我正在创建一个应用程序,其中在纵向模式下我有一个活动,其中包含一个包含列表视图的片段,并且在单击该列表视图时,调用第二个活动以使用第二个片段显示数据,但问题是当第二个活动时片段,即Frag2被称为其onActivityCreated()方法未被调用。为什么这样?
MainActivity.xml
肖像模式
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.ankit.fragprac2.MainActivity">
<fragment
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/frag1"
android:name="com.example.ankit.fragprac2.Frag1"
/>
</LinearLayout>
横向模式
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/frag1"
android:name="com.example.ankit.fragprac2.Frag1"
android:layout_weight="1"/>
<fragment
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/frag2"
android:name="com.example.ankit.fragprac2.Frag2"
android:layout_weight="1"/>
</LinearLayout>
MainActivity.java
public class MainActivity extends AppCompatActivity implements Frag1.Comm {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void respond(int i)
{
FragmentManager fm=getFragmentManager();
Frag2 fg2= (Frag2) fm.findFragmentById(R.id.frag2);
if(fg2!=null && fg2.isVisible())
{
fg2.setData(i);
}
else
{
Intent in=new Intent(this,SecondActivity.class);
in.putExtra("position",i);
startActivity(in);
}
}
}
Fragment1.xml
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/list"/>
</RelativeLayout>
Fragment1.java
public class Frag1 extends Fragment {
ListView lv;
Comm c1;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.activity_frag1,container,false);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
String[] s=getResources().getStringArray(R.array.topics);
c1 = (Comm) getActivity();
lv = getActivity().findViewById(R.id.list);
lv.setAdapter(new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_1,s));
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
c1.respond(i);
}
});
}
interface Comm
{
void respond(int i);
}
}
Fragment2.xml
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/text1"
android:layout_centerHorizontal="true"
android:textSize="20dp"
android:textStyle="bold"
android:textColor="#000"/>
</RelativeLayout>
Fragment2.java
public class Frag2 extends Fragment {
TextView t;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.activity_frag2,container,false);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Toast.makeText(getActivity(),"OAC",Toast.LENGTH_SHORT).show();
t=getActivity().findViewById(R.id.text1);
// s1=new String[getResources().getStringArray(R.array.data).length];
// Toast.makeText(getActivity(),""+s1.length,Toast.LENGTH_SHORT).show();
if(savedInstanceState!=null)
{
String s=savedInstanceState.getString("data",null);
t.setText(s);
}
}
public void setData(int i)
{ String[] s1 =getResources().getStringArray(R.array.data);
t.setText(s1[i]);
}
@Override
public void onSaveInstanceState(Bundle outState) {
outState.putString("data",t.getText().toString());
}
}
SecondActivity.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.ankit.fragprac2.SecondActivity">
<fragment
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/frag21"
android:name="com.example.ankit.fragprac2.Frag2"/>
</RelativeLayout>
SecondActivity.java
public class SecondActivity extends AppCompatActivity {
int i;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
Bundle b= getIntent().getExtras();
if(b!=null)
{
i= b.getInt("position",0);
}
FragmentManager fm=getFragmentManager();
Frag2 fga2= (Frag2) fm.findFragmentById(R.id.frag21);
fga2.setData(i);
}
}
答案 0 :(得分:0)
在SecondActivity.onCreate()
中,移动此代码:
FragmentManager fm=getFragmentManager();
Frag2 fga2= (Frag2) fm.findFragmentById(R.id.frag21);
fga2.setData(i);
至SecondActivit.onStart()
。
在fga2.setData(i)
中使用onCreate
时,尚未创建活动;它正在被创造。因此,尚未调用片段的onActivityCreated()
方法。
其他说明:
Activity
应该FragmentActivity
而不是AppCompatActivity
。getSupportFragmentManager().findFragmentById
来获取片段。希望这会有所帮助。