Java 片段上的绑定:NullPointerException
我正在尝试将“firstname”从registerFragmentOne传递到registerFragmentTwo。但每次我启动应用程序时,它都会突然关闭。我从Logcat收到此错误: 在com.application.name.registerFragmentTwo.onCreateView上 即:Java 片段上的绑定:NullPointerException,java,android,android-fragments,android-viewpager,Java,Android,Android Fragments,Android Viewpager,我正在尝试将“firstname”从registerFragmentOne传递到registerFragmentTwo。但每次我启动应用程序时,它都会突然关闭。我从Logcat收到此错误: 在com.application.name.registerFragmentTwo.onCreateView上 即: String frag1 = bundle.getString("firstname"); 我在两个片段上声明了Bundle 注册人姓名: package com.sholomon.who.
String frag1 = bundle.getString("firstname");
我在两个片段上声明了Bundle
注册人姓名:
package com.sholomon.who.who;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AlphaAnimation;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class registerFragmentOne extends Fragment {
private Button fButton;
private EditText fName;
private TextView fTextView;
private Animation shake;
private boolean flagAnimate = false;
private final Animation in = new AlphaAnimation(0.0f , 1.0f);
private final Animation out = new AlphaAnimation(1.0f, 0.0f);
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_register_fragment_one, container, false);
fButton = (Button) view.findViewById(R.id.fButton);
fName = (EditText) view.findViewById(R.id.fName);
fTextView = (TextView) view.findViewById(R.id.fTextView);
// Animation List
shake = AnimationUtils.loadAnimation(getActivity(), R.anim.shake);
in.setDuration(500);
out.setDuration(500);
fName.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
String getName = fName.getText().toString();
int getNameCount = getName.replaceAll("\\s+","").length();
if(getNameCount >= 1 && !flagAnimate) {
fTextView.startAnimation(in);
fTextView.setVisibility(View.VISIBLE);
flagAnimate= true;
} else if(getNameCount == 0){
fTextView.startAnimation(out);
fTextView.setVisibility(View.INVISIBLE);
flagAnimate= false;
}
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void afterTextChanged (Editable s){
// TODO Auto-generated method stub
}
});
fButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(fName.length() < 1) {
fName.startAnimation(shake);
} else {
String firstName = fName.getText().toString();
Bundle bundle = new Bundle();
bundle.putString("firstname", firstName);
registerFragmentTwo fragobj = new registerFragmentTwo();
fragobj.setArguments(bundle);
Toast.makeText(getActivity(), bundle.getString("firstname"), Toast.LENGTH_LONG).show();
((RegisterActivity)getActivity()).setViewPager(1);
}
}
});
return view;
}
}
我做得对吗?我不知道为什么在加载第二个片段后Bundle的值消失了。我试着在加载第二个片段之前将其烤熟,它在加载下一个片段之前具有值
编辑:整个logcat错误
FATAL EXCEPTION: main
Process: com.application.name, PID: 8683
java.lang.NullPointerException
at com.sholomon.application.name.onCreateView(registerFragmentTwo.java:50)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2199)
at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:651)
at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:167)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1236)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1084)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1614)
at android.view.View.measure(View.java:16834)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:824)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:500)
at android.view.View.measure(View.java:16834)
at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:934)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:973)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:400)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:742)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:607)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2333)
at android.view.View.measure(View.java:16834)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2246)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1312)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1509)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1189)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6223)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:788)
at android.view.Choreographer.doCallbacks(Choreographer.java:591)
at android.view.Choreographer.doFrame(Choreographer.java:560)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:774)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5292)
at java.lang.reflect.Method.invokeNative(Native Meth
ViewPager在显示某些片段之前创建并缓存这些片段。在本例中,第二个片段是在用户开始键入第一个片段之前创建的。这意味着在创建参数包之前执行
onCreateView()
要解决此问题,请将
bundle.getString()
的代码放在不同的生命周期回调中,例如onResume()
ViewPager在显示某些片段之前创建并缓存它们。在本例中,第二个片段是在用户开始键入第一个片段之前创建的。这意味着在创建参数包之前执行onCreateView()
要解决此问题,请将
bundle.getString()
的代码放在不同的生命周期回调中,例如onResume()
当bundle中的数据为空时,会发生Null指针异常。
在第二个片段中,首先使用下面的片段检查捆绑包是否为空
Bundle bundle = getArguments():
if(bundle !=null){
// Do your work
}else{
//Show error message
}
当捆绑包中的数据为空时,就会发生Null指针异常。 在第二个片段中,首先使用下面的片段检查捆绑包是否为空
Bundle bundle = getArguments():
if(bundle !=null){
// Do your work
}else{
//Show error message
}
您需要一个新的实例sttic builder来传递参数 像这样
public static MyFragment newInstance(String name, int age) {
Bundle bundle = new Bundle();
bundle.putString("name", name);
bundle.putInt("age", age);
MyFragment fragment = new MyFragment();
fragment.setArguments(bundle);
return fragment;
}
或者,您可以在活动中放入args并执行以下操作:
getActivity.getArgs()
请参阅此链接
您需要一个新的实例sttic builder来传递参数 像这样
public static MyFragment newInstance(String name, int age) {
Bundle bundle = new Bundle();
bundle.putString("name", name);
bundle.putInt("age", age);
MyFragment fragment = new MyFragment();
fragment.setArguments(bundle);
return fragment;
}
或者,您可以在活动中放入args并执行以下操作:
getActivity.getArgs()
请参阅此链接
(代表问题作者发布)
我忘记了在MainActivity中声明Bundle,这是RegisterActivity,其中声明了片段
在片段之间进行通信不应将数据直接传递给另一个片段。应该有一个接口侦听器,以便活动保存数据并将其传递给第二个片段。(代表问题作者发布)
我忘记了在MainActivity中声明Bundle,这是RegisterActivity,其中声明了片段
在片段之间进行通信不应将数据直接传递给另一个片段。应该有一个接口侦听器,以便activity保存数据并将其传递给第二个片段。您只是告诉我们错误发生的位置,但错误本身是什么?您需要添加
onCreateView()
method在你的问题中。@PrisonMike jsut添加了整个logshow your registerFragmentTwo code@ישבבאךת代码>bundle.getString(),正如OP一开始所说的。你只是告诉我们错误发生在哪里,但错误本身是什么?你需要添加onCreateView()
方法。@PrisonMike jsut添加了整个logshow your registerFragmentTwo code@正如OP在一开始所说的。加载第二个片段后,它是空的。加载第二个片段后,它是空的。好的,我尝试将Bundle get参数和String fragg1=Bundle.getString(“firstname”)放在registerFragmentTwo的onStart和onResume中。但在加载第二个frag后,它仍然是null@Transit要对此进行调试,请设置断点或添加Log.d()
调用,以查看在主活动和两个片段中执行生命周期回调的顺序。您也应该在ViewPager适配器的相关方法中执行同样的操作。@Transit可能更直接地设置文本比使用捆绑包更有效。@Transit还可以查看官方Android文档以了解有关的信息。谢谢@Code peeditorok我试着放置捆绑包get参数和字符串frag1=bundle.getString(“firstname”)在registerFragmentTwo中的onStart和onResume内部。但在加载第二个frag后,它仍然是null@Transit要对此进行调试,请设置断点或添加Log.d()
调用,以查看在主活动和两个片段中执行生命周期回调的顺序。您也应该在ViewPager适配器的相关方法中执行同样的操作。@Transit可能更直接地设置文本比使用捆绑包更有效。@Transit还可以查看官方Android文档以了解有关的信息。谢谢@Code peedient
public static MyFragment newInstance(String name, int age) {
Bundle bundle = new Bundle();
bundle.putString("name", name);
bundle.putInt("age", age);
MyFragment fragment = new MyFragment();
fragment.setArguments(bundle);
return fragment;
}