Android Studio My Application Keeps Stopping

[qq_39190125]

代码如下
MainActivity：
package com.example.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.List;

public class MainActivity extends AppCompatActivity {
private String[] data = {"算法与数据结构","光电子学","JAVA",
"Python","Android移动系统开发","Matlab","高频电子电路",
"C++程序设计","通信原理","现代通信系统"
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
MainActivity.this,android.R.layout.simple_list_item_1,data);
ListView listView=(ListView) findViewById(R.id.list_view);
listView.setAdapter(adapter);




BottomFragment
package com.example.myapplication;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class BottomFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.bottom_layout, container, false);
return view;
}
}



UpFragment
package com.example.myapplication;



import android.os.Bundle;

import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class UpFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState){
View view = inflater.inflate(R.layout.bottom_layout,container,false);
return view;

}
}


activitya_main
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">



<fragment
android:id="@+id/up_layout"
android:name="com.example.myapplication.UpFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="9"
/>
<fragment
android:id="@+id/bottom_layout"
android:name="com.example.myapplication.BottomFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
/>


</LinearLayout>


bottom_layout
<?xml version="1.0" encoding="utf-8"?>
<android.support.percent.PercentFrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/button1"
android:text="课程列表"
android:layout_gravity="left"
app:layout_widthPercent="50%"
app:layout_heightPercent="100%"
/>
<Button
android:id="@+id/button2"
android:text="关于我们"
android:layout_gravity="right"
app:layout_widthPercent="50%"
app:layout_heightPercent="100%"
/>


</android.support.percent.PercentFrameLayout>


bottom_layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"></ListView>
</LinearLayout>

[jklwan]

两个bottom_layout布局？UpFragment也用的bottom_layout？检查布局 ListView在bottom_layout中，那就在BottomFragment中对ListView进行操作，不要在Activity中操作。

[SemiraChen]

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 说明listview为空呗，并没有找到他的Id 试下先 找fragment的id Fragment fragment=(Fragment) findViewById(R.id.bottom_layout); 然后通过fragment找listview ListView listView=fragment.findViewById(R.id.list_view); 试下，我也不确定。

[SemiraChen]

Android Studio My Application Keeps Stopping 这句不是重点哇， 崩了肯定会说在哪行崩了的哇。

[qq_39190125]

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.myapplication, PID: 10893 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6669) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference at com.example.myapplication.MainActivity.onCreate(MainActivity.java:23) at android.app.Activity.performCreate(Activity.java:7136) at android.app.Activity.performCreate(Activity.java:7127) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)  at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)  at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)  at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)  at android.os.Handler.dispatchMessage(Handler.java:106)  at android.os.Looper.loop(Looper.java:193)  at android.app.ActivityThread.main(ActivityThread.java:6669)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)  I/Process: Sending signal. PID: 10893 SIG: 9 Application terminated.