恢复到app时，尝试在空对象引用上写入字段'int android.app.Fragment.mNextAnim' [英] Attempt to write to field 'int android.app.Fragment.mNextAnim' on a null object reference when resume to app
问题描述
我有从list获取数据的列表的活动，我有取消选中所有复选框的菜单项。第一次参加活动时工作正常，但是当我从这个活动中退出应用程序时，当我返回应用程序时应用程序进入睡眠状态
i have activity with list that get the data from firebase, i have menu item that uncheck all the checkboxes. its work fine when first get to the activity but while i exit the app from this activity and the app goes to sleep when i return to app i get
异常java.lang.NullPointerException：尝试在空对象引用上写入字段'int
android.app.Fragment.mNextAnim'
android.app.BackStackRecord.run（BackStackRecord.java： 779）
android.app.FragmentManagerImpl.execPendingActions
（FragmentManager.java:1582）android.app.FragmentManagerImpl $ 1.run
（FragmentManager.java:483）android.os.Handler.handleCallback
（Handler.java:751）android.os.Handler.dispatchMessage
（Handler.java:95）android.os.Looper.loop（Looper.java:154）
android.app .ActivityThread.main（ActivityThread.java:6688）
java.lang.reflect.Method.invoke（Method.java）
com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run
（ZygoteInit.java:1468)com.android.internal.os.ZygoteInit.main
（ZygoteInit.java:1358 ）
Exception java.lang.NullPointerException: Attempt to write to field 'int android.app.Fragment.mNextAnim' on a null object reference android.app.BackStackRecord.run (BackStackRecord.java:779) android.app.FragmentManagerImpl.execPendingActions (FragmentManager.java:1582) android.app.FragmentManagerImpl$1.run (FragmentManager.java:483) android.os.Handler.handleCallback (Handler.java:751) android.os.Handler.dispatchMessage (Handler.java:95) android.os.Looper.loop (Looper.java:154) android.app.ActivityThread.main (ActivityThread.java:6688) java.lang.reflect.Method.invoke (Method.java) com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:1468) com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1358)
我试着理解为什么我得到null但没有成功，我调试我的应用程序，问题出在函数setIconPercent中（ ）
i tried to understand why i get the null but didnt succed, i debug my app and the problem is in the function setIconPercent()
我的活动：
package com.nadav.weddingcalc.activity_best_list;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Handler;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.NavUtils;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.Toast;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.joanfuentes.hintcase.HintCase;
import com.joanfuentes.hintcase.RectangularShape;
import com.joanfuentes.hintcaseassets.hintcontentholders.SimpleHintContentHolder;
import com.joanfuentes.hintcaseassets.shapeanimators.RevealRectangularShapeAnimator;
import com.joanfuentes.hintcaseassets.shapeanimators.UnrevealRectangularShapeAnimator;
import com.nadav.weddingcalc.R;
import com.squareup.picasso.Picasso;
public class ActivityBest extends AppCompatActivity {
static ListView lv;
private AdapterActivityBest adapterActivityBest;
DatabaseReference mDatabase;
FirebaseUser user;
static private FirebaseAuth auth;
DatabaseReference myRef;
static AdView mAdView;
public String numOfRows;
MenuItem it;
Menu men;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_activity_place);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
final ProgressBar pBar = (ProgressBar) findViewById(R.id.progresbar);
mAdView = (AdView) findViewById(R.id.adView);
AdRequest adRequest = new AdRequest.Builder().
addTestDevice(getString(R.string.ad_test_device_nexus5x))
.addTestDevice("0E9830DF43C4EB440157B8C079727CF9")
.build();
mAdView.loadAd(adRequest);
auth = FirebaseAuth.getInstance();
mDatabase = FirebaseDatabase.getInstance().getReference();
user = auth.getCurrentUser();
lv = (ListView) findViewById(R.id.lv);
adapterActivityBest = new AdapterActivityBest(getApplicationContext() ,lv, this);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setVisibility(View.INVISIBLE);
lv.setAdapter(adapterActivityBest);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
FirebaseDatabase database = FirebaseDatabase.getInstance();
FirebaseUser user = auth.getCurrentUser();
myRef = database.getReference("users");
myRef.child(user.getUid()).child("list Best").orderByChild("orderNum").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
adapterActivityBest.removeAllll();
adapterActivityBest.notifyDataSetChanged();
if (!snapshot.hasChildren()) {
auth = FirebaseAuth.getInstance();
mDatabase = FirebaseDatabase.getInstance().getReference();
FirebaseUser user = auth.getCurrentUser();
String[] temp = getResources().getStringArray(R.array.Best_list);
int[] arrDividers = {0,5,10,18,24,31,37,46};
int[] arrSectors = {1,4,6,7,8,9,11,12,13,14,15,17,19,23,25,27,29,39,43,49,50,51,52};
for(int i=0; i<=55 ; i++){
boolean flag = false;
for(int j=0; j<=22; j++) {
if (i == arrSectors[j]) {
ObjectActivityBest ob = new ObjectActivityBest("false", temp[i], i, "sector");
mDatabase.child("users").child(user.getUid()).child("list Best").child(ob.name+"").setValue(ob);
flag = true;
}
}
for(int j=0; j<=7; j++) {
if (i == arrDividers[j]) {
ObjectActivityBest ob = new ObjectActivityBest("false", temp[i], i, "divider");
mDatabase.child("users").child(user.getUid()).child("list Best").child(ob.name+"").setValue(ob);
flag = true;
}
}
if(!flag){
ObjectActivityBest ob = new ObjectActivityBest("false", temp[i], (i), "item");
mDatabase.child("users").child(user.getUid()).child("list Best").child(ob.name+"").setValue(ob);
}
}
} else {
int countchecks=0;
FirebaseDatabase database = FirebaseDatabase.getInstance();
FirebaseUser user = auth.getCurrentUser();
myRef = database.getReference("users");
for (DataSnapshot messageSnapshot : snapshot.getChildren()) {
String name = (String) messageSnapshot.child("name").getValue();
String check = (String) messageSnapshot.child("check").getValue();
int orderNum = ((Long) messageSnapshot.child("orderNum").getValue()).intValue();
String sector = (String) messageSnapshot.child("sector").getValue();
ObjectActivityBest e = new ObjectActivityBest(check, name, orderNum, sector);
switch(e.sector){
case "sector":
switch(e.name){
case "צלם":
e.name = "בחירת צלם";
mDatabase.child("users").child(user.getUid()).child("list Best").child(e.orderNum+"").setValue(e);
break;
case "קייטרינג":
e.name = "בחירת קייטרינג";
mDatabase.child("users").child(user.getUid()).child("list Best").child(e.orderNum+"").setValue(e);
break;
case "דיגיי":
e.name = "בחירת תקליטן";
mDatabase.child("users").child(user.getUid()).child("list Best").child(e.orderNum+"").setValue(e);
break;
}
adapterActivityBest.addSectionHeaderItem(e);
break;
case "divider":
adapterActivityBest.addDividerHeaderItem(e);
break;
default:
adapterActivityBest.addItem(e);
break;
}
if(e.check.equals("true")){
if(e.name.equals("בחירת אולם")){
countchecks= countchecks+20;
}else{
if((e.orderNum>0&&e.orderNum<=9)){
countchecks+=5;
}else if(e.orderNum>=11 && e.orderNum<=15){
countchecks+=2;
}else{
countchecks++;
}
}
}
}
setIconPercent(countchecks);
}
pBar.setVisibility(View.INVISIBLE);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
// launchAutomaticHint();
}
}, 0);
}
private void setIconPercent(int countchecks) {
TypedArray imgs = getResources().obtainTypedArray(R.array.random_imgs);
it = men.findItem(R.id.action_check);
it.setIcon(ContextCompat.getDrawable(getApplicationContext(), imgs.getResourceId(countchecks/5, -1)));
imgs.recycle();
if(countchecks%5==0){
it = men.findItem(R.id.action_text);
it.setVisible(false);
it = men.findItem(R.id.action_check);
it.setVisible(true);
}else{
it = men.findItem(R.id.action_check);
it.setVisible(false);
it = men.findItem(R.id.action_text);
it.setVisible(true);
it.setTitle(countchecks+"%");
}
}
public void makeTextLong(String s){
Context context = getApplicationContext();
Toast.makeText(context,s,Toast.LENGTH_LONG).show();
}
public Menu getMen() {
return men;
}
public MenuItem getIt() {
return it;
}
public String getNumOfRows() {
return numOfRows;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
getMenuInflater().inflate(R.menu.percentage_menu, menu);
men = menu;
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(com.nadav.weddingcalc.R.menu.percentage_menu, menu);
men = menu;
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
android.app.Fragment fragment = null;
//noinspection SimplifiableIfStatement
switch (id) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
// try{
// this.finish();
// }catch(Exception e){
// makeTextLong("crash");
// }
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
推荐答案
您有这个空指针，因为您没有为片段维护堆栈。
当你恢复活动时，碎片的实例被破坏而且没有重新初始化。
所以你需要维护片段堆栈并检查片段堆栈是否为空
You got this null pointer because you doesn't maintain a stack for the fragments. While you resume your activity the instance of the fragments destroyed and it is not reinitialized. So you need to maintain the fragment stack and check for the fragment stack if it is null
这篇关于恢复到app时，尝试在空对象引用上写入字段'int android.app.Fragment.mNextAnim'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
