我是Android开发的新手，我正在使用listview ..我的代码没有任何错误但是当我尝试运行它时，应用程序崩溃了。
这是我的MainActivity代码：
package com.example.view;
import java.util.ArrayList;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;
public class MainActivity extends Activity {
ListView lv;
ArrayList<ListViewItem> items;
CustomListViewAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv = (ListView) findViewById(R.id.listView);
items = new ArrayList<MainActivity.ListViewItem>();
items.add(new ListViewItem(R.drawable.ic_launcher, "Item1", "Item1 Description"));
items.add(new ListViewItem(R.drawable.ic_launcher, "Item2", "Item2 Description"));
items.add(new ListViewItem(R.drawable.ic_launcher, "Item3", "Item3 Description"));
items.add(new ListViewItem(R.drawable.ic_launcher, "Item4", "Item4 Description"));
adapter = new CustomListViewAdapter(this, items);
lv.setAdapter(adapter);
}
class ListViewItem
{
private int thumbnailResource;
private String title;
private String subTitle;
public ListViewItem()
{
}
public ListViewItem(int thumbnailResource, String title, String subTitle)
{
this.thumbnailResource = thumbnailResource;
this.title = title;
this.subTitle = subTitle;
}
public int getThumbnailResource()
{
return thumbnailResource;
}
public void setThumbnailResource(int thumbnailResource)
{
this.thumbnailResource = thumbnailResource;
}
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}
public String getSubTitle()
{
return subTitle;
}
public void setSubTitle(String subTitle)
{
this.subTitle = subTitle;
}
}
}
这是我的适配器类：
package com.example.view;
import java.util.ArrayList;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.view.MainActivity.ListViewItem;
public class CustomListViewAdapter extends ArrayAdapter<ListViewItem>
{
LayoutInflater inflater;
ArrayList<ListViewItem> items;
public CustomListViewAdapter(Activity context, ArrayList<ListViewItem> items)
{
super(context, R.layout.list_item_row, items);
this.items = items;
this.inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public View getView(final int position, View convertView, ViewGroup parent)
{
ListViewItem item = items.get(position);
View rowview = inflater.inflate(R.layout.list_item_row, parent, false);
ImageView imgView = (ImageView) rowview.findViewById(R.id.imgThumbnail);
TextView txtTitle = (TextView) rowview.findViewById(R.id.txtTitle);
TextView txtSubTitle = (TextView) rowview.findViewById(R.id.txtSubTitle);
CheckBox chkBox = (CheckBox) rowview.findViewById(R.id.checkbox);
imgView.setImageResource(item.getThumbnailResource());
txtTitle.setText(item.getTitle());
txtSubTitle.setText(item.getSubTitle());
return rowview;
}
}
这是行
的xml文件<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:android1="http://schemas.android.com/apk/res/android"
android:id="@+id/relativeLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="5dip" >
<ImageView
android:layout_width="78dip"
android:layout_height="78dip"
android:id="@+id/imgThumbnail"
android:layout_alignParentLeft="true"
android:layout_centerInParent="true"
android:layout_marginLeft="-3dip"
android:scaleType="centerInside">
</ImageView>
<TextView
android:textAppearance="?android:attr/textAppearanceLarge"
android:layout_height="wrap_content"
android:text="TextView"
android:layout_width="wrap_content"
android:id="@+id/txtTitle"
android:layout_toRightOf="@+id/imgThumbnail"
android:layout_marginTop="6dip"
android:layout_marginLeft="6dip">
</TextView>
<TextView
android:layout_height="wrap_content"
android:text="TextView"
android:layout_width="wrap_content"
android:id="@+id/txtSubTitle"
android:layout_toRightOf="@+id/imgThumbnail"
android:layout_below="@+id/txtTitle"
android:layout_marginTop="3dip"
android:layout_marginLeft="6dip">
</TextView>
<ListView
android1:id="@+id/listView"
android1:layout_width="match_parent"
android1:layout_height="wrap_content"
android1:layout_alignLeft="@+id/imgThumbnail"
android1:layout_alignTop="@+id/txtTitle"
android1:layout_marginLeft="17dp" >
</ListView>
<CheckBox
android:id="@+id/checkbox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_marginLeft="4px"
android:layout_marginRight="10px" />
</RelativeLayout>
这些是logcat错误
06-27 14:59:38.748: E/MoreInfoHPW_ViewGroup(11621): Parent view is not a TextView
06-27 14:59:38.773: E/AndroidRuntime(11621): FATAL EXCEPTION: main
06-27 14:59:38.773: E/AndroidRuntime(11621): Process: com.example.view, PID: 11621
06-27 14:59:38.773: E/AndroidRuntime(11621): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.view/com.example.view.MainActivity}: java.lang.NullPointerException
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2340)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.ActivityThread.access$800(ActivityThread.java:157)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.os.Handler.dispatchMessage(Handler.java:102)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.os.Looper.loop(Looper.java:157)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.ActivityThread.main(ActivityThread.java:5293)
06-27 14:59:38.773: E/AndroidRuntime(11621): at java.lang.reflect.Method.invokeNative(Native Method)
06-27 14:59:38.773: E/AndroidRuntime(11621): at java.lang.reflect.Method.invoke(Method.java:515)
06-27 14:59:38.773: E/AndroidRuntime(11621): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
06-27 14:59:38.773: E/AndroidRuntime(11621): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
06-27 14:59:38.773: E/AndroidRuntime(11621): at dalvik.system.NativeStart.main(Native Method)
06-27 14:59:38.773: E/AndroidRuntime(11621): Caused by: java.lang.NullPointerException
06-27 14:59:38.773: E/AndroidRuntime(11621): at com.example.view.MainActivity.onCreate(MainActivity.java:27)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.Activity.performCreate(Activity.java:5389)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
06-27 14:59:38.773: E/AndroidRuntime(11621): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2246)
06-27 14:59:38.773: E/AndroidRuntime(11621): ... 11 more
答案 0 :(得分：1)
你在这一行收到错误 lv.setAdapter（adapter）;
我确信 activity_main.xml 布局文件中不存在ListView。
您已将ListView放入activity_main.xml文件中。
您在行文件的布局中错误地添加了ListView。
答案 1 :(得分：0)
请尝试这种方式，希望这有助于您解决问题。
<强> activity_main.xml中
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
<强> list_item_row.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="10dp"
android:gravity="center">
<ImageView
android:layout_width="78dp"
android:layout_height="78dp"
android:id="@+id/imgThumbnail"
android:adjustViewBounds="true">
</ImageView>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical"
android:layout_marginLeft="5dp">
<TextView
android:textAppearance="?android:attr/textAppearanceLarge"
android:layout_height="wrap_content"
android:text="TextView"
android:layout_width="wrap_content"
android:id="@+id/txtTitle">
</TextView>
<TextView
android:layout_height="wrap_content"
android:text="TextView"
android:layout_width="wrap_content"
android:id="@+id/txtSubTitle"
android:layout_marginTop="3dp">
</TextView>
</LinearLayout>
<CheckBox
android:id="@+id/checkbox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"/>
</LinearLayout>
<强> MainActivity.java
public class MainActivity extends Activity {
ListView lv;
ArrayList<ListViewItem> items;
CustomListViewAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv = (ListView) findViewById(R.id.listView);
items = new ArrayList<MainActivity.ListViewItem>();
items.add(new ListViewItem(R.drawable.ic_launcher, "Item1", "Item1 Description"));
items.add(new ListViewItem(R.drawable.ic_launcher, "Item2", "Item2 Description"));
items.add(new ListViewItem(R.drawable.ic_launcher, "Item3", "Item3 Description"));
items.add(new ListViewItem(R.drawable.ic_launcher, "Item4", "Item4 Description"));
adapter = new CustomListViewAdapter(this, items);
lv.setAdapter(adapter);
}
class ListViewItem
{
private int thumbnailResource;
private String title;
private String subTitle;
public ListViewItem()
{
}
public ListViewItem(int thumbnailResource, String title, String subTitle)
{
this.thumbnailResource = thumbnailResource;
this.title = title;
this.subTitle = subTitle;
}
public int getThumbnailResource()
{
return thumbnailResource;
}
public void setThumbnailResource(int thumbnailResource)
{
this.thumbnailResource = thumbnailResource;
}
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}
public String getSubTitle()
{
return subTitle;
}
public void setSubTitle(String subTitle)
{
this.subTitle = subTitle;
}
}
class CustomListViewAdapter extends BaseAdapter
{
Activity context;
ArrayList<ListViewItem> items;
public CustomListViewAdapter(Activity context, ArrayList<ListViewItem> items)
{
this.items = items;
this.context = context;
}
@Override
public int getCount() {
return items.size();
}
@Override
public Object getItem(int position) {
return items.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public View getView(final int position, View convertView, ViewGroup parent)
{
ViewHolder holder;
if(convertView==null){
holder = new ViewHolder();
convertView = LayoutInflater.from(context).inflate(R.layout.list_item_row,null,false);
holder.imgView = (ImageView) convertView.findViewById(R.id.imgThumbnail);
holder.txtTitle = (TextView) convertView.findViewById(R.id.txtTitle);
holder.txtSubTitle = (TextView) convertView.findViewById(R.id.txtSubTitle);
holder.chkBox = (CheckBox) convertView.findViewById(R.id.checkbox);
convertView.setTag(holder);
}else{
holder = (ViewHolder)convertView.getTag();
}
holder.imgView.setImageResource( items.get(position).getThumbnailResource());
holder.txtTitle.setText( items.get(position).getTitle());
holder.txtSubTitle.setText( items.get(position).getSubTitle());
return convertView;
}
class ViewHolder {
ImageView imgView;
TextView txtTitle;
TextView txtSubTitle;
CheckBox chkBox;
}
}
}