我尝试在mainactivity.java的myfragment.xml中将文本设置为TextView 但发生以下错误。
这是我的main_activity.java
@Override
public boolean onQueryTextChange(String newText) {
if(aBoolean){
RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.relative);
relativeLayout.setVisibility(View.INVISIBLE);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.setCustomAnimations(R.anim.top_to_bottom, R.anim.bottom_to_top);
dropdown dropdown = new dropdown();
fragmentTransaction.add(R.id.fragment_container,dropdown);
fragmentTransaction.commit();
dropdown.setTextView("Heading1","HelloWorld");
aBoolean=false;
}
else {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
dropdown dropdown = new dropdown();
fragmentTransaction.add(R.id.fragment_container,dropdown);
fragmentTransaction.commit();
dropdown.setTextView("Heading1","HelloWorld");
}
我在片段文件
中为settext编写了一个方法dropdown.java
public class dropdown extends Fragment {
View main_view;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.fragment_dropdown, container, false);
main_view = v;
TextView textView = (TextView) v.findViewById(R.id.heading1);
textView.setText("hello");
return v;
}
public void setTextView(String id, String text){
TextView textView = (TextView) main_view.findViewById(R.id.heading1);
textView.setText("HelloWorld");
}
}
运行时发生以下错误
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.app.Fragment.getId()' on a null object reference
此错误显示在dropdown.setTextView（＆＃34; Heading1＆＃34;，＆＃34; HelloWorld＆＃34;）;
的行中答案 0 :(得分：0)
代码不够。但让我猜问题..
我认为你的片段在android.app包中，而你是android.support.v4.app.Fragment
答案 1 :(得分：0)
如果我是你，我会这样做。
Bundle bundle = new Bundle();
bundle.putString("KEY_STRING", "HELLOWORLD");
fragmentTransaction.setArguments(bundle);
然后从Fragment Class
String Helloworld = getArguments().getString("KEY_STRING");
textView.setText(Helloworld);
答案 2 :(得分：0)
找出那里的错误，每当我在搜索视图中输入文本时，新的下拉列表就会创建对象。这就是我得到空对象引用的原因。所以声明为最终变量。解决问题。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final dropdown dropdown = new dropdown();
searchView = (SearchView) findViewById (R.id.search_view);
searchView.setQueryHint("search");
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String query) {
return false;
}
@Override
public boolean onQueryTextChange(String newText) {
if(aBoolean){
RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.relative);
relativeLayout.setVisibility(View.INVISIBLE);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.setCustomAnimations(R.anim.top_to_bottom, R.anim.bottom_to_top);
fragmentTransaction.replace(R.id.fragment_container,dropdown);
fragmentTransaction.commit();
aBoolean=false;
}
else{
dropdown.setTextView(R.id.heading1,"Heading1");
}
return false;
}
});}