DB這裏是我的課。

package shoppy.online.com.cart_db; 

import android.content.ContentValues; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 

public class Cart_DB { 

public static SQLiteDatabase mDatabase; 
public static String CREATE_CART_TABLE; 
public static String CART_TABLE = "cart"; 
public static Cart_model[] cartData; 

public static void CreateAllToDoTable() { 
    createTodoTable(); 
} 

private static void createTodoTable() { 
    try { 
     Cart_DB.CREATE_CART_TABLE = "CREATE TABLE IF NOT EXISTS " 
       + Cart_DB.CART_TABLE + "(" 
       + "id INTEGER PRIMARY KEY AUTOINCREMENT," 
       + "productID TEXT," + "productName TEXT," 
       + "productPrice TEXT," + "productSellingPrice TEXT," 
       + "productDiscount TEXT," + "productQty TEXT," 
       + "shippingCharge TEXT," + "productDeliDays TEXT," 
       + "productCode TEXT," + "storeName TEXT," 
       + "productAvgRates TEXT," + "productImage TEXT," 
       + "productSlug TEXT," + "finalQty TEXT," 
       + "finalShip TEXT," + "productColorID TEXT," 
       + "productColor TEXT," + "productSizeID TEXT," 
       + "productSize TEXT," + "productStock TEXT" + ")"; 
     Cart_DB.mDatabase.execSQL(Cart_DB.CREATE_CART_TABLE); 
    } catch (Exception e) { 
    } 
} 

public static Cart_model[] getAllItems() { 
    Cursor c = mDatabase.query(CART_TABLE, null, null, null, null, null, 
      null); 
    cartData = new Cart_model[c.getCount()]; 
    c.moveToFirst(); 

    int i = 0; 
    while (c.isAfterLast() == false) { 
     cartData[i] = new Cart_model(); 
     cartData[i].setID(c.getInt(0)); 
     cartData[i].setProductID(c.getString(1)); 
     cartData[i].setProductName(c.getString(2)); 
     cartData[i].setProductPrice(c.getString(3)); 
     cartData[i].setProductSellingPrice(c.getString(4)); 
     cartData[i].setProductDiscount(c.getString(5)); 
     cartData[i].setProductQty(c.getString(6)); 
     cartData[i].setShippingCharge(c.getString(7)); 
     cartData[i].setProductDeliDays(c.getString(8)); 
     cartData[i].setProductCode(c.getString(9)); 
     cartData[i].setStoreName(c.getString(10)); 
     cartData[i].setProductAvgRates(c.getString(11)); 
     cartData[i].setProductImage(c.getString(12)); 
     cartData[i].setProductSlug(c.getString(13)); 
     cartData[i].setFinalQty(c.getString(14)); 
     cartData[i].setFinalShip(c.getString(15)); 
     cartData[i].setProductColorID(c.getString(16)); 
     cartData[i].setProductColor(c.getString(17)); 
     cartData[i].setProductSizeID(c.getString(18)); 
     cartData[i].setProductSize(c.getString(19)); 
     cartData[i].setProductStock(c.getString(20)); 
     i++; 
     c.moveToNext(); 
    } 
    return cartData; 
} 

public static void insertAllCart(String productID, String productName, 
     String productPrice, String productSellingPrice, 
     String productDiscount, String productQty, String shippingCharge, 
     String productDeliDays, String productCode, String storeName, 
     String productAvgRates, String productImage, String productSlug, 
     String finalQty, String finalShip, String productColorID, 
     String productColor, String productSizeID, String productSize, 
     String productStock) { 
    ContentValues val = new ContentValues(); 
    val.put("productID", productID); 
    val.put("productName", productName); 
    val.put("productPrice", productPrice); 
    val.put("productSellingPrice", productSellingPrice); 
    val.put("productDiscount", productDiscount); 
    val.put("productQty", productQty); 
    val.put("shippingCharge", shippingCharge); 
    val.put("productDeliDays", productDeliDays); 
    val.put("productCode", productCode); 
    val.put("storeName", storeName); 
    val.put("productAvgRates", productAvgRates); 
    val.put("productImage", productImage); 
    val.put("productSlug", productSlug); 
    val.put("finalQty", finalQty); 
    val.put("finalShip", finalShip); 
    val.put("productColorID", productColorID); 
    val.put("productColor", productColor); 
    val.put("productSizeID", productSizeID); 
    val.put("productSize", productSize); 
    val.put("productStock", productStock); 

    @SuppressWarnings("unused") 
    long value = mDatabase.insert(CART_TABLE, null, val); 
} 

public static void updateCartData(Cart_model c) { 
    ContentValues value = new ContentValues(); 
    value.put("productID", c.productID); 
    value.put("productName", c.productName); 
    value.put("productPrice", c.productPrice); 
    value.put("productSellingPrice", c.productSellingPrice); 
    value.put("productDiscount", c.productDiscount); 
    value.put("productQty", c.productQty); 
    value.put("shippingCharge", c.shippingCharge); 
    value.put("productDeliDays", c.productDeliDays); 
    value.put("productCode", c.productCode); 
    value.put("storeName", c.storeName); 
    value.put("productAvgRates", c.productAvgRates); 
    value.put("productImage", c.productImage); 
    value.put("productSlug", c.productSlug); 
    value.put("finalQty", c.finalQty); 
    value.put("finalShip", c.finalShip); 
    value.put("productColorID", c.productColorID); 
    value.put("productColor", c.productColor); 
    value.put("productSizeID", c.productSizeID); 
    value.put("productSize", c.productSize); 
    value.put("productStock", c.productStock); 
    mDatabase.update(CART_TABLE, value, "id = " + c.ID, null); 
} 

public static void deleteCartData(Cart_model d) { 
    mDatabase.delete(CART_TABLE, "id = " + d.ID, null); 
} 
}

MainActivity

public class MainActivity extends AppCompatActivity implements OnClickListener { 
protected FrameLayout frameLayout; 
protected DrawerLayout mDrawerLayout; 
protected ListView mDrawerList; 
protected ActionBarDrawerToggle mDrawerToggle; 
protected static int position; 
protected static boolean isLaunch = true; 

Toolbar toolbar; 

RelativeLayout prof_head; 
protected TextView profile_name, track_order; 
protected TextView login; 
TextView contact_us; 
TextView faqs; 
TextView about_us; 
TextView tvChar; 
protected RoundedImageView img; 
protected FrameLayout fam; 

private CharSequence mTitle; 

private String[] navMenuTitles; 
private TypedArray navMenuIcons; 

private ArrayList<NavDrawerItem> navDrawerItems; 
private NavDrawerListAdapter adapter; 

SharedPreferences sharedPreferences; 
protected String MyPREFERENCES = "MyPrefs"; 
public static String name, pass, uname, pImg; 
public static String id; 
public static ArrayList<Cart_model> listdata; 
public static ArrayList<Wishlist_model> listdata1; 
Cart_model[] data; 
Bundle kek; 

@SuppressLint("NewApi") 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    kek = savedInstanceState; 
    navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items); 

    navMenuIcons = getResources() 
      .obtainTypedArray(R.array.nav_drawer_icons); 

    frameLayout = (FrameLayout) findViewById(R.id.frame_container); 
    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); 
    mDrawerList = (ListView) findViewById(R.id.list_slidermenu); 

    toolbar = (Toolbar) findViewById(R.id.toolbar_headers); 

    setSupportActionBar(toolbar); 
    getCartData(); 
    getWishData(); 

    LayoutInflater inflater = getLayoutInflater(); 
    View listHeaderView = inflater.inflate(R.layout.profile_header, null, 
      false); 
    View listFooterView = inflater 
      .inflate(R.layout.nav_footer, null, false); 
    mDrawerList.addHeaderView(listHeaderView); 
    mDrawerList.addFooterView(listFooterView); 

    navDrawerItems = new ArrayList<NavDrawerItem>(); 

    navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons 
      .getResourceId(0, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons 
      .getResourceId(1, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons 
      .getResourceId(2, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons 
      .getResourceId(3, -1), true, "22")); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons 
      .getResourceId(4, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons 
      .getResourceId(5, -1), true, "50+")); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[6], navMenuIcons 
      .getResourceId(6, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[7], navMenuIcons 
      .getResourceId(7, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[8], navMenuIcons 
      .getResourceId(8, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[9], navMenuIcons 
      .getResourceId(9, -1), true, "22")); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[10], navMenuIcons 
      .getResourceId(10, -1))); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[11], navMenuIcons 
      .getResourceId(11, -1), true, "50+")); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[12], navMenuIcons 
      .getResourceId(12, -1), true, "50+")); 
    navDrawerItems.add(new NavDrawerItem(navMenuTitles[13], navMenuIcons 
      .getResourceId(13, -1), true, "50+")); 

    navMenuIcons.recycle(); 

    mDrawerList.setOnItemClickListener(new OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, 
       int position, long id) { 
      displayView(position); 
     } 
    }); 

    adapter = new NavDrawerListAdapter(getApplicationContext(), 
      navDrawerItems); 
    mDrawerList.setAdapter(adapter); 

    getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
    getSupportActionBar().setHomeButtonEnabled(true); 
    mDrawerList.setItemChecked(1, true); 

    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, 
      R.drawable.ic_drawer, R.string.app_name) { 
    }; 
    mDrawerLayout.setDrawerListener(mDrawerToggle); 

    // mDrawerToggle.setDrawerIndicatorEnabled(false); 

    if (isLaunch) { 
     isLaunch = false; 
     displayView(1); 
    } 

    sharedPreferences = getSharedPreferences(MyPREFERENCES, 
      Context.MODE_PRIVATE); 
    id = sharedPreferences.getString("id", null); 
    name = sharedPreferences.getString("email", null); 
    uname = sharedPreferences.getString("name", null); 
    pass = sharedPreferences.getString("password", null); 
    pImg = sharedPreferences.getString("profileImg", null); 

    prof_head = (RelativeLayout) findViewById(R.id.prof_head); 
    prof_head.setOnClickListener(this); 
    profile_name = (TextView) findViewById(R.id.profile_name); 
    img = (RoundedImageView) findViewById(R.id.roundedImage); 
    fam = (FrameLayout) findViewById(R.id.flProfil); 
    tvChar = (TextView) findViewById(R.id.tvChar); 
    track_order = (TextView) findViewById(R.id.track_order); 
    track_order.setOnClickListener(this); 
    login = (TextView) findViewById(R.id.login); 
    login.setOnClickListener(this); 
    contact_us = (TextView) findViewById(R.id.contact_us); 
    contact_us.setOnClickListener(this); 
    faqs = (TextView) findViewById(R.id.faqs); 
    faqs.setOnClickListener(this); 
    about_us = (TextView) findViewById(R.id.about_us); 
    about_us.setOnClickListener(this); 

    int status = 0; 
    int resourceId = getResources().getIdentifier("status_bar_height", 
      "dimen", "android"); 
    if (resourceId > 0) { 
     status = getResources().getDimensionPixelSize(resourceId); 
    } 

    float scale = getResources().getDisplayMetrics().density; 
    int paddingdp = (int) (16 * scale + 0.5f); 
    int heightdp = 0; 
    if ((getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_LARGE) { 
     heightdp = (int) (200 * scale + 0.5f); 

    } else { 
     heightdp = (int) (130 * scale + 0.5f); 
    } 

    // int statusbar = (int) (25 * scale + 0.5f); 

    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) { 
     toolbar.setPadding(0, status, 0, 0); 
     // listHeaderView.setPadding(32, 84, 32, 32); 
     prof_head.setPadding(paddingdp, paddingdp + status, paddingdp, 
       paddingdp); 
     LayoutParams params = (LayoutParams) prof_head.getLayoutParams(); 
     params.height = heightdp + status; 
     prof_head.setLayoutParams(params); 
    } else { 
    } 

    if (name.equals("user_email")) { 
     login.setText("Login"); 
     profile_name.setText("Welcome User"); 
     img.setVisibility(View.VISIBLE); 
     img.setImageResource(R.drawable.images); 
     fam.setVisibility(View.GONE); 
    } else if (!name.equals("user_email")) { 
     login.setText("Logout"); 
     profile_name.setText(name); 
     if (pImg.equals("")) { 
      fam.setVisibility(View.VISIBLE); 
      img.setVisibility(View.GONE); 
      String tag = (String) name.subSequence(0, 1); 
      tvChar.setText(tag); 
     } else { 
      Picasso.with(getApplicationContext()).load(pImg).into(img); 
     } 
    } 

}

來源

2016-01-13 V-rund Puro-hit

您是否使用與'HomeFragment'參數的構造函數？也可以從'MainActivity'上放置'onCreate'的代碼 – LordRaydenMK

您還可以具體說明NPE出現的確切代碼行嗎？謝謝！ – fasteque

@fasteque at'Cursor c = mDatabase.query（CART_TABLE，null，null，null，null，null，null）;' –

經過大量的調試終於解決了這個問題。因爲@fasteque指出我在我的開始屏幕中啓動了mDatabase。

所以我在MainActivity做了一些小的改動，現在它像魅力一樣工作。

這裏是我的變化

if (Cart_DB.mDatabase == null) { 
     Cart_DB.mDatabase = openOrCreateDatabase("CART", 
       SQLiteDatabase.CREATE_IF_NECESSARY, null); 
} 

if (Wishlist_DB.mDatabase == null) { 
     Wishlist_DB.mDatabase = openOrCreateDatabase("WISHLIST", 
       SQLiteDatabase.CREATE_IF_NECESSARY, null); 
}

來源

2016-01-13 11:23:50

應用程序在長時間處於後臺時崩潰

回答

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