我想为android studio中的列表视图设置自定义布局
我在activity_main.xml文件中添加了一个列表视图
<ListView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent" />
并创建一个名为row.xml的布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:layout_width="40dp"
android:layout_height="40dp"
android:id="@+id/icon"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Medium"
android:id="@+id/text1"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="small"
android:id="@+id/text2"/>
</LinearLayout>
</LinearLayout>
和MainActivity.java文件包括：
公共类MainActivity扩展了AppCompatActivity {
ListView list;
String [] titles;
String [] description;
int[]imgs = {R.drawable.fb,R.drawable.chat,R.drawable.gplus,R.drawable.instagram};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Resources res = getResources();
titles = res.getStringArray(R.array.titles);
description = res.getStringArray(R.array.description);
list = (ListView) findViewById(R.id.list);
MyAdapter adapter = new MyAdapter(this,titles,imgs,description);
list.setAdapter(adapter);
}
class MyAdapter extends ArrayAdapter{
Context context;
int[] imgs;
String[] myTitles;
String[] myDescription;
MyAdapter (Context c , String[] titles , int[] imgs , String[]Description){
super(c,R.layout.row,R.id.text1,titles);
this.context = c;
this.imgs = imgs;
this.myDescription = description;
this.myTitles = titles;
}
@Override
public View getView(int position , View convertView , ViewGroup parent){
LayoutInflater layoutInflater = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View row = layoutInflater.inflate(R.layout.row,null,true);
ImageView images = (ImageView) findViewById(R.id.icon);
TextView myTitle = (TextView) findViewById(R.id.text1);
TextView myDescription = (TextView) findViewById(R.id.text2);
images.setImageResource(imgs[position]);
myTitle.setText(titles[position]);
myDescription.setText(description[position]);
return row;
}
}
}
当我运行应用程序时，显示：不幸的是，应用程序已停止。
如何解决这个问题？
错误日志：
AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at com.example.nik.myapplication.MainActivity$MyAdapter.getView(MainActivity.java:57)
at android.widget.AbsListView.obtainView(AbsListView.java:2207)
at android.widget.ListView.makeAndAddView(ListView.java:1845)
at android.widget.ListView.fillDown(ListView.java:678)
at android.widget.ListView.fillFromTop(ListView.java:739)
at android.widget.ListView.layoutChildren(ListView.java:1661)
at android.widget.AbsListView.onLayout(AbsListView.java:2037)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:985)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:435)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1670)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1528)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1441)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14118)
at android.view.ViewGroup.layout(ViewGroup.java:4474)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2183)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1947)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1139)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4879)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:776)
at android.view.Choreographer.doCallbacks(Choreographer.java:579)
at android.view.Choreographer.doFrame(Choreographer.java:548)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:762)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5341)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:929)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
这是你的答案：
@Override
public View getView(int position , View convertView , ViewGroup parent){
LayoutInflater layoutInflater = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View row = layoutInflater.inflate(R.layout.row,null,true);
ImageView images = (ImageView) row.findViewById(R.id.icon);
TextView myTitle = (TextView) row.findViewById(R.id.text1);
TextView myDescription = (TextView) row.findViewById(R.id.text2);
images.setImageResource(imgs[position]);
myTitle.setText(titles[position]);
myDescription.setText(description[position]);
return row;
}
这就是为什么这是你的答案：
你有一个空指针异常，因为你在你的活动上调用了findViewById而不是你刚刚膨胀的视图。由于活动没有包含ID图标，text1或text2的字段，因此您无法获得任何结果。当您尝试设置它们时，它会抛出异常。
希望有所帮助！