晚上好，我正在创建一个应用程序，我需要帮助解决此错误。
log cat of the error:java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at cqdevelopers.incrediblediet.Fragment3.getAddressKeyValueFile(Fragment3.java:90)
at cqdevelopers.incrediblediet.Fragment3.onCreateView(Fragment3.java:25)
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05-16 02:25:21.711 6498-6498/cqdevelopers.incrediblediet E/AndroidRuntime: FATAL EXCEPTION: main
Process: cqdevelopers.incrediblediet, PID: 6498
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at cqdevelopers.incrediblediet.Fragment3.getAddressKeyValueFile(Fragment3.java:90)
at cqdevelopers.incrediblediet.Fragment3.onCreateView(Fragment3.java:25)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1177)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
at android.support.v4.view.ViewPager$3.run(ViewPager.java:254)
at android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1920)
at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:2050)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2108)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2403)
at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1737)
at android.app.Activity.dispatchTouchEvent(Activity.java:2765)
at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60)
at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60)
at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2364)
at android.view.View.dispatchPointerEvent(View.java:9514)
at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4230)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4096)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3642)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3695)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3661)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3787)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3669)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3844)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3642)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3695)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3661)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3669)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3642)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5922)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5896)
at android.view.
Fragment3.java：
public class Fragment3 extends Fragment {
private EditText editText;
private TextView textView;
private Button button;
@Override
public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment3_layout, container, false);
getAddressKeyValueFile();
editText = (EditText) v.findViewById(R.id.tvadress);
textView = (TextView) v.findViewById(R.id.textView);
button = (Button) v.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String address = null;
address = editText.getText().toString();
textView.setText(address);
setAddressKeyValueFile(address);
}
});
return v;
}
private void getAddressKeyValue() {
SharedPreferences sharedPreferences = this.getActivity().getSharedPreferences("r", Context.MODE_PRIVATE);
String key = getString(R.string.address);
String existingAddress = sharedPreferences.getString(key, null);
if (existingAddress != null) {
TextView textView = (TextView) getActivity().findViewById(R.id.textView);
textView.setText(existingAddress);
}
}
private void setAddressKeyValue(String address)
{
SharedPreferences sharedPreferences = this.getActivity().getSharedPreferences("d" ,Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
String key = getString(R.string.address);
editor.putString(key,address);
editor.commit();
}
private void getAddressKeyValueFile()
{
Context context = getContext().getApplicationContext();
String fileName = getString(R.string.filename);
SharedPreferences sharedPreferences = context.getSharedPreferences(fileName,Context.MODE_PRIVATE);
String key = getString(R.string.address);
String existingAddress = sharedPreferences.getString(key,null);
if(existingAddress != null)
{
TextView textView = (TextView) getActivity().findViewById(R.id.textView);
textView.setText(existingAddress);
}
}
private void setAddressKeyValueFile(String address)
{
Context context = getContext().getApplicationContext();
String fileName = getString(R.string.filename);
SharedPreferences sharedPreferences = context.getSharedPreferences(fileName,Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
String key = getString(R.string.address);
editor.putString(key, address);
editor.commit();
}
}
和fragment3.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="cqdevelopers.incrediblediet.MainActivity$PlaceholderFragment">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/tvadress"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="register"
android:id="@+id/textView2"
android:layout_marginTop="23dp"
android:layout_below="@+id/button"
android:layout_centerHorizontal="true" />
<Button
style="?android:attr/buttonStyleSmall"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="New Button"
android:id="@+id/button"
android:layout_below="@+id/tvadress"
android:layout_centerHorizontal="true" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:id="@+id/textView"
android:layout_marginTop="29dp"
android:layout_below="@+id/textView2"
android:layout_centerHorizontal="true" />
</RelativeLayout>
请查看异常并让我知道我在哪里做错了，感谢您的帮助。
答案 0 :(得分：0)
更改getAddressKeyValueFile的位置
//getAddressKeyValueFile();
editText = (EditText) v.findViewById(R.id.tvadress);
textView = (TextView) v.findViewById(R.id.textView);
getAddressKeyValueFile();
并删除行：
TextView textView = (TextView) getActivity().findViewById(R.id.textView);
答案 1 :(得分：0)
这行代码textView = (TextView) v.findViewById(R.id.textView);正试图从活动的布局中获取ID为TexView的{{1}}，而不是来自片段的布局。
你应该改变：
textView为：
TextView textView = (TextView) getActivity().findViewById(R.id.textView);
textView.setText(existingAddress);
同时使用if(textView!=null){
textView.setText(existingAddress);
}
和getAddressKeyValueFile()方法。
此外，在getAddressKeyValue()方法中，只有在onCreateView(...)初始化后才能致电getAddressKeyValueFile();。
答案 2 :(得分：0)
private void getAddressKeyValueFile()
{
Context context = getContext().getApplicationContext();
String fileName = getResources.getString(R.string.filename);
SharedPreferences sharedPreferences = context.getSharedPreferences(fileName,Context.MODE_PRIVATE);
String key = getResources.getString(R.string.address);
String existingAddress = sharedPreferences.getString(key,null);
if(existingAddress != null)
{
TextView textView = (TextView) getActivity().findViewById(R.id.textView);
textView.setText(existingAddress);
}
}
而不是
getString(R.string.filename)
更改为
getResources.getString(R.string.filename)
另外，在setAddressKeyValue方法中进行类似的更改。