Java I'；我试图使用BaseAdapter用占位符数据填充ListView，并将其放入片段中，但由于某种原因，应用程序在启动时崩溃
谢谢你抽出时间 主要活动Java I'；我试图使用BaseAdapter用占位符数据填充ListView，并将其放入片段中，但由于某种原因，应用程序在启动时崩溃,java,android,Java,Android,谢谢你抽出时间 主要活动 import android.app.FragmentManager; import android.app.FragmentTransaction; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.Toolbar; import android.view.Menu; import android.vie
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FragmentB fragB = new FragmentB();
FragmentManager fragManager = getFragmentManager();
FragmentTransaction fragTransaction = fragManager.beginTransaction();
fragTransaction.add(R.id.cmll,fragB,"fragB");
fragTransaction.commit();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
import android.app.Fragment;
import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class FragmentB extends Fragment {
private Context myContext;
@Override
public void onAttach(Context context) {
myContext=context;
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_b_layout, container, false);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ListView listView = (ListView) getActivity().findViewById(R.id.listView);
MyBaseAdapter adapter = new MyBaseAdapter(myContext);
listView.setAdapter(adapter);
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
}
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
public class MyBaseAdapter extends BaseAdapter {
private Context myContext;
private ArrayList<ListViewInfo> list;
public MyBaseAdapter(Context context) {
myContext = context;
list = new ArrayList<>();
String[] test_10char = {"AaaAaaAaaA","BbbBbbBbbB","CccCccCccC"};
String[] test_3char = {"Aaa","Bbb","Ccc"};
int[] ints = {R.drawable.test_sunny,R.drawable.test_sunny,R.drawable.test_sunny};
for (int i = 0; i < 3; i++) {
list.add(new ListViewInfo(test_10char[i], test_3char[i], ints[i]));
}
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View singleRowView = inflater.inflate(R.layout.list_item_layout,parent,false);
TextView date = (TextView) singleRowView.findViewById(R.id.textView1);
TextView temp = (TextView) singleRowView.findViewById(R.id.textView2);
ImageView icon = (ImageView) singleRowView.findViewById(R.id.imageView1);
ListViewInfo tempLVI = list.get(position);
date.setText(tempLVI.getDate());
temp.setText(tempLVI.getTemp());
icon.setImageResource(tempLVI.getImageID());
return singleRowView;
}
}
提前感谢您的帮助。我不知道问题出在哪里。
getViewcontext context=parent.getContext（）
到
我希望这对你有帮助。你能包括日志吗？我对android和编程都是新手。这就是你要找的：03-22 21:42:08.421 4130-4130/com.askowitz.eli.myweatherapp E/AndroidRuntime:FATAL EXCEPTION:mainproces:com.askowitz.eli.myweatherapp，PID:4130 java.lang.NullPointerException:尝试调用虚拟方法'java.lang.Object android.content.Context.getSystemService（java.lang.String）'在com.askowitz.eli.myweatherapp.MyBaseAdapter.getView（MyBaseAdapter.java:52）上的空对象引用上执行。是。这是完整的日志吗？通常它不止几行..我编辑了这篇文章，包括了我认为相关的所有内容。如果我遗漏了什么，我可以肯定地补充一下，非常感谢你。成功了。我真的很感激。
03-22 21:42:08.421 4130-4130/com.eli.myweatherapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.eli.myweatherapp, PID: 4130
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
at com.eli.myweatherapp.MyBaseAdapter.getView(MyBaseAdapter.java:52)
at android.widget.AbsListView.obtainView(AbsListView.java:2387)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1270)
at android.widget.ListView.onMeasure(ListView.java:1182)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1438)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:724)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1438)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:724)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:17485)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:728)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:464)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:664)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:731)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1438)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:724)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1438)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:724)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:17485)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2636)
at android.view.View.measure(View.java:17485)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2031)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1193)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1400)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1078)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5875)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5290)
at java.lang.reflect.Method.invoke(Native Method)
at java.lan
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
LayoutInflater inflater = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);