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我想顯示一個由BottonNavigationView使用的片段內的棘手的列表視圖（除其他事項外）。我所做的是，創建一個包含BottomNavigationView的主要活動，以及包含其他視圖的片段。 listView應該連接到Firebase數據庫。對於文件區域的代碼如下：添加一個棘手的列表視圖片段爲BottomNavigationView
JobList.java
package com.example.sherwin.todo;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
public class JobList extends Fragment {
public JobList() {
}
public static JobList newInstance() {
JobList fragment = new JobList();
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_job_list, container, false);
// Create a new Adapter
final ArrayAdapter<String> adapter = new ArrayAdapter<>(getActivity(),
android.R.layout.simple_list_item_1, android.R.id.text1);
// Get ListView object from xml
final ListView listView = (ListView)rootView.findViewById(R.id.listView);
// Assign adapter to ListView
listView.setAdapter(adapter);
// Connect to the Firebase database
FirebaseDatabase database = FirebaseDatabase.getInstance();
// Get a reference to the todoItems child items it the database
final DatabaseReference myRef = database.getReference("JOBS");
// Assign a listener to detect changes to the child items
// of the database reference.
myRef.addChildEventListener(new ChildEventListener() {
// This function is called once for each child that exists
// when the listener is added. Then it is called
// each time a new child is added.
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String previousChildName) {
String value = dataSnapshot.getKey();
adapter.add(value);
}
// This function is called each time a child item is removed.
public void onChildRemoved(DataSnapshot dataSnapshot) {
String value = dataSnapshot.getKey();
adapter.remove(value);
}
// The following functions are also required in ChildEventListener implementations.
public void onChildChanged(DataSnapshot dataSnapshot, String previousChildName) {
}
public void onChildMoved(DataSnapshot dataSnapshot, String previousChildName) {
}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w("TAG:", "Failed to read value.", error.toException());
}
});
///to send to next page
Button nextPage = (Button) rootView.findViewById(R.id.addNewJob);
// Capture button clicks
nextPage.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Start NewActivity.class
Intent myIntent = new Intent(getContext(),
JobForm.class);
startActivity(myIntent);
}
});
return rootView;
}
}
MainActivity.java
package com.example.name.todo;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private TextView mTextMessage;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
Fragment selectedFragment = null;
switch (item.getItemId()) {
case R.id.navigation_home:
selectedFragment = HomePage.newInstance();
break;
case R.id.navigation_job:
selectedFragment = JobList.newInstance();
break;
case R.id.navigation_machine:
selectedFragment = MachinePage.newInstance();
break;
case R.id.navigation_mail:
selectedFragment = MessagePage.newInstance();
break;
case R.id.navigation_resources:
selectedFragment = ResourcePage.newInstance();
break;
}
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.content, selectedFragment);
transaction.commit();
return true;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}
}
fragment_job_list.xml
<?xml version="1.0" encoding="utf-8"?>
<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"
android:orientation="vertical">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="2.8">
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_above="@+id/addNewJob"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"></ListView>
<Button
android:id="@+id/addNewJob"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:text="@string/add_job" />
</RelativeLayout>
</LinearLayout>
的logcat中吐出來的是以下幾點：
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.name.todo/com.example.name.todo.JobList}: java.lang.ClassCastException: com.example.name.todo.JobList cannot be cast to android.app.Activity
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2567)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.ClassCastException: com.example.name.todo.JobList cannot be cast to android.app.Activity
at android.app.Instrumentation.newActivity(Instrumentation.java:1078)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2557)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
我不知道該從哪裏做什麼幫助，將不勝感激。
謝謝
它是一個ClassCastException。您是否驗證AndroidManifest.xml文件中的活動條目？ – JohnC
謝謝@JohnC我確實看過清單，看到它將碎片聲明爲活動（導致錯誤）。我更新了它們，現在完美地工作。謝謝。 –
不客氣。我很高興它有幫助！ – JohnC