我在Android上写了一个书籍搜索应用程序，当我点击按钮开始搜索时，我的应用程序强制关闭我的代码有问题 - 活动。从日志开始，我想也许我使用了处理程序或线程或适配器不正确，但我无法弄明白。请帮助，谢谢。
活动档案：
package com.example.doubanbook.activity;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.SimpleAdapter.ViewBinder;
import com.example.doubanbook.R;
import com.example.doubanbook.book.BookSearchInfo;
import com.example.doubanbook.book.PaseSearchReasult;
import com.example.doubanbook.book.Util;
public class SearchBookActivity extends Activity {
private EditText searchEditText = null;
private Button searchButton = null;
private ListView lv = null;
private Handler hd ;
private List<Map<String, Object>> listItems = new ArrayList<Map<String, Object>>();
private SimpleAdapter adapt = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.searchbook);
searchEditText = (EditText) findViewById(R.id.search_et);
searchButton = (Button) findViewById(R.id.search_button);
lv = (ListView) findViewById(R.id.lv);
searchButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
String keystr = searchEditText.getText().toString();
new DownloadThread("https://api.douban.com/v2/book/search?q="
+ keystr).start();
}
});
hd = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
ArrayList<BookSearchInfo> infos = (ArrayList<BookSearchInfo>) msg.obj;
for (int i = 0; i < infos.size(); i++) {
Map<String, Object> listItem = new HashMap<String, Object>();
listItem.put("title", infos.get(i).getTitle());
listItem.put("author", infos.get(i).getAuthor());
listItem.put("isbn", infos.get(i).getIsbn());
listItem.put("publisher", infos.get(i).getPublisher());
listItem.put("rate", infos.get(i).getRate());
listItem.put("image", infos.get(i).getCover());
listItems.add(listItem);
}
adapt = new SimpleAdapter(SearchBookActivity.this, listItems,
R.layout.search_listitem,
new String[] { "title", "author", "isbn", "publisher",
"rate", "image" }, new int[] { R.id.tv1,
R.id.tv2, R.id.tv3, R.id.tv4, R.id.iv });
adapt.setViewBinder(new ViewBinder() {
@Override
public boolean setViewValue(View view, Object data,
String textRepresentation) {
if ((view instanceof ImageView)
& (data instanceof Bitmap)) {
ImageView iv = (ImageView) view;
Bitmap bm = (Bitmap) data;
iv.setImageBitmap(bm);
return true;
}
return false;
}
});
lv.setAdapter(adapt);
}
};
}
class DownloadThread extends Thread {
String url = null;
public DownloadThread(String urlstr) {
url = urlstr;
}
public void run() {
String result = Util.Download(url);
PaseSearchReasult mess = new PaseSearchReasult(result);
ArrayList<BookSearchInfo> infos = mess.ResultCollection();
Message msg = Message.obtain();
msg.obj = infos;
hd.sendMessage(msg);
}
}
}
布局xml文件：
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="center"
android:gravity="center"
android:text="search" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<EditText
android:id="@+id/search_et"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_gravity="center"
android:layout_weight="3"
android:background="@null"
android:gravity="center"
android:textColor="#ffffff"
android:hint="type your keyword" />
<Button
android:id="@+id/search_btn"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_gravity="center"
android:text="search"
android:layout_weight="1" />
</LinearLayout>
<ListView
android:id="@+id/lv"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
</ScrollView>
列出项目xml文件：
<?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"
android:orientation="vertical" >
<ImageView
android:id="@+id/iv"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="1" />
<TextView
android:id="@+id/lv1"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="1" />
<TextView
android:id="@+id/lv2"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="1" />
<TextView
android:id="@+id/lv3"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="1" />
<TextView
android:id="@+id/lv4"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="1" />
</LinearLayout>
记录信息：
04-14 14:33:38.269: E/OpenGLRenderer(1263): Getting MAX_TEXTURE_SIZE from GradienCache
04-14 14:33:38.273: E/OpenGLRenderer(1263): MAX_TEXTURE_SIZE: 16384
04-14 14:33:38.285: E/OpenGLRenderer(1263): Getting MAX_TEXTURE_SIZE from Caches::initConstraints()
04-14 14:33:38.285: E/OpenGLRenderer(1263): MAX_TEXTURE_SIZE: 16384
04-14 14:33:43.145: E/AndroidRuntime(1263): FATAL EXCEPTION: main
04-14 14:33:43.145: E/AndroidRuntime(1263): Process: com.example.doubanbook, PID: 1263
04-14 14:33:43.145: E/AndroidRuntime(1263): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.doubanbook/com.example.doubanbook.activity.SearchBookActivity}: java.lang.NullPointerException
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.os.Handler.dispatchMessage(Handler.java:102)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.os.Looper.loop(Looper.java:136)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-14 14:33:43.145: E/AndroidRuntime(1263): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 14:33:43.145: E/AndroidRuntime(1263): at java.lang.reflect.Method.invoke(Method.java:515)
04-14 14:33:43.145: E/AndroidRuntime(1263): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-14 14:33:43.145: E/AndroidRuntime(1263): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-14 14:33:43.145: E/AndroidRuntime(1263): at dalvik.system.NativeStart.main(Native Method)
04-14 14:33:43.145: E/AndroidRuntime(1263): Caused by: java.lang.NullPointerException
04-14 14:33:43.145: E/AndroidRuntime(1263): at com.example.doubanbook.activity.SearchBookActivity.onCreate(SearchBookActivity.java:45)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.Activity.performCreate(Activity.java:5231)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-14 14:33:43.145: E/AndroidRuntime(1263): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-14 14:33:43.145: E/AndroidRuntime(1263): ... 11 more
答案 0 :(得分：1)
这里的ID不对：
searchButton = (Button) findViewById(R.id.search_button);
因为在你的layout.xml中你输入了一个稍微不同的id：
android:id="@+id/search_btn"
==＆GT;只需在布局和活动中使用相同的 ID并且应该可以正常工作，否则findViewById将返回null，因为它无法找到id。
答案 1 :(得分：1)
SearchBookActivity.java
中第45行有一个NullPointerException您可以从堆栈跟踪的这一行告诉：
04-14 14:33:43.145: E/AndroidRuntime(1263): Caused by: java.lang.NullPointerException
04-14 14:33:43.145: E/AndroidRuntime(1263): at com.example.doubanbook.activity.SearchBookActivity.onCreate(SearchBookActivity.java:45)
当您调用方法或引用null对象的成员时，会发生这种情况。
如果您的代码直接映射到您的代码行，则错误的来源很可能就在此行中：
searchButton.setOnClickListener(new OnClickListener() {
您正在使用findById进行R.id.search_et - 但也许您打算使用R.id.search_btn