我是编程方面的新手，我有一个奇怪的问题。我尝试在后台长时间从背景中恢复应用程序，并使用NullPointerException进行崩溃。
这是logcat的错误
05-06 14:19:28.278: W/~~~~~~~~~~~~~~~~MainActivity(12129): onSaveInstanceState() com.main.MainActivity@43087bb0 fragment: PrivateCabinetFragment{430d2ae0 #0 id=0x7f09005e PrivateCabinetFragment}
05-06 14:19:35.168: E/BaseFragment(13342): onCreate
05-06 14:19:35.168: D/AndroidRuntime(13342): Shutting down VM
05-06 14:19:35.168: W/dalvikvm(13342): threadid=1: thread exiting with uncaught exception (group=0x4158cba8)
05-06 14:19:35.168: E/AndroidRuntime(13342): FATAL EXCEPTION: main
05-06 14:19:35.168: E/AndroidRuntime(13342): Process: com, PID: 13342
05-06 14:19:35.168: E/AndroidRuntime(13342): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.main.MainActivity}: java.lang.NullPointerException
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.ActivityThread.access$800(ActivityThread.java:135)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.os.Handler.dispatchMessage(Handler.java:102)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.os.Looper.loop(Looper.java:136)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-06 14:19:35.168: E/AndroidRuntime(13342): at java.lang.reflect.Method.invokeNative(Native Method)
05-06 14:19:35.168: E/AndroidRuntime(13342): at java.lang.reflect.Method.invoke(Method.java:515)
05-06 14:19:35.168: E/AndroidRuntime(13342): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-06 14:19:35.168: E/AndroidRuntime(13342): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-06 14:19:35.168: E/AndroidRuntime(13342): at dalvik.system.NativeStart.main(Native Method)
05-06 14:19:35.168: E/AndroidRuntime(13342): Caused by: java.lang.NullPointerException
05-06 14:19:35.168: E/AndroidRuntime(13342): at com.main.MainActivity.setUnreadedMessages(MainActivity.java:151)
05-06 14:19:35.168: E/AndroidRuntime(13342): at com.main.PrivateCabinetFragment.onCreate(PrivateCabinetFragment.java:104)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.support.v4.app.Fragment.performCreate(Fragment.java:1437)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:877)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1070)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.support.v4.app.FragmentManagerImpl.dispatchCreate(FragmentManager.java:1856)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:210)
05-06 14:19:35.168: E/AndroidRuntime(13342): at com.main.BaseActivity.onCreate(BaseActivity.java:55)
05-06 14:19:35.168: E/AndroidRuntime(13342): at com.main.MainActivity.onCreate(MainActivity.java:65)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.Activity.performCreate(Activity.java:5231)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-06 14:19:35.168: E/AndroidRuntime(13342): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
05-06 14:19:35.168: E/AndroidRuntime(13342): ... 11 more
这是我的代码
package com.main;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.inputmethod.InputMethodManager;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.R;
import com.connection.ActionGetData;
import com.data.Constants;
public class MainActivity extends BaseActivity implements OnClickListener, DialogInterface.OnCancelListener {
private final static String CLASS_TAG = MainActivity.class.getSimpleName();
private Fragment mContent;
private PrivateCabinetFragment privateCabinetFrag;
private SettingsFragment settingsFragment;
private NewOrderMainFragment stayOrderFragment;
private PopularQuestionListFragment questionsFragment;
private PaymentsMenu paymentsMenu;
private MessageMain messageMain;
private MyRequestOrdersListFragment requestList;
private ImageView service;
private ImageView helpAndSupport;
private ImageView payments;
private ImageView settings;
private RelativeLayout btnService;
private RelativeLayout btnHelpAndSupport;
private RelativeLayout btnPayments;
private RelativeLayout btnSettings;
private RelativeLayout btnMessages;
private ImageView btnSupportStayOrder;
private TextView btnSupportRequestOrders;
private TextView btnSupportPopularQuestion;
private ImageView messages;
private TextView tvNewMessages;
private RelativeLayout dashBoard;
private LinearLayout toggleButton;
private Bundle extras;
private String fragment_tag = "";
private FragmentManager frag_manager;
private int onBackpress = 0;
public static boolean sDisableFragmentAnimations = false;
protected Animation animUp;
protected Animation animDown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
Log.e(CLASS_TAG,"savedInstanceState"+ savedInstanceState);
if (savedInstanceState != null) {
Log.e(CLASS_TAG, "savedInstanceState" + savedInstanceState.isEmpty());
Log.i(CLASS_TAG, "savedInstance != null");
Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
} else {
setContentView(R.layout.main_activity);
overridePendingTransition(R.anim.slide_in_left, R.anim.slide_out_left);
extras = getIntent().getExtras();
tvNewMessages = (TextView) findViewById(R.id.tv_new_messages);
service = (ImageView) findViewById(R.id.iv_services_main_board);
btnService = (RelativeLayout) findViewById(R.id.rl_services_main_board);
btnService.setOnClickListener(this);
helpAndSupport = (ImageView) findViewById(R.id.iv_support_main_board);
btnHelpAndSupport = (RelativeLayout) findViewById(R.id.rl_support_main_board);
btnHelpAndSupport.setOnClickListener(this);
payments = (ImageView) findViewById(R.id.iv_payments_main_board);
btnPayments = (RelativeLayout) findViewById(R.id.rl_payments_main_board);
btnPayments.setOnClickListener(this);
messages = (ImageView) findViewById(R.id.iv_message_main_board);
btnMessages = (RelativeLayout) findViewById(R.id.rl_message_main_board);
btnMessages.setOnClickListener(this);
settings = (ImageView) findViewById(R.id.iv_settings_main_board);
btnSettings = (RelativeLayout) findViewById(R.id.rl_settings_main_board);
btnSettings.setOnClickListener(this);
toggleButton = (LinearLayout) findViewById(R.id.ll_toggle_container);
toggleButton.setBackgroundDrawable((getResources().getDrawable(R.drawable.top_panel_background)));
dashBoard = (RelativeLayout) findViewById(R.id.dash_board);
btnSupportStayOrder = (ImageView) findViewById(R.id.iv_new_order);
btnSupportStayOrder.setOnClickListener(this);
btnSupportPopularQuestion = (TextView) findViewById(R.id.tv_popular_questions);
btnSupportPopularQuestion.setOnClickListener(this);
btnSupportRequestOrders = (TextView) findViewById(R.id.tv_my_orders);
btnSupportRequestOrders.setOnClickListener(this);
questionsFragment = new PopularQuestionListFragment();
privateCabinetFrag = new PrivateCabinetFragment();
settingsFragment = new SettingsFragment();
stayOrderFragment = new NewOrderMainFragment();
paymentsMenu = new PaymentsMenu();
messageMain = new MessageMain();
requestList = new MyRequestOrdersListFragment();
animUp = AnimationUtils.loadAnimation(this, R.anim.anim_up);
animDown = AnimationUtils.loadAnimation(this, R.anim.anim_down);
frag_manager = getSupportFragmentManager();
service.setBackgroundResource(R.drawable.services_main_board_pressed);
if (extras != null) {
boolean payments = extras.getBoolean(Constants.EXTRAS_MAIN_ACTIVITY_PAY_FRAGMENT);
if (payments) {
fragment_tag = PaymentsMenu.class.getSimpleName();
pushFragmentsWithoutAnimation(paymentsMenu, fragment_tag);
}
} else {
fragment_tag = PrivateCabinetFragment.class.getSimpleName();
pushFragmentsWithoutAnimation(privateCabinetFrag, fragment_tag);
}
}
}
public void setUnreadedMessages(int count) {
if (count > 0) {
tvNewMessages.setVisibility(View.VISIBLE);
tvNewMessages.setText(Integer.toString(count));
} else {
tvNewMessages.setVisibility(View.INVISIBLE);
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
Log.w("~~~~~~~~~~~~~~~~" + CLASS_TAG, "onSaveInstanceState() " + toString() + " fragment: " + mContent);
try {
frag_manager.putFragment(outState, "mContent", mContent);
} catch (Exception e) {
Log.e(CLASS_TAG, "!!!!!!!!");
e.printStackTrace();
}
super.onSaveInstanceState(outState);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
Log.w("~~~~~~~~~~~~~~~~" + CLASS_TAG, "onRestoreInstanceState() " + toString() + " fragment: " + mContent.getClass().getSimpleName());
mContent = frag_manager.getFragment(savedInstanceState, "mContent");
Log.i(CLASS_TAG, "savedInstance != null");
super.onRestoreInstanceState(savedInstanceState);
}
public void pushFragments(Fragment fragment, String tag) {
onBackpress = 0;
String old_tag = "";
try {
old_tag = mContent.getClass().getSimpleName();
} catch (Exception e) {
e.printStackTrace();
old_tag = "new";
}
mContent = fragment;
if (old_tag.equals(tag)) {
} else {
clearFragments();
// frag_manager.popBackStack(null,
// FragmentManager.POP_BACK_STACK_INCLUSIVE);
FragmentTransaction ft = frag_manager.beginTransaction();
ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_left).replace(R.id.frame_container, fragment, tag);
ft.commit();
if (getCurrentFocus() != null) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
}
}
}
public void clearFragments() {
sDisableFragmentAnimations = true;
frag_manager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
public void pushFragmentsWithoutAnimation(Fragment fragment, String tag) {
onBackpress = 0;
String old_tag = "";
try {
old_tag = mContent.getClass().getSimpleName();
} catch (Exception e) {
e.printStackTrace();
old_tag = "new";
}
mContent = fragment;
if (old_tag.equals(tag)) {
} else {
clearFragments();
FragmentTransaction ft = frag_manager.beginTransaction();
ft.replace(R.id.frame_container, fragment, tag);
ft.commit();
if (getCurrentFocus() != null) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
}
}
}
public void navigateTo(Fragment fragment) {
onBackpress = 0;
mContent = fragment;
frag_manager.beginTransaction().setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_left, R.anim.slide_in_right, R.anim.slide_out_right)
.replace(R.id.frame_container, fragment).addToBackStack(Integer.toString(frag_manager.getBackStackEntryCount() + 1)).commit();
if (getCurrentFocus() != null) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
}
}
public void navigateBack() {
Log.v(CLASS_TAG, "navigateBack()");
onBackpress = 0;
final int cnt = frag_manager.getBackStackEntryCount();
Log.v(CLASS_TAG, "stack depth: " + cnt);
if (cnt >= 1) {
frag_manager.popBackStack();
if (getCurrentFocus() != null) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), 0);
}
} else {
onBackPressed();
Log.v(CLASS_TAG, "Can't navigate");
}
}
@Override
public void onBackPressed() {
if (clients_Data.getClientAcc().size() < 2) {
if (onBackpress >= 1) {
hideProgressDialog();
if (clients_Data.isLogedIn()) {
ActionGetData.doLogOut();
finish();
}
super.onBackPressed();
} else if (onBackpress < 1) {
Toast.makeText(this, getString(R.string.push_for_exit), Toast.LENGTH_SHORT).show();
}
onBackpress++;
} else {
super.onBackPressed();
MainActivity.this.overridePendingTransition(R.anim.slide_in_right, R.anim.slide_out_right);
}
}
public void isPayments() {
hideTopPanel();
payments.setBackgroundResource(R.drawable.payments_main_board_pressed);
helpAndSupport.setBackgroundResource(R.drawable.support_main_bord_unpressed);
messages.setBackgroundResource(R.drawable.message_main_board_unpressed);
service.setBackgroundResource(R.drawable.services_main_board_unpressed);
settings.setBackgroundResource(R.drawable.settings_main_board_unpressed);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.rl_support_main_board:
helpAndSupport.setBackgroundResource(R.drawable.support_main_bord_pressed);
btnSupportPopularQuestion.setTextColor(getResources().getColor(R.color.top_panel_text_color_selected));
btnSupportPopularQuestion.setBackgroundColor(getResources().getColor(R.color.top_panel_background_selected));
btnSupportRequestOrders.setTextColor(getResources().getColor(R.color.top_panel_text_color_unselected));
btnSupportRequestOrders.setBackgroundColor(getResources().getColor(R.color.top_panel_background_unselected));
btnSupportStayOrder.setImageResource(R.drawable.stay_order_unselected);
fragment_tag = PopularQuestionListFragment.class.getSimpleName();
pushFragments(questionsFragment, fragment_tag);
messages.setBackgroundResource(R.drawable.message_main_board_unpressed);
service.setBackgroundResource(R.drawable.services_main_board_unpressed);
settings.setBackgroundResource(R.drawable.settings_main_board_unpressed);
payments.setBackgroundResource(R.drawable.payments_main_board_unpressed);
break;
case R.id.tv_popular_questions:
btnSupportPopularQuestion.setTextColor(getResources().getColor(R.color.top_panel_text_color_selected));
btnSupportPopularQuestion.setBackgroundColor(getResources().getColor(R.color.top_panel_background_selected));
btnSupportRequestOrders.setBackgroundColor(getResources().getColor(R.color.top_panel_background_unselected));
btnSupportRequestOrders.setTextColor(getResources().getColor(R.color.top_panel_text_color_unselected));
btnSupportStayOrder.setImageResource(R.drawable.stay_order_unselected);
fragment_tag = PopularQuestionListFragment.class.getSimpleName();
pushFragments(questionsFragment, fragment_tag);
break;
case R.id.tv_my_orders:
btnSupportRequestOrders.setBackgroundColor(getResources().getColor(R.color.top_panel_background_selected));
btnSupportRequestOrders.setTextColor(getResources().getColor(R.color.top_panel_text_color_selected));
btnSupportPopularQuestion.setTextColor(getResources().getColor(R.color.top_panel_text_color_unselected));
btnSupportPopularQuestion.setBackgroundColor(getResources().getColor(R.color.top_panel_background_unselected));
btnSupportStayOrder.setImageResource(R.drawable.stay_order_unselected);
fragment_tag = MyRequestOrdersListFragment.class.getSimpleName();
pushFragments(requestList, fragment_tag);
break;
case R.id.iv_new_order:
btnSupportStayOrder.setImageResource(R.drawable.stay_order_selected);
btnSupportPopularQuestion.setTextColor(getResources().getColor(R.color.top_panel_text_color_unselected));
btnSupportPopularQuestion.setBackgroundColor(getResources().getColor(R.color.top_panel_background_unselected));
btnSupportRequestOrders.setBackgroundColor(getResources().getColor(R.color.top_panel_background_unselected));
btnSupportRequestOrders.setTextColor(getResources().getColor(R.color.top_panel_text_color_unselected));
fragment_tag = NewOrderMainFragment.class.getSimpleName();
pushFragments(stayOrderFragment, fragment_tag);
break;
case R.id.rl_payments_main_board:
hideTopPanel();
payments.setBackgroundResource(R.drawable.payments_main_board_pressed);
fragment_tag = PaymentsMenu.class.getSimpleName();
pushFragments(paymentsMenu, fragment_tag);
helpAndSupport.setBackgroundResource(R.drawable.support_main_bord_unpressed);
messages.setBackgroundResource(R.drawable.message_main_board_unpressed);
service.setBackgroundResource(R.drawable.services_main_board_unpressed);
settings.setBackgroundResource(R.drawable.settings_main_board_unpressed);
break;
case R.id.rl_services_main_board:
hideTopPanel();
service.setBackgroundResource(R.drawable.services_main_board_pressed);
privateCabinetFrag = new PrivateCabinetFragment();
fragment_tag = PrivateCabinetFragment.class.getSimpleName();
pushFragments(privateCabinetFrag, fragment_tag);
helpAndSupport.setBackgroundResource(R.drawable.support_main_bord_unpressed);
messages.setBackgroundResource(R.drawable.message_main_board_unpressed);
settings.setBackgroundResource(R.drawable.settings_main_board_unpressed);
payments.setBackgroundResource(R.drawable.payments_main_board_unpressed);
break;
case R.id.rl_settings_main_board:
hideTopPanel();
settings.setBackgroundResource(R.drawable.settings_main_board_pressed);
fragment_tag = SettingsFragment.class.getSimpleName();
pushFragments(settingsFragment, fragment_tag);
messages.setBackgroundResource(R.drawable.message_main_board_unpressed);
service.setBackgroundResource(R.drawable.services_main_board_unpressed);
payments.setBackgroundResource(R.drawable.payments_main_board_unpressed);
helpAndSupport.setBackgroundResource(R.drawable.support_main_bord_unpressed);
break;
case R.id.rl_message_main_board:
hideTopPanel();
messages.setBackgroundResource(R.drawable.message_main_board_pressed);
service.setBackgroundResource(R.drawable.services_main_board_unpressed);
payments.setBackgroundResource(R.drawable.payments_main_board_unpressed);
helpAndSupport.setBackgroundResource(R.drawable.support_main_bord_unpressed);
settings.setBackgroundResource(R.drawable.settings_main_board_unpressed);
fragment_tag = MessageMain.class.getSimpleName();
pushFragments(messageMain, fragment_tag);
break;
}
}
public void hideTopPanel() {
if (dashBoard.isShown()) {
// dashBoard.startAnimation(animUp);
dashBoard.setVisibility(View.GONE);
}
}
public void showTopPanel() {
if (!dashBoard.isShown()) {
dashBoard.setVisibility(View.VISIBLE);
dashBoard.startAnimation(animDown);
}
}
@Override
protected void onPause() {
Log.e(CLASS_TAG,"ON onPause");
// TODO Auto-generated method stub
super.onPause();
onBackpress = 0;
}
@Override
protected void onResume() {
Log.e(CLASS_TAG,"ON onResume");
// TODO Auto-generated method stub
super.onResume();
onBackpress = 0;
}
@Override
protected void onStart() {
Log.e(CLASS_TAG,"ON Start");
super.onStart();
}
}
答案 0 :(得分：1)
堆栈跟踪表示您仍然在超类onCreate()中，它会重新创建片段并回调MainActivity setUnreadedMessages()。此时，tvNewMessages等成员变量未初始化。
通常，片段不应与托管活动具有此类依赖关系。考虑在那里重新设计。