在我的代码中获取nullpointer异常
我正在制作联系人列表申请表。我有一个名为搜索按钮的按钮，当它被点击时，我正在读取文本框中写的名字并在这里搜索数据库是我的代码：
public class SearchResultsActivity extends Activity {
public DatabaseAdapter db;
public ArrayList<String> myList;
public ListView listview;
private TextView view;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list);
view = (TextView) findViewById(R.id.textView1);
db = new DatabaseAdapter(this);
myList = new ArrayList<String>();
getSearchResults();
//getAllContacts();
printList();
}
public void getSearchResults(){
db.open();
db.getContactbyName(view.getText().toString());
Cursor c = db.getContactbyName(view.getText().toString());
if (c.moveToFirst()) {
do {
DisplayContact(c);
} while (c.moveToNext());
}
db.close();
}
public void printList(){
listview = (ListView)findViewById(R.id.contactcListView);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, android.R.id.text1, myList);
listview.setAdapter(adapter);
}
public void getAllContacts() {
db.open();
Cursor c = db.getAllContacts();
if (c.moveToFirst()) {
do {
DisplayContact(c);
} while (c.moveToNext());
}
db.close();
}
public void DisplayContact(Cursor c) {
String entry = "";
// if you add another attribute to your table, you need to change 3 into x
for (int i=1; i<5;i++){
entry += c.getString(i) + "\n";
}
myList.add(entry);
}
}
在我的代码中，getAllContacts（）方法工作正常并打印所有联系人。但是，当我尝试搜索联系人时，我得到一个nullpointer异常，应用程序关闭。有谁能看到这个问题？
这是日志猫：
由于
如果你不能阅读它，那么这是另一个版本的logcat：）
03-26 11:52:37.983: D/dalvikvm(12524): GC_CONCURRENT freed 78K, 7% free 12818K/13703K,
paused 10ms+3ms, total 45ms
03-26 11:52:37.988: D/AbsListView(12524): [unregisterDoubleTapMotionListener]
03-26 11:52:37.993: I/MotionRecognitionManager(12524): .unregisterListener : /
listener count = 0->0, listener=android.widget.AbsListView$4@42464368
03-26 11:55:53.778: I/Process(12524): Sending signal. PID: 12524 SIG: 9
03-26 11:56:42.238: E/SensorManager(13254): thread start
03-26 11:56:42.238: D/SensorManager(13254): registerListener :: handle = 0 name=
LSM330DLC 3-axis Accelerometer delay= 200000 Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@4243e698
03-26 11:56:42.308: D/SensorManager(13254): unregisterListener:: Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@4243e698
03-26 11:56:42.308: D/Sensors(13254): Remain listener = Sending .. normal delay 200ms
03-26 11:56:42.308: I/Sensors(13254): sendDelay --- 200000000
03-26 11:56:42.308: D/SensorManager(13254): JNI - sendDelay
03-26 11:56:42.308: I/SensorManager(13254): Set normal delay = true
03-26 11:56:42.333: D/SensorManager(13254): registerListener :: handle = 0 name=
LSM330DLC 3-axis Accelerometer delay= 200000 Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@4243e698
03-26 11:56:43.808: D/SensorManager(13254): registerListener :: handle = 0 name=
LSM330DLC 3-axis Accelerometer delay= 200000 Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@42474b30
03-26 11:56:43.823: D/dalvikvm(13254): GC_CONCURRENT freed 119K, 7% free 12450K/13319K,
paused 2ms+2ms, total 21ms
03-26 11:56:43.823: D/dalvikvm(13254): WAIT_FOR_CONCURRENT_GC blocked 6ms
03-26 11:56:43.843: D/SensorManager(13254): unregisterListener:: Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@42474b30
03-26 11:56:43.843: I/SensorManager(13254): Set min delay = 200000
03-26 11:56:43.843: I/SensorManager(13254): Before sending... delay = 200000
03-26 11:56:43.843: D/Sensors(13254): Remain listener =
android.view.OrientationEventListener$SensorEventListenerImpl@4243e698
03-26 11:56:43.843: I/Sensors(13254): sendDelay --- 200000000
03-26 11:56:43.843: D/SensorManager(13254): JNI - sendDelay
03-26 11:56:43.848: D/SensorManager(13254): unregisterListener:: Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@4243e698
03-26 11:56:43.848: D/Sensors(13254): Remain listener = Sending .. normal delay 200ms
03-26 11:56:43.848: I/Sensors(13254): sendDelay --- 200000000
03-26 11:56:43.848: D/SensorManager(13254): JNI - sendDelay
03-26 11:56:43.848: I/SensorManager(13254): Set normal delay = true
03-26 11:56:43.873: D/SensorManager(13254): registerListener :: handle = 0 name=
LSM330DLC 3-axis Accelerometer delay= 200000 Listener=
android.view.OrientationEventListener$SensorEventListenerImpl@42474b30
03-26 11:56:44.003: W/IInputConnectionWrapper(13254): getSelectedText on inactive
InputConnection
03-26 11:56:44.003: W/IInputConnectionWrapper(13254): setComposingText on inactive
InputConnection
03-26 11:56:44.003: W/IInputConnectionWrapper(13254): getExtractedText on inactive
InputConnection
03-26 11:56:45.658: D/AbsListView(13254): Get MotionRecognitionManager
03-26 11:56:45.673: D/AndroidRuntime(13254): Shutting down VM
03-26 11:56:45.673: W/dalvikvm(13254): threadid=1: thread exiting with uncaught
exception (group=0x417922a0)
03-26 11:56:45.678: E/AndroidRuntime(13254): FATAL EXCEPTION: main
03-26 11:56:45.678: E/AndroidRuntime(13254): java.lang.RuntimeException: Unable to
start activity
ComponentInfo{cs306.hw2.database/cs306.hw2.database.SearchResultsActivity}:
java.lang.NullPointerException 03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.ActivityThread.access$600(ActivityThread.java:140)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.os.Handler.dispatchMessage(Handler.java:99)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.os.Looper.loop(Looper.java:137)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.ActivityThread.main(ActivityThread.java:4898)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
java.lang.reflect.Method.invokeNative(Native Method)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
java.lang.reflect.Method.invoke(Method.java:511)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
dalvik.system.NativeStart.main(Native Method)
03-26 11:56:45.678: E/AndroidRuntime(13254): Caused by: java.lang.NullPointerException
03-26 11:56:45.678: E/AndroidRuntime(13254): at
s306.hw2.database.SearchResultsActivity.getSearchResults(SearchResultsActivity.java:34)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
cs306.hw2.database.SearchResultsActivity.onCreate(SearchResultsActivity.java:27)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.Activity.performCreate(Activity.java:5206)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083)
03-26 11:56:45.678: E/AndroidRuntime(13254): at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)
03-26 11:56:45.678: E/AndroidRuntime(13254): ... 11 more
这是layour文件
<ListView
android:id="@+id/contactcListView"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
3 个答案:
答案 0 :(得分：0)
这条线对我来说似乎是一个问题：
listview = (ListView)findViewById(R.id.contactcListView);
什么是“contactcListView”？我没有在任何地方看到这样的事情。
NPE是最容易解决的问题之一。堆栈跟踪会告诉您发生的文件和行号。您所要做的就是找到哪个引用为null以及为什么。
答案 1 :(得分：0)
没有
view = (TextView) findViewById(R.id.textView1);
在您的布局xml中定义。
view必须为null。
你认为NPE在这里得到了：
Cursor c = db.getContactbyName(view.getText().toString());
请尝试：
<ListView
android:id="@+id/contactcListView"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/textView1"/>
</ListView>
</LinearLayout>
答案 2 :(得分：0)
打开ddms预期并运行应用程序
复制日志
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